Neurology_Adams

Neurology_Adams. on looking to the right and down. D. Paralysis of right superior rectus. Characteristic: right eye does not move upward when eyes are turned to the right. Field: vertical diplopia (with red line displaced superiorly) increasing on looking to the right and up. E. Paralysis of right superior oblique. Characteristic: right eye does not move downward when eyes are turned to the left. Field: vertical diplopia (with red line displaced inferiorly) increasing on looking to the left and down. F. Paralysis of right inferior oblique. Characteristic: right eye does not move upward when eyes are turned to the left. Field: vertical diplopia (with red line displaced superiorly) increasing on looking to the left and up.


Neurology_Adams

Neurology_Adams. Source: Adapted by permission from Leigh and Zee. Figure 13-8. MRI of orbital pseudotumor showing bilateral swelling of the extraocular muscles and adjacent orbital contents. A “streaming” appearance of the fat as shown in the right retro-orbital compartment is characteristic. The process in this patient responded to corticosteroids. Figure 13-9. Diagram of the pathways subserving the pupillary light reflex. (Redrawn with permission from Bradford CA [ed]: Basic Ophthalmology, 7th ed. San Francisco, American Academy of Ophthalmology, 1975.) Figure 13-10. Congenital Horner syndrome on the patient’s left. In addition to the miosis and ptosis, the patient’s left iris is gray in color and the right, brown.


Neurology_Adams

Neurology_Adams. Good lightreactionin both eyesMore anisocoriain darknessthan in lightMore anisocoriain light thanin darknessPoor lightreactionin one eyeIs there moreanisocoria in darknessor in light?Look for‘‘dilation lag’’of the smaller pupilCompletelyimmobileSector palsyof irissphincterSphincteris notsupersensitiveSphincterissupersensitiveIristransilluminatespupil margintornTest for cholinergicsupersensitivity withMecholyl 2.5% orpilocarpine 0.1%Test foranticholinergicblockade withpilocarpine 1%Adie’s tonic pupilHorner syndromeSimple anisocoriaSmaller pupildilates‘‘Dilation lag’’of smallerpupilImpairedlight reactionbut no sector palsyof iris sphincter ordistortion of stromaNeither pupildilatesNo dilation lagIris damageThird-nerve palsy‘‘Atropinic’’mydriasisdue toeye-dropsPostganglionicHornerPreganglionic orcentral HornerNo dilationDilationPupil fails to constrictPupil constrictsCheck light reactionExamine irissphincter at slit lampApraclonidinetest1%Hydroxyamphetaminetest


Neurology_Adams

Neurology_Adams. Figure 13-11. A schematic approach for sorting out the nature of anisocoria. (Adapted by permission from Thompson and Pilley.) Chapter 13 Disorders of Ocular Movement and Pupillary Function Deafness, Dizziness, and Disorders of Equilibrium


Neurology_Adams

Neurology_Adams. Sounds alert us to danger; spoken words are the universal means of communication; music is one of our most exalted aesthetic pleasures. The loss of hearing excludes the individual from many important external stimuli, and adjustment to this deprivation imposes profound challenge. Vestibular function ensures one’s ability to stand steadily, stabilize eye position during head movement, and move about gracefully. Hence, an understanding of the functions of the eighth cranial nerves and their derangements by disease is as much the concern of the neurologist as the otologist. Generally, the association of vertigo and deafness signifies a disease of the end organs for hearing and vestibular function, or of the eighth nerve. The precise locus of the disease is determined by tests of labyrinthine and auditory function, described further on, and by findings on neurologic examination and imaging studies that implicate the primary and secondary connections of the eighth cranial nerve.


Neurology_Adams

Neurology_Adams. The vestibulocochlear, or eighth, cranial nerve has two separate components: the cochlear nerve, which subserves hearing, and the vestibular nerve, which is concerned with equilibrium (balance) and orientation of the body and eyes to the surrounding world. The acoustic division has its cell bodies in the spiral ganglion of the cochlea. This ganglion is composed of bipolar cells, the peripheral processes of which convey auditory impulses from the specialized neuroepithelium of the inner ear, the spiral organ of Corti. This is the end organ of hearing, wherein sound is transduced into nerve impulses. It consists of approximately 15,000 neuroepithelial (hair) cells that rest on the basilar membrane, which extends along the entire 2.5 turns of the cochlea. Projecting from the inner surface of each hair cell are approximately 60 very fine filaments, or stereocilia, which are embedded in the tectorial membrane, a gelatinous structure overlying the organ of Corti (Fig. 14-1). Sound causes


Neurology_Adams

Neurology_Adams. of each hair cell are approximately 60 very fine filaments, or stereocilia, which are embedded in the tectorial membrane, a gelatinous structure overlying the organ of Corti (Fig. 14-1). Sound causes the basilar membrane to vibrate; upward displacement of the basilar membrane bends the relatively fixed stereocilia and provides a stimulus adequate for activating the hair cells. The stimulus is then transmitted to the sensory fibers of the cochlear nerve, which emanate from the base of each hair cell.


Neurology_Adams

Neurology_Adams. Each afferent auditory fiber and the hair cell with which it is connected have a minimum threshold at one frequency (“characteristic” or “best” frequency). The basilar membrane vibrates at different frequencies throughout its length, according to the frequency of the sound stimulus. In this way, the fibers of the cochlear nerve respond to the full range of audible sound and can differentiate and resolve complexes of sounds.


Neurology_Adams

Neurology_Adams. The inner hair cells, numbering about 3,500, are of particular importance, because they synapse with approximately 90 percent of the 30,000 afferent cochlear neurons. The central processes of the primary auditory neurons constitute the cochlear division of the eighth cranial nerve. In addition, the nerve contains approximately 500 efferent fibers, which arise from the superior olivary nuclei (80 percent from the contralateral nucleus and 20 percent from the ipsilateral one) and synapse with the afferent neurons from the hair cells (Rasmussen). The function of this efferent pathway is not clear. It is thought to play some part in the auditory processing generated in the ear itself, possibly to enhance the sharpness of sound perception by a feedback mechanism. The eighth nerve also contains adrenergic postganglionic fibers that are derived from the cervical autonomic chain and innervate the cochlea and labyrinth. Their function has been the subject of investigation but remains unknown.


Neurology_Adams

Neurology_Adams. The semicircular ducts, utricle, and saccule, collectively comprising the vestibular apparatus, contain the sense organs for the detection of angular and linear acceleration. They are filled with an intracellular fluid, endolymph, and are surrounded by cerebrospinal fluid (perilymph) within excavated spaces of the temporal bone, the semicircular canals. The latter term, canal, is used interchangeably with the proper description, ducts, to describe the vestibular apparatus.


Neurology_Adams

Neurology_Adams. The vestibular division of the eighth nerve arises from cells in the vestibular, or Scarpa ganglion, which is situated in the internal auditory meatus. This ganglion is also composed of bipolar cells, the peripheral processes of which emanate from hair cells of the specialized sensory epithelium of the labyrinthine apparatus. The sensory epithelium is located on hillocks (cristae) in the dilated openings or ampullae of the semicircular ducts, where they are called the cristae ampullaris, and in the utricle and saccule, where they are called maculae acusticae. The hair cells of the maculae are covered by the otolithic membrane, or otolith, which is composed of calcium carbonate crystals embedded in a gelatinous matrix. The sensory cells of the cristae are covered by a sail-shaped gelatinous mass called a cupula (see Fig. 14-1). The labyrinthine semicircular ducts transduce angular acceleration of the head, and the otoliths transduce linear acceleration, including the effects of


Neurology_Adams

Neurology_Adams. mass called a cupula (see Fig. 14-1). The labyrinthine semicircular ducts transduce angular acceleration of the head, and the otoliths transduce linear acceleration, including the effects of gravity.


Neurology_Adams

Neurology_Adams. The central fibers from the cells of the spiral and vestibular ganglia travel in a common trunk, the eighth cranial nerve, which enters the cranial cavity through the internal auditory meatus (accompanied by the facial and intermediate nerves). They traverse the cerebellopontine angle and enter the lateral brainstem at the junction of the pons and medulla. Here the cochlear and vestibular fibers become separated. The cochlear fibers bifurcate and terminate almost at once in the dorsal and ventral cochlear nuclei. The fibers from each cochlear nucleus pursue separate crossing and ascending pathways; they pass to both inferior colliculi (mainly to the opposite side) via the lateral lemnisci. Secondary acoustic fibers project via the trapezoid body and lateral lemniscus to the medial geniculate bodies, a special component of the thalamic sensory system (Fig. 14-2). Some fibers terminate in the trapezoid body and superior olivary complex and sub-serve such reflex functions as auditory


Neurology_Adams

Neurology_Adams. bodies, a special component of the thalamic sensory system (Fig. 14-2). Some fibers terminate in the trapezoid body and superior olivary complex and sub-serve such reflex functions as auditory attention, sound localization, auditory startle, and oculopostural orientation to sound.


Neurology_Adams

Neurology_Adams. Both excitatory and inhibitory neurons are located at every level of these pathways. At all levels there are strong commissural connections through which auditory signals come to be represented bilaterally in the cerebrum. From the medial geniculate bodies, fibers project to the cortex via the auditory radiations—relatively compact bundles that course ventrolaterally through the posterior parts of the putamen before dispersing and ending in the transverse gyri of Heschl and other auditory cortical areas (Tanaka et al).


Neurology_Adams

Neurology_Adams. The auditory cortical field comprises the superior temporal gyrus and the upper bank of the sylvian fissure (Brodmann area 41; see Fig. 21-1), or primary auditory cortex, and the surrounding secondary and tertiary cortices in the adjacent temporal lobe. The latter are of particular importance in the interpretation of sound (Celesia) including spoken language. Bilateral temporal lobe lesions involving the geniculocortical fasciculi result in cortical deafness, although such lesions are rare. Unilateral cortical lesions do not affect hearing, but defects in function such as dichotic listening can be detected by specialized tests. At several levels of these ascending fiber systems, there is feedback to lower structures.


Neurology_Adams

Neurology_Adams. The vestibular fibers of the eighth nerve terminate in the four vestibular nuclei: superior (Bechterew), lateral (Deiters), medial (triangular, or Schwalbe), and inferior (spinal, or descending). In addition, some of the fibers from the semicircular ducts project directly to the cerebellum via the juxtarestiform body and terminate in the flocculonodular lobe and adjacent vermian cortex (consequently, these structures are called the “vestibulocerebellum,” as noted in Chap. 5). Efferent fibers from this portion of the cerebellar cortex, in turn, project ipsilaterally to the vestibular nuclei and to the fastigial nucleus; fibers from the fastigial nucleus project back to the contralateral vestibular nuclei, again via the juxtarestiform body. Thus each side of the cerebellum exerts an influence on the vestibular nuclei of both sides (Fig. 14-3; see also Chap. 4).


