Neurology_Adams

Neurology_Adams. because of cerebrovascular autoregulation, and hence, little increase in CSF pressure. Extremely low blood pressure (BP), in the range of a mean of 40 mm Hg, however, cannot be compensated for and correspondingly, lowers the CSF pressure (it follows that CSF pressure is zero, when the heart stops).


Neurology_Adams

Neurology_Adams. In contrast to the limited effect caused by changes in arterial BP, increased venous pressure exerts an almost immediate effect on CSF pressure by increasing the volume of blood in the cerebral veins, venules, and dural sinuses. If the jugular veins are compressed, there is a rise of ICP that is transmitted to the lumbar subarachnoid space (unless there is a spinal subarachnoid block). This was the basis of the now little used Queckenstedt test, mentioned in Chap. 2. In the case of a spinal block, pressure on the abdominal wall, which affects the spinal veins below the point of subarachnoid block, will still increase the lumbar CSF pressure. The valsalva maneuver, as well as coughing, sneezing, and straining, causes an increased intrathoracic pressure, which is transmitted to the jugular and then to the cerebral and spinal veins, and directly to the CSF compartment through the intervertebral foramina. The jugular venous valves prevent unimpeded transmission of thoracic pressure to the


Neurology_Adams

Neurology_Adams. then to the cerebral and spinal veins, and directly to the CSF compartment through the intervertebral foramina. The jugular venous valves prevent unimpeded transmission of thoracic pressure to the cranial veins but this threshold can be exceeded if central and jugular venous pressures become greatly elevated. Mediastinal tumors, by obstructing the superior vena cava, have the same effect.


Neurology_Adams

Neurology_Adams. The inhalation or retention of CO2 raises the blood PCO2 and correspondingly decreases the pH of the CSF. By a mechanism that is not fully understood, this acidification of the CSF acts as a potent cerebral vasodilator, causing an increase in cerebral blood flow and blood volume, thus leading to intracranial hypertension. Hyperventilation, which reduces PCO2, has the opposite effect; it increases the pH and cerebral vascular resistance and thereby decreases CSF pressure; this maneuver of lowering the arterial CO2 content by hyperventilation is used in the treatment of acutely raised ICP. DISTURBANCES OF CEREBROSPINAL FLUID PRESSURE, VOLUME, AND CIRCULATION


Neurology_Adams

Neurology_Adams. The intact cranium and vertebral canal, together with the relatively inelastic dura, form a rigid container, such that an increase in the volume of any of its contents—brain, blood, or CSF—will elevate the ICP. Furthermore, an increase in any one of these components must be at the expense of the other two, a relationship that is known as the Monro-Kellie model. Small increments in brain volume do not immediately raise ICP because of the countervailing buffering effect of displacement of CSF from the cranial cavity into the spinal canal. To a lesser extent, there is deformation of the brain and stretching of the infoldings of the relatively unyielding dura, specifically, the falx cerebri between the hemispheres and the tentorium between the hemispheres and cerebellum. Once these compensating measures have been exhausted, a mass within one dural compartment leads to displacement, or “herniation” of brain tissue from that compartment into an adjacent one. Any further increment in brain


Neurology_Adams

Neurology_Adams. measures have been exhausted, a mass within one dural compartment leads to displacement, or “herniation” of brain tissue from that compartment into an adjacent one. Any further increment in brain volume necessarily reduces the volume of intracranial blood contained in the veins and dural sinuses. Also, the CSF is formed more slowly in circumstances of raised ICP. These accommodative volume-pressure relationships occur concurrently and are subsumed under the term intracranial elastance (the change in ICP for a given change in intracranial volume, or its inverse, compliance, the latter term used often in clinical work). As the volume of brain, blood, or CSF continue to increase, the accommodative mechanisms fail and ICP rises exponentially, as in an idealized elastance (compliance) curve. The shape of the normal curve begins a steep ascent at an ICP of approximately 25 mm Hg. After this point, small increments in intracranial volume result in marked elevations in ICP.


Neurology_Adams

Neurology_Adams. The numerical difference between ICP and mean BP within the cerebral vessels is termed cerebral perfusion pressure (CPP). Besides the aforementioned brain tissue shifts, which are discussed more fully in relation to coma and other clinical signs in Chap. 16, elevation in ICP that approaches the level of mean systemic BP eventually causes a widespread reduction in cerebral blood flow. In its most severe form, this results in global ischemia and produces brain death. Lesser degrees of raised ICP and reduced cerebral perfusion cause correspondingly less severe, but still widespread, cerebral infarction that is similar to what arises after cardiac arrest. In all circumstances, not only the severity but also the rapidity and duration of reduced cerebral perfusion, are the main determinants of the degree of cerebral damage. These are theoretical models that guide practice but are often found to be imprecise in clinical work.


Neurology_Adams

Neurology_Adams. Lundberg has been credited with recording and analyzing intraventricular pressures over long periods of time in patients with brain tumors. He found ICP to be subject to periodic spontaneous fluctuations, of which he described three types of pressure waves, designated as A, B, and C (Fig. 29-2). B-waves are ballistic waveforms that follows the blood pressure wave and are the result of blood entering the basal cerebral vessels (see below for further comments on B-waves). C-waves follow the respiratory cycle and are a complex result of several transmitted pressures from the thorax to the spinal fluid compartment.


Neurology_Adams

Neurology_Adams. Only the A-waves have proved to be entirely separable from arterial (B-waves) and respiratory (C-waves) pulsations and are of most clinical consequence. They consist of prolonged rhythmic wave-like elevations of ICP, up to 50 mm Hg, occurring every 15 to 30 min and lasting about 1 min, or of smaller but more protracted elevations. They are apparent only when the trend of ICP is monitored over many minutes or longer. These plateau waves, as they have come to be known, coincide with an increase in intracranial blood volume, presumably as a result of a temporary failure of cerebrovascular autoregulation. Rosner and Becker observed many years ago that plateau waves are sometimes preceded by a brief period of mild systemic hypotension. In their view, this slight hypotension induces cerebral vasodilatation in order to maintain normal blood flow. Upon recovery of the BP, the response in cerebrovascular tone is delayed, thereby allowing intracranial blood volume to accumulate in the dilated


Neurology_Adams

Neurology_Adams. in order to maintain normal blood flow. Upon recovery of the BP, the response in cerebrovascular tone is delayed, thereby allowing intracranial blood volume to accumulate in the dilated vascular bed, and raising ICP in the form of a plateau wave. In support of this explanation is the observation that a brief period of induced elevation of BP paradoxically restores the normal cerebrovascular tone and leads to an abrupt cessation of a plateau wave.


Neurology_Adams

Neurology_Adams. The configuration of the Lundberg B-waves, which are ballistic ICP waveforms corresponding to the inflow of blood into the cerebral vessels during systole, give some sense of cerebral dynamics. They have a dicrotic notch, just as the blood pressure wave, and the two small peaks, termed for convenience P1 and P2 (some have detected a P3), give an approximate indicator of cerebral compliance (or elastance), a higher P2 corresponding to less compliant intracranial contents (see insert top of Fig. 29-2).


Neurology_Adams

Neurology_Adams. The high rates of mortality and morbidity associated with acute cerebral mass lesions is in part related to uncontrolled elevations in ICP. As mentioned earlier, ICP in a resting and reclining adult is generally 3 to 7 mm Hg (lower when an individual is upright). For clinical trials and research, levels above 15 mm Hg are considered abnormal but are not in themselves hazardous; in fact, adequate cerebral perfusion can be maintained at an ICP of 40 mm Hg provided BP remains normal. A higher ICP or a lower BP may combine to reduce CPP and cause diffuse ischemic damage. Causes of Raised ICP In clinical practice, there are several mechanisms for elevated ICP: 1.


Neurology_Adams

Neurology_Adams. Causes of Raised ICP In clinical practice, there are several mechanisms for elevated ICP: 1. A cerebral or extracerebral mass such as brain tumor; cerebral infarction with edema; traumatic contusion; parenchymal, subdural, or extradural hematoma; or abscess, all of which are localized but deform the adjacent brain. The brain deformation is compartmentalized, or constrained by the rigid dural partitions surrounding the compartment containing the mass. 2. Generalized brain swelling, as occurs in ischemic–anoxic states, acute hepatic failure, hypertensive encephalopathy, hypercarbia, and Reye hepatocerebral syndrome. In these disorders, the increase in pressure can reduce cerebral perfusion, but tissue shifts are minimal because the effect of the addition of mass to the brain is uniformly distributed throughout the cranial contents. 3.


Neurology_Adams

Neurology_Adams. 3. An increase in venous pressure because of cerebral venous sinus thrombosis, heart failure, or obstruction of the superior mediastinal or jugular veins. 4. Obstruction to the flow and absorption of CSF. If the obstruction is within the ventricles or in the subarachnoid space at the base of the brain, hydrocephalus results. Extensive meningeal disease from several potential causes (infectious, carcinomatous, granulomatous, hemorrhagic) is another mechanism of blockage to CSF flow. If the block is confined to the absorptive sites adjacent to the cerebral convexities and superior sagittal sinus, the ventricles remain normal in size or enlarge only slightly, because the pressure over the convexities approximates the pressure within the lateral ventricles (see further on). 5.


Neurology_Adams

Neurology_Adams. 5. Any process that expands the volume of CSF (meningitis, subarachnoid hemorrhage) or hat increases CSF production (choroid plexus tumor). In this situation, there may be a pressure gradient between the cerebral and spinal compartments, resulting in hydrocephalus. Clinical Features of Raised ICP (See Also Chap. 16) The typical clinical manifestations of increased ICP in children and adults are headache, nausea and vomiting, drowsiness, ocular palsies, and papilledema. Papilledema may result in periodic visual obscurations and if it protracted, optic atrophy and blindness may follow (see


Neurology_Adams

Neurology_Adams. Chap. 12 for further discussion of papilledema and optic nerve atrophy). The practice of monitoring ICP with a pressure device inserted into the cranial cavity has permitted approximate correlations to be made between clinical signs and the levels of ICP. However, the neurologic signs of a large intracranial mass, namely pupillary dilatation, abducens palsies, drowsiness, and the Cushing response, as discussed below and in Chaps. 16 and 34, are caused, not by raised pressure, but by displacement of brain tissue, and therefore they do not bear a strict relationship to ICP.


Neurology_Adams

Neurology_Adams. As a rule, patients with normal blood pressure retain mental alertness when ICP rises to 25 to 40 mm Hg unless there is concurrent shift of brain tissue that compresses the brainstem. Stated another way, coma generally cannot be attributed to elevated ICP alone. Only when ICP exceeds 40 to 50 mm Hg does cerebral blood flow diminish to a degree that results in loss of consciousness. Further elevations are followed imminently by global ischemia and brain death. From our own observations, the brain shift and herniation that causes the pupil to dilate on the side of a mass lesion generally occurs at an ICP of 28 to 34 mm Hg. (Again, this is not a direct effect of the elevated ICP.) There are instances in which the dissociation between ICP and clinical signs is striking, for example, a mass in the medial temporal lobe that is contiguous to the third nerve will compress the nerve at a time when ICP is little raised, and slowly growing lesions, which raise ICP slowly and allow for


Neurology_Adams

Neurology_Adams. a mass in the medial temporal lobe that is contiguous to the third nerve will compress the nerve at a time when ICP is little raised, and slowly growing lesions, which raise ICP slowly and allow for compensation cause few clinical signs. Likewise, unilateral or bilateral abducens palsies do not have a consistent relationship to the degree of elevation of ICP. Rather, abducens palsies are found when raised ICP is a result of diffusely distributed brain swelling, hydrocephalus, meningitic processes, or pseudotumor cerebri.


Neurology_Adams

Neurology_Adams. The consequences of increased ICP take on special features in infants and small children, whose cranial sutures have not closed. The head enlarges and the eyes may bulge. Then the clinical problem involves differentiation from other types of enlargement of the head with or without hydrocephalus, such as constitutional macrocrania or an enlarged brain (megalencephaly; or hereditary metabolic diseases such as Krabbe disease, Alexander disease, Tay-Sachs disease, Canavan spongy degeneration of the brain), and from subdural hematoma or hygroma, neonatal ventricular hemorrhage, and various cysts and tumors.


Neurology_Adams

Neurology_Adams. There had been evidence, mainly from retrospective cohorts of patients with traumatic brain injury, that the outcome in patients with intracranial mass lesions was better if the ICP was maintained at levels well below those that compromise cerebral perfusion. An ICP below 15 or 20 mm Hg is often given as a therapeutic target, as the elastance curve becomes steep beyond this level and small increments in cerebral volume may cause large elevations in pressure. However, guiding treatment by the direct measurement of ICP has not yielded beneficial results, as typified by the BEST-TRIP trial (Chesnut et al) and—after several decades of popularity—the advantage of such devices over clinical and imaging signs of increasing mass effect is less certain. It does appear that lowering ICP and decompressing the brain by craniectomy after traumatic injury (see the DECRA trial, Cooper et al; and RESCUE-ICP, Hutchinson et al) or with cerebral swelling from stroke, greatly reduces mortality and it has


Neurology_Adams

Neurology_Adams. the brain by craniectomy after traumatic injury (see the DECRA trial, Cooper et al; and RESCUE-ICP, Hutchinson et al) or with cerebral swelling from stroke, greatly reduces mortality and it has been presumed that this is the result of a reduction of ICP. It is difficult, however, to separate this effect of decompression from the parallel amelioration of intracranial tissue shifts. (It should be noted that the reduction in mortality is usually at the expense of increased numbers of survivors in a vegetative or disabled state). Nevertheless, in a patient who cannot be examined because of induced paralysis or sedation, or who will be subjected to a procedure that risks further elevating ICP, monitoring seems sensible.


Neurology_Adams

Neurology_Adams. The problem in demonstrating an advantage to monitoring may partly be a matter of the level of ICP at which treatment is instituted and the proper selection of patients for treatment. Contributing to the decision to institute monitoring are the prospects of ameliorating the underlying lesion, the patient’s age, and associated medical disease(s). Despite the several discouraging trials noted above, our practice has been to measure ICP with an indwelling fiberoptic monitor or intraventricular catheter in otherwise salvageable patients who are stuporous or comatose, and in whom a traumatic or other intracranial mass has caused either a shift of intracranial structures or severe generalized brain swelling. Published guidelines suggest that monitoring should be undertaken in patients with severe traumatic brain injury if they are over 40 years of age, and have a Glasgow Coma Score below 9 (see Chap. 34). The monitor is generally placed on the same side as a mass lesion.


Neurology_Adams

Neurology_Adams. The emergency management of raised ICP is considered in greater detail in Chaps. 33 and 34, where the subject is discussed in relation to stroke and cerebral trauma. This is a condition of ventricular enlargement as a result of an obstruction to the normal flow of CSF. The sites of obstruction may be at the third ventricle, aqueduct of Sylvius, at the medullary foramina (Luschka and Magendie, Fig. 29-1), or in the basal or convexity subarachnoid spaces. Because of the obstruction, CSF accumulates within the ventricles under increasing pressure, enlarging the ventricles, and expanding the hemispheres. As noted earlier, in the infant or young child, the head increases in size because the expanding cerebral hemispheres separate the sutures of the cranial bones.


Neurology_Adams

Neurology_Adams. Regarding terminology, the term hydrocephalus (literally, “water brain”) is frequently, but incorrectly, applied to any enlargement of the ventricles, even if consequent to cerebral atrophy, that is, hydrocephalus ex vacuo, or to ventricular enlargement because of failure of development of the brain, a state known as colpocephaly. Reference to these conditions as hydrocephalic is so common that it is unlikely to change; the use of “tension hydrocephalus,” although not widely adopted, may be useful to separate enlargement caused by pressure from passive enlargement of the ventricles.


Neurology_Adams

Neurology_Adams. In 1914, Dandy and Blackfan introduced the also somewhat ambiguous but now well-established terms communicating and noncommunicating (obstructive) hydrocephalus. The concept of communicating hydrocephalus was based on the observations that dye injected into a lateral ventricle would diffuse readily downward into the lumbar subarachnoid space and that air injected into the lumbar subarachnoid space would pass upward into the ventricular system; in other words, the ventricles were in communication with each other and the spinal subarachnoid space. If the lumbar spinal fluid remained colorless after the injection of dye into the ventricles, the hydrocephalus was assumed to be obstructive, or noncommunicating. In actuality, the distinction between these two types is not fundamental, because all forms of true hydrocephalus are obstructive at some level, and the obstruction is virtually never complete. Pathogenesis of Hydrocephalus


Neurology_Adams

Neurology_Adams. Pathogenesis of Hydrocephalus There are several sites of predilection of obstruction to the flow of CSF. One foramen of Monro may be blocked by a tumor or by horizontal displacement of central brain structures from a large cerebral mass. An essential, perhaps self-evident aspect of hydrocephalus is that the accumulation of CSF and expansion of the ventricular system is unidirectional, by which is meant that the ventricle(s) proximal to the obstruction expands, not the ones distal to obstruction. A useful adage, attributed to Ayer, is that the ventricle closest to the obstruction enlarges the most; meaning, for example, that occlusion of the basal CSF pathways causes a disproportionate enlargement of the fourth ventricle, and a mass within the fourth ventricle leads to a greater dilatation of the third than of the lateral ventricles.


Neurology_Adams

Neurology_Adams. Some examples suffice to describe the relationship between the site of obstruction and the configuration of the subsequent hydrocephalus. Obstruction may cause expansion of one lateral ventricle or a portion of it. Tumors within the third ventricle (e.g., colloid cyst) block the egress of CSF from both foramina of Monro, leading to dilatation of both lateral ventricles. The aqueduct of Sylvius, narrow to begin with, may be occluded by a number of developmental or acquired lesions (e.g., congenital atresia or forking, perinatally acquired gliosis, ependymitis, hemorrhage, or tumor), and lead to dilatation of the third and both lateral ventricles. If the obstruction is in the fourth ventricle, the dilatation includes the aqueduct. Other sites of obstruction of the CSF in the ventricular pathways are at the foramina of Luschka and Magendie (e.g., congenital failure of opening of the foramina, Dandy-Walker syndrome). More common is a blockage to flow of CSF in the subarachnoid space


Neurology_Adams

Neurology_Adams. pathways are at the foramina of Luschka and Magendie (e.g., congenital failure of opening of the foramina, Dandy-Walker syndrome). More common is a blockage to flow of CSF in the subarachnoid space around the brainstem caused by inflammatory or fibrosing meningitis. This form of obstruction results in enlargement of the entire ventricular system, including the fourth ventricle.


Neurology_Adams

Neurology_Adams. Another potential site of obstruction is in the subarachnoid spaces over the cerebral convexities. A matter of considerable practical as well as theoretical interest is whether a meningeal obstruction at the site of the arachnoidal villi, or a blockage of the venous sinuses into which the CSF is absorbed, can result in hydrocephalus. Russell, in her extensive neuropathologic material and review of the literature, could not find a well-documented example of either of these suggested etiologies, and the same is true of the pathologic material collected by our colleague R.D. Adams. Moreover, experiments in animals in which all the draining veins had been occluded, tension hydrocephalus with enlarging lateral ventricles was produced in only a few cases. More often, the site of obstruction in meningitis or subarachnoid hemorrhage is in the basal cisterns. Yet Gilles and Davidson have stated that hydrocephalus in children may be the result of a congenital absence, or deficient number of


Neurology_Adams

Neurology_Adams. in meningitis or subarachnoid hemorrhage is in the basal cisterns. Yet Gilles and Davidson have stated that hydrocephalus in children may be the result of a congenital absence, or deficient number of arachnoidal villi, and Rosman and Shands have reported an instance that they attributed to increased intracranial venous pressure. Our hesitation in accepting such examples stems from the difficulty that the pathologist has in judging the patency of the basilar subarachnoid space. This is much more reliably visualized by radiologic than by neuropathologic means. Theoretically, if the obstruction is near (or in) the superior sagittal sinus, the CSF should accumulate under pressure outside as well as inside the brain, so that there is no gradient from the ventricles across the mantle of the substance of the cerebral hemispheres and the ventricles should not enlarge at all, or only slightly, and only after a prolonged period.


Neurology_Adams

Neurology_Adams. The infrequently encountered imaging picture of enlarged subarachnoid spaces over and between the cerebral hemispheres, coupled with modest enlargement of the lateral ventricles has been referred to as external hydrocephalus. Although such a condition does exist, many of the cases so designated have proved to be examples of subdural hygromas or arachnoid cysts. The condition is now seen after surgical hemicraniectomy, if the bone is not replaced. Processes such as subarachnoid hemorrhage, or cerebral hemorrhage or brain abscess that rupture into the ventricles and rapidly expand the volume of CSF produce the most dramatic forms of acute hydrocephalus. An obstruction of the CSF pathways in these conditions may also be found within the ventricular system or at the basal meninges. The corresponding clinical syndrome of acute hydrocephalus is described below.


Neurology_Adams

Neurology_Adams. An increase in the rate of formation or decrease in the rate of absorption would be expected to cause accumulation of CSF and increased ICP but the only examples of overproduction of CSF are papillomas of the choroid plexus, and even in this circumstance, there is usually an associated ventricular obstruction, either of the third or fourth ventricle or of one lateral ventricle. Sometimes in these cases there is both a generalized dilatation of the ventricular system and basal cisterns (possibly because of increased CSF volume), and an asymmetrical enlargement of the lateral ventricles caused by obstruction of one foramen of Monro. Syndromes of Hydrocephalus


Neurology_Adams

Neurology_Adams. Syndromes of Hydrocephalus Ventricular enlargement gives rise to various syndromes depending on the age of the patient and the rapidity of evolution. The type that occurs early in life, before fusion of the cranial sutures, leads to enlargement of the head. If the cranial sutures have fused and the accumulation of CSF is very gradual, the head remains normal in size and the ventricular enlargement may remain asymptomatic or later in life cause gait, urinary and cognitive difficulties. A special form of the latter is arrested or compensated hydrocephalus of late adult life that is one of the causes of normal-pressure hydrocephalus that is addressed in Chap. 6 and in the following text.


Neurology_Adams

Neurology_Adams. The cranial bones fuse by the end of the third year; for the head to enlarge, the tension hydrocephalus must develop before this time. It may begin in utero, but usually happens in the first few months of life. Even up to 5 years of age (and very rarely beyond this time), a marked increase of ICP, particularly if it evolves rapidly, may separate the newly formed sutures (diastasis). Hydrocephalus, even of mild degree, also molds the shape of the skull in early life, and in radiographs, the inner table is unevenly thinned, an appearance referred to as “beaten silver,” or as convolutional or digital markings. The frontal skull regions are unusually prominent (bossed) and the skull tends to be brachiocephalic, except in the Dandy-Walker syndrome where, because of bossing of the occiput from enlargement of the posterior fossa, the head is dolichocephalic. With marked enlargement of the skull, the face looks relatively small and pinched, and the skin over the cranial bones is tight and


Neurology_Adams

Neurology_Adams. enlargement of the posterior fossa, the head is dolichocephalic. With marked enlargement of the skull, the face looks relatively small and pinched, and the skin over the cranial bones is tight and thin, revealing prominent distended veins. The usual causes of this disorder are (1) intraventricular matrix hemorrhages in premature infants, (2) fetal and neonatal infections, (3) type II Chiari malformation, (4) aqueductal atresia and stenosis, and (5) the Dandy-Walker syndrome.


Neurology_Adams

Neurology_Adams. In congenital hydrocephalus, the head usually enlarges rapidly and soon surpasses the 97th percentile. The anterior and posterior fontanels are tense even when the child is in the upright position. The infant is fretful, feeds poorly, and may vomit frequently. With continued enlargement of the brain, torpor sets in and the infant appears languid, uninterested in his surroundings, and unable to sustain activity. Later, the upper eyelids are retracted, and the eyes tend to turn down; there is paralysis of upward gaze, and the sclerae above the irises are visible. This is the “setting-sun sign” that has been incorrectly attributed to downward pressure of the frontal lobes on the roofs of the orbits. The fact that it disappears on shunting the lateral and third ventricles indicates that it is caused by hydrocephalic pressure on the mesencephalic tegmentum. Gradually, if left untreated, the infant adopts a posture of flexed arms and flexed or extended legs. Signs of corticospinal tract


Neurology_Adams

Neurology_Adams. is caused by hydrocephalic pressure on the mesencephalic tegmentum. Gradually, if left untreated, the infant adopts a posture of flexed arms and flexed or extended legs. Signs of corticospinal tract damage are usually elicitable. Movements are feeble, and sometimes the arms are tremulous. There is no papilledema, but the optic discs become atrophic, pale and vision is reduced.


Neurology_Adams

Neurology_Adams. If the hydrocephalus is arrested, the infant or child is usually developmentally delayed in motor function but often surprisingly verbal. In extreme circumstances, the head may be so large that the child cannot hold it up and must remain in bed. If the head is only moderately enlarged, the child may be able to sit but not stand, or stand but not walk. Acute exacerbations of hydrocephalus or a febrile illness may cause vomiting, stupor, or coma.


Neurology_Adams

Neurology_Adams. The special features of congenital hydrocephalus associated with the Chiari malformation, aqueductal atresia and stenosis, and the Dandy-Walker syndrome are discussed in Chap. 37. Also mentioned here is a rare condition termed “bobble head” syndrome that is caused by a suprachiasmatic arachnoid cyst or by third ventricular enlargement, as discussed in Chap. 30. These lesions cause the child’s head to move forward and backward or side-to-side constantly or intermittently at about 2 to 3 Hz. There is no direct connection to another rhythmic head movement, spasmus nutans (listed in some books as “mutans”), or to seesaw nystagmus described in Chap. 13, but the location of the causative lesions, in and adjacent to the third ventricle, is similar in all of them.


Neurology_Adams

Neurology_Adams. Here, the ventricular enlargement becomes evident only after the cranial sutures have closed (Fig. 29-3). The causes of obstruction to the flow of CSF are diverse, and although some are clearly congenital, symptoms may be delayed as late as adolescence, or early adult life, or even later. In some instances, the condition gives rise to normal-pressure hydrocephalus, as discussed below and in Chap. 6. The clinical features of occult hydrocephalus and the course of the illness are quite variable. We have seen a few cases in adults in whom the gait disturbance from congenital aqueductal stenosis appeared abruptly enough to give the impression of a cerebellar or frontal stroke. For unexplained reasons, the symptoms of previously occult hydrocephalus may also appear abruptly after minor cranial trauma. A suck reflex and grasp reflexes of the hands and feet are variably present; plantar reflexes are sometimes extensor. Last, there may be urinary urgency leading to sphincteric incontinence,


Neurology_Adams

Neurology_Adams. trauma. A suck reflex and grasp reflexes of the hands and feet are variably present; plantar reflexes are sometimes extensor. Last, there may be urinary urgency leading to sphincteric incontinence, often without the patient’s awareness.


Neurology_Adams

Neurology_Adams. Chapter 30 discusses occult hydrocephalus caused by intracranial tumor growth.


Neurology_Adams

Neurology_Adams. Surprisingly, little has been written about this condition despite its frequency in clinical practice. It is seen most often following subarachnoid hemorrhage from a ruptured aneurysm, less often with bleeding from an arteriovenous malformation or from deep intracerebral hemorrhage that dissects into the ventricles. It may also occur as the result of obstruction of the CSF pathways in the fourth ventricle by a tumor or cerebellar–brainstem hemorrhage, or within the basal cisterns by neoplastic infiltration of the meninges, although this last process tends to evolve more subacutely. The patient complains of a headache of varying severity and may have visual obscuration, vomiting, and then becomes drowsy or stuporous over a period of minutes or hours. Bilateral Babinski signs are found, and in advanced stages, which are associated with coma, there is increased tone in the lower limbs and extensor posturing. Early in the process, the pupils are normal in size and the eyes may rove


Neurology_Adams

Neurology_Adams. and in advanced stages, which are associated with coma, there is increased tone in the lower limbs and extensor posturing. Early in the process, the pupils are normal in size and the eyes may rove horizontally; as the ventricles continue to enlarge, the pupils become miotic, the eyes then cease roving and assume an aligned forward position, or there may be bilateral abducens palsies and limitation of upward gaze. The speed with which hydrocephalus develops determines whether there is accompanying papilledema.


Neurology_Adams

Neurology_Adams. If this condition is left untreated, the pupils eventually dilate symmetrically, the eyes no longer respond to oculocephalic maneuvers, and the limbs become flaccid. Or, there is an unanticipated cardiac or respiratory arrest, even at an early stage of evolution of the hydrocephalus; this complication is seen particularly in children with masses, particularly at the foramen magnum, and may be presaged by brain compression at the level of the perimesencephalic cisterns, detectable by imaging studies. Treatment is by drainage of CSF, usually effected by a ventricular catheter or, if there is undoubted communication between all the CSF compartments, by lumbar puncture. The latter may pose some risk if spinal fluid is withdrawn rapidly or there is a sizeable leak of fluid through the spinal dura at the site of the puncture, thereby creating a pressure gradient between the cerebral and spinal regions. Neuropathologic Effects of Hydrocephalus


Neurology_Adams

Neurology_Adams. Expansion of the lateral ventricles tends to be maximal in the frontal horns, explaining the hydrocephalic impairment of frontal lobe functions and of basal ganglionic–frontal motor and gait activity in many forms of hydrocephalus. The central white matter yields to pressure, while the cortical gray matter, thalami, basal ganglia, and brainstem structures remain relatively unaffected. There is an increase in the content of interstitial fluid in the tissue adjacent to the lateral ventricles (transependymal flow), readily detected by MRI (see Fig. 29-3). Myelinated fibers and axons are injured, but not to the extent that one might expect from the degree of compression; minor degrees of astrocytic gliosis and loss of oligodendrocytes in the affected tissue are present to a decreasing extent away from the ventricles and represent a chronic hydrocephalic atrophy of the brain. The ventricles are characteristically denuded of ependyma, and the choroid plexuses are flattened and fibrotic. The


Neurology_Adams

Neurology_Adams. from the ventricles and represent a chronic hydrocephalic atrophy of the brain. The ventricles are characteristically denuded of ependyma, and the choroid plexuses are flattened and fibrotic. The lumens of cerebral capillaries in biopsy preparations are said to be narrowed—a finding that is difficult to evaluate.


Neurology_Adams

Neurology_Adams. In meningeal and ependymal diseases, hydrocephalus may develop and reach a stable state. It is then said to be “compensated” in the sense that formation of CSF equilibrates with absorption. Once equilibrium is attained, the ICP gradually falls, though it still maintains a gradient from ventricle to basal cistern to cerebral subarachnoid space. A stage is reached where the CSF pressure reaches a high normal level of 150 to 200 mm H2O, but the patient nonetheless eventually manifests the cerebral effects of the hydrocephalic state. The name given to this condition by Adams and colleagues and Hakim and Adams was normal-pressure hydrocephalus (NPH).


Neurology_Adams

Neurology_Adams. There continues to be controversy regarding the frequency of this condition in older adults, and there have even been reasonable arguments questioning the existence of the entity as a coherent disorder or syndrome and, in response to guidelines for treatment issued by the American Academy of Neurology (see Halperin et al) there has certainly been divergence of opinion (Saper). As to the frequency of the disorder, estimates vary widely and depend on the age group studied but Jaraj and colleagues using four cohorts, estimated the prevalence as 0.2 percent of those aged 70 to 79 and 5.9 percent of those over 80.


Neurology_Adams

Neurology_Adams. A triad of clinical findings is characteristic of NPH: a slowly progressive gait disorder is usually the earliest feature, followed by impairment of mental function and later, sphincter incontinence. The reader should be alerted to the fact that the fully developed triad is not usually present in the early stages of the process. Grasp reflexes in the feet and falling attacks may also occur, but there are no Babinski signs. Headaches are infrequently a complaint, and there is no papilledema.


Neurology_Adams

Neurology_Adams. The gait disturbance that accompanies NPH may be of several different types, as discussed in Chap. 6. These are difficult to classify and only vaguely simulate the patterns observed in Parkinson disease or cerebellar ataxia, but certain features predominate. Most often, there is unsteadiness and impairment of balance and shortening of the step length, with the greatest difficulty being encountered on stairs and curbs (Fisher, 1982). Weakness and tiredness of the legs are frequent complaints, although examination discloses no paresis or ataxia. An impression of Parkinson disease may be conveyed, with short steps and slightly stooped, forward-leaning posture, but the resemblance is superficial because there is typically no shuffling, nor is there festination, rigidity, slowness of alternating movement, or tremor. Some patients present with unexplained falls, often helplessly backward, but on casual inspection the gait may betray little abnormality except a minimal reduction in step


Neurology_Adams

Neurology_Adams. movement, or tremor. Some patients present with unexplained falls, often helplessly backward, but on casual inspection the gait may betray little abnormality except a minimal reduction in step length and overall slowness. When the condition remains untreated, the steps become shorter, with more frequent shuffling and falls; eventually standing and sitting and even turning over in bed become impossible. Fisher referred to this advanced state as “hydrocephalic astasia–abasia.”


Neurology_Adams

Neurology_Adams. The mental changes in the cases we have encountered have been, broadly speaking, “frontal” in character and embodied mainly apathy, dullness in thinking and actions, and slight inattention. Memory trouble is eventually a component of the overall problem and has been predominant in some cases, for which reason the diagnosis of Alzheimer disease is sometimes considered before the discovery of hydrocephalus, but as a rule, the gait derangement of NPH is fairly obvious by the time memory function is substantially impaired. There is usually a degree of affective indifference, but the patient reports little in the way of emotionality. Patients who display gait difficulty with prominent and progressive verbal, graphical, and calculation difficulties are more likely to have a degenerative or cerebrovascular disease. In those cases, the difficulty with walking and stability is ostensibly a result of frontal lobe disease, either degenerative or infarctive, as discussed in Chap. 6.


Neurology_Adams

Neurology_Adams. or cerebrovascular disease. In those cases, the difficulty with walking and stability is ostensibly a result of frontal lobe disease, either degenerative or infarctive, as discussed in Chap. 6. Unfortunately, beyond the above-noted defects that are elicitable by routine testing, we have not found neuropsychologic tests of great value in the diagnosis of NPH.


Neurology_Adams

Neurology_Adams. Urinary symptoms appear relatively later in the illness. Initially, they consist of urinary urgency and frequency. Later, the urgency is associated with incontinence, and ultimately there is frontal lobe incontinence,” in which the patient is indifferent to his lapses of continence, and bowel control becomes similarly disordered.


Neurology_Adams

Neurology_Adams. The cause of the syndrome of NPH in most cases cannot be established and on weak grounds, asymptomatic fibrosing meningitis is often presumed to have been present. An uncertain proportion of cases can be traced to congenital aqueductal stenosis that has allowed normal brain function into adulthood and, for unknown reasons, decompensates; a few of our patients have become symptomatic after mild head trauma. This is probably the most common imputed cause of the syndrome but again, on uncertain grounds. An identical syndrome may follow subarachnoid hemorrhage from ruptured aneurysm, resolved acute meningitis or a chronic meningitis (tubercular, fungal, syphilitic, or other), Paget disease of the base of the skull, mucopolysaccharidosis of the meninges, and achondroplasia.


Neurology_Adams

Neurology_Adams. That the mechanical effect of ventricular enlargement on the adjacent brain is responsible for the syndrome is supported by Fisher’s observations (2002) that a reduction in ventricular size caused by extrinsic compression from subdural collections has been associated with clinical improvement. One presumes that the main clinical features are due to dysfunction of the frontal lobes and their connections with the striatum, from mechanical pressure or distortion, but this is conjecture. Diagnosis of NPH


Neurology_Adams

Neurology_Adams. Verification of the diagnosis of NPH, and the selection of patients for ventriculoatrial or ventriculoperitoneal shunt has presented difficulties. The CT scan, as shown in Fig. 29-4, displays enlarged ventricles without convolutional atrophy. This disproportionate enlargement of the ventricular system in comparison to the degree of cortical atrophy is judged by the CT and MRI appearance, but there is no broadly agreed upon method for its determination. Various unwieldy formulas have been designed to assess this ratio. As a group, patients who have a sustained response to drainage of CSF by shunting, as described below, have had the first two elements of the clinical triad (fewer than half of our successfully treated patients have reached the point of incontinence) and their lateral ventricular span at the level of the anterior horns has been in excess of approximately 39 mm (a true dimension calculated from CT or MRI scans). MRI may show some degree of transependymal egress of water


Neurology_Adams

Neurology_Adams. span at the level of the anterior horns has been in excess of approximately 39 mm (a true dimension calculated from CT or MRI scans). MRI may show some degree of transependymal egress of water surrounding the ventricles, but this is not usually the case, and this sign is sometimes difficult to differentiate from the periventricular white matter change that is ubiquitous in the elderly. There may be an indication of inadequate pulsatile flow of CSF through the aqueduct as appreciated on T2-weighted MRI.


Neurology_Adams

Neurology_Adams. A lumbar puncture is often performed for diagnostic purposes and the pressure measured carefully but here too, there is no uniformly agreed upon approach. In most cases of NPH, the CSF pressure is above 150 mm H2O with the patient fully relaxed, but the disorder has occurred, at least as judged by improvement with shunting, with lower pressures, in a few instances as low as 120 mm H2O. Drainage of large amounts of CSF (20 to 30 mL or more) by lumbar puncture often results in clinical improvement in stance and gait for a few days, usually with a delay of hours or a day after the puncture so the patient and family must be depended upon to report these changes and these reports are prone to excessive optimism. Objective improvement in gait after spinal drainage, measured by reduced time to walk a predetermined distance and fewer steps than prior to drainage, is one way to select patients for shunt operations when the clinical picture is not entirely clear, but the even this test is not


Neurology_Adams

Neurology_Adams. walk a predetermined distance and fewer steps than prior to drainage, is one way to select patients for shunt operations when the clinical picture is not entirely clear, but the even this test is not infallible. Several small series suggest that a negative test does not preclude benefit from shunting (see Walchenbach et al). However, in these same series, improvement after removal of CSF has had a high predictive value for success of shunting.


Neurology_Adams

Neurology_Adams. When there has been doubt as to the effects of lumbar puncture, one appropriate course is to admit the patient to the hospital, and insert a lumbar drain for up to 3 days, removing approximately 50 mL of CSF daily in order to observe the response in gait and mentation. It is worthwhile to quantify the speed and facility of gait two or three times before the lumbar puncture or drainage and to perform this testing at periodic intervals for several days after the procedure in order to be certain that improvement is genuine. Even more persuasive is a definite improvement followed days later by worsening of gait.


Neurology_Adams

Neurology_Adams. Monitoring of CSF pressure over a day or more may show intermittent rises of pressure, possibly corresponding to the A-waves of Lundberg, but this undertaking is not generally practical and is now done by only a few centers. According to Katzman and Hussey, the infusion of normal saline into the lumbar subarachnoid space at a rate of 0.76 mL/min in NPH provokes a rise in pressure to greater than 300 mm H2O that is not observed in normal individuals. Theoretically, this test or any of its derivatives, such as the one proposed by Børgesen and Gjerris, should reflect the adequacy of CSF absorption, but they too, have yielded unpredictable results. Radionuclide cisternography had been used in the past to demonstrate persistence of CSF labeling in the ventricles and, although we still use it occasionally in uncertain cases of NPH, it is no longer considered a compelling test. Treatment of NPH in Adults


Neurology_Adams

Neurology_Adams. Treatment of NPH in Adults The development of ventricular shunt tubing with one-way valves opened the way to successful treatment of hydrocephalus. CSF is diverted directly into the peritoneal cavity (ventriculoperitoneal shunt), or less often, a ventriculoatrial or ventriculopleural shunt is used. The valve can be selected for a desired fixed opening pressure, or a variable valve can be inserted and adjustments can be made by an external magnetic device. Gratifying success can be obtained, often a complete or nearly complete restoration of mental function and gait after several weeks or months, by the placement of a shunt.


Neurology_Adams

Neurology_Adams. The most consistent improvement has been attained in the minority of patients in whom a cause can be established (subarachnoid hemorrhage, chronic meningitis, or tumor of the third ventricle). As already noted, other predictors of success are considerable enlargement of the ventricles in comparison to the degree of cortical atrophy, CSF pressures above 150 mm H2O, and improvement after spinal puncture, but none of these is entirely dependable.


Neurology_Adams

Neurology_Adams. Deviations from the characteristic syndrome such as the occurrence of dementia without gait disorder or the presence of apraxias, aphasias, and other focal cerebral signs are associated with poorer outcomes after shunting. Fisher, on analyzing successfully shunted cases, noted that almost without exception, gait disturbance was an early and prominent symptom. Uncertainties of diagnosis increase with advancing age owing to the frequent association of degenerative dementia and vascular lesions. However, in Fisher’s experience, age alone did not exclude NPH as a cause of gait disorder, and long duration of gait symptoms did not preclude a salutary outcome from shunting. In patients who are averse to the shunting procedure or who have medical conditions that make the surgery inadvisable, it is sometimes possible to produce a reasonable improvement in gait by repeating the drainage of large amounts of fluid every few weeks. It is usually feasible to discontinue anticoagulants for a brief


Neurology_Adams

Neurology_Adams. is sometimes possible to produce a reasonable improvement in gait by repeating the drainage of large amounts of fluid every few weeks. It is usually feasible to discontinue anticoagulants for a brief period to accommodate shunting or lumbar puncture but the small risk of stroke in patients with atrial fibrillation or cardiac valvular diseases must be considered.


Neurology_Adams

Neurology_Adams. Between the many reported series of NPH treated with shunting, outcomes vary greatly—almost certainly in part dependent on the accuracy of the initial diagnosis and the duration of symptoms. For example, 45 patients reported by Shaw and associates, 69 percent improved in speed of gait, 63 percent improved at least 2 points in MMSE (mini-mental status examination), and 69 percent improved in UPDRS, a standard overall score of assessing Parkinson disease (Chap. 38). While only 38 percent improved on multiple measures, only 15 percent improved on none. These are representative or better than other comparable series. Gauging what happens to incontinence after shunting is difficult and there is little information but we have had patients with advanced disease who reported some improvement, contrary to the usual dictum. Not all neurologists agree to such an optimistic assessment of the benefits of shunting and they also point to the limited durability of effect in case series, such as the


Neurology_Adams

Neurology_Adams. to the usual dictum. Not all neurologists agree to such an optimistic assessment of the benefits of shunting and they also point to the limited durability of effect in case series, such as the one from Kahlon and colleagues with long-term follow-up, and high rate of complications, approximately 10 percent in some series (see editorial by Saper in response to AAN Guidelines).


Neurology_Adams

Neurology_Adams. The potential failure of shunting must be anticipated in patients whose clinical features do not conform to the typical syndrome or whose disease has advanced to the stage of long-standing incontinence or dementia. In some in stances, a lack of improvement, or marked improvement followed by subacute deterioration is explained by inadequate decompression, which justifies a revision of the shunt or downward adjustment of a variable pressure valve. Overdrainage causes headaches that may be chronic or orthostatic and may be associated with small subdural collections of fluid. These fluid collections, or hygromas, consisting of CSF and proteinaceous fluid derived from blood products, are generally innocuous and do not require drain age unless they enlarge or cause focal neurologic symptoms or, rarely, seizures.


Neurology_Adams

Neurology_Adams. Although shunting is relatively simple as a surgical procedure, it has complications, the main ones being a postoperative subdural hematoma (the bridging dural veins stretch and rupture but the procedure has been performed safely in patients who must take anticoagulants after shunting); infection of the valve and catheter, sometimes with ventriculitis and occasionally bacteremia; occlusion of the tip of the catheter in the ventricle; and, particularly in infants and children, the “slit ventricle syndrome” (see below). Orthostatic headaches can be overcome by raising the opening pressure of the shunt valve. Misplacement of the catheter may rarely transect tracts in the deep hemispheral white matter and cause serious neurologic deficits, mainly hemiplegia. It is our impression that this occurs more often when the catheter is inserted from the posterior rather than through the frontal or parietal regions. The incidence of catheter blockage is reduced by placing it in the anterior horn of


Neurology_Adams

Neurology_Adams. more often when the catheter is inserted from the posterior rather than through the frontal or parietal regions. The incidence of catheter blockage is reduced by placing it in the anterior horn of the ventricle (usually the right side is used), where there is no choroid plexus. Meticulous aseptic technique and the preoperative and postoperative administration of antibiotics have apparently reduced the incidence of shunt infections but the latter has been difficult to establish. Most shunts in adults are brought to termination in the peritoneum (ventriculoperitoneal shunt). Perforation of the stomach or bowel is possible. Rare complications of ventriculoatrial shunting are pulmonary hypertension and pulmonary embolism and nephritis, which are caused by low-level infection of the shunt tube with Staphylococcus.


Neurology_Adams

Neurology_Adams. Puncture of the floor of the third ventricle by endoscopic techniques (“third ventriculostomy”) has been explored as an alternative to shunting, especially in children with congenital aqueductal stenosis. Cinalli and colleagues have suggested, and we concur based on experience with a limited number of our own adult patients, that third ventriculostomy is sometimes an effective treatment of shunt failure but Sankey et al had disappointing long-term results when the procedure was used as a primary approach.


Neurology_Adams

Neurology_Adams. Once the CSF is shunted, the ventricles may diminish in size within a week or two, even when the hydrocephalus has been present for a year or more. This indicates that hydrocephalic compression of the cerebrum is at least partly reversible. Indeed, in Black’s series, the ventricles failed to return to normal in only 1 of his 11 shunted patients, and in that patient, there was no clinical improvement. Clinical improvement occurs within a few weeks, the gait disturbance being slower to reverse than the mental disorder. Symptoms of cerebral atrophy because of Alzheimer disease and related conditions are not altered by shunting, but this approach to the treatment of degenerative dementia has been periodically, and unadvisedly, resurrected, as discussed by Silverberg and associates.


Neurology_Adams

Neurology_Adams. The use of acetazolamide to reduce CSF volume and pressure has gone through periods of popularity for treating NPH in adults (comments about its use in children are found below) and Alperin et al have shown imaging changes of reduced periventricular white matter changes, presumed to be a reflection of transependymal transgression of water, but clinical effects in our patients have been minimal. A few case series. For example, by Aimard and colleagues have reported benefit. Treatment of Infantile and Childhood Hydrocephalus


Neurology_Adams

Neurology_Adams. Here one encounters more difficulties than in the treatment of the adult disorder. The ventricular catheter may wander or become obstructed and require revision. Peritoneal pseudocysts may form (most shunts in children are ventriculoperitoneal). Another unexpected complication has been collapse of the ventricles, the so-called “slit ventricle” syndrome (the appearance of the ventricles on imaging studies is slit-like). This occurs more frequently in young children, although we have observed it in adults. These patients develop an intracranial low-pressure syndrome with severe generalized headaches, often with nausea and vomiting, whenever they sit up or stand. Some children become ataxic, irritable, or obtunded, or may vomit repeatedly. The CSF pressure is extremely low and the volume of CSF is much reduced. In babies, the cranium may fail to grow even though the brain is of normal size. In most shunted patients with slit ventricle syndrome, the ICP in the upright position is


Neurology_Adams

Neurology_Adams. of CSF is much reduced. In babies, the cranium may fail to grow even though the brain is of normal size. In most shunted patients with slit ventricle syndrome, the ICP in the upright position is diminished to 30 mm H2O. To correct the condition, one would imagine that replacing the shunt valve with another that opens under a higher pressure or raising the opening pressure of an adjustable valve would suffice. Indeed, this may be successful. But once the condition is established, the most effective measure has been the placement of an antisiphon device, which prevents valve flow when the patient stands. (See further on for a discussion of intracranial hypotension in adults.)


Neurology_Adams

Neurology_Adams. Whether to shunt all hydrocephalic infants soon after birth is a controversial issue. In several series of cases that have been treated in this way, the number surviving with normal mental function has been small (see review of Leech and Brumback). The report of Dennis and associates is representative. They examined 78 shunted hydrocephalic children and found that 56 (72 percent) had full-scale IQs between 70 and 100; in 22 patients, the IQ was between 100 and 115; in 3 patients, it was below 70, and in 3 others, it was above 115. Mental functions improved unevenly and performance scores lagged behind verbal ones at all levels.


Neurology_Adams

Neurology_Adams. The use of the carbonic anhydrase inhibitor acetazolamide or other diuretics to inhibit CSF formation in children with hydrocephalus has not been successful in the hands of our colleagues, but several authors believe that by giving 250 to 500 mg of acetazolamide orally daily, shunting can be avoided in both adult normal-pressure, and infantile hydrocephalus (Aimard et al; Shinnar et al).


Neurology_Adams

Neurology_Adams. Usually in the context of adult hydrocephalus due to aqueductal stenosis, a rare but distinct parkinsonian syndrome occurs that may be responsive to levodopa (Zeidler). It is particularly prone to occur if there is shunted hydrocephalus and has also been a craniotomy without replacement of the bone. The syndrome usually indicates failure of the shunt. MRI sometimes shows periaqueductal and dorsal midbrain edema, including in the region of the substantia nigra (see Fig. 29-5); the mechanism of these changes is not clear. Positron emission tomography with 18FDOPA has given evidence of reduced uptake in the caudate and putamen, suggesting a functional failure of the nigrostriatal dopamine system (Racette). Shunt malfunction in children also may be heralded by upward gaze palsy (“setting-sun sign”) or even a dorsal midbrain (Parinaud) syndrome, including abnormal papillary reaction, upper lid retraction, paralysis of convergence, skew deviation, and convergence–retraction nystagmus.


Neurology_Adams

Neurology_Adams. sign”) or even a dorsal midbrain (Parinaud) syndrome, including abnormal papillary reaction, upper lid retraction, paralysis of convergence, skew deviation, and convergence–retraction nystagmus. Shunting or shunt revision usually leads to reversal of both syndromes, but there may be a delay of days or weeks and it is often difficult to find the ideal pressure setting for the valve.


Neurology_Adams

Neurology_Adams. Occlusion of the major dural venous sinuses (superior longitudinal and lateral) results in increased ICP. This is not surprising in view of the direct effect of venous obstruction on CSF pressure. One such form, caused by lateral sinus thrombosis, was referred to by Symonds as “otitic hydrocephalus,” a name that he later conceded was inaccurate insofar as the ventricles are not enlarged in this circumstance. Venous congestion that complicates heart failure and superior mediastinal obstruction also raise the CSF pressure, again without enlargement of the ventricles. This may happen as well with large, high-flow arteriovenous malformations of the brain. The effects of cerebral venous occlusion are considered further in the discussion of pseudotumor cerebri (below) and in Chap. 33 in the context of thrombosis of the cerebral venous sinuses. The role of compression of the large venous channels in cases of raised ICP from a mass has not been fully explored, but it may explain some of the


Neurology_Adams

Neurology_Adams. of thrombosis of the cerebral venous sinuses. The role of compression of the large venous channels in cases of raised ICP from a mass has not been fully explored, but it may explain some of the intractable aspects of these cases.


Neurology_Adams

Neurology_Adams. This term was coined by Nonne in 1914 and has remained a useful means of designating a syndrome of headache, papilledema (unilateral or bilateral), minimal or absent focal neurologic signs, and normal CSF composition, all occurring in the absence of enlarged ventricles, or an intracranial mass on CT scanning, or MRI. Being a syndrome and not a disease, pseudotumor cerebri has a number of causes or pathogenetic associations. However, the most common form of the syndrome has no firmly established cause, that is, it is idiopathic and is generally referred to as idiopathic intracranial hypertension.


Neurology_Adams

Neurology_Adams. This syndrome was described in 1897 by Quincke, who called it “serous meningitis.” It is particularly frequent in overweight adolescent girls and young women, attaining an incidence of 19 to 21 per 100,000 in this group, as compared with 1 to 2 per 100,000 in the general population (Radhakrishnan et al). The features of increased ICP develop over a period of weeks or months. Relatively unremitting but fluctuating headache, described as dull or a feeling of pressure, is the cardinal symptom; it can be mainly occipital, generalized, or somewhat asymmetrical. Other, less-frequent complaints are blurred vision, a vague dizziness, minimal horizontal diplopia, transient visual obscurations that often coincide with the peak intensity of the headache, shoulder and neck pains, or a trifling numbness of the face on one side. Rarely, the presenting feature may be a nasal CSF leak, as pointed out by Clarke and colleagues. Self-audible bruits have been reported by some patients; this has been


Neurology_Adams

Neurology_Adams. of the face on one side. Rarely, the presenting feature may be a nasal CSF leak, as pointed out by Clarke and colleagues. Self-audible bruits have been reported by some patients; this has been attributed to turbulence created by differences in pressure between the cranial and jugular veins.


Neurology_Adams

Neurology_Adams. The patient is then discovered to have flagrant papilledema, raising the specter of a brain tumor. Rarely, papilledema is only minimally developed or absent or, conversely, papilledema alone, without headache, is the only manifestation of the disease. The risk of visual loss, and the severity of headache make the formerly used term benign intracranial hypertension less appropriate. The CSF pressure is found to be elevated by lumbar puncture, usually in the range of 250 to 450 mm H2O, but it is not clear whether the brain itself is swollen or, as is more likely, the increased pressure is the result of a change in the pressure within the CSF and venous compartments. When the CSF pressure is monitored for many hours, there are fluctuations taking the form of irregularly occurring plateau waves of increased pressure lasting 20 to 30 min, and then falling abruptly near to normal (Johnston and Paterson).


Neurology_Adams

Neurology_Adams. Aside from papilledema, there is remarkably little to be found on neurologic examination, perhaps slight unilateral or bilateral abducens palsy, fine nystagmus on far lateral gaze, or minor sensory change on the face or trunk. Visual field testing usually shows minor peripheral constriction with enlargement of the blind spots. As the process continues, more severe constriction of the fields, with greater nasal or inferior nasal loss, is found, often inevident to the patient. These issues are elaborated below. Enlargement of the blind spot is the result of displacement of the retina from the edges of the swollen disc. Central acuity is spared initially and the patient, in advanced cases, is left with an island of preserved central vision. These patients are at particular risk of visual loss. A study of 66 men with pseudotumor (9 percent of a larger cohort) by Bruce and colleagues suggested that there is a higher risk of vision loss than in women. Profound disc edema, significant early


Neurology_Adams

Neurology_Adams. A study of 66 men with pseudotumor (9 percent of a larger cohort) by Bruce and colleagues suggested that there is a higher risk of vision loss than in women. Profound disc edema, significant early visual loss and perhaps being of African-American descent are other risks for visual loss.


Neurology_Adams

Neurology_Adams. Exceptionally, particularly in children, an otherwise typical Bell’s palsy may occur (Chutorian et al). Mentation and alertness are preserved, and the patient seems surprisingly well aside from the headaches, which infrequently become severe enough to limit daily activity. Examinations by CT and MRI show the ventricles to be normal in size or small. The sella may be enlarged and filled with CSF (see “empty sella” in Chap. 30), the posterior globes may be compressed and the perioptic subarachnoid spaces, expanded. Variable attenuation of the transverse sinuses has also been pointed out (see Friedman and colleagues). These are helpful but not indispensible features of the syndrome. There is no MRI evidence of change in the density of the brain, but edema may be seen in the optic nerves.


Neurology_Adams

Neurology_Adams. In recent years, attention has been called to the ostensibly high rate of overdiagnosis of pseudotumor, for example, by Fisayo and colleagues in a large neuro-ophthalmology clinic. Almost 40 percent of cases referred to them probably had other diagnoses and the main sources of error included poor or misinterpreted ophthalmoscopic examination of the optic nerve. Benign headaches in obese women were responsible for many of their reported cases when strict criteria for the diagnosis of pseudotumor were applied.


Neurology_Adams

Neurology_Adams. As remarked above, most affected patients are overweight young women of short stature, often with menstrual irregularities, but the condition also occurs in children or adolescents, in whom there is no clear sex predominance, and in men (Digre and Corbett). We have had experience with several familial instances of pseudotumor, for example, affecting mother and daughter. In obese women without the pseudotumor syndrome, CSF pressure usually does not differ from that of normal individuals (Corbett and Mehta).


Neurology_Adams

Neurