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InternalMed_Harrison. Hypoglycemia may cause transient loss of consciousness, typically in individuals with type 1 or type 2 diabetes treated with insulin. The clinical features associated with impending or actual hypoglycemia include tremor, palpitations, anxiety, diaphoresis, hunger, and paresthesias. These symptoms are due to autonomic activation to counter the falling blood glucose. Hunger, in particular, is not a typical premonitory feature of syncope. Hypoglycemia also impairs neuronal function, leading to fatigue, weakness, dizziness, and cognitive and behavioral symptoms. Diagnostic difficulties may occur in individuals in strict glycemic control; repeated hypoglycemia impairs the counterregulatory response and leads to a loss of the characteristic warning symptoms that are the hallmark of hypoglycemia.


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InternalMed_Harrison. Patients with cataplexy experience an abrupt partial or complete loss of muscular tone triggered by strong emotions, typically anger or laughter. Unlike syncope, consciousness is maintained throughout the attacks, which typically last between 30 s and 2 min. There are no premonitory symptoms. Cataplexy occurs in 60–75% of patients with narcolepsy. The clinical interview and interrogation of eyewitnesses usually allow differentiation of syncope from falls due to vestibular dysfunction, cerebellar disease, extrapyramidal system dysfunction, and other gait disorders. If the fall is accompanied by head trauma, a postconcussive syndrome, amnesia for the precipitating events, and/or the presence of loss of consciousness may contribute to diagnostic difficulty.


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InternalMed_Harrison. Apparent loss of consciousness can be a manifestation of psychiatric disorders such as generalized anxiety, panic disorders, major depression, and somatization disorder. These possibilities should be considered in individuals who faint frequently without prodromal symptoms. Such patients are rarely injured despite numerous falls. There are no clinically significant hemodynamic changes concurrent with these episodes. In contrast, transient loss of consciousness due to vasovagal syncope precipitated by fear, stress, anxiety, and emotional distress is accompanied by hypotension, bradycardia, or both.


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InternalMed_Harrison. The goals of the initial evaluation are to determine whether the transient loss of consciousness was due to syncope; to identify the cause; and to assess risk for future episodes and serious harm (Table 27-1). The initial evaluation should include a detailed history, thorough questioning of eyewitnesses, and a complete physical and neurologic examination. Blood pressure and heart rate should be measured in the supine position and after 3 min of standing to determine whether orthostatic hypotension is present. An ECG should be performed if there is suspicion of syncope due to an arrhythmia or underlying cardiac disease. Relevant electrocardiographic abnormalities include bradyarrhythmias or tachyarrhythmias, AV block, ischemia, old myocardial infarction, long QT syndrome, and bundle branch block. This initial assessment will lead to the identification of a cause of syncope in approximately 50% of patients and also allows stratification of patients at risk for cardiac mortality.


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InternalMed_Harrison. Laboratory Tests Baseline laboratory blood tests are rarely helpful in identifying the cause of syncope. Blood tests should be performed when specific disorders, e.g., myocardial infarction, anemia, and secondary autonomic failure, are suspected (Table 27-2).


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InternalMed_Harrison. Autonomic Nervous System Testing (Chap. 454) Autonomic testing, including tilt-table testing, can be performed in specialized centers. Autonomic testing is helpful to uncover objective evidence of autonomic failure and also to demonstrate a predisposition to neurally mediated syncope. Autonomic testing includes assessments of parasympathetic autonomic nervous system function (e.g., heart rate variability to deep respiration and a Valsalva maneuver), sympathetic cholinergic function (e.g., thermoregulatory sweat response and quantitative sudomotor axon reflex test), and sympathetic adrenergic function (e.g., blood pressure response to a Valsalva maneuver and a tilt-table test with beat-to-beat blood pressure measurement). The hemodynamic abnormalities demonstrated on tilt-table test (Figs. 27-3 and 27-4) may be useful in distinguishing orthostatic hypotension due to autonomic failure from the hypotensive bradycardic response of neurally mediated syncope. Similarly, the tilt-table test


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InternalMed_Harrison. 27-3 and 27-4) may be useful in distinguishing orthostatic hypotension due to autonomic failure from the hypotensive bradycardic response of neurally mediated syncope. Similarly, the tilt-table test may help identify patients with syncope due to immediate or delayed orthostatic hypotension.


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InternalMed_Harrison. Carotid sinus massage should be considered in patients with symptoms suggestive of carotid sinus syncope and in patients over age 50 years with recurrent syncope of unknown etiology. This test should only be carried out under continuous ECG and blood pressure monitoring and should be avoided in patients with carotid bruits, plaques, or stenosis.


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InternalMed_Harrison. Cardiac Evaluation ECG monitoring is indicated for patients with a high pretest probability of arrhythmia causing syncope. Patients should be monitored in hospital if the likelihood of a life-threatening arrhythmia is high, e.g., patients with severe structural or coronary artery disease, nonsustained ventricular tachycardia, trifascicular heart block, prolonged QT interval, Brugada syndrome ECG pattern, or family history of sudden cardiac death (Table 27-1). Outpatient Holter monitoring is recommended for patients who experience frequent syncopal episodes (one or more per week), whereas loop recorders, which continually record and erase cardiac rhythm, are indicated for patients with suspected arrhythmias with low risk of sudden cardiac death. Loop recorders may be external (recommended for evaluation of episodes that occur at a frequency of greater than one per month) or implantable (if syncope occurs less frequently).


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InternalMed_Harrison. Echocardiography should be performed in patients with a history of cardiac disease or if abnormalities are found on physical examination or the ECG. Echocardiographic diagnoses that may be responsible for syncope include aortic stenosis, hyper-trophic cardiomyopathy, cardiac tumors, aortic dissection, and pericardial tamponade. Echocardiography also has a role in risk stratification based on the left ventricular ejection fraction. Treadmill exercise testing with ECG and blood pressure monitoring should be performed in patients who have experienced syncope during or shortly after exercise. Treadmill testing may help identify exercise-induced arrhythmias (e.g., tachycardia-related AV block) and exercise-induced exaggerated vasodilation.


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InternalMed_Harrison. Electrophysiologic studies are indicated in patients with structural heart disease and ECG abnormalities in whom noninvasive investigations have failed to yield a diagnosis. Electrophysiologic studies have low sensitivity and specificity and should only be performed when a high pretest probability exists. Currently, this test is rarely performed to evaluate patients with syncope. Psychiatric Evaluation Screening for psychiatric disorders may be appropriate in patients with recurrent unexplained syncope episodes. Tilt-table testing, with demonstration of symptoms in the absence of hemodynamic change, may be useful in reproducing syncope in patients with suspected psychogenic syncope. PART 2 Cardinal Manifestations and Presentation of Diseases Mark F. Walker, Robert B. Daroff


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InternalMed_Harrison. PART 2 Cardinal Manifestations and Presentation of Diseases Mark F. Walker, Robert B. Daroff Dizziness is an imprecise symptom used to describe a variety of sensations that include vertigo, light-headedness, faintness, and imbalance. When used to describe a sense of spinning or other motion, dizziness is designated as vertigo. Vertigo may be physiologic, occurring during or after a sustained head rotation, or it may be pathologic, due to vestibular dysfunction. The term light-headedness is commonly applied to presyncopal sensations due to brain hypoperfusion but also may refer to disequilibrium and imbalance. A challenge to diagnosis is that patients often have difficulty distinguishing among these various symptoms, and the words they choose do not reliably indicate the underlying etiology.


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InternalMed_Harrison. There are a number of potential causes of dizziness. Vascular disorders cause presyncopal dizziness as a result of cardiac dysrhythmia, orthostatic hypotension, medication effects, or other causes. Such presyncopal sensations vary in duration; they may increase in severity until loss of consciousness occurs, or they may resolve before loss of consciousness if the cerebral ischemia is corrected. Faintness and syncope, which are discussed in detail in Chap. 27, should always be considered when one is evaluating patients with brief episodes of dizziness or dizziness that occurs with upright posture.


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InternalMed_Harrison. Vestibular causes of dizziness (vertigo or imbalance) may be due to peripheral lesions that affect the labyrinths or vestibular nerves or to involvement of the central vestibular pathways. They may be paroxysmal or due to a fixed unilateral or bilateral vestibular deficit. Acute unilateral lesions cause vertigo due to a sudden imbalance in vestibular inputs from the two labyrinths. Bilateral lesions cause imbalance and instability of vision (oscillopsia) when the head moves. Other causes of dizziness include nonvestibular imbalance and gait disorders (e.g., loss of proprioception from sensory neuropathy, parkinsonism) and anxiety.


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InternalMed_Harrison. When evaluating patients with dizziness, questions to consider include the following: (1) Is it dangerous (e.g., arrhythmia, transient ischemic attack/stroke)? (2) Is it vestibular? (3) If vestibular, is it peripheral or central? A careful history and examination often provide sufficient information to answer these questions and determine whether additional studies or referral to a specialist is necessary. APPROACH TO THE PATIENT:


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InternalMed_Harrison. APPROACH TO THE PATIENT: When a patient presents with dizziness, the first step is to delineate more precisely the nature of the symptom. In the case of vestibular disorders, the physical symptoms depend on whether the lesion is unilateral or bilateral, and whether it is acute or chronic and progressive. Vertigo, an illusion of self or environmental motion, implies asymmetry of vestibular inputs from the two labyrinths or in their central pathways that is usually acute. Symmetric bilateral vestibular hypofunction causes imbalance but no vertigo. Because of the ambiguity in patients’ descriptions of their symptoms, diagnosis based simply on symptom characteristics is typically unreliable. The history should focus closely on other features, including whether this is the first attack, the duration of this and any prior episodes, provoking factors, and accompanying symptoms.


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InternalMed_Harrison. Dizziness can be divided into episodes that last for seconds, minutes, hours, or days. Common causes of brief dizziness (seconds) include benign paroxysmal positional vertigo (BPPV) and orthostatic hypotension, both of which typically are provoked by changes in head and body position. Attacks of vestibular migraine and Ménière’s disease often last hours. When episodes are of intermediate duration (minutes), transient ischemic attacks of the posterior circulation should be considered, although migraine and a number of other causes are also possible.


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InternalMed_Harrison. Symptoms that accompany vertigo may be helpful in distinguishing peripheral vestibular lesions from central causes. Unilateral hearing loss and other aural symptoms (ear pain, pressure, fullness) typically point to a peripheral cause. Because the auditory pathways quickly become bilateral upon entering the brainstem, central lesions are unlikely to cause unilateral hearing loss, unless the lesion lies near the root entry zone of the auditory nerve. Symptoms such as double vision, numbness, and limb ataxia suggest a brainstem or cerebellar lesion. Because dizziness and imbalance can be a manifestation of a variety of neurologic disorders, the neurologic examination is important in the evaluation of these patients. Particular focus should be given to assessment of eye movements, vestibular function, and hearing.


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InternalMed_Harrison. The range of eye movements and whether they are equal in each eye should be observed. Peripheral eye movement disorders (e.g., cranial neuropathies, eye muscle weakness) are usually disconjugate (different in the two eyes). One should check pursuit (the ability to follow a smoothly moving target) and saccades (the ability to look back and forth accurately between two targets). Poor pursuit or inaccurate (dysmetric) saccades usually indicates central pathology, often involving the cerebellum. Finally, one should look for spon taneous nystagmus, an involuntary back-and-forth movement of the eyes. Nystagmus is most often of the jerk type, in which a slow drift (slow phase) in one direction alternates with a rapid saccadic movement (quick phase or fast phase) in the opposite direction that resets the position of the eyes in the orbits. Except in the case of acute vestibulopathy (e.g., vestibular neuritis), if primary position nystagmus is easily seen in the light, it is probably due to a


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InternalMed_Harrison. the position of the eyes in the orbits. Except in the case of acute vestibulopathy (e.g., vestibular neuritis), if primary position nystagmus is easily seen in the light, it is probably due to a central cause. Two forms of nystagmus that are characteristic of lesions of the cerebellar pathways are vertical nystagmus with downward changes direction with gaze (gaze-evoked nystagmus). By contrast, tagmus. Use of Frenzel eyeglasses (self-illuminated goggles with convex lenses that blur the patient’s vision but allow the examiner to see the eyes greatly magnified) can aid in the detection of peripheral vestibular nystagmus, because they reduce the patient’s ability to use visual fixation to suppress nystagmus. Table 28-1 outlines key find ings that help distinguish peripheral from central causes of vertigo.


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InternalMed_Harrison. The most useful bedside test of peripheral vestibular function is the head impulse test, in which the vestibuloocular reflex (VOR) is assessed with small-amplitude (~20 degrees) rapid head rotations. While the patient fixates on a target, the head is rotated to the left or right. If the VOR is deficient, the rotation is followed by a catch up saccade in the opposite direction (e.g., a leftward saccade after a rightward rotation). The head impulse test can identify both uni lateral (catch-up saccades after rotations toward the weak side) and in both directions).


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InternalMed_Harrison. All patients with episodic dizziness, especially if provoked by positional change, should be tested with the Dix-Hallpike maneu ver. The patient begins in a sitting position with the head turned fEATuRES of PERiPHERAL AnD CEnTRAL vERTigo • Nystagmus from an acute peripheral lesion is unidirectional, with fast phases beating away from the ear with the lesion. Nystagmus that changes direction with gaze is due to a central lesion. mixed vertical-torsional nystagmus occurs in BPPV, but pure vertical or pure torsional nystagmus is a central sign. from a peripheral lesion may be inhibited by visual fixation, whereas central nystagmus is not suppressed. • Absence of a head impulse sign in a patient with acute prolonged vertigo should suggest a central cause. • Unilateral hearing loss suggests peripheral vertigo. Findings such as diplopia, dysarthria, and limb ataxia suggest a central disorder.


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InternalMed_Harrison. • Unilateral hearing loss suggests peripheral vertigo. Findings such as diplopia, dysarthria, and limb ataxia suggest a central disorder. 45 degrees; holding the back of the head, the examiner then lowers the patient into a supine position with the head extended backward by about 20 degrees while watching the eyes. Posterior canal BPPV can be diagnosed confidently if transient upbeating-torsional nystagmus is seen. If no nystagmus is observed after 15–20 s, the patient is raised to the sitting position, and the procedure is repeated with the head turned to the other side. Again, Frenzel goggles may improve the sensitivity of the test.


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InternalMed_Harrison. Dynamic visual acuity is a functional test that can be useful in assessing vestibular function. Visual acuity is measured with the head still and when the head is rotated back and forth by the examiner (about 1–2 Hz). A drop in visual acuity during head motion of more than one line on a near card or Snellen chart is abnormal and indicates vestibular dysfunction.


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InternalMed_Harrison. The choice of ancillary tests should be guided by the history and examination findings. Audiometry should be performed whenever a vestibular disorder is suspected. Unilateral sensorineural hearing loss supports a peripheral disorder (e.g., vestibular schwannoma). Predominantly low-frequency hearing loss is characteristic of Ménière’s disease. Electronystagmography or videonystagmography includes recordings of spontaneous nystagmus (if present) and measurement of positional nystagmus. Caloric testing assesses the responses of the two horizontal semicircular canals. The test battery often includes recording of saccades and pursuit to assess central ocular motor function. Neuroimaging is important if a central vestibular disorder is suspected. In addition, patients with unexplained unilateral hearing loss or vestibular hypofunction should undergo magnetic resonance imaging (MRI) of the internal auditory canals, including administration of gadolinium, to rule out a schwannoma.


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InternalMed_Harrison. Treatment of vestibular symptoms should be driven by the underlying diagnosis. Simply treating dizziness with vestibular suppressant medications is often not helpful and may make the symptoms worse and prolong recovery. The diagnostic and specific treatment approaches for the most commonly encountered vestibular disorders are discussed below. An acute unilateral vestibular lesion causes constant vertigo, nausea, vomiting, oscillopsia (motion of the visual scene), and imbalance. These symptoms are due to a sudden asymmetry of inputs from the two labyrinths or in their central connections, simulating a continuous rotation of the head. Unlike BPPV, continuous vertigo persists even when the head remains still.


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InternalMed_Harrison. When a patient presents with an acute vestibular syndrome, the most important question is whether the lesion is central (e.g., a cerebellar or brainstem infarct or hemorrhage), which may be life-threatening, or peripheral, affecting the vestibular nerve or labyrinth (vestibular neuritis). Attention should be given to any symptoms or signs that point to central dysfunction (diplopia, weakness or numbness, dysarthria). The pattern of spontaneous nystagmus, if present, may be helpful (Table 28-1). If the head impulse test is normal, an acute peripheral vestibular lesion is unlikely. A central lesion cannot always be excluded with certainty based on symptoms and examination alone; thus, older patients with vascular risk factors who present with an acute vestibular syndrome should be evaluated for the possibility of stroke even when there are no specific findings that indicate a central lesion.


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InternalMed_Harrison. Most patients with vestibular neuritis recover spontaneously, but glucocorticoids can improve outcome if administered within 3 days of symptom onset. Antiviral medications are of no proven benefit and are not typically given unless there is evidence to suggest herpes zoster oticus (Ramsay Hunt syndrome). Vestibular suppressant medications may reduce acute symptoms but should be avoided after the first several days because they may impede central compensation and recovery. Patients should be encouraged to resume a normal level of activity as soon as possible, and directed vestibular rehabilitation therapy may accelerate improvement.


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InternalMed_Harrison. 150 BENIgN PAROXYSMAL POSITIONAL VERTIgO BPPV is a common cause of recurrent vertigo. Episodes are brief (<1 min and typically 15–20 s) and are always provoked by changes in head position relative to gravity, such as lying down, rolling over in bed, rising from a supine position, and extending the head to look upward. The attacks are caused by free-floating otoconia (calcium carbonate crystals) that have been dislodged from the utricular macula and have moved into one of the semicircular canals, usually the posterior canal. When head position changes, gravity causes the otoconia to move within the canal, producing vertigo and nystagmus. With posterior canal BPPV, the nystagmus beats upward and torsionally (the upper poles of the eyes beat toward the affected lower ear). Less commonly, the otoconia enter the horizontal canal, resulting in a horizontal nystagmus when the patient is lying with either ear down. Superior (also called anterior) canal involvement is rare. BPPV is treated


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InternalMed_Harrison. the otoconia enter the horizontal canal, resulting in a horizontal nystagmus when the patient is lying with either ear down. Superior (also called anterior) canal involvement is rare. BPPV is treated with repositioning maneuvers that use gravity to remove the otoconia from the semicircular canal. For posterior canal BPPV, the Epley maneuver (Fig. 28-1) is the most commonly used procedure. For more refractory cases of BPPV, patients can be taught a variant of this maneuver that they can perform alone at home. A demonstration of the Epley maneuver is available online (http:// www.dizziness-and-balance.com/disorders/bppv/bppv.html).


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InternalMed_Harrison. Vestibular symptoms occur frequently in migraineurs, sometimes as a headache aura but usually independent of headache. The duration of vertigo may be from minutes to hours, and some patients also experience more prolonged periods of disequilibrium (lasting days to weeks). Motion sensitivity and sensitivity to visual motion (e.g., movies) are common in patients with vestibular migraine. Although data from controlled studies are generally lacking, vestibular migraine typically is treated with medications that are used for prophylaxis of migraine headaches. Antiemetics may be helpful to relieve symptoms at the time of an attack. Attacks of Ménière’s disease consist of vertigo and hearing loss, as well as pain, pressure, and/or fullness in the affected ear. The low-frequency


InternalMed_Harrison

InternalMed_Harrison. PART 2 Cardinal Manifestations and Presentation of Diseases hearing loss and aural symptoms are key features that distinguish Ménière’s disease from other peripheral vestibulopathies and from vestibular migraine. Audiometry at the time of an attack shows a characteristic asymmetric low-frequency hearing loss; hearing commonly improves between attacks, although permanent hearing loss may eventually occur. Ménière’s disease is thought to be due to excess fluid (endolymph) in the inner ear; hence the term endolymphatic hydrops. Patients suspected of having Ménière’s disease should be referred to an otolaryngologist for further evaluation. Diuretics and sodium restriction are the initial treatments. If attacks persist, injections of gentamicin into the middle ear are typically the next line of therapy. Full ablative procedures (vestibular nerve section, labyrinthectomy) are seldom required.


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InternalMed_Harrison. Vestibular schwannomas (sometimes termed acoustic neuromas) and other tumors at the cerebellopontine angle cause slowly progressive unilateral sensorineural hearing loss and vestibular hypofunction. These patients typically do not have vertigo, because the gradual vestibular deficit is compensated centrally as it develops. The diagnosis often is not made until there is sufficient hearing loss to be noticed. The examination will show a deficient response to the head impulse test when the head is rotated toward the affected side. As noted above, patients with unexplained unilateral sensorineural hearing loss or vestibular hypofunction require MRI of the internal auditory canals to look for a schwannoma.


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InternalMed_Harrison. Patients with bilateral loss of vestibular function also typically do not have vertigo, because vestibular function is lost on both sides simultaneously, and there is no asymmetry of vestibular input. Symptoms include loss of balance, particularly in the dark, where vestibular input is most critical, and oscillopsia during head movement, such as while walking or riding in a car. Bilateral vestibular hypofunction may be (1) idiopathic and progressive, (2) part of a neurodegenerative disorder, or (3) iatrogenic, due to medication ototoxicity (most commonly


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InternalMed_Harrison. FIguRE 28-1 Modified Epley maneuver for treatment of benign paroxysmal positional vertigo of the right (top panels) and left (bottom panels) posterior semicircular canals. Step 1. With the patient seated, turn the head 45 degrees toward the affected ear. Step 2. Keeping the head turned, lower the patient to the head-hanging position and hold for at least 30 s and until nystagmus disappears. Step 3. Without lifting the head, turn it 90 degrees toward the other side. Hold for another 30 s. Step 4. Rotate the patient onto her side while turning the head another 90 degrees, so that the nose is pointed down 45 degrees. Hold again for 30 s. Step 5. Have the patient sit up on the side of the table. After a brief rest, the maneuver should be repeated to confirm successful treatment. (Figure adapted from http://www.dizziness-and-balance.com/ disorders/bppv/movies/Epley-480x640.avi.) gentamicin or other aminoglycoside antibiotics). Other causes include bilateral vestibular schwannomas


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InternalMed_Harrison. adapted from http://www.dizziness-and-balance.com/ disorders/bppv/movies/Epley-480x640.avi.) gentamicin or other aminoglycoside antibiotics). Other causes include bilateral vestibular schwannomas (neurofibromatosis type 2), autoimmune disease, superficial siderosis, and meningeal-based infection or tumor. It also may occur in patients with peripheral polyneuropathy; in these patients, both vestibular loss and impaired proprioception may contribute to poor balance. Finally, unilateral processes such as vestibular neuritis and Ménière’s disease may involve both ears sequentially, resulting in bilateral vestibulopathy.


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InternalMed_Harrison. Examination findings include diminished dynamic visual acuity (see above) due to loss of stable vision when the head is moving, abnormal head impulse responses in both directions, and a Romberg sign. Responses to caloric testing are reduced. Patients with bilateral vestibular hypofunction should be referred for vestibular rehabilitation therapy. Vestibular suppressant medications should not be used, as they will increase the imbalance. Evaluation by a neurologist is important not only to confirm the diagnosis but also to consider any other associated neurologic abnormalities that may clarify the etiology.


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InternalMed_Harrison. Central lesions causing vertigo typically involve vestibular pathways in the brainstem and/or cerebellum. They may be due to discrete lesions, such as from ischemic or hemorrhagic stroke (Chap. 446), demyelination (Chap. 458), or tumors (Chap. 118), or they may be due to neurodegenerative conditions that include the vestibulocerebellum (Chap. 448). Subacute cerebellar degeneration may be due to immune, including paraneoplastic, processes (Chaps. 122 and 450). Table 28-1 outlines important features of the history and examination that help to identify central vestibular disorders. Acute central vertigo is a medical emergency, due to the possibility of life-threatening stroke or hemorrhage. All patients with suspected central vestibular disorders should undergo brain MRI, and the patient should be referred for full neurologic evaluation.


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InternalMed_Harrison. Psychological factors play an important role in chronic dizziness. First, dizziness may be a somatic manifestation of a psychiatric condition such as major depression, anxiety, or panic disorder (Chap. 465e). Second, patients may develop anxiety and autonomic symptoms as a consequence or comorbidity of an independent vestibular disorder. One particular form of this has been termed variously phobic postural vertigo, psychophysiologic vertigo, or chronic subjective dizziness. These patients have a chronic feeling (months or longer) of dizziness and disequilibrium, an increased sensitivity to self-motion and visual motion (e.g., movies), and a particular intensification of symptoms when moving through complex visual environments such as supermarkets (visual vertigo). Although there may be a past history of an acute vestibular disorder (e.g., vestibular neuritis), the neurootologic examination and vestibular testing are normal or indicative of a compensated vestibular deficit, indicating


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InternalMed_Harrison. past history of an acute vestibular disorder (e.g., vestibular neuritis), the neurootologic examination and vestibular testing are normal or indicative of a compensated vestibular deficit, indicating that the ongoing subjective dizziness cannot be explained by a primary vestibular disorder. Anxiety disorders are particularly common in patients with chronic dizziness and contribute substantially to the morbidity. Thus, treatment with antianxiety medications (selective serotonin reuptake inhibitors [SSRIs]) and cognitive-behavioral therapy may be helpful. Vestibular rehabilitation therapy is also sometimes beneficial. Vestibular suppressant medications generally should be avoided. This condition should be suspected when the patient states, “My dizziness is so bad, I’m afraid to leave my house” (agoraphobia).


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InternalMed_Harrison. Table 28-2 provides a list of commonly used medications for suppression of vertigo. As noted, these medications should be reserved for short-term control of active vertigo, such as during the first few days of acute vestibular neuritis, or for acute attacks of Ménière’s disease. They are less helpful for chronic dizziness and, as previously stated, may hinder central compensation. An exception is that benzodiazepines may attenuate psychosomatic dizziness and the associated anxiety, although SSRIs are generally preferable in such patients. Benzodiazepines Diazepam 2.5 mg 1–3 times daily Clonazepam 0.25 mg 1–3 times daily days 4–6; 60 mg daily days 7–9; 40 mg daily days 10–12; 20 mg daily days 13–15; 10 mg daily days 16–18, 20, 22


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InternalMed_Harrison. Benzodiazepines Diazepam 2.5 mg 1–3 times daily Clonazepam 0.25 mg 1–3 times daily days 4–6; 60 mg daily days 7–9; 40 mg daily days 10–12; 20 mg daily days 13–15; 10 mg daily days 16–18, 20, 22 Selective serotonin reuptake inhibitorsh aAll listed drugs are approved by the U.S. Food and Drug Administration, but most are not approved for the treatment of vertigo. bUsual oral (unless otherwise stated) starting dose in adults; a higher maintenance dose can be reached by a gradual increase. cFor motion sickness only. dFor benign paroxysmal positional vertigo. eFor Ménière’s disease. fFor vestibular migraine. gFor acute vestibular neuritis (started within 3 days of onset). hFor psychosomatic vertigo.


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InternalMed_Harrison. Vestibular rehabilitation therapy promotes central adaptation processes that compensate for vestibular loss and also may help habituate motion sensitivity and other symptoms of psychosomatic dizziness. The general approach is to use a graded series of exercises that progressively challenge gaze stabilization and balance. Jeffrey M. Gelfand, Vanja C. Douglas


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InternalMed_Harrison. Fatigue is one of the most common symptoms in clinical medicine. It is a prominent manifestation of a number of systemic, neurologic, and psychiatric syndromes, although a precise cause will not be identified in a substantial minority of patients. Fatigue refers to an inherently subjective human experience of physical and mental weariness, sluggishness, and exhaustion. In the context of clinical medicine, fatigue is most typically and practically defined as difficulty initiating or maintaining voluntary mental or physical activity. Nearly everyone who has ever been ill with a self-limited infection has experienced this near-universal symptomatology, and fatigue is usually brought to medical attention only when it is either of unclear cause or the severity is out of proportion with what would be expected for the associated trigger. Fatigue should be distinguished from muscle weakness, a reduction of neuromuscular power (Chap. 30); most patients complaining of fatigue are not truly weak


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InternalMed_Harrison. be expected for the associated trigger. Fatigue should be distinguished from muscle weakness, a reduction of neuromuscular power (Chap. 30); most patients complaining of fatigue are not truly weak when direct muscle power is tested. By definition, fatigue is also distinct from somnolence and dyspnea on exertion, although patients may use the word fatigue to describe those two symptoms. The task facing clinicians when a patient presents with fatigue is to identify an underlying cause if one exists and to develop 152 a therapeutic alliance, the goal of which is to spare patients expensive and fruitless diagnostic workups and steer them toward effective therapy.


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InternalMed_Harrison. Variability in the definitions of fatigue and the survey instruments used in different studies makes it difficult to arrive at precise figures about the global burden of fatigue. The point prevalence of fatigue was 6.7% and the lifetime prevalence was 25% in a large National Institute of Mental Health survey of the U.S. general population. In primary care clinics in Europe and the United States, between 10 and 25% of patients surveyed endorsed symptoms of prolonged (present for >1 month) or chronic (present for >6 months) fatigue, but fatigue was the primary reason for seeking medical attention in only a minority of patients. In a community survey of women in India, 12% reported chronic fatigue. By contrast, the prevalence of chronic fatigue syndrome, as defined by the U.S. Centers for Disease Control and Prevention, is low (Chap. 464e).


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InternalMed_Harrison. DIFFERENTIAL DIAgNOSIS Psychiatric Disease Fatigue is a common somatic manifestation of many major psychiatric syndromes, including depression, anxiety, and somatoform disorders. Psychiatric symptoms are reported in more than three-quarters of patients with unexplained chronic fatigue. Even in patients with systemic or neurologic syndromes in which fatigue is independently recognized as a manifestation of disease, comorbid psychiatric symptoms or disease may still be an important source of interaction.


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InternalMed_Harrison. Neurologic Disease Patients complaining of fatigue often say they feel weak, but upon careful examination, objective muscle weakness is rarely discernible. If found, muscle weakness must then be localized to the central nervous system, peripheral nervous system, neuromuscular junction, or muscle and the appropriate follow-up studies obtained (Chap. 30). Fatigability of muscle power is a cardinal manifestation of some neuromuscular disorders such as myasthenia gravis and can be distinguished from fatigue by finding clinically apparent diminution of the amount of force that a muscle generates upon repeated contraction (Chap. 461). Fatigue is one of the most common and bothersome symptoms reported in multiple sclerosis (MS) (Chap. 458), affecting nearly 90% of patients; fatigue in MS can persist between MS attacks and does not necessarily correlate with magnetic resonance imaging (MRI) disease activity. Fatigue is also increasingly identified as a troublesome feature of many other


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InternalMed_Harrison. persist between MS attacks and does not necessarily correlate with magnetic resonance imaging (MRI) disease activity. Fatigue is also increasingly identified as a troublesome feature of many other neurodegenerative diseases, including Parkinson’s disease, central dysautonomias, and amyotrophic lateral sclerosis. Poststroke fatigue is a well-described but poorly understood entity with a widely varying prevalence. Episodic fatigue can be a premonitory symptom of migraine. Fatigue is also a frequent result of traumatic brain injury, often occurring in association with depression and sleep disorders.


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InternalMed_Harrison. Sleep Disorders Obstructive sleep apnea is an important cause of excessive daytime sleepiness in association with fatigue and should be investigated using overnight polysomnography, particularly in those with prominent snoring, obesity, or other predictors of obstructive sleep apnea (Chap. 319). Whether the cumulative sleep deprivation that is common in modern society contributes to clinically apparent fatigue is not known (Chap. 38).


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InternalMed_Harrison. Endocrine Disorders Fatigue, sometimes in association with true muscle weakness, can be a heralding symptom of hypothyroidism, particularly in the context of hair loss, dry skin, cold intolerance, constipation, and weight gain. Fatigue in association with heat intolerance, sweating, and palpitations is typical of hyperthyroidism. Adrenal insufficiency can also manifest with unexplained fatigue as a primary or prominent symptom, often in association with anorexia, weight loss, nausea, myalgias, and arthralgias; hyponatremia and hyperkalemia may be present at time of diagnosis. Mild hypercalcemia can cause fatigue, which may be relatively vague, whereas severe hypercalcemia can lead


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InternalMed_Harrison. PART 2 Cardinal Manifestations and Presentation of Diseases to lethargy, stupor, and coma. Both hypoglycemia and hyperglycemia can cause lethargy, often in association with confusion; chronic diabetes, particularly type 1 diabetes, is also associated with fatigue independent of glucose levels. Fatigue may also accompany Cushing’s disease, hypoaldosteronism, and hypogonadism. Liver and Kidney Disease Both chronic liver failure and chronic kidney disease can cause fatigue. Over 80% of hemodialysis patients complain of fatigue, which makes this one of the most common patient-reported symptoms in chronic kidney disease.


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InternalMed_Harrison. Obesity Obesity is associated with fatigue and sleepiness independent of the presence of obstructive sleep apnea. Obese patients undergoing bariatric surgery experience improvement in daytime sleepiness sooner than would be expected if the improvement were solely the result of weight loss and resolution of sleep apnea. A number of other factors common in obese patients are likely contributors as well, including depression, physical inactivity, and diabetes. Malnutrition Although fatigue can be a presenting feature of malnutrition, nutritional status may also be an important comorbidity and contributor to fatigue in other chronic illnesses, including cancer-associated fatigue.


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InternalMed_Harrison. Infection Both acute and chronic infections commonly lead to fatigue as part of the broader infectious syndrome. Evaluation for undiagnosed infection as the cause of unexplained fatigue, and particularly prolonged or chronic fatigue, should be guided by the history, physical examination, and infectious risk factors, with particular attention to risk for tuberculosis, HIV, chronic hepatitis B and C, and endocarditis. Infectious mononucleosis may cause prolonged fatigue that persists for weeks to months following the acute illness, but infection with the Epstein-Barr virus is only very rarely the cause of unexplained chronic fatigue. Drugs Many medications, drug use, drug withdrawal, and chronic alcohol use can all lead to fatigue. Medications that are more likely to be causative in this context include antidepressants, antipsychotics, anxiolytics, opiates, antispasticity agents, antiseizure agents, and beta blockers.


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InternalMed_Harrison. Cardiovascular and Pulmonary Fatigue is one of the most taxing patient-reported symptoms of congestive heart failure and chronic obstructive pulmonary disease and negatively affects quality of life. Malignancy Fatigue, particularly in association with unexplained unintended weight loss, can be a sign of occult malignancy, but this is only rarely identified as causative in patients with unexplained chronic fatigue in the absence of other telltale signs or symptoms. Cancer-related fatigue is experienced by 40% of patients at time of diagnosis and greater than 80% of patients later in the disease course. Hematologic Chronic or progressive anemia may present with fatigue, sometimes in association with exertional tachycardia and breathlessness. Anemia may also contribute to fatigue in chronic illness. Low serum ferritin in the absence of anemia may also cause fatigue that is reversible with iron replacement.


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InternalMed_Harrison. Systemic Inflammatory/Rheumatologic Disorders Fatigue is a prominent complaint in many chronic inflammatory disorders, including systemic lupus erythematosus, polymyalgia rheumatica, rheumatoid arthritis, inflammatory bowel disease, antineutrophil cytoplasmic antibody (ANCA)–associated vasculitis, sarcoidosis, and Sjögren’s syndrome, but is not usually an isolated symptom. Pregnancy Fatigue is very commonly reported by women during all stages of pregnancy and postpartum.


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InternalMed_Harrison. Pregnancy Fatigue is very commonly reported by women during all stages of pregnancy and postpartum. Disorders of unclear Cause Chronic fatigue syndrome (Chap. 464e) and fibromyalgia (Chap. 396) incorporate chronic fatigue as part of the syndromic definition when present in association with a number of other inclusion and exclusion criteria, as discussed in detail in their respective chapters. The pathophysiology of each is unknown. Idiopathic chronic fatigue is used to describe the syndrome of unexplained chronic fatigue in the absence of enough additional clinical features to meet the diagnostic criteria for chronic fatigue syndrome. APPROACH TO THE PATIENT:


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InternalMed_Harrison. A detailed history focusing on the quality, pattern, time-course, associated symptoms, and alleviating factors of fatigue is critical in defining the syndrome, determining whether fatigue is the appropriate designation, determining whether the symptoms are acute or chronic, and determining whether fatigue is primarily mental, physical, or both in order to direct further evaluation and treatment. The review of systems should attempt to distinguish fatigue from excessive daytime sleepiness, dyspnea on exertion, exercise intolerance, and muscle weakness. The presence of fever, chills, night sweats, or weight loss should raise suspicion for an occult infection or malignancy. A careful review of prescription, over-the-counter, herbal, and recreational drug and alcohol use is mandatory. Circumstances surrounding the onset of symptoms and potential triggers should be investigated. The social history is important, with attention paid to job stress and work hours, the social support network,


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InternalMed_Harrison. surrounding the onset of symptoms and potential triggers should be investigated. The social history is important, with attention paid to job stress and work hours, the social support network, and domestic affairs including a screen for intimate partner violence. Sleep habits and sleep hygiene should be questioned. The impact of fatigue on daily functioning is important to understand the patient’s experience and gauge recovery and the success of treatment.


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InternalMed_Harrison. The physical examination of patients with fatigue is guided by the history and differential diagnosis. A detailed mental status examination should be performed with particular attention to symptoms of depression and anxiety. A formal neurologic examination is required to determine whether objective muscle weakness is present. This is usually a straightforward exercise, although occasionally patients with fatigue have difficulty sustaining effort against resistance and sometimes report that generating full power requires substantial mental effort. On confrontational testing, they are able to generate full power for only a brief period before suddenly giving way to the examiner. This type of weakness is often referred to as breakaway weakness and may or may not be associated with pain. This is contrasted with weakness due to lesions in the motor tracts or lower motor unit, in which the patient’s resistance can be overcome in a smooth and steady fashion and full power can never be


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InternalMed_Harrison. This is contrasted with weakness due to lesions in the motor tracts or lower motor unit, in which the patient’s resistance can be overcome in a smooth and steady fashion and full power can never be generated. Occasionally, a patient may demonstrate fatigable weakness, in which power is full when first tested but becomes weak upon repeat evaluation without interval rest. Fatigable weakness, which usually indicates a problem of neuromuscular transmission, never has the sudden breakaway quality that one occasionally observes in patients with fatigue. If the presence or absence of muscle weakness cannot be determined with the physical examination, electromyography with nerve conductions studies can be a helpful ancillary test.


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InternalMed_Harrison. The general physical examination should screen for signs of cardiopulmonary disease, malignancy, lymphadenopathy, organomegaly, infection, liver failure, kidney disease, malnutrition, endocrine abnormalities, and connective tissue disease. Although the diagnostic yield of the general physical examination may be relatively low in the context of evaluation of unexplained chronic fatigue, elucidating the cause of 2% of cases in one prospective analysis, the yield of a detailed neuropsychiatric and mental status evaluation is likely to be much higher, revealing a potential explanation for fatigue in up to 75–80% of patients in some series. Furthermore, the rite of physical examination demonstrates a thorough and systematic approach to the patient’s complaint and helps build trust and a therapeutic alliance.


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InternalMed_Harrison. Laboratory testing is likely to identify the cause of chronic fatigue in only about 5% of cases. Beyond a few standard screening tests, laboratory evaluation should be guided by the history and physical examination; extensive testing is more likely to lead to false-positive results that require explanation and unnecessary investigation and should be avoided in lieu of frequent clinical follow-up. A reasonable approach to screening includes a complete blood count with differential (to screen for anemia, infection, and malignancy), electrolytes (including sodium, potassium, and calcium), glucose, renal function, liver function, and thyroid function. Testing for HIV and adrenal function can also be considered. Published guidelines defining chronic fatigue syndrome also recommend an erythrocyte sedimentation rate (ESR) as part of the evaluation for mimics, but unless the value is very high, such nonspecific testing in the absence of other features is unlikely to clarify the situation.


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InternalMed_Harrison. sedimentation rate (ESR) as part of the evaluation for mimics, but unless the value is very high, such nonspecific testing in the absence of other features is unlikely to clarify the situation. Routine screening with an antinuclear antibody (ANA) test is also unlikely to be informative in isolation and is frequently positive at low titers in otherwise healthy adults. Additional unfocused studies, such as whole-body imaging scans, are usually not indicated; in addition to their inconvenience, potential risk, and cost, they often reveal unrelated incidental findings that can prolong the workup unnecessarily.


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InternalMed_Harrison. The first priority of treatment is to address the underlying disorder or disorders that account for fatigue, because this can be curative in select contexts and palliative in others. Unfortunately, in many chronic illnesses, fatigue may be refractory to traditional disease-modifying therapies, and it is important in such cases to evaluate for other potential contributors, because the cause may be multifactorial. Antidepressant treatment (Chap. 466) may be helpful for treatment of chronic fatigue when symptoms of depression are present and may be most effective in the context of a multimodal approach. However, antidepressants can also cause fatigue and should be discontinued if they are not clearly effective. Cognitive-behavioral therapy has also been demonstrated to be helpful in the context of chronic fatigue syndrome as well as cancer-associated fatigue. Graded exercise therapy in which physical exercise, most typically walking, is gradually increased with attention to target heart


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InternalMed_Harrison. of chronic fatigue syndrome as well as cancer-associated fatigue. Graded exercise therapy in which physical exercise, most typically walking, is gradually increased with attention to target heart rates to avoid overexertion, was shown to modestly improve walking times and self-reported fatigue measures in patients in the United Kingdom with chronic fatigue syndrome in the large 2011 randomized controlled PACE trial. Psychostimulants such as amphetamines, modafinil, and armodafinil can help increase alertness and concentration and reduce excessive daytime sleepiness in certain clinical contexts, which may in turn help with symptoms of fatigue in a minority of patients, but they have generally proven to be unhelpful in randomized trials for treating fatigue in posttraumatic brain injury, Parkinson’s disease, and MS.


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InternalMed_Harrison. Development of more effective therapy for fatigue is hampered by limited knowledge of the biologic basis of this symptom. Tentative data suggests that proinflammatory cytokines, such as interleukin 1β and tumor necrosis factor α, might mediate fatigue in some patients; thus, cytokine antagonists represent one possible future approach.


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InternalMed_Harrison. Acute fatigue significant enough to require medical evaluation is more likely to lead to an identifiable medical, neurologic, or psychiatric cause than unexplained chronic fatigue. Evaluation of unexplained chronic fatigue most commonly leads to diagnosis of a psychiatric condition or remains unexplained. Identification of a previously undiagnosed serious or life-threatening culprit etiology is rare on longitudinal follow-up in patients with unexplained chronic fatigue. Complete resolution of unexplained chronic fatigue is uncommon, at least over the short term, but multidisciplinary treatment approaches can lead to symptomatic improvements that can substantially improve quality of life. neurologic Causes of weakness and Paralysis Michael J. Aminoff Normal motor function involves integrated muscle activity that is modulated by the activity of the cerebral cortex, basal ganglia, cer-30154


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InternalMed_Harrison. PART 2 Cardinal Manifestations and Presentation of Diseases ebellum, red nucleus, brainstem reticular formation, lateral vestibular nucleus, and spinal cord. Motor system dysfunction leads to weakness or paralysis, discussed in this chapter, or to ataxia (Chap. 450) or abnormal movements (Chap. 449). Weakness is a reduction in the power that can be exerted by one or more muscles. It must be distinguished from increased fatigability (i.e., the inability to sustain the performance of an activity that should be normal for a person of the same age, sex, and size), limitation in function due to pain or articular stiffness, or impaired motor activity because severe proprioceptive sensory loss prevents adequate feedback information about the direction and power of movements. It is also distinct from bradykinesia (in which increased time is required for full power to be exerted) and apraxia, a disorder of planning and initiating a skilled or learned movement unrelated to a significant motor


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InternalMed_Harrison. from bradykinesia (in which increased time is required for full power to be exerted) and apraxia, a disorder of planning and initiating a skilled or learned movement unrelated to a significant motor or sensory deficit (Chap. 36).


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InternalMed_Harrison. Paralysis or the suffix “-plegia” indicates weakness so severe that a muscle cannot be contracted at all, whereas paresis refers to less severe weakness. The prefix “hemi-” refers to one-half of the body, “para-” to both legs, and “quadri-” to all four limbs. The distribution of weakness helps to localize the underlying lesion. Weakness from involvement of upper motor neurons occurs particularly in the extensors and abductors of the upper limb and the flexors of the lower limb. Lower motor neuron weakness depends on whether involvement is at the level of the anterior horn cells, nerve root, limb plexus, or peripheral nerve—only muscles supplied by the affected structure are weak. Myopathic weakness is generally most marked in proximal muscles. Weakness from impaired neuromuscular transmission has no specific pattern of involvement. Weakness often is accompanied by other neurologic abnormalities that help indicate the site of the responsible lesion (Table 30-1).


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InternalMed_Harrison. Tone is the resistance of a muscle to passive stretch. Increased tone may be of several types. Spasticity is the increase in tone associated with disease of upper motor neurons. It is velocity-dependent, has a sudden release after reaching a maximum (the “clasp-knife” phenomenon), and predominantly affects the antigravity muscles (i.e., upper-limb flexors and lower-limb extensors). Rigidity is hypertonia that is present throughout the range of motion (a “lead pipe” or “plastic” stiffness) and affects flexors and extensors equally; it sometimes has a cogwheel quality that is enhanced by voluntary movement of the contralateral limb (reinforcement). Rigidity occurs with certain extrapyramidal disorders, such as Parkinson’s disease. Paratonia (or gegenhalten) is increased tone that varies irregularly in a manner seemingly related to the degree of relaxation, is present throughout the range of motion, and affects flexors and extensors equally; it usually results from disease of the frontal


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InternalMed_Harrison. in a manner seemingly related to the degree of relaxation, is present throughout the range of motion, and affects flexors and extensors equally; it usually results from disease of the frontal lobes. Weakness with decreased tone (flaccidity) or normal tone occurs with disorders of motor units. A motor unit consists of a single lower motor neuron and all the muscle fibers that it innervates.


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InternalMed_Harrison. Muscle bulk generally is not affected by upper motor neuron lesions, although mild disuse atrophy eventually may occur. By contrast, atrophy is often conspicuous when a lower motor neuron lesion is responsible for weakness and also may occur with advanced muscle disease.


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InternalMed_Harrison. Muscle stretch (tendon) reflexes are usually increased with upper motor neuron lesions, but may be decreased or absent for a variable period immediately after onset of an acute lesion. Hyperreflexia is usually—but not invariably—accompanied by loss of cutaneous reflexes (such as superficial abdominals; Chap. 437) and, in particular, by an extensor plantar (Babinski) response. The muscle stretch reflexes are depressed with lower motor neuron lesions directly involving specific reflex arcs. They generally are preserved in patients with myopathic weakness except in advanced stages, when they sometimes are attenuated. In disorders of the neuromuscular junction, reflex responses may be affected by preceding voluntary activity of affected muscles; such activity may lead to enhancement of initially depressed reflexes in Lambert-Eaton myasthenic syndrome and, conversely, to depression of initially normal reflexes in myasthenia gravis (Chap. 461).


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InternalMed_Harrison. The distinction of neuropathic (lower motor neuron) from myopathic weakness is sometimes difficult clinically, although distal weakness is likely to be neuropathic, and symmetric proximal weakness myopathic. Fasciculations (visible or palpable twitch within a muscle due to the spontaneous discharge of a motor unit) and early atrophy indicate that weakness is neuropathic.


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InternalMed_Harrison. PATHOgENESIS upper Motor Neuron Weakness Lesions of the upper motor neurons or their descending axons to the spinal cord (Fig. 30-1) produce weakness through decreased activation of lower motor neurons. In general, distal muscle groups are affected more severely than proximal ones, and axial movements are spared unless the lesion is severe and bilateral. Spasticity is typical but may not be present acutely. Rapid repetitive movements are slowed and coarse, but normal rhythmicity is maintained. With corticobulbar involvement, weakness occurs in the lower face and tongue; extraocular, upper facial, pharyngeal, and jaw muscles are typically spared. Bilateral corticobulbar lesions produce a pseudobulbar palsy: dysarthria, dysphagia, dysphonia, and emotional lability accompany bilateral facial weakness and a brisk jaw jerk. Electromyogram (EMG) (Chap. 442e) shows that with weakness of the upper motor neuron type, motor units have a diminished maximal discharge frequency.


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InternalMed_Harrison. Lower Motor Neuron Weakness This pattern results from disorders of lower motor neurons in the brainstem motor nuclei and the anterior horn of the spinal cord or from dysfunction of the axons of these neurons as they pass to skeletal muscle (Fig. 30-2). Weakness is due to a decrease in the number of muscle fibers that can be activated through a loss of α motor neurons or disruption of their connections to muscle. Loss of γ motor neurons does not cause weakness but decreases tension on the muscle spindles, which decreases muscle tone and attenuates the stretch reflexes. An absent stretch reflex suggests involvement of spindle afferent fibers. When a motor unit becomes diseased, especially in anterior horn cell diseases, it may discharge spontaneously, producing fasciculations. When α motor neurons or their axons degenerate, the denervated muscle fibers also may discharge spontaneously. These single muscle


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InternalMed_Harrison. FIguRE 30-1 The corticospinal and bulbospinal upper motor neuron pathways. Upper motor neurons have their cell bodies in layer V of the primary motor cortex (the precentral gyrus, or Brodmann’s area 4) and in the premotor and supplemental motor cortex (area 6). The upper motor neurons in the primary motor cortex are somatotopically organized (right side of figure).


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InternalMed_Harrison. Axons of the upper motor neurons descend through the sub-cortical white matter and the posterior limb of the internal capsule. Axons of the pyramidal or corticospinal system descend through the brainstem in the cerebral peduncle of the midbrain, the basis pontis, and the medullary pyramids. At the cervicomedullary junction, most corticospinal axons decussate into the contralateral corticospinal tract of the lateral spinal cord, but 10–30% remain ipsilateral in the anterior spinal cord. Corticospinal neurons synapse on premotor interneurons, but some—especially in the cervical enlargement and those connecting with motor neurons to distal limb muscles—make direct mono-synaptic connections with lower motor neurons. They innervate most densely the lower motor neurons of hand muscles and are involved in the execution of learned, fine movements. Corticobulbar neurons are similar to corticospinal neurons but innervate brainstem motor nuclei.


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InternalMed_Harrison. Bulbospinal upper motor neurons influence strength and tone but are not part of the pyramidal system. The descending ventromedial bulbospinal pathways originate in the tectum of the midbrain (tectospinal pathway), the vestibular nuclei (vestibulospinal pathway), and the reticular formation (reticulospinal pathway). These pathways influence axial and proximal muscles and are involved in the maintenance of posture and integrated movements of the limbs and trunk. The descending ventrolateral bulbospinal pathways, which originate predominantly in the red nucleus (rubrospinal pathway), facilitate distal limb muscles. The bulbospinal system sometimes is referred to as the extrapyramidal upper motor neuron system. In all figures, nerve cell bodies and axon terminals are shown, respectively, as closed circles and forks. FIguRE 30-2 Lower motor neurons are divided into α and γ types.


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InternalMed_Harrison. FIguRE 30-2 Lower motor neurons are divided into α and γ types. The larger α motor neurons are more numerous and innervate the extrafusal muscle fibers of the motor unit. Loss of α motor neurons or disruption of their axons produces lower motor neuron weakness. The smaller, less numerous γ motor neurons innervate the intrafusal muscle fibers of the muscle spindle and contribute to normal tone and stretch reflexes. The α motor neuron receives direct excitatory input from corticomotoneurons and primary muscle spindle afferents. The α and γ motor neurons also receive excitatory input from other descending upper motor neuron pathways, segmental sensory inputs, and interneurons. The α motor neurons receive direct inhibition from Renshaw cell interneurons, and other interneurons indirectly inhibit the α and γ motor neurons.


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InternalMed_Harrison. A muscle stretch (tendon) reflex requires the function of all the illustrated structures. A tap on a tendon stretches muscle spindles (which are tonically activated by γ motor neurons) and activates the primary spindle afferent neurons. These neurons stimulate the α motor neurons in the spinal cord, producing a brief muscle contraction, which is the familiar tendon reflex. fiber discharges, or fibrillation potentials, cannot be seen but can be recorded with EMG. Weakness leads to delayed or reduced recruitment of motor units, with fewer than normal activated at a particular discharge frequency.


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InternalMed_Harrison. Neuromuscular Junction Weakness Disorders of the neuromuscular junctions produce weakness of variable degree and distribution. The number of muscle fibers that are activated varies over time, depending on the state of rest of the neuromuscular junctions. Strength is influenced by preceding activity of the affected muscle. In myasthenia gravis, for example, sustained or repeated contractions of affected muscle decline in strength despite continuing effort (Chap. 461). Thus, fatigable weakness is suggestive of disorders of the neuromuscular junction, which cause functional loss of muscle fibers due to failure of their activation.


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InternalMed_Harrison. Myopathic Weakness Myopathic weakness is produced by a decrease in the number or contractile force of muscle fibers activated within motor units. With muscular dystrophies, inflammatory myopathies, or myopathies with muscle fiber necrosis, the number of muscle fibers is reduced within many motor units. On EMG, the size of each motor unit action potential is decreased, and motor units must be recruited more rapidly than normal to produce the desired power. Some myopathies produce weakness through loss of contractile force of muscle fibers or through relatively selective involvement of type II (fast) 156 fibers. These myopathies may not affect the size of individual motor unit action potentials and are detected by a discrepancy between the electrical activity and force of a muscle.


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InternalMed_Harrison. Psychogenic Weakness Weakness may occur without a recognizable organic basis. It tends to be variable, inconsistent, and with a pattern of distribution that cannot be explained on a neuroanatomic basis. On formal testing, antagonists may contract when the patient is supposedly activating the agonist muscle. The severity of weakness is out of keeping with the patient’s daily activities.


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InternalMed_Harrison. Hemiparesis Hemiparesis results from an upper motor neuron lesion above the midcervical spinal cord; most such lesions are above the foramen magnum. The presence of other neurologic deficits helps localize the lesion. Thus, language disorders, for example, point to a cortical lesion. Homonymous visual field defects reflect either a cortical or a subcortical hemispheric lesion. A “pure motor” hemiparesis of the face, arm, and leg often is due to a small, discrete lesion in the posterior limb of the internal capsule, cerebral peduncle, or upper pons. Some brainstem lesions produce “crossed paralyses,” consisting of ipsilateral cranial nerve signs and contralateral hemiparesis (Chap. 446). The absence of cranial nerve signs or facial weakness suggests that a hemiparesis is due to a lesion in the high cervical spinal cord, especially if associated with the Brown-Séquard syndrome (Chap. 456).


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InternalMed_Harrison. Acute or episodic hemiparesis usually results from focal structural lesions, particularly rapidly expanding lesions, or an inflammatory process. Subacute hemiparesis that evolves over days or weeks may relate to subdural hematoma, infectious or inflammatory disorders (e.g., cerebral abscess, fungal granuloma or meningitis, parasitic infection, multiple sclerosis, sarcoidosis), or primary and metastatic neoplasms. AIDS may present with subacute hemiparesis due to toxoplasmosis or primary central nervous system (CNS) lymphoma. Chronic hemiparesis that evolves over months usually is due to a neoplasm or vascular malformation, a chronic subdural hematoma, or a degenerative disease. PART 2 Cardinal Manifestations and Presentation of Diseases


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InternalMed_Harrison. PART 2 Cardinal Manifestations and Presentation of Diseases Investigation of hemiparesis (Fig. 30-3) of acute origin starts with a computed tomography (CT) scan of the brain and laboratory studies. If the CT is normal, or in subacute or chronic cases of hemiparesis, magnetic resonance imaging (MRI) of the brain and/or cervical spine (including the foramen magnum) is performed, depending on the clinical accompaniments.


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InternalMed_Harrison. Paraparesis Acute paraparesis is caused most commonly by an intra-spinal lesion, but its spinal origin may not be recognized initially if the legs are flaccid and areflexic. Usually, however, there is sensory loss in the legs with an upper level on the trunk, a dissociated sensory loss suggestive of a central cord syndrome (Chap. 456), or hyperreflexia in the legs with normal reflexes in the arms. Imaging the spinal cord (Fig. 30-3) may reveal compressive lesions, infarction (proprioception usually is spared), arteriovenous fistulas or other vascular anomalies, or transverse myelitis (Chap. 456). Diseases of the cerebral hemispheres that produce acute paraparesis include anterior cerebral artery ischemia (shoulder shrug also is affected), superior sagittal sinus or cortical venous thrombosis, and acute hydrocephalus.


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InternalMed_Harrison. Paraparesis may result from a cauda equina syndrome, for example, after trauma to the low back, a midline disk herniation, or an intraspinal tumor; although the sphincters are often affected, hip flexion often is spared, as is sensation over the anterolateral thighs. Rarely, paraparesis is caused by a rapidly evolving anterior horn cell disease (such as poliovirus or West Nile virus infection), peripheral neuropathy (such as Guillain-Barré syndrome; Chap. 460), or myopathy (Chap. 462e). Subacute or chronic spastic paraparesis is caused by upper motor neuron disease. When associated with lower-limb sensory loss and sphincter involvement, a chronic spinal cord disorder should be considered (Chap. 456). If hemispheric signs are present, a parasagittal meningioma or chronic hydrocephalus is likely. The absence of spasticity in a long-standing paraparesis suggests a lower motor neuron or myopathic etiology.


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InternalMed_Harrison. Hemiparesis UMN signs Cerebral signs Proximal Restricted Paraparesis Quadriparesis Monoparesis Distal LMN signs* Alert UMN signs LMN signs* UMN signs LMN signs* EMG and NCS UMN pattern LMN pattern Myopathic pattern Anterior horn, root, or peripheral nerve disease Muscle or neuromuscular junction disease * or signs of myopathy † If no abnormality detected, consider spinal MRI. ‡ If no abnormality detected, consider myelogram or brain MRI. NoYes NoYes DISTRIBUTION OF WEAKNESS Brain CT or MRI† Spinal MRI‡ FIguRE 30-3 An algorithm for the initial workup of a patient with weakness. CT, computed tomography; EMG, electromyography; LMN, lower motor neuron; MRI, magnetic resonance imaging; NCS, nerve conduction studies; UMN, upper motor neuron.


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InternalMed_Harrison. Investigations typically begin with spinal MRI, but when upper motor neuron signs are associated with drowsiness, confusion, seizures, or other hemispheric signs, brain MRI should also be performed, sometimes as the initial investigation. Electrophysiologic studies are diagnostically helpful when clinical findings suggest an underlying neuromuscular disorder.


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InternalMed_Harrison. Quadriparesis or generalized Weakness Generalized weakness may be due to disorders of the CNS or the motor unit. Although the terms often are used interchangeably, quadriparesis is commonly used when an upper motor neuron cause is suspected, and generalized weakness is used when a disease of the motor units is likely. Weakness from CNS disorders usually is associated with changes in consciousness or cognition and accompanied by spasticity, hyperreflexia, and sensory disturbances. Most neuromuscular causes of generalized weakness are associated with normal mental function, hypotonia, and hypoactive muscle stretch reflexes. The major causes of intermittent weakness are listed in Table 30-2. A patient with generalized fatigability without objective weakness may have the chronic fatigue syndrome (Chap. 464e).


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InternalMed_Harrison. ACUTE qUAdRIPARESIS Quadriparesis with onset over minutes may result from disorders of upper motor neurons (such as from anoxia, hypotension, brainstem or cervical cord ischemia, trauma, and systemic metabolic abnormalities) or muscle (electrolyte disturbances, certain inborn errors of muscle energy metabolism, toxins, and periodic paralyses). Onset over hours to weeks may, in addition to these disorders, be due to lower motor neuron disorders such as Guillain-Barré syndrome (Chap. 460). In obtunded patients, evaluation begins with a CT scan of the brain. If upper motor neuron signs are present but the patient is alert, the initial test is usually an MRI of the cervical cord. If weakness is lower motor neuron, myopathic, or uncertain in origin, the clinical approach begins with blood studies to determine the level of muscle enzymes and electrolytes and with EMG and nerve conduction studies.


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InternalMed_Harrison. SUBACUTE OR CHRONIC qUAdRIPARESIS Quadriparesis due to upper motor neuron disease may develop over weeks to years from chronic myelopathies, multiple sclerosis, brain or spinal tumors, chronic subdural hematomas, and various metabolic, toxic, and infectious disorders. It may also result from lower motor neuron disease, a chronic neuropathy (in which weakness is often most profound distally), or myopathic weakness (typically proximal). When quadriparesis develops acutely in obtunded patients, evaluation begins with a CT scan of the brain. If upper motor neuron signs have developed acutely but the patient is alert, the initial test is usually CAuSES of EPiSoDiC gEnERALizED wEAKnESS 1. Electrolyte disturbances, e.g., hypokalemia, hyperkalemia, hypercalcemia, hypernatremia, hyponatremia, hypophosphatemia, hypermagnesemia 2. a. b. Metabolic defects of muscle (impaired carbohydrate or fatty acid utilization; abnormal mitochondrial function) 3. Neuromuscular junction disorders a. b.


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InternalMed_Harrison. a. b. Metabolic defects of muscle (impaired carbohydrate or fatty acid utilization; abnormal mitochondrial function) 3. Neuromuscular junction disorders a. b. 4. Central nervous system disorders a. Transient ischemic attacks of the brainstem b. c. 5. Lack of voluntary effort a. b. c. an MRI of the cervical cord. When onset has been gradual, disorders 157 of the cerebral hemispheres, brainstem, and cervical spinal cord can usually be distinguished clinically, and imaging is directed first at the clinically suspected site of pathology. If weakness is lower motor neuron, myopathic, or uncertain in origin, laboratory studies to determine the levels of muscle enzymes and electrolytes, and EMG and nerve conduction studies help to localize the pathologic process.


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InternalMed_Harrison. Monoparesis Monoparesis usually is due to lower motor neuron disease, with or without associated sensory involvement. Upper motor neuron weakness occasionally presents as a monoparesis of distal and nonantigravity muscles. Myopathic weakness rarely is limited to one limb. ACUTE MONOPARESIS If weakness is predominantly distal and of upper motor neuron type and is not associated with sensory impairment or pain, focal cortical ischemia is likely (Chap. 446); diagnostic possibilities are similar to those for acute hemiparesis. Sensory loss and pain usually accompany acute lower motor neuron weakness; the weakness commonly localizes to a single nerve root or peripheral nerve, but occasionally reflects plexus involvement. If lower motor neuron weakness is likely, evaluation begins with EMG and nerve conduction studies.


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InternalMed_Harrison. SUBACUTE OR CHRONIC MONOPARESIS Weakness and atrophy that develop over weeks or months are usually of lower motor neuron origin. When associated with sensory symptoms, a peripheral cause (nerve, root, or plexus) is likely; otherwise, anterior horn cell disease should be considered. In either case, an electrodiagnostic study is indicated. If weakness is of the upper motor neuron type, a discrete cortical (precentral gyrus) or cord lesion may be responsible, and appropriate imaging is performed.


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InternalMed_Harrison. Distal Weakness Involvement of two or more limbs distally suggests lower motor neuron or peripheral nerve disease. Acute distal lower-limb weakness results occasionally from an acute toxic polyneuropathy or cauda equina syndrome. Distal symmetric weakness usually develops over weeks, months, or years and, when associated with numbness, is due to peripheral neuropathy (Chap. 459). Anterior horn cell disease may begin distally but is typically asymmetric and without accompanying numbness (Chap. 452). Rarely, myopathies present with distal weakness (Chap. 462e). Electrodiagnostic studies help localize the disorder (Fig. 30-3).


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InternalMed_Harrison. Proximal Weakness Myopathy often produces symmetric weakness of the pelvic or shoulder girdle muscles (Chap. 462e). Diseases of the neuromuscular junction, such as myasthenia gravis (Chap. 461), may present with symmetric proximal weakness often associated with ptosis, diplopia, or bulbar weakness and fluctuating in severity during the day. In anterior horn cell disease, proximal weakness is usually asymmetric, but it may be symmetric if familial. Numbness does not occur with any of these diseases. The evaluation usually begins with determination of the serum creatine kinase level and electrophysiologic studies.


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InternalMed_Harrison. Weakness in a Restricted Distribution Weakness may not fit any of these patterns, being limited, for example, to the extraocular, hemifacial, bulbar, or respiratory muscles. If it is unilateral, restricted weakness usually is due to lower motor neuron or peripheral nerve disease, such as in a facial palsy. Weakness of part of a limb is commonly due to a peripheral nerve lesion such as an entrapment neuropathy. Relatively symmetric weakness of extraocular or bulbar muscles frequently is due to a myopathy (Chap. 462e) or neuromuscular junction disorder (Chap. 461). Bilateral facial palsy with areflexia suggests Guillain-Barré syndrome (Chap. 460). Worsening of relatively symmetric weakness with fatigue is characteristic of neuromuscular junction disorders. Asymmetric bulbar weakness usually is due to motor neuron disease. Weakness limited to respiratory muscles is uncommon and usually is due to motor neuron disease, myasthenia gravis, or polymyositis/ dermatomyositis (Chap. 388).


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InternalMed_Harrison. CHAPTER 30 Neurologic Causes of Weakness and Paralysis numbness, Tingling, and Sensory Loss Michael J. Aminoff Normal somatic sensation reflects a continuous monitoring process, little of which reaches consciousness under ordinary conditions. 31158 PART 2 Cardinal Manifestations and Presentation of Diseases By contrast, disordered sensation, particularly when experienced as painful, is alarming and dominates the patient’s attention. Physicians should be able to recognize abnormal sensations by how they are described, know their type and likely site of origin, and understand their implications. Pain is considered separately in Chap. 18.


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InternalMed_Harrison. Abnormal sensory symptoms can be divided into two categories: positive and negative. The prototypical positive symptom is tingling (pins and needles); other positive sensory phenomena include itch and altered sensations that are described as pricking, bandlike, lightning-like shooting feelings (lancinations), aching, knifelike, twisting, drawing, pulling, tightening, burning, searing, electrical, or raw feelings. Such symptoms are often painful. Positive phenomena usually result from trains of impulses generated at sites of lowered threshold or heightened excitability along a peripheral or central sensory pathway. The nature and severity of the abnormal sensation depend on the number, rate, timing, and distribution of ectopic impulses and the type and function of nervous tissue in which they arise. Because positive phenomena represent excessive activity in sensory pathways, they are not necessarily associated with a sensory deficit (loss) on examination.


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InternalMed_Harrison. Negative phenomena represent loss of sensory function and are characterized by diminished or absent feeling that often is experienced as numbness and by abnormal findings on sensory examination. In disorders affecting peripheral sensation, at least one-half the afferent axons innervating a particular site are probably lost or functionless before a sensory deficit can be demonstrated by clinical examination. If the rate of loss is slow, however, lack of cutaneous feeling may be unnoticed by the patient and difficult to demonstrate on examination, even though few sensory fibers are functioning; if it is rapid, both positive and negative phenomena are usually conspicuous. Subclinical degrees of sensory dysfunction may be revealed by sensory nerve conduction studies or somatosensory evoked potentials (Chap. 442e). Whereas sensory symptoms may be either positive or negative, sensory signs on examination are always a measure of negative phenomena.


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InternalMed_Harrison. Whereas sensory symptoms may be either positive or negative, sensory signs on examination are always a measure of negative phenomena. Paresthesias and dysesthesias are general terms used to denote positive sensory symptoms. The term paresthesias typically refers to tingling or pins-and-needles sensations but may include a wide variety of other abnormal sensations, except pain; it sometimes implies that the abnormal sensations are perceived spontaneously. The more general term dysesthesias denotes all types of abnormal sensations, including painful ones, regardless of whether a stimulus is evident.


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InternalMed_Harrison. Another set of terms refers to sensory abnormalities found on examination. Hypesthesia or hypoesthesia refers to a reduction of cutaneous sensation to a specific type of testing such as pressure, light touch, and warm or cold stimuli; anesthesia, to a complete absence of skin sensation to the same stimuli plus pinprick; and hypalgesia or analgesia, to reduced or absent pain perception (nociception). Hyperesthesia means pain or increased sensitivity in response to touch. Similarly, allodynia describes the situation in which a nonpainful stimulus, once perceived, is experienced as painful, even excruciating. An example is elicitation of a painful sensation by application of a vibrating tuning fork. Hyperalgesia denotes severe pain in response to a mildly noxious stimulus, and hyperpathia, a broad term, encompasses all the phenomena described by hyperesthesia, allodynia, and hyperalgesia. With hyperpathia, the threshold for a sensory stimulus is increased and perception is delayed, but


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InternalMed_Harrison. a broad term, encompasses all the phenomena described by hyperesthesia, allodynia, and hyperalgesia. With hyperpathia, the threshold for a sensory stimulus is increased and perception is delayed, but once felt, it is unduly painful.


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InternalMed_Harrison. Disorders of deep sensation arising from muscle spindles, tendons, and joints affect proprioception (position sense). Manifestations include imbalance (particularly with eyes closed or in the dark), clumsiness of precision movements, and unsteadiness of gait, which are referred to collectively as sensory ataxia. Other findings on examination usually, but not invariably, include reduced or absent joint position and vibratory sensibility and absent deep tendon reflexes in the affected limbs. The Romberg sign is positive, which means that the patient sways markedly or topples when asked to stand with feet close together and eyes closed. In severe states of deafferentation involving deep sensation, the patient cannot walk or stand unaided or even sit unsupported. Continuous involuntary movements (pseudoathetosis) of the outstretched hands and fingers occur, particularly with eyes closed.


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InternalMed_Harrison. Cutaneous receptors are classified by the type of stimulus that optimally excites them. They consist of naked nerve endings (nociceptors, which respond to tissue-damaging stimuli, and thermoreceptors, which respond to noninjurious thermal stimuli) and encapsulated terminals (several types of mechanoreceptor, activated by physical deformation of the skin). Each type of receptor has its own set of sensitivities to specific stimuli, size and distinctness of receptive fields, and adaptational qualities.


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InternalMed_Harrison. Afferent fibers in peripheral nerve trunks traverse the dorsal roots and enter the dorsal horn of the spinal cord (Fig. 31-1). From there, the polysynaptic projections of the smaller fibers (unmyelinated and small myelinated), which subserve mainly nociception, itch, temperature sensibility, and touch, cross and ascend in the opposite anterior and lateral columns of the spinal cord, through the brainstem, to the ventral posterolateral (VPL) nucleus of the thalamus and ultimately project to the postcentral gyrus of the parietal cortex (Chap. 18). This is the spinothalamic pathway or anterolateral system. The larger fibers, which subserve tactile and position sense and kinesthesia, project rostrally in the posterior and posterolateral columns on the same side of the spinal cord and make their first synapse in the gracile or cuneate nucleus of the lower medulla. Axons of second-order neurons decussate and ascend in the medial lemniscus located medially in the medulla and in the tegmentum


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InternalMed_Harrison. first synapse in the gracile or cuneate nucleus of the lower medulla. Axons of second-order neurons decussate and ascend in the medial lemniscus located medially in the medulla and in the tegmentum of the pons and midbrain and synapse in the VPL nucleus; third-order neurons project to parietal cortex as well as to other cortical areas. This large-fiber system is referred to as the posterior column–medial lemniscal pathway (lemniscal, for short). Although the fiber types and functions that make up the spinothalamic and lemniscal systems are relatively well known, many other fibers, particularly those associated with touch, pressure, and position sense, ascend in a diffusely distributed pattern both ipsilaterally and contra-laterally in the anterolateral quadrants of the spinal cord. This explains why a complete lesion of the posterior columns of the spinal cord may be associated with little sensory deficit on examination.


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InternalMed_Harrison. Nerve conduction studies and nerve biopsy are important means of investigating the peripheral nervous system, but they do not evaluate the function or structure of cutaneous receptors and free nerve endings or of unmyelinated or thinly myelinated nerve fibers in the nerve trunks. Skin biopsy can be used to evaluate these structures in the dermis and epidermis.


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InternalMed_Harrison. The main components of the sensory examination are tests of primary sensation (pain, touch, vibration, joint position, and thermal sensation) (Table 31-1). The examiner must depend on patient responses, and this complicates interpretation. Further, examination may be limited in some patients. In a stuporous patient, for example, sensory examination is reduced to observing the briskness of withdrawal in response to a pinch or another noxious stimulus. Comparison of responses on the two sides of the body is essential. In an alert but uncooperative patient, it may not be possible to examine cutaneous sensation, but some idea of proprioceptive function may be gained by noting the patient’s best performance of movements requiring balance and precision.


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InternalMed_Harrison. Primary Sensation The sense of pain usually is tested 159 with a clean pin, which is then discarded. The patient is asked to close the eyes and focus on the pricking or unpleasant quality of the stimulus, not just the pressure or touch sensation elicited. Areas of hypalgesia should be mapped by proceeding radially from the most hypalgesic site. Temperature sensation to both hot and cold is best tested with small containers filled with water of the desired temperature. An alternative way to test cold sensation is to touch a metal object, such as a tuning fork at room temperature, to the skin. For testing warm temperatures, the tuning fork or another metal object may be held under warm water of the desired temperature and then used. The appreciation of both cold and warmth should be tested because different receptors respond to each. Touch usually is tested with a wisp of cotton or a fine camel hair brush, minimizing pressure on the skin. In general, it is better to avoid testing touch


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InternalMed_Harrison. because different receptors respond to each. Touch usually is tested with a wisp of cotton or a fine camel hair brush, minimizing pressure on the skin. In general, it is better to avoid testing touch nucleus of on hairy skin because of the profusion of the sensory endings that surround each hair follicle. The patient is MIDBRAIN tested with the eyes closed and should indicate as soon as the stimulus is perceived, indicating its location.


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InternalMed_Harrison. Joint position testing is a measure of proprioception. With the patient’s eyes closed, joint position is tested in the distal interphalangeal joint of the great toe and fingers. The digit is held by its sides, distal to the joint Principal sensory nucleus of V PONS being tested, and moved passively while more proximalMedial lemniscus joints are stabilized—the patient indicates the change in position or direction of movement. If errors are made, more proximal joints are tested. A test of proxi-Nucleus of mal joint position sense, primarily at the shoulder, isfuniculus gracilis performed by asking the patient to bring the two index Nucleus of fingers together with arms extended and eyes closed. funiculus cuneatus Normal individuals can do this accurately, with errors Spinothalamic tract of 1 cm or less. Nucleus of


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InternalMed_Harrison. funiculus cuneatus Normal individuals can do this accurately, with errors Spinothalamic tract of 1 cm or less. Nucleus of The sense of vibration is tested with an oscillating tuning fork that vibrates at 128 Hz. Vibration is tested over bony points, beginning distally; in the feet, it is tested over the dorsal surface of the distal phalanx of the big toes and at the malleoli of the ankles, and in the hands, it is tested dorsally at the distal phalanx of the fingers. If abnormalities are found, more proximal sites should be examined. Vibratory thresholds at the same site in the patient and the examiner may be compared for control purposes. Quantitative Sensory Testing Effective sensory testing devices are commercially available. Quantitative sen-


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InternalMed_Harrison. Quantitative Sensory Testing Effective sensory testing devices are commercially available. Quantitative sen- FIguRE 31-1 The main somatosensory pathways. The spinothalamic tract (pain, sory testing is particularly useful for serial evaluation of thermal sense) and the posterior column–lemniscal system (touch, pressure, joint cutaneous sensation in clinical trials. Threshold testing position) are shown. Offshoots from the ascending anterolateral fasciculus (spino for touch and vibratory and thermal sensation is the thalamic tract) to nuclei in the medulla, pons, and mesencephalon and nuclear most widely used application. terminations of the tract are indicated. (From AH Ropper, MA Samuels: Adams and Victor’s Principles of Neurology, 9th ed. New York, McGraw-Hill, 2009.) Cortical Sensation The most commonly used tests of cortical function are two-point discrimination, touch localization, and bilateral simultaneous stimulation


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InternalMed_Harrison. In patients with sensory complaints, testing should begin in the and tests for graphesthesia and stereognosis. Abnormalities of these center of the affected region and proceed radially until sensation is sensory tests, in the presence of normal primary sensation in an alert perceived as normal. The distribution of any abnormality is defined cooperative patient, signify a lesion of the parietal cortex or thalaand compared to root and peripheral nerve territories (Figs. 31-2 mocortical projections. If primary sensation is altered, these cortical and 31-3). Some patients present with sensory symptoms that do discriminative functions usually will be abnormal also. Comparisons not fit an anatomic localization and are accompanied by either no should always be made between analogous sites on the two sides of abnormalities or gross inconsistencies on examination. The exam-the body because the deficit with a specific parietal lesion is likely to iner should consider whether the sensory


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InternalMed_Harrison. on the two sides of abnormalities or gross inconsistencies on examination. The exam-the body because the deficit with a specific parietal lesion is likely to iner should consider whether the sensory symptoms are a disguised be unilateral. request for help with psychologic or situational problems. Sensory Two-point discrimination is tested with special calipers, the points examination of a patient who has no neurologic complaints can of which may be set from 2 mm to several centimeters apart and then be brief and consist of pinprick, touch, and vibration testing in the applied simultaneously to the test site. On the fingertips, a normal hands and feet plus evaluation of stance and gait, including the individual can distinguish about a 3-mm separation of points. Romberg maneuver (Chap. 438). Evaluation of stance and gait also Touch localization is performed by light pressure for an instant tests the integrity of motor and cerebellar systems. with the examiner’s fingertip or a wisp of


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InternalMed_Harrison. Evaluation of stance and gait also Touch localization is performed by light pressure for an instant tests the integrity of motor and cerebellar systems. with the examiner’s fingertip or a wisp of cotton wool; the patient,


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InternalMed_Harrison. CHAPTER 31 Numbness, Tingling, and Sensory Loss Pain Temperature, heat Temperature, cold Touch Joint position Pinprick Warm metal object Cold metal object Cotton wisp, fine brush Tuning fork, 128 Hz Cutaneous nociceptors Cutaneous thermoreceptors for hot Cutaneous thermoreceptors for cold Cutaneous mechanoreceptors, also naked endings Mechanoreceptors, especially pacinian corpuscles Passive movement of specific joints Joint capsule and tendon endings, muscle spindles Large SpTh, also D SpTh SpTh Lem, also D and SpTh Lem, also D Lem, also D PART 2 Cardinal Manifestations and Presentation of Diseases Abbreviations: D, diffuse ascending projections in ipsilateral and contralateral anterolateral columns; Lem, posterior column and lemniscal projection, ipsilateral; SpTh, spinothalamic projection, contralateral.


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InternalMed_Harrison. whose eyes are closed, is required to identify the site of touch. Bilateral simultaneous stimulation at analogous sites (e.g., the dorsum of both hands) can be carried out to determine whether the perception of touch is extinguished consistently on one side (extinction or neglect). Graphesthesia refers to the capacity to recognize, with eyes closed, letters or numbers drawn by the examiner’s fingertip on the palm of the hand. Once again, interside comparison is of prime importance. Inability to recognize numbers or letters is termed agraphesthesia.


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InternalMed_Harrison. Stereognosis refers to the ability to identify common objects by palpation, recognizing their shape, texture, and size. Common standard objects such as keys, paper clips, and coins are best used. Patients with normal stereognosis should be able to distinguish a dime from a penny and a nickel from a quarter without looking. Patients should feel the object with only one hand at a time. If they are unable to identify it in one hand, it (lumbo-inguinal n.) Lat. cut. n. of thigh Intermed. & med. cut. n’s. of thigh (from femoral n.) Saphenous n. (from femoral n.) Deep peroneal n. (from common peroneal n.) Med. & lat. plantar n’s. (from posttibial n.) Great auricular n. Ant. cut. n. of neck Supraclavicular n’s. Med. cut. n. of arm & intercostobrachial n. Med. cut. n. Dorsal n. of penis Scrotal branch of perineal n. Obturator n. Lat. cut. n. of calf (from common peroneal n.) Superfcial peroneal n. (from common peroneal n.)


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InternalMed_Harrison. Med. cut. n. Dorsal n. of penis Scrotal branch of perineal n. Obturator n. Lat. cut. n. of calf (from common peroneal n.) Superfcial peroneal n. (from common peroneal n.) Sural n. (from tibial n.) should be placed in the other for comparison. Individuals who are unable to identify common objects and coins in one hand but can do so in the other are said to have astereognosis of the abnormal hand. Sensory symptoms and signs can result from lesions at many different levels of the nervous system from the parietal cortex to the peripheral sensory receptor. Noting their distribution and nature is the most important way to localize their source. Their extent, configuration, symmetry, quality, and severity are the key observations.


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InternalMed_Harrison. Dysesthesias without sensory findings by examination may be difficult to interpret. To illustrate, tingling dysesthesias in an acral distribution (hands and feet) can be systemic in origin, e.g., secondary to hyperventilation, or induced by a medication such as acetazolamide. Greater } occipital nervesLesser n. Great auricular n. Ant. cut. n. of neck C5 C6 T1 Supraclavicular n’s. Post. Axillary n. 3 (circumflex) 4 cut. rami Lat. of cut. Post cut. n. of arm thor.rami (from radial n.) n’s. 8 9 Lower 10 L1 Lat. cut. of arm 11 (from radial n.) 12 Med. (from musculocut n.) S1 cut. n. Post. rami of of lumbar sacral forearm Iliohypo-Radial n. gastric n. & coccygeal n’s. Med. cut. n. of arm & intercostobrachial n. Post. cut. n. of forearm (from radial n.) Lat. cut. n. of forearm Inf. med. cluneal n. Inf. med. n. of thigh Post cut. n. of thigh Lat. cut. n.of calf (from common femoral n.) Saphenous n. (from femoral n.) Superficial peroneal n. (from common peroneal n.)