Neurology_Adams

Neurology_Adams. The lateral and medial vestibular nuclei also have important connections with the spinal cord, mainly via the uncrossed lateral vestibulospinal tract and the crossed and uncrossed medial vestibulospinal tracts (Fig. 14-4). Presumably, vestibular effects on posture are mediated via these pathways—the axial muscles being acted upon predominantly by the medial vestibulospinal tract and the limb muscles, by the lateral tract. The nuclei of the third, fourth, and sixth cranial nerves come under the influence of the vestibular nuclei through the projection pathways, mainly the medial longitudinal fasciculus described in Chap. 13. In addition, all the vestibular nuclei have afferent and efferent connections with the pontine reticular formation (see Fig. 14-4). The latter connections subserve vestibuloocular and vestibulospinal reflexes that are essential for clear vision and stable posture.


Neurology_Adams

Neurology_Adams. Finally, there are projections from the vestibular nuclei to the cerebral cortex, specifically to the regions of the intraparietal sulcus and superior sylvian gyrus. In the monkey, these projections are almost exclusively contralateral, terminating near the “face area” of the first somatosensory cortex (area 2 of Brodmann). Lesions in the posterior insula impair the sense of verticality, body orientation, and movement. Whether the vestibular nuclei project to the thalamus in humans is not entirely settled; most anatomists indicate that there are no such direct connections.


Neurology_Adams

Neurology_Adams. These brief remarks convey some notion of the complexity of the anatomic and functional organization of the vestibular system (for a full discussion, see the monographs of Brodal and of Baloh and Honrubia). In view of the proximity of cochlear and vestibular elements, it is understandable that acoustic and vestibular functions are often affected together in the course of disease although each may also be affected separately. DEAFNESS, TINNITUS, AND OTHER DISORDERS OF AUDITORY PERCEPTION Figures from a National Health Survey (National Institute on Deafness and Other Communication Disorders) indicated that approximately 28 million Americans of all ages had a significant degree of deafness and that 2 million were profoundly deaf. More than one-third of persons older than age 75 years were handicapped to some extent by hearing loss.


Neurology_Adams

Neurology_Adams. Deafness is of three general types: (1) Conductive deafness, caused by a defect in the mechanism by which sound is transformed (amplified) and conducted to the cochlea. These are disorders of the external or middle ear—obstruction of the external auditory canal by atresia or cerumen, thickening of the tympanic membrane from infection or trauma, chronic otitis media, otosclerosis (the main cause of deafness in early adult life), and obstruction of the eustachian tube. (2) Sensorineural deafness (also called, imprecisely, nerve deafness), which is caused by disease of the cochlea or of the cochlear division of the eighth cranial nerve. Although cochlear and eighth nerve causes of deafness have conventionally been combined in one (sensorineural) category, the neurologist recognizes that the symptoms and causes of the two are quite different and that it is more practical to think of them as cochlear (end organ) and retrocochlear (nerve) deafness. (3) Central deafness, caused by lesions of


Neurology_Adams

Neurology_Adams. and causes of the two are quite different and that it is more practical to think of them as cochlear (end organ) and retrocochlear (nerve) deafness. (3) Central deafness, caused by lesions of the cochlear nuclei and their connections with the primary auditory receptive areas in the temporal lobes. For example, complete tone deafness, which is probably inherited as an autosomal dominant trait, is a central disorder.


Neurology_Adams

Neurology_Adams. The two peripheral forms of deafness—conductive and sensorineural deafness—must be distinguished from each other, because important remedial measures are available, particularly for the former. In differentiating them, the tuning-fork tests are often of value. When a vibrating fork, preferably of 512-Hz frequency, is held about 2.5 cm from the ear (test for air conduction), sound waves can be appreciated only as they are transmitted through the middle ear; they will be reduced with disease in this location. When the vibrating fork is applied to the skull (test for bone conduction), the sound waves are conveyed directly to the cochlea, without intervention of the sound-transmission apparatus of the middle ear, and will therefore not be reduced or lost in outer or middle ear disease. Normally air conduction is better than bone conduction, and the sound transmitted though the air is appreciated for about twice as long as that passing through the bone.


Neurology_Adams

Neurology_Adams. These principles form the basis for several simple tests of auditory function. In the Weber test, the vibrating fork is applied to the forehead in the midline (or to a central incisor). A normal person hears the bone-conducted sound equally in both ears. In nerve deafness, the sound is localized to the normal ear for the reasons noted previously; in conductive deafness, the sound is perceived as louder in the affected ear because interference from ambient sounds is muted on the affected side. In the Rinne test, the fork is applied to the mastoid process. At the moment the patient indicates that the sound ceases, the fork is held at the auditory meatus. In middle ear deafness, the sound cannot be heard by air conduction after bone conduction has ceased (abnormal Rinne test). In nerve deafness, the reverse may be true (normal Rinne test), but more saliently, both air and bone conduction are quantitatively decreased. The Schwabach test consists of comparing the patient’s bone conduction


Neurology_Adams

Neurology_Adams. the reverse may be true (normal Rinne test), but more saliently, both air and bone conduction are quantitatively decreased. The Schwabach test consists of comparing the patient’s bone conduction with that of the normal examiner.


Neurology_Adams

Neurology_Adams. In general, early sensorineural deafness is characterized by a partial loss of perception of high-pitched sounds and conductive deafness by a partial loss of low-pitched sounds. This can be ascertained by the use of tuning forks of different frequencies but most accurately by the use of an audiometer and the construction of an audiogram, which reveals the entire range of hearing at a glance. The audiogram is an essential test in the evaluation of hearing loss and the point of departure for subsequent diagnostic evaluation. A ticking watch (infrequently found on doctor’s wrists or pockets any longer) or rubbing the patient’s hair together near the ear can be used as a surrogate test of gross hearing for the bedside, but these maneuvers emit mostly high-frequency sound and will not detect low-frequency conductive loss.


Neurology_Adams

Neurology_Adams. A cochlear type of hearing loss can be recognized by the presence of the symptoms of recruitment and diplacusis. Recruitment refers to a heightened perception of loudness once the threshold for hearing has been exceeded; thus the patient’s retort “You don’t have to shout” when the examiner raises his voice (see the following text). Diplacusis refers to a defect in frequency discrimination that is manifest by a lack of clarity of spoken syllables or by the perception that music is out of tune and unpleasant (described by patients as a “mushiness” of sounds).


Neurology_Adams

Neurology_Adams. Because each cochlear nucleus is connected with the cortex of both temporal lobes, hearing is unaffected by unilateral cerebral lesions as already mentioned. Deafness caused by brainstem lesions is observed only rarely, as a massive lesion is required to interrupt both the crossed and uncrossed projections from the cochlear nuclei—so massive, as a rule, that other neurologic abnormalities usually make the testing of hearing impossible. A number of special tests prove to be helpful in distinguishing cochlear from retrocochlear (nerve) lesions. Although an absolute distinction cannot be made on the basis of any one test, the results taken together (particularly loudness recruitment, speech discrimination and tone decay) make it possible to predict the site of the lesion with considerable accuracy. These tests, usually carried out by an otologist or audiologist, include the following: 1.


Neurology_Adams

Neurology_Adams. Loudness recruitment. This phenomenon, mentioned previously, is thought to depend on the selective destruction of low-intensity elements subserved by the external hair cells of the organ of Corti. The high-intensity elements are preserved, so that loudness is appreciated only at high intensities. In testing for loudness recruitment, the difference in hearing between the two ears is estimated and the loudness of the pure-tone stimulus of a given frequency delivered to each ear is then increased by regular increments. In nonrecruiting deafness (characteristic of a nerve lesion), the original difference in hearing persists in all comparisons of loudness, since both highand low-intensity fibers are affected. In recruiting deafness (which occurs with a lesion in the organ of Corti—e.g., Ménière disease, the more affected ear gains in loudness and may finally be equal to the better one. In bilateral disease, recruitment is assessed by the intensity of the stimulus that causes discomfort,


Neurology_Adams

Neurology_Adams. disease, the more affected ear gains in loudness and may finally be equal to the better one. In bilateral disease, recruitment is assessed by the intensity of the stimulus that causes discomfort, about 100 dB (decibels) in normal persons.


Neurology_Adams

Neurology_Adams. 2. Speech discrimination. This consists of presenting the patient with a list of 50 phonetically balanced monosyllabic words (e.g., thin, sin) at suprathreshold levels. The speech-discrimination score is the percentage of the 50 words correctly repeated by the patient. Marked reduction (less than 30 percent) in the speech-discrimination scores is characteristic of eighth nerve (retrocochlear) lesions. 3.


Neurology_Adams

Neurology_Adams. 3. Audiometry. Continuous and interrupted tones are presented at various frequencies. Tracings are made, measuring the increments by which the patient must increase the volume in order to continue to hear the continuous and interrupted tones just above threshold. Clinically, analysis has shown that there are four basic configurations, referred to as types I to IV Békésy audiograms. Type III or IV usually indicate the presence of a retrocochlear lesion, the type II response points to a lesion of the cochlea itself, and type I is considered normal. Related tests, such as threshold tone decay and the short increment sensitivity index, were formerly used to a greater extent than they are currently; therefore, we have not described them here. 4.


Neurology_Adams

Neurology_Adams. 4. Brainstem auditory evoked potentials, or response (BAEP, or BAER) (see Chap. 2). This method provides very refined information as to the integrity of primary and secondary auditory pathways from the cochlea to the superior colliculus. It has the advantage of being accurate in uncooperative and even comatose patients as well as infants who cannot cooperate with audiometry. It is of some value in detecting small acoustic and vestibular schwannomas; in localizing brainstem lesions such as those caused by demyelination; in corroborating the state of brain death, in which all waves, except occasionally the eighth nerve (wave I), responses are abolished; and in assessing sensorineural damage in neonates who have had meningitis or been exposed to ototoxic medications. 5.


Neurology_Adams

Neurology_Adams. 5. The acoustic-stapedial reflex can be used as a measure of conduction in the auditory (and the facial) nerve. This reflex normally protects the cochleas from excessively loud sound. When sound of intensity greater than 70 to 90 dB above threshold hearing reaches the inner ear, the stapedius muscles on both sides contract reflexively, relaxing the tympanum and offering impedance to further sound. It may be tested by insufflating the external auditory canal with pressured air and measuring the change in pressure that follows immediately after a loud sound. The response is muted in patients with conductive hearing loss because of the mechanical restriction of ossicular movement, but otherwise the test is sensitive to cochlear and acoustic nerve lesions.


Neurology_Adams

Neurology_Adams. This is the other major manifestation of cochlear and auditory disease. Tinnitus aurium literally means “ringing of the ears” (Latin tinnire, “to ring or jingle”) and refers to sounds originating in the ear, although they need not be ringing in character. Buzzing, humming, whistling, roaring, hissing, clicking, chirping, or pulse-like sounds are also reported. Some otologists use the term tinnitus cerebri to distinguish other head noises from those that arise in the ear, but the term tinnitus when used without qualification refers to tinnitus aurium.


Neurology_Adams

Neurology_Adams. Tinnitus is a remarkably common symptom, affecting more than 37 million Americans, according to Marion and Cevette. It may be defined as any sensation of sound for which there is no source outside the individual. Two basic types are recognized, tonal and nontonal (nonvibratory and vibratory, in the terminology of Fowler). The tonal type is by far the more common and is what is meant when the unqualified term tinnitus is used. It is also called subjective tinnitus, because it can be heard only by the patient. The nontonal form is sometimes objective, in the sense that under certain conditions the tinnitus can be heard by the examiner as well as by the patient. In either case, whether tinnitus is produced in the inner ear or in some other part of the head and neck, sensory auditory neurons must be stimulated, for only the auditory neural pathways can transmit an impulse that will be perceived as sound.


Neurology_Adams

Neurology_Adams. According to a large survey conducted by Stouffer and Tyler, about one-third of patients report that persistent tinnitus is unilateral; the others experience it bilaterally or with a lateralized predominance. Many more patients have brief episodes of tinnitus and are concerned enough to bring the symptom to the attention of a physician; some are produced by loud noises or by the ingestion of common drugs, such as aspirin but most such cases are transient and innocuous.


Neurology_Adams

Neurology_Adams. These head noises are mechanical in origin and are conducted to the inner ear through the various hard or soft structures or the fluid or gaseous media of the body. They are not caused by a primary dysfunction of the auditory neural mechanism but have their origin in the contraction of muscles of the eustachian tube, middle ear (stapedius, tensor tympani), palate (palatal myoclonus), or pharynx (muscles of deglutition), or in vascular structures near the ear. One of the common forms of subjective tinnitus is a self-audible bruit, the source of which is the turbulent flow of blood in the large vessels of the neck or in an arteriovenous malformation or glomus jugulare tumor. The sound is pulsatile and appreciated by the patient as emanating from one side of the cranium, but it is only sometimes detectable by the examiner.


Neurology_Adams

Neurology_Adams. Other noteworthy causes of pulsatile tinnitus are pseudotumor cerebri or raised intracranial pressure of any type, in which the noise is attributed to a pressure gradient between the cranial and cervical venous structures and the resulting venous turbulence; thyroid enlargement with increased venous blood flow. Other causes include intracranial aneurysm; aortic stenosis; and vascular tumors of the skull, such as histiocytosis X. In the case of a vascular tumor or a large arteriovenous malformation, the examiner may hear the bruit over the mastoid process. Obliteration of the sound by gentle compression of the jugular vein on the symptomatic side is a useful indicator of a venous origin. It has been suggested that diseases that raise the cardiac output markedly (such as severe anemia) may cause pulsatile tinnitus. A flow-related carotid bruit—originating from fibromuscular dysplasia, atherosclerotic stenosis, carotid dissection, and enhanced blood flow in a vessel contralateral to a


Neurology_Adams

Neurology_Adams. cause pulsatile tinnitus. A flow-related carotid bruit—originating from fibromuscular dysplasia, atherosclerotic stenosis, carotid dissection, and enhanced blood flow in a vessel contralateral to a carotid occlusion—has also been incriminated. However, carotid artery stenosis infrequently causes a self-audible bruit. The same holds for diseases of the vertebral artery. In 100 consecutive cases of pulsatile tinnitus collected by Sismanis and Smoker, the most common causes were intracranial hypertension, glomus tumors, and carotid disease. One must be cautious in overinterpreting this symptom, because normal persons can hear their pulse when lying with one ear on a pillow, and introspective individuals may become excessively worried about it. We have suggested that normal variations in the size and location of the jugular bulb may explain some benign cases (Adler and Ropper).


Neurology_Adams

Neurology_Adams. Another type of tinnitus is the rhythmic clicking of palatal myoclonus caused by intermittent contraction of the tensor tympani or stapedius muscles, termed middle ear myoclonus as discussed in Chap. 4 with other forms of tremor. This process has been treated with a variety of medications, including diazepam or, in extremely annoying cases, by section of the offending muscles (Badia et al). Clicking noises caused by palatal myoclonus have also been successfully treated by the injection of botulinum toxin into the soft palatal tissues (Jamieson et al). In the unusual process of superior canal dehiscence (Llyod Minor syndrome) there are odd auditory experiences including enhanced sensitivity to one’s own voice (autophony) and heart sounds, and vertigo induced by sound (Tullio phenomenon). This condition is discussed further on.


Neurology_Adams

Neurology_Adams. This is the common persistent form of tinnitus that arises in the middle or inner ear and is associated in a proportion of patients with cochlear damage. For this reason, the first step in analysis after the clinical examination is an audiogram. Under ideal acoustic circumstances (in a soundproof room having an ambient noise level of 18 dB or less), slight tinnitus is present in 80 to 90 percent of adults (“physiologic tinnitus”). The ambient noise level in ordinary living conditions usually exceeds 35 dB and is of sufficient intensity to mask physiologic tinnitus. Tinnitus because of disease of the middle ear and auditory neural mechanisms may also be masked by environmental noise and hence becomes troublesome only in quiet surroundings—at night, in the country, etc.


Neurology_Adams

Neurology_Adams. Most often, subjective tinnitus signifies a disorder of the tympanic membrane, ossicles of the middle ear, inner ear, or eighth nerve. As already remarked, a majority of patients who complain of persistent tinnitus have some degree of deafness as well. Tinnitus that is localized to one ear and is described as having a tonal character (such as a ringing, bell-like, or like a high and steady musical tone) is particularly likely to be associated with impairment of cochlear or neural function. Tinnitus associated with sensorineural hearing loss of high frequency is often described as “chirping,” and that of low frequency as “whooshing” or blowing (Marion and Cevette). Tinnitus as a result of middle ear disease (e.g., otosclerosis) tends to be more constant than the tinnitus of sensorineural disorders; it is of variable intensity and lower pitch and is characterized by clicks, pops, and rushing sounds.


Neurology_Adams

Neurology_Adams. As remarked previously, the pitch of tinnitus associated with a conductive hearing loss is generally of low frequency (median frequency of 490 Hz, with a range of 90 to 1,450 Hz). That which accompanies sensorineural loss is higher (median frequency of 3,900 Hz, with a range of 545 to 7,500 Hz). This rule does not apply to Ménière disease, in which the tinnitus is usually described as a low-pitched whoosh, buzz, or roar (median frequency of 320 Hz, with a range of 90 to 900 Hz), thus resembling the tinnitus that accompanies a conductive rather than a sensorineural hearing loss (Nodar and Graham). The tinnitus of Ménière disease often fluctuates in intensity, like the hearing loss.


Neurology_Adams

Neurology_Adams. The mechanism of tonal tinnitus has not been established although a number of theories have been postulated. One supposition attributes tinnitus to an overactivity or disinhibition of hair cells adjacent to a part of the cochlea that has been injured. Other postulates a decoupling of hair cells from the tectorial membrane. Yet a third theory is based on the finding of an abnormal discharge pattern of afferent neurons, attributed to ephaptic transmission between nerve fibers that have been damaged by vascular compression (Møller).


Neurology_Adams

Neurology_Adams. Relief of unilateral tinnitus in certain selected cases has reportedly been achieved by vascular decompression of the eighth nerve in a manner comparable to hemifacial spasm, superior oblique myokymia, and some cases of trigeminal neuralgia (Jannetta). However, for most forms of tinnitus, there is little effective treatment (see the review by Lockwood et al). Many patients become reconciled to its presence once the benign nature of the disorder is explained to them. It is possible to fit some patients with a special audiologic instrument, like a hearing aid, that masks the tinnitus by delivering a sound of like pitch and intensity. Patients who are likely to benefit can be identified during the audiogram by noting improvement in tinnitus with the application of superimposed tones. Also, a hearing aid that improves audition may suppress or diminish tinnitus. Antiepileptic drugs and tocainide hydrochloride have been suggested as treatments, but have not been helpful in our experience.


Neurology_Adams

Neurology_Adams. a hearing aid that improves audition may suppress or diminish tinnitus. Antiepileptic drugs and tocainide hydrochloride have been suggested as treatments, but have not been helpful in our experience. Some success in reducing the symptom has been achieved with small doses of amitriptyline at night. In extreme circumstances some groups have experimented with implanted stimulators on the temporal cortex.


Neurology_Adams

Neurology_Adams. If bilateral tinnitus is the basis of persistent complaints, one often discovers that the patient is anxious or depressed, in which case a careful history will reveal the other features of these disorders. Treatment then must be directed to the psychiatric symptoms. In their review, Lockwood and colleagues suggest that all patients with undifferentiated tinnitus be protected from loud sounds and ototoxic drugs (the main ones being aminoglycoside antibiotics, certain loop diuretics, neurotoxic chemotherapies such as cisplatin, and perhaps high doses of aspirin). The American Tinnitus Association website may be helpful to some patients as a source of reassurance (http://www.ata.org). Tinnitus that is unilateral, pulsatile, or fluctuating and associated with vertigo should be investigated by appropriate neurologic and audiologic studies. Other Disorders of Auditory Perception


Neurology_Adams

Neurology_Adams. On occasion, pontine lesions may be accompanied by complex auditory illusions, sometimes with the qualities of true hallucinations (pontine auditory hallucinosis) as in the patients, one of whom was ours, described by Cascino and Adams. These consist of alternating musical tones, like those of an organ; a jumble of sound, like a symphony orchestra tuning up; or siren-like or buzzing sounds, like a swarm of bees. These auditory sense disturbances are more complex than neurosensory tinnitus but less formed than temporal lobe hallucinations. They are usually associated with impairment of hearing in one or both ears and other neurologic signs related to the pontine lesion. An unpleasant degree of hyperacusis in the contralateral ear has also been reported with upper pontine tegmental lesions. BAEPs reveal intact cochlear, auditory nerve, and cochlear nuclear responses. As in the case of peduncular visual hallucinosis, patients realize that the sounds are unreal, that is, they have insight


Neurology_Adams

Neurology_Adams. BAEPs reveal intact cochlear, auditory nerve, and cochlear nuclear responses. As in the case of peduncular visual hallucinosis, patients realize that the sounds are unreal, that is, they have insight into their illusory nature.


Neurology_Adams

Neurology_Adams. Another well recognized but inexplicable type of auditory hallucinosis occurs in elderly patients with longstanding neurosensory deafness. All day long, or for several hours at a time, they hear songs, symphonies, choral music, or familiar or unfamiliar melodies interrupted only by other ambient noise, sleep, or conversations that engage their attention. The “choice” of music has been referable, not surprisingly, to the individual’s earlier life. Our patients, like those reported by Hammeke and colleagues, have been neither depressed nor demented, and antiepileptic and neuroleptic drugs have had no effect. Activation of the right auditory cortex on single-photon emission tomography (SPECT) and magnetoencephalography has been reported in such a case by Kasai and colleagues. The problem may be analogous to the one of Charles Bonnet syndrome, in which elderly individuals with failing vision experience rich visual hallucinations. We find it puzzling that pontine lesions are implicated in


Neurology_Adams

Neurology_Adams. be analogous to the one of Charles Bonnet syndrome, in which elderly individuals with failing vision experience rich visual hallucinations. We find it puzzling that pontine lesions are implicated in some cases, as mentioned previously.


Neurology_Adams

Neurology_Adams. Complex auditory hallucinations may occur as part of temporal lobe seizures arising from a variety of temporal lobe lesions. Conversely, seizures may be induced by musical sounds as well as by other auditory stimuli. These topics are discussed in Chaps. 15 and 21. Paracusis, a condition in which a sound, tune, or a voice is repeated for several seconds, is also a cerebral auditory phenomenon, similar in a sense to the visual phenomenon of palinopsia. The precise anatomy is unknown. The auditory hallucinations of schizophrenia have been extensively studied in relation to activity of the temporal lobes, as discussed in Chap. 49.


Neurology_Adams

Neurology_Adams. Another phenomenon commented on here casually is the phenomenon of repeatedly experiencing parts of a recently heard song or melody, an “ear worm.” The problem is self-limiting but occasionally becomes a chronic medical complaint akin to auditory hallucinosis, probably an obsessive complaint but rarely attributed, on uncertain grounds, to temporal lobe seizures.


Neurology_Adams

Neurology_Adams. The common causes are otosclerosis, otitis media, and trauma. Of the various types of progressive conductive deafness, otosclerosis is the most frequent, being the cause of about half the cases of bilateral (but not necessarily symmetrical) deafness that have their onset in early adult life, usually in the second or third decade. A predilection to otosclerosis is transmitted as an autosomal dominant trait with variable penetrance. Pathologically, it is characterized by an overgrowth of labyrinthine capsular bone around the oval window, leading to progressive fixation of the stapes. The remarkable advances in microotologic surgery designed to mobilize or replace the stapes and to reconstruct the ossicular chain, have greatly altered the prognosis in this disease; significant improvement in hearing can now be achieved in the majority of patients.


Neurology_Adams

Neurology_Adams. The use of antibiotic drugs has markedly reduced the incidence of purulent otitis media, both the acute and chronic forms, which in former years were common causes of conductive hearing loss in children. Repeated attacks of serous otitis media are, however, still an important cause of this type of deafness.


Neurology_Adams

Neurology_Adams. Fractures of the temporal bone, particularly those in the long axis of the petrous pyramid, may damage middle ear structures; frequently there is bleeding into the middle ear as well, and a ruptured tympanic membrane. Transverse fractures through the petrous pyramid are more likely to damage both the cochlear–labyrinthine structures and the facial nerve. Other diseases of the temporal bone—such as Paget disease, fibrous dysplasia, and osteopetrosis—may impair hearing by compression of the cochlear nerve. It should be noted that rupture of the tympanic membrane, as for example from blast injury does not cause much hearing loss; in the case of a blast, the cause of reduced hearing is cochlear damage.


Neurology_Adams

Neurology_Adams. This has many causes. The common high-frequency sensorineural type of hearing loss in the aged (presbycusis) is probably a result of neuronal degeneration, that is, progressive loss of spiral ganglion neurons (Suga and Lindsay). Explosions or intense, sustained noise in certain industrial settings or from gun blasts or even rock music may result in a high-tone sensorineural hearing loss from cochlear damage. Certain antimicrobial drugs (namely, the aminoglycoside group and vancomycin) damage cochlear hair cells and, after prolonged use, can result in severe hearing loss. If these drugs have been used to treat bacterial meningitis, it may be difficult to determine whether the antibiotic or the infection is the cause. A variety of other commonly used drugs are ototoxic, including certain neurotoxic cancer chemotherapies, especially platinum containing drugs, usually in a dose-dependent fashion (see Nadol). Quinine and acetylsalicylic acid may impair sensorineural function transiently.


Neurology_Adams

Neurology_Adams. The cochlea of a neonate may have been damaged in utero by rubella in the pregnant mother. Mumps, acute purulent meningitis (particularly from Pneumococcus and Haemophilus), or chronic infection spreading from the middle to the inner ear may cause nerve deafness in childhood. The meningeal infection spreads along the cochlear aqueduct, a structure that connects the cerebrospinal fluid (CSF) space with the perilymph of the cochlea. Measles vaccination, Mycoplasma pneumoniae infection, and scarlet fever have been associated with acute deafness, with or without vestibular symptoms. It is uncertain whether the deafness in these cases is due to direct infection of the cochlea or represents an autoimmune reaction directed to the inner ear. Also, the inner ear contains melanocytes, and their involvement in Vogt-Koyanagi-Harada disease adds dysacusis, tinnitus, and sensorineural deafness to the usual manifestations of vitiligo of the eyebrows, poliosis (depigmented forelock of hair), iritis,


Neurology_Adams

Neurology_Adams. in Vogt-Koyanagi-Harada disease adds dysacusis, tinnitus, and sensorineural deafness to the usual manifestations of vitiligo of the eyebrows, poliosis (depigmented forelock of hair), iritis, retinal depigmentation, and recurrent meningitis. Meningeal hemosiderosis, a rare process that results from repeated bouts of subarachnoid hemorrhage, also causes eighth nerve damage and deafness, presumably as a toxic effect of iron deposition in the meninges adjacent to the nerve. Cases of acute sensorineural hearing loss or reduced acuity have occurred following CSF drainage or lumbar puncture, likely either the result of traction on the cochlear nerve due to pressure gradients, or endolymphatic hydrops (see further on) through a patent cochlear aqueduct. Most cases are transient.


Neurology_Adams

Neurology_Adams. Episodic deafness in one ear, even without vertigo, proves in most instances to be the result of Ménière disease (see further on). Otologists have described a progressive sensorineural type of hearing loss as a late manifestation of congenital syphilis, sometimes occurring despite prior treatment with adequate doses of penicillin. It has been claimed that the long-term administration of steroids may be useful in such cases. The pathologic basis of the hearing loss has not been determined and the causal relationship to congenital syphilis remains to be established.


Neurology_Adams

Neurology_Adams. The auditory nerve may be involved by tumors of the cerebellopontine angle or by mycotic, lymphomatous, carcinomatous, tuberculous, Listeria, melioidosis, or other types of chronic meningitis and rarely, in sarcoidosis. Lymphomatous meningitis has a particular predilection to cause unilateral hearing loss; we have seen several such cases in which no other cranial nerves were infiltrated. Carcinomatous meningitis may do the same but almost always in the context of other cranial and spinal nerve palsies (see Chap. 31). Of the solid tumors, the ones that involve the auditory nerve most frequently are schwannomas, neurofibromas, meningiomas, dermoids, and metastatic carcinoma. In neurofibromatosis type II, the involvement by vestibular and acoustic schwannomas is typically bilateral as discussed in Chap. 37. Unilateral deafness may also result from demyelinative plaques, infarction, or tumor involving the cochlear nerve fibers or nuclei in the brainstem. Rarely, deafness is the result of


Neurology_Adams

Neurology_Adams. in Chap. 37. Unilateral deafness may also result from demyelinative plaques, infarction, or tumor involving the cochlear nerve fibers or nuclei in the brainstem. Rarely, deafness is the result of bilateral lesions of the temporal lobes (see Chap. 22). The condition called pure word deafness, a type of aphasia, is also caused by left temporal lobe disease; despite normal pure-tone perception and audiometry and normal brainstem auditory evoked potentials, spoken words cannot be understood. This condition is discussed in Chap. 23.


Neurology_Adams

Neurology_Adams. Of equal concern to neurologists is the onset in an adult of sudden and permanent unilateral hearing loss without vertigo and lacking all the other features of Ménière disease. The clinical syndrome has been described by Fetterman and colleagues. Little is known about the pathogenesis of this (idiopathic) syndrome. A vascular causation (occlusion of the cochlear artery or arterial spasm) has been postulated, on uncertain grounds. We do not know how to interpret the findings of DeFelice and colleagues as well as others, who report that the posterior communicating arteries are absent in a disproportionate number of patients with sudden hearing loss. A few cases are due to complicated herpes zoster and mumps parotitis, but aside from these there is no proven relationship to the usual viral respiratory infections. An immune-mediated cause may also be operative in some patients, a hypothesis that has led some neurologists and otologists to treat such patients with a brief course of


Neurology_Adams

Neurology_Adams. viral respiratory infections. An immune-mediated cause may also be operative in some patients, a hypothesis that has led some neurologists and otologists to treat such patients with a brief course of corticosteroids. In a prospective report of the natural history of 88 cases of acute sensorineural hearing loss, two-thirds recovered their hearing completely within a few days or a week or two (Mattox and Simmons). In the remaining patients, recovery was much slower and often incomplete; in this latter group, the hearing loss was predominantly for high tones and in some cases was associated with varying degrees of vertigo and hypoactive caloric responses.


Neurology_Adams

Neurology_Adams. The same problem has been reported to follow cardiopulmonary bypass surgery and has been ascribed, without confirmation, to microemboli. Less often, such an event follows general anesthesia for nonotologic surgery (Evan et al); the pathogenesis is obscure. None of the currently popular therapeutic agents—such as histamine, calcium channel blockers, anticoagulants, inhalation of carbogen (30 percent carbon dioxide), and corticosteroids—seems to clearly affect the outcome of sudden unilateral or bilateral deafness without vertigo. Nonetheless, as mentioned, corticosteroids are often prescribed, based on the uncertain theory that this illness is analogous to an immune form of vestibular neuritis.


Neurology_Adams

Neurology_Adams. A large number of genetically determined syndromes that feature a neural or conductive type of deafness—some congenital and others having their onset in childhood or early adult life—have come to light (see articles by Tekin et al and Gorlin et al). The majority of cases of congenital deafness are inherited as an autosomal recessive trait with no other syndromic features. In most of the remainder, inheritance is autosomal dominant in type and in a small number, it is sex linked.


Neurology_Adams

Neurology_Adams. The singular genetic advance in this field has been the identification in recessive nonsyndromic deafness of a mutation of the connexin-26 gene on chromosome 13 (designated GJB2). This mutation is found in half of recessive familial cases of pure deafness; what is more striking is that the same gene abnormality occurs in 37 percent of cases of sporadic congenital deafness, almost certainly from a spontaneous mutation (Estivill et al and Morell et al). The connexin protein is a component of gap junctions and the mutation is theorized to interfere with the recycling of potassium from the cochlear hair cells to the endolymph. As a result of the human genome project, more than 20 other gene loci have been detected that may be related to congenital deafness syndromes; these have been summarized by Tekin and colleagues, but none, except the one for connexin, accounts for more than a very small proportion of cases. These unattached, nonsyndromic types of congenital deafness are denominated


Neurology_Adams

Neurology_Adams. by Tekin and colleagues, but none, except the one for connexin, accounts for more than a very small proportion of cases. These unattached, nonsyndromic types of congenital deafness are denominated by genes in a family called DFN (for DeaFNess); for example, the connexin mutation is in DFNB1. The mutations in this gene can be recessive, dominant or X-linked. The genetic errors involve either cytoskeletal or structural proteins of the organ of Corti or the ion channel apparatus.


Neurology_Adams

Neurology_Adams. It is remarkable that deafness is a component of over 400 more complex different genetic syndromes (e.g., Waardenburg, branchio-oto-renal, Stickler, Pendred, Usher, Alport, Bartter, among many others listed in the table and those omitted because of their rarity). Among these, the finding of a mutation in a gene called PAX3 in the Waardenburg syndrome in the early 1990s began a flood of other gene defects underlying the many disorders that had been described on clinical grounds over the previous century. The mutations that give rise to some of these diseases, particularly the Usher syndrome, may also cause nonsyndromic congenital deafness. The syndromic forms of genetic deafness have been classified largely on the basis of their associated defects: retinitis pigmentosa, malformations of the external ear; integumentary abnormalities such as hyperkeratosis, hyperplasia or scantiness of eyebrows, albinism, large hyperpigmented or hypopigmented areas, ocular abnormalities such as


Neurology_Adams

Neurology_Adams. of the external ear; integumentary abnormalities such as hyperkeratosis, hyperplasia or scantiness of eyebrows, albinism, large hyperpigmented or hypopigmented areas, ocular abnormalities such as hypertelorism, severe myopia, optic atrophy, and congenital and juvenile cataracts, cerebellar ataxia, myoclonus, and mental deficiency; skeletal abnormalities; and renal, thyroid, or cardiac abnormalities. Deafness is also a feature of several mitochondrial disorders, particularly the Kearns-Sayre syndrome and occasionally the MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis, and stroke-like episodes) syndrome. The Wolfram syndrome, of which sensorineural deafness is a major feature, can have either a nuclear or mitochondrial genetic origin. Table 14-1 summarizes this and the other main hereditary syndromes. Chinnery et al have summarized the mitochondrial causes of deafness. Chapters 37 and 39 discuss further the association of neurosensory deafness with degenerative and


Neurology_Adams

Neurology_Adams. other main hereditary syndromes. Chinnery et al have summarized the mitochondrial causes of deafness. Chapters 37 and 39 discuss further the association of neurosensory deafness with degenerative and developmental neurologic disease.


Neurology_Adams

Neurology_Adams. Differing from the degenerations is a group of acoustic aplasias. Four types of inner ear aplasia have been described: (1) Michel defect, a complete absence of the otic capsule and eighth nerve; (2) Mondini defect, an incomplete development of the bony and membranous labyrinths and the spiral ganglion; (3) Scheibe defect, a membranous cochleosaccular dysplasia with atrophy of the vestibular and cochlear nerves; and (4) rare chromosomal aberrations (trisomies) characterized by abnormality of the end organ and absence of the spiral ganglion.


Neurology_Adams

Neurology_Adams. It is possible to distinguish hysterical and feigned deafness from that caused by structural disease in several ways. In the case of bilateral deafness, the distinction can be made by observing a blink (cochleo-orbicular reflex) or an alteration in skin sweating (psychogalvanic skin reflex) in response to loud sound. Unilateral hysterical deafness may be detected by an audiometer, with both ears connected, or by whispering into the bell of a stethoscope attached to the patient’s ears, closing first one and then the other tube without the patient’s knowledge. The elicitation of the first two waves of the brainstem auditory evoked potentials provides indisputable evidence that sounds are reaching the receptive auditory structures and that the patient should be capable of hearing sounds. A brief episode of deafness with fully preserved consciousness may rarely be caused by seizure activity in one temporal lobe (epileptic suppression of hearing).


Neurology_Adams

Neurology_Adams. Dizziness and other sensations of imbalance are, along with headache, back pain, and fatigue, among the most frequent complaints in medicine (Kroenke and Mangelsdorff). The significance of these complaints varies greatly. For the most part they are benign, but there is always the possibility that they signal an ominous neurologic disorder. Diagnosis of the underlying disease demands that the complaint of dizziness be analyzed correctly—the nature of the disturbance of function being determined first and then its anatomic localization. This approach to neurologic diagnosis is invaluable in the patient whose main complaint is dizziness.


Neurology_Adams

Neurology_Adams. The term dizziness is applied by the patient to a number of different sensory and psychic experiences—a feeling of rotation or whirling as well as nonrotatory swaying, weakness, faintness, light-headedness, or unsteadiness. Blurring of vision, feelings of unreality, syncope, and even petit mal or other seizure phenomena may be called “dizzy spells.” These experiences fall into four categories: (1) vertigo, a physical sensation of motion of self or the environment; (2) near syncope, a sensation of faintness; (3) disequilibrium, a disorder of imbalance of stance or gait; and (4) ill-defined light-headedness, or “giddiness,” a symptom that often accompanies anxiety. Hence, close questioning of the patient as to how he is using the term dizziness is a necessary first step in clinical work.


Neurology_Adams

Neurology_Adams. Several mechanisms are responsible for the maintenance of a balanced posture and for awareness of the position of the body in relation to its surroundings and to gravity. Continuous afferent impulses from the eyes, labyrinths, muscles, and joints inform us of the position of different parts of the body. In response to these impulses, the adaptive movements necessary to maintain equilibrium are carried out. Normally, we are unaware of these adjustments because they operate largely at a reflex level. The most important of the afferent impulses are the following. 1. Visual information from the retinae and possibly proprioceptive impulses from the ocular muscles, enable us to judge the distance of objects from the body. This information is coordinated with sensory information from the labyrinths and neck (see the following text) to stabilize gaze during movements of the head and body. 2.


Neurology_Adams

Neurology_Adams. Impulses from the labyrinths, which function as highly specialized spatial proprioceptors and register changes in the velocity of motion (either acceleration or deceleration) and position of the body in relation to the gravitational vertical. The cristae of the three semicircular ducts sense angular acceleration of the head in the three planes of roll, pitch and yaw, and the maculae of the saccule and utricle sense linear acceleration and gravitational pull. In each of these structures, displacement of sensory hair cells is the effective stimulus. In the semicircular ducts, this is accomplished by movement of the endolymphatic fluid, which, in turn, is induced by rotation of the head. In the utricle and saccule, the hairs are displaced by the movement of the otoliths in response to gravity, thus generating a force that displaces the otoliths. This end organ is a force transducer that converts the generated force into neural impulses that are conducted down the vestibular nerve to the


Neurology_Adams

Neurology_Adams. thus generating a force that displaces the otoliths. This end organ is a force transducer that converts the generated force into neural impulses that are conducted down the vestibular nerve to the vestibular nuclei. In either case (angular and linear acceleration), the force causes depolarization of the nerve terminals and initiation of impulses in the vestibular nerve, with the production of two main reflex responses: the vestibuloocular, which stabilizes the eyes, and the vestibulospinal, which stabilizes the position of the head and body.


Neurology_Adams

Neurology_Adams. 3.


Neurology_Adams

Neurology_Adams. Impulses from the proprioceptors of the joints and muscles are essential to all reflex, postural, and volitional movements. Those from the neck are of special importance in relating the position of the head to the rest of the body. The sense organs listed previously are connected with the cerebellum and pathways in the brainstem, particularly the vestibular nuclei and, via the medial longitudinal fasciculi, with the ocular motor nuclei. These cerebellar and brainstem structures are the important coordinators of the sensory data and provide for postural adjustments and the maintenance of equilibrium. They are the basis of the mechanisms whereby the perceptions of one’s self (the body schema) and one’s surroundings (the environmental schema) are matched. Accordingly, any disease that disrupts these neural mechanisms may give rise to vertigo and disequilibrium. The interdependence of the two schemata (self and environment) is ascribed to the fact that the various sense organs—retinal,


Neurology_Adams

Neurology_Adams. these neural mechanisms may give rise to vertigo and disequilibrium. The interdependence of the two schemata (self and environment) is ascribed to the fact that the various sense organs—retinal, labyrinthine, and proprioceptive—are usually activated simultaneously by any body movement.


Neurology_Adams

Neurology_Adams. One element of the sense of stable equilibrium derives from the ability to match visual and positional information during motion. Through reflex mechanisms, we come to see objects as stationary, while we are moving (mainly the ocular fixation reflex) and moving objects as having motion when we are either moving or stationary (vestibuloocular reflex). At times, especially when our own sensory information is incomplete, we mistake movement of our surroundings for movements of our own body. A well-known example is the feeling of movement that one experiences in a stationary train when a neighboring train is moving.


Neurology_Adams

Neurology_Adams. A factor that influences equilibrium is the effect of aging on all the afferent structures that subserve stability. The elderly may lose their balance on extending the neck, and their peripheral sensory afferents are often impaired, as are the protective postural mechanisms, making falls more frequent. A destructive lesion of one or both labyrinths may leave an elderly person permanently unbalanced, whereas a younger person largely compensates for the loss. Clinical Characteristics of Vertigo


Neurology_Adams

Neurology_Adams. Clinical Characteristics of Vertigo A careful history and physical examination usually afford the basis for separating true vertigo from the dizziness caused by near syncope, gait disorder, and anxiety. Any illusion or hallucination of motion in any plane qualifies as vertigo. The recognition of vertigo is usually not difficult when the patient states that objects in the environment have spun around or moved rhythmically in one direction or that a sensation of whirling of the head and body was experienced. A distinction is sometimes drawn between subjective vertigo, meaning a sense of turning of one’s body, and objective vertigo, an illusion of movement of the environment, but its significance is limited.


Neurology_Adams

Neurology_Adams. Often, however, the patient is not so explicit and a number of related experiences may be described. The feeling may be described as to-and-fro or up-and-down movement of the body, usually of the head, or the patient may compare the feeling to that imparted by the pitch and roll of a ship. Or the floor or walls may seem to tilt or to sink or rise up. In walking, the patient may have felt unsteady and veered to one side, or may have had a sensation of leaning or being pulled to the ground or to one side or another (pulsion or static tilt), as though being drawn by a strong magnet. This feeling is particularly characteristic of vertigo. Oscillopsia, a rhythmic, jerking, illusory movement of the environment, is another effect of vestibular disorder, especially if induced by movement of the head. Observant patients may actually note this rhythmic movement of the environment due to nystagmus.


Neurology_Adams

Neurology_Adams. Some patients may be able to identify their symptoms only when asked to compare them with the feeling of movement they experience when they come to a halt after rapid rotation. If the patient is unobservant or imprecise in descriptions, a helpful tactic is to provoke sensations by rapid rotation, or by asking the patient to stoop for a minute and straighten up; having him stand relaxed for 3 min and checking his blood pressure for orthostatic effect; and, particularly, having him hyperventilate for 3 min. Should the patient be unable to distinguish among these several types of induced dizziness or to ascertain the similarity of one of the types to his own condition, the history is probably too inaccurate for purposes of diagnosis.


Neurology_Adams

Neurology_Adams. When the patient’s symptoms are mild or poorly described, small items of the history—a desire to keep still and a disinclination to stoop or walk during an attack, a tendency to list to one side, an aggravation of symptoms by turning over in bed or closing his eyes, a sense of imbalance when making a quick turn on foot or in a car, and a preference for one position of the body or head—help to identify them as vertigo. At the other end of the scale are attacks of such abruptness and severity as to virtually throw the patient to the ground. Independently occurring vertiginous attacks of the usual variety mark these falling episodes as part of Ménière disease (see further on). On the other hand, a dizzy sensation that is not made worse markedly by vigorous shaking of the head is unlikely to relate to vertigo, particularly that type due to peripheral vestibular disease.


Neurology_Adams

Neurology_Adams. All but the mildest forms of vertigo are accompanied by some degree of nausea, vomiting, pallor, perspiration, and some difficulty with walking. The patient may simply be disinclined to walk or may walk unsteadily and veer to one side, or he may be unable to walk at all if the vertigo is intense. Forced to lie down, the patient realizes that one position, usually on one side with eyes closed, reduces the vertigo and nausea, and that the slightest motion of the head aggravates them. One common form of vertigo, benign positional vertigo (see further on), occurs with the repositioning that accompanies lying down, sitting up, turning, or looking upwards. The source of the gait ataxia associated with vertigo (vertiginous ataxia) is recognized by the patient as being “in the head,” not in the control of the legs and trunk. It is noteworthy that the coordination of individual movements of the limbs is not impaired in these circumstances—a point of difference from most instances of cerebellar


Neurology_Adams

Neurology_Adams. of the legs and trunk. It is noteworthy that the coordination of individual movements of the limbs is not impaired in these circumstances—a point of difference from most instances of cerebellar disease. Loss of consciousness as part of a vertiginous attack nearly always signifies another type of disorder (seizure or faint).


Neurology_Adams

Neurology_Adams. Nonvertiginous Types of Dizziness It is important to distinguish vertigo from the more common complaints for which the term dizziness is used by patients. These include the feeling of impending fainting (near syncope), a disorder of gait (disequilibrium), and an ill-defined feeling of lightheadedness. Many patients in the last category who initially complain of dizziness will, on closer questioning, describe his symptoms as a “distant feeling,” “walking on air,” “inability to focus,” or some other unnatural sensation in the head. These sensory experiences are particularly common in states characterized by anxiety or panic attacks—often, but not always, with depression.


Neurology_Adams

Neurology_Adams. This constellation of nonvertiginous symptoms has been loosely referred to as “phobic,” “functional,” and “psychogenic” vertigo. Every clinician encounters numerous such patients. In Brandt’s (1996) extensive experience, phobic vertigo (his term) was second only to benign positional vertigo (described below) as a cause of consultation in his dizziness clinic. He relates the disorder to anxiety and panic spells, but finds that it exists more often as an independent entity that is subject to improvement after careful explanation and reassurance. We agree with Furman and Jacobs that the term psychiatric dizziness, if used at all, should be restricted to dizziness that occurs as part of a recognized psychiatric syndrome, notably extreme anxiety disorder. Often, there is a component of avoidance of crowds, open spaces and tight circumstances. There seems to be little point in signifying the nonvertiginous symptoms with separate designations based on the settings in which they commonly


Neurology_Adams

Neurology_Adams. of crowds, open spaces and tight circumstances. There seems to be little point in signifying the nonvertiginous symptoms with separate designations based on the settings in which they commonly occur (“supermarket syndrome,” “motorist disorientation syndrome,” “phobic postural vertigo,” “street neurosis”) but they do emphasize the psychogenic nature and may facilitate recognition of the syndrome. Furman and Jacobs have related anxiety-type dizziness to minor degrees of vestibular dysfunction, but we have not found it possible to determine whether there is a genuine labyrinthine disorder in all of these patients.


Neurology_Adams

Neurology_Adams. Oculomotor disorders, such as ophthalmoplegia with diplopia, may be a source of spatial disorientation and brief sensations of vertigo, mild nausea, and staggering. These symptoms are maximal when the patient looks in the direction of action of the paralyzed muscle; it is attributable to the receipt of two conflicting visual images. Some normal persons may experience such symptoms for brief periods when first adjusting to bifocal glasses. In a peculiar symptom called the Tullio phenomenon, a loud sound, or yawning, produces a brief sensation of vertigo or tilting of the environment. Some patients with this symptom are found to have an absence or thinning of the bony roof of the superior semicircular canal, which can be detected by thin (1 mm) slice CT. This disorder (Llyod Minor syndrome) is a form of perilymphatic fistula caused by a spontaneous or traumatic dehiscence of the bone of the superior canal. Occasionally, patients with Ménière disease report this symptom.


Neurology_Adams

Neurology_Adams. Other causes of dizziness are more difficult for the physician and patient to define. In severe anemic states, particularly pernicious anemia, and in aortic stenosis, easy fatigability and languor may be attended by light-headedness, related particularly to postural change and exertion. In the emphysematous patient, physical effort may be associated with weakness and peculiar cephalic sensations, and violent paroxysms of coughing may lead to giddiness and even fainting (tussive syncope) because of impaired venous return to the heart. The dizziness that often accompanies acute hypertension is difficult to evaluate; sometimes it is an expression of anxiety, or it may conceivably be the result of an unstable adjustment of cerebral blood flow. It is doubtful that chronic hypertension causes dizziness, although many of the medications for its treatment certainly can cause the symptom.


Neurology_Adams

Neurology_Adams. Postural nonvertiginous dizziness is another state in which inadequate vasomotor reflexes prevent a constant cerebral circulation; it is notably frequent in persons with orthostatic hypotension of any cause, for example, in those taking antihypertensive drugs, as well as in patients with a polyneuropathy that has an autonomic component. Such persons, on rising abruptly from a recumbent or sitting position, experience a swaying type of dizziness, dimming of vision, and spots before the eyes that last for several seconds. The patient is forced to stand still and steady himself by holding onto a nearby object. Occasionally, a syncopal attack may occur at this time (see Chap. 18). Hypoglycemia gives rise to yet another form of dizziness, marked by a sense of hunger and attended by trembling, sweating, and other autonomic symptoms. Drug intoxication—particularly with alcohol, sedatives, and antiepileptic drugs—may induce a nonspecific dizziness and, at advanced stages of intoxication, true


Neurology_Adams

Neurology_Adams. and other autonomic symptoms. Drug intoxication—particularly with alcohol, sedatives, and antiepileptic drugs—may induce a nonspecific dizziness and, at advanced stages of intoxication, true vertigo.


Neurology_Adams

Neurology_Adams. In practice, it may nonetheless be difficult to separate these types of dizziness from vertigo, for there may, or may not be, feelings of rotation, impulsion, up-and-down movement, oscillopsia, or other disturbance of motion. The ancillary symptoms of true vertigo—namely, nausea, vomiting, tinnitus and deafness, staggering, and the relief obtained by sitting or lying still—are also absent. Furthermore, it is not an uncommon circumstance to find more than one type of dizziness in an individual who is carefully tested. The Neurologic and Otologic Causes of Vertigo


Neurology_Adams

Neurology_Adams. The fact that vertigo may constitute the aura of an epileptic seizure supports the view that this symptom may have a cerebrocortical origin. Indeed, electrical stimulation of the cerebral cortex in an unanesthetized patient, either of the posterolateral aspects of the temporal lobe or the inferior parietal lobule adjacent to the sylvian fissure, may evoke intense vertigo. The occurrence of vertigo as the initial symptom of a seizure is, however, infrequent. In such cases, a sensation of movement—either of the body away from the side of the lesion or of the environment in the opposite direction—lasts for a few seconds before being submerged in other seizure activity. Vertiginous epilepsy of this type should be differentiated from vestibulogenic seizures, in which an excessive vestibular discharge serves as the stimulus for a seizure. The latter is a rare form of reflex epilepsy, in which tests that induce vertigo may provoke the seizure (see Chap. 16).


Neurology_Adams

Neurology_Adams. The issue of migraine as a cause of vertigo has occasioned much discussion. Several authoritative clinicians attribute many instances of otherwise unexplained dizziness and vertigo to migraine with aura, but it is not entirely clear whether they are referring to an attack of basilar migraine, usually in children (migrainous vertigo), or to episodes of vague disequilibrium or vertigo at various times in migraineurs, which has been more typical in our experience. A survey by Neuhauser and colleagues found that 7 to 9 percent of patients had conventional migrainous symptoms during or before a vertiginous attack, and in half of those the vertigo was regularly associated with migraine.


Neurology_Adams

Neurology_Adams. Lesions of the cerebellum produce vertigo depending on which part of this structure is involved. Large, destructive processes in the cerebellar hemispheres and vermis, such as cerebellar hemorrhage may, or at times may not, cause vertigo. However, strokes in the territory of the medial branch of the posterior inferior cerebellar artery (which arises distal to the branches to the medulla, and therefore does not involve the lateral medulla) causes intense vertigo and vomiting that is indistinguishable from that caused by labyrinthine disorder. In two such pathologically studied cases, a large zone of infarction extended to the midline and involved the flocculonodular lobe (Duncan et al). Falling in these cases was toward the side of the lesion; nystagmus was present on gaze to each side but was more prominent on gaze to the side of the infarct. These findings have been confirmed by CT and MRI (Amarenco et al). Early in the course of an acute attack of vertigo, when it may be difficult


Neurology_Adams

Neurology_Adams. was more prominent on gaze to the side of the infarct. These findings have been confirmed by CT and MRI (Amarenco et al). Early in the course of an acute attack of vertigo, when it may be difficult to assess the gait and the quality of nystagmus, it may be necessary to exclude a cerebellar infarct or hemorrhage by use of imaging procedures.


Neurology_Adams

Neurology_Adams. Labyrinthine disease, on the other hand, causes predominantly unidirectional nystagmus with the fast phase opposite to the side of the impaired labyrinth, and swaying or falling toward the involved side—that is, the direction of the nystagmus is opposite to that of the falling and past pointing (the latter referring to overshooting a target by the patient’s finger with eyes closed, as originally described by Bárány [1921]). Ataxia and dysarthria are, of course, typical of many forms of cerebellar disease but may be minimal or absent in cerebellar hemorrhage and some infarctions as well as being lacking in all forms of vestibular disease.


Neurology_Adams

Neurology_Adams. The topic of vertigo with fluctuating ischemia in the territory of the basilar and vertebral arteries (transient ischemic attack [TIA]) and the problem of subclavian steal syndrome are discussed further on under “Vertigo of Brainstem Origin” and in Chap. 33. Also common in practice is vertigo caused by the demyelinating lesions of multiple sclerosis, as noted in the later section.


Neurology_Adams

Neurology_Adams. Biemond and DeJong described a kind of nystagmus and vertigo originating in the upper cervical roots and the muscles and ligaments that they innervate (so-called cervical vertigo). Spasm of the cervical muscles, trauma to the neck, and irritation of the upper cervical sensory roots were said to produce asymmetrical spinovestibular stimulation and thus to evoke nystagmus, prolonged vertigo, and disequilibrium. Toole and Tucker demonstrated a reduced flow through these vessels (in cadavers) when the head was rotated or hyperextended. In our view, the existence of “cervical vertigo,” or at least these interpretations of it, is open to question. However, we acknowledge having encountered patients with cervical dystonia who describe something akin to vertigo, and this may speak to a relationship between cervical proprioceptors and vertigo. Causes of vertigo other than Ménière disease that originate in the vestibular nerve are discussed further on.


Neurology_Adams

Neurology_Adams. Causes of vertigo other than Ménière disease that originate in the vestibular nerve are discussed further on. In summary, for all practical purposes, vertigo indicates a disorder of the vestibular end organs, the vestibular division of the eighth nerve, or the vestibular nuclei in the brainstem and their immediate connections, including the inferior cerebellum. Although lesions of the cerebral cortex, eyes, and perhaps the cervical muscles may give rise to vertigo, they are not common sources of the symptom, and vertigo is rarely the dominant manifestation of disease in these structures. The clinical problem resolves by deciding which portion of the labyrinthine–vestibular apparatus is involved. Usually this determination can be made on the basis of the form of the vertiginous attack, the nature of the ancillary symptoms and signs, and tests of labyrinthine function. These tests are described below, followed by a description of the common labyrinthine– vestibular syndromes.


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Tests of Labyrinthine Function

Neurology_Adams. Tests of Labyrinthine Function


Neurology_Adams

Neurology_Adams. The most rudimentary test of labyrinthine function is simply to have the patient shake his head from side-to-side in an attempt to elicit symptoms that simulate the dizziness that has been described and to observe the degree of postural instability during this maneuver. Falling and marked intensification of the dizziness is almost always an indication of labyrinthine disease. Also, nystagmus may be evoked, indicating a vestibular instability. More informative in identifying a diseased labyrinth is the “rapid head impulse” test, which is conducted by asking the patient to fixate on a target and then for the examiner to rotate the patient’s head quickly by 10 degrees (an explanation must be given to encourage the patient to relax the neck muscles and remain focused on the fixation point). The eyes are observed for a slippage from the target; this is most evident by a quick saccadic return to the point of focus. Ocular instability is observed when the patient turns his head toward the


Neurology_Adams

Neurology_Adams. The eyes are observed for a slippage from the target; this is most evident by a quick saccadic return to the point of focus. Ocular instability is observed when the patient turns his head toward the side of the affected labyrinth. This use of the vestibuloocular reflex is said by Halmagyi and Crener to be among the most dependable bedside tests of labyrinthine function.


Neurology_Adams

Neurology_Adams. Maneuvers designed to elicit positional vertigo by rapidly changing from a seated to a supine position with the head turned to one side bring about vertigo in a number of conditions but are specifically intended to detect benign positional vertigo and are described further on.


Neurology_Adams

Neurology_Adams. A number of other interesting but less well validated tests that bring out instabilities in station and gait may be used to supplement the conventional tests for vestibular dysfunction. The Unterberger-Fukuda maneuver requires the patient to march in place with eyes closed and arms outstretched. Normally, less than 15 degrees or so of rotation is displayed; asymmetry of labyrinthine function is manifest as excessive rotation away from the diseased side. A related test involves having the patient walk around a chair with eyes closed; an increasing or decreasing radius is indicative of an imbalance between the two sides of the labyrinthine apparatus. Both of these tests, however, often show abnormalities with cerebellar disease as well, in which the patient veers to the affected side. The sensitivity of maneuvers such as these has been questioned. We can only comment that they seem in our experience to demonstrate vestibulocerebellar lesions.


Neurology_Adams

Neurology_Adams. Vestibular (labyrinthine) stimulation can also be produced by rotating the patient in a Bárány chair or any type of swivel chair. The patient is asked not to fixate or is defocused with Frenzel lenses during rotation to avoid the effects of optokinetic nystagmus. The normal response is nystagmus in the direction opposite to rotation. In contrast, if the patient is asked to focus on his own thumb in an outstretched arm, there should be no nystagmus if the rotational velocity is slow; the ability to suppress this vestibuloocular response reflects the integrity of the vestibular organ and nerve on the side toward the direction of rotation. Electronystagmography (ENG) provides a more refined method of detecting disordered labyrinthine function because it permits the accurate recording of eye movements without visual fixation. ENG is usually coupled with caloric stimulation or with modern devices for rotational testing that allow precise control of the velocity, acceleration, and extent of


Neurology_Adams

Neurology_Adams. without visual fixation. ENG is usually coupled with caloric stimulation or with modern devices for rotational testing that allow precise control of the velocity, acceleration, and extent of rotation beyond what can be done with a traditional chair.


Neurology_Adams

Neurology_Adams. Irrigation of the ear canal alternately with cold and warm water (caloric testing) may be used to disclose a reduction in labyrinthine function in the form of an impairment or loss of thermally induced nystagmus on the involved side. Caloric testing is accomplished by having the patient lay supine on the examining table with the head tilted forward 30 degrees to bring the horizontal semicircular canal into a vertical plane, the position of maximal sensitivity of this canal to thermal stimuli. Each external auditory canal is irrigated for 30 s, first with water at 30°C (86°F) and then at 44°C (111.2°F), with a pause of at least 5 min between each irrigation. In normal persons, cold water induces a slight tonic deviation of the eyes to the side being irrigated, followed, after a latent period of about 20 s, by nystagmus to the opposite side (direction of the fast phase). Warm water induces nystagmus to the irrigated side. (As noted in Chap. 16, this is the basis for the mnemonic COWS:


Neurology_Adams

Neurology_Adams. of about 20 s, by nystagmus to the opposite side (direction of the fast phase). Warm water induces nystagmus to the irrigated side. (As noted in Chap. 16, this is the basis for the mnemonic COWS: cold opposite, warm same, referring to the direction of fast phase of the nystagmus.) In normal subjects, the nystagmus usually persists for 90 to 120 s, although the range is considerably larger. Nausea and symptoms of excessive reflex vagal activity may occur in sensitive individuals.


Neurology_Adams

Neurology_Adams. Simultaneous irrigation of both canals with cold water causes a tonic downward deviation of the eyes with nystagmus (quick component) upward. Bilateral irrigation with warm water yields a tonic upward movement and nystagmus in the opposite direction (“cold upward, warm down, referring again to the fast phase of nystagmus; “CUWD”). Caloric testing will reliably answer whether the vestibular end organs react, and comparison of the responses from the two ears will indicate which one is paretic. Recording of eye movements during the test allows quantification of these responses. Galvanic stimulation of the labyrinths is effective but offers no particular advantage over caloric stimulation. Ménière Disease and Other Forms of Labyrinthine Vertigo


Neurology_Adams

Neurology_Adams. Labyrinthine disorders are the most common causes of true vertigo. Ménière disease is characterized by paroxysmal attacks of vertigo associated with fluctuating tinnitus and deafness. One or the other of the latter two symptoms may be absent during the initial attacks of vertigo, but invariably they assert themselves as the disease progresses and increase in severity during acute attacks. Ménière disease affects the sexes about equally and has its onset most frequently in the fifth decade of life, although it may begin earlier or later. Cases of Ménière disease usually occur as a sporadic trait, but hereditary forms, both autosomal dominant and recessive, have been described (see reviews by Konigsmark). The main pathologic changes consist of an increase in the volume of endolymph and distention of the endolymphatic system (endolymphatic hydrops). It had been speculated several decades ago that the paroxysmal attacks of vertigo are related to ruptures of the membranous labyrinth and


Neurology_Adams

Neurology_Adams. of the endolymphatic system (endolymphatic hydrops). It had been speculated several decades ago that the paroxysmal attacks of vertigo are related to ruptures of the membranous labyrinth and release of potassium-containing endolymph into the perilymph, changes that have a paralyzing effect on vestibular nerve fibers and lead to degeneration of the delicate cochlear hair cells (Friedmann). An immune pathogenesis has also been proposed, based tentatively on the presence of circulating antibodies putatively against heat shock protein in some patients.


Neurology_Adams

Neurology_Adams. In typical Ménière disease, the attacks of vertigo are abrupt and last for several minutes to an hour or longer. The vertigo is unmistakably whirling or rotational and usually so severe that the patient cannot stand or walk. Varying degrees of nausea and vomiting, low-pitched tinnitus, a feeling of fullness in one ear and a diminution in hearing are practically always associated. Nystagmus is present during the acute attack; it is horizontal in type, usually with a rotary component and with the slow phase to the side of the affected ear. On attempting to touch a target with the eyes closed, there is past pointing as well as a tendency to fall toward the affected ear when standing or walking. The patient prefers to lie with the faulty ear uppermost and is disinclined to look toward the normal side, which exaggerates the nystagmus and dizziness. As the attack subsides, hearing improves, as does the sensation of fullness in the ear; with further attacks, however, there is a progressive


Neurology_Adams

Neurology_Adams. side, which exaggerates the nystagmus and dizziness. As the attack subsides, hearing improves, as does the sensation of fullness in the ear; with further attacks, however, there is a progressive increase in deafness.


Neurology_Adams

Neurology_Adams. The attacks vary considerably in frequency and severity. They may recur several times weekly for many weeks on end, or there may be remissions of several years’ duration. Frequently recurring attacks may give rise to a mild chronic state of disequilibrium and a reluctance to move the head or to turn quickly. With milder forms of the disease, the patient may complain more of head discomfort and of difficulty in concentrating than of vertigo and then may be considered to signify anxiety. Symptoms of anxiety are common in patients with Ménière disease, particularly in those with frequent severe attacks.


Neurology_Adams

Neurology_Adams. A small proportion of patients with Ménière disease experience sudden, violent falling attacks. These episodes have been referred to by the quaint name “otolithic catastrophe of Tumarkin,” who attributed them to deformation of the otolithic membrane of the utricle and saccule. Patients characteristically describe a sensation of being pushed or knocked to the ground without warning, or there may be a sudden movement or tilt of the environment just before the fall. Consciousness is not lost, and vertigo of the usual type and its accompaniments are not part of the falling attack, although some patients become aware of these symptoms after falling. The attacks may occur early or late in the course of the disease. Typically, several attacks occur over a period of a year or less and remit spontaneously (Baloh et al). An initial attack must be distinguished from other types of drop attacks, but the occurrence of the more typical vertiginous attacks of Ménière disease, with deafness and


Neurology_Adams

Neurology_Adams. spontaneously (Baloh et al). An initial attack must be distinguished from other types of drop attacks, but the occurrence of the more typical vertiginous attacks of Ménière disease, with deafness and tinnitus, clarifies the diagnosis.


Neurology_Adams

Neurology_Adams. The hearing loss in Ménière disease usually precedes the first attack of vertigo but it may appear later. Episodic deafness without vertigo has been called cochlear Ménière syndrome. As already mentioned, with recurrent attacks, there is a saltatory progressive unilateral hearing loss (in most series only 10 percent of cases involve both ears, but Baloh places the figure closer to 30 percent). Early in the disease, deafness affects mainly the low tones and fluctuates in severity; actually, tones below 500 Hz are affected early on, and this loss is not evident to the patient. Without measurable fluctuations in pure-tone audiometric thresholds, the diagnosis is left uncertain. Later the fluctuations cease and high tones are affected. Speech discrimination is relatively preserved. The attacks of vertigo usually cease when the hearing loss is complete but there may be an interval of months or longer before this occurs. Audiometry reveals a sensorineural type of deafness, with air and bone


Neurology_Adams

Neurology_Adams. of vertigo usually cease when the hearing loss is complete but there may be an interval of months or longer before this occurs. Audiometry reveals a sensorineural type of deafness, with air and bone conduction equally depressed. Provided that deafness is not complete, loudness recruitment can be demonstrated in the involved ear (see earlier).


Neurology_Adams

Neurology_Adams. During an acute attack of Ménière disease, rest in bed is effective treatment, as the patient can usually find a position in which vertigo is minimal. The antihistaminic agents—cyclizine and meclizine, or transdermal scopolamine—are useful in the more protracted cases. Promethazine is an effective vestibular suppressant, as is trimethobenzamide (given in 200-mg suppositories), which also suppresses nausea and vomiting. For many years, a low-salt diet in combination with ammonium chloride or potassium and diuretics has been used in the treatment of Ménière disease, but the value of this regimen has never been established. The same is true for dehydrating agents such as oral glycerol and more recently introduced calcium channel blockers. Mild sedative drugs may help the anxious patient between attacks. The administration of corticosteroids was at one time popular but they have never been proven effective; transtympanic irrigation with dexamethasone is still practiced by some otologists


Neurology_Adams

Neurology_Adams. attacks. The administration of corticosteroids was at one time popular but they have never been proven effective; transtympanic irrigation with dexamethasone is still practiced by some otologists but neither of these approaches is currently popular.


Neurology_Adams

Neurology_Adams. If the attacks are very frequent and disabling, permanent relief can be obtained by surgical means. Destruction of the labyrinth should be considered only in patients with strictly unilateral disease and who have reached the point of complete or nearly complete loss of hearing. In patients with bilateral disease or significant retention of hearing, the vestibular portion of the eighth nerve can be sectioned. Currently, an endolymphatic–subarachnoid shunt is the operation favored by some surgeons, and selective destruction of the vestibule by a cryogenic probe or transtympanic injection of gentamicin is favored by others. Decompression of the eighth cranial nerve, by separating it from an adjacent vessel, as suggested by Janetta (1984), is still a controversial measure and probably better suited to the treatment of sustained and disabling but unexplained vertigo, rather than the treatment of Ménière disease. The decision to undertake any surgical procedure must be tempered by the fact


Neurology_Adams

Neurology_Adams. suited to the treatment of sustained and disabling but unexplained vertigo, rather than the treatment of Ménière disease. The decision to undertake any surgical procedure must be tempered by the fact that a majority of the patients, who are middle-aged, stabilize spontaneously in a few years.


Neurology_Adams

Neurology_Adams. This disorder of labyrinthine function is more frequent than Ménière disease and—while it does not have the same implications in the long term, an acute attack can be quite disabling. It is characterized by paroxysmal vertigo and nystagmus that occur only with the assumption of certain positions of the head, particularly lying down or rolling over in bed, bending over and straightening up, or tilting the head backward. It is common for the patient to report that the paroxysm of vertigo began in the middle of the night or early morning, presumably while shifting position during sleep and rapidly making one ear dependent, on rolling over to get out of bed, or to turn off an alarm. Brandt and colleagues (1994) prefers the descriptive adjective positioning vertigo to positional vertigo, insofar as the symptoms are induced not by a particular head position but only by rapid changes in head position. This disorder was first described by Bárány (1921) but Dix and Hallpike emphasized its


Neurology_Adams

Neurology_Adams. as the symptoms are induced not by a particular head position but only by rapid changes in head position. This disorder was first described by Bárány (1921) but Dix and Hallpike emphasized its benign nature and were responsible for its further characterization, particularly the discrete positional movements that provoke it. Individual episodes last for less than a minute, but these may recur periodically for several days or for many months—rarely for years. As a rule, examination discloses no abnormalities of hearing or other identifiable lesions in the ear or elsewhere. A thorough summary of the condition has been given by Furman and Cass.


Neurology_Adams

Neurology_Adams. The diagnosis of this disorder is settled at the bedside by moving the patient from the sitting position to recumbency, with the head tilted 30 to 40 degrees over the end of the table and 30 to 45 degrees to one side, as originally described by Dix and Hallpike (Fig. 14-5). This need not be done abruptly but should occur in one smooth motion over a few seconds or less. After a latency of a few seconds, this maneuver provokes a paroxysm of vertigo; the patient may become frightened and grasp the examiner or the table or struggle to sit up. The dysfunctional ear is the one that is downward when vertigo is elicited. We cannot refute the contention made by von Brevern and colleagues that the right labyrinth is more often responsible. The vertigo is accompanied by oscillopsia and nystagmus with the rapid components away from the affected (dependent) ear. The nystagmus is predominantly torsional with an additional vertical component in the eye opposite the affected ear according to Baloh


Neurology_Adams

Neurology_Adams. the rapid components away from the affected (dependent) ear. The nystagmus is predominantly torsional with an additional vertical component in the eye opposite the affected ear according to Baloh and colleagues. The induced vertigo and nystagmus last no more than 30 to 40 s and usually less than 15 s. Changing from a recumbent to a sitting position reverses the direction of vertigo and nystagmus (position-changing nystagmus), and this is perhaps the most certain sign that the disorder originates in the labyrinth. With repetition of the maneuver, vertigo and nystagmus become less apparent, and after three or four trials, they can no longer be elicited (referred to as “fatigue”); they can be reproduced in their original severity only after a protracted period of rest. The head-hanging maneuver does not always evoke vertigo and nystagmus in patients whose histories are otherwise consistent with the diagnosis of benign paroxysmal vertigo; therefore, Froehling and coworkers do not insist


Neurology_Adams

Neurology_Adams. does not always evoke vertigo and nystagmus in patients whose histories are otherwise consistent with the diagnosis of benign paroxysmal vertigo; therefore, Froehling and coworkers do not insist on it for diagnosis if the history is compatible but without the sign, we are uncertain how to confirm the diagnosis. It may still be appropriate to prescribe the corrective exercises as a trial.


Neurology_Adams

Neurology_Adams. Such attacks of vertigo may come and go for years, particularly in the elderly, and require no treatment. At the other end of the scale is the rare patient with positional vertigo of such persistence and severity as to require surgical intervention. Baloh and colleagues, in their study of 240 cases of benign positional vertigo, found that 17 percent had their onset within several days or weeks after cerebral trauma and 15 percent after presumed viral neurolabyrinthitis. The significance of these preceding events is unclear, insofar as they did not appear to influence the clinical symptoms or course of the disorder. The provocative suggestion has been made on the basis of small epidemiologic studies such as the one by Jeong and colleagues that osteoporosis is associated with an increased frequency of the disorder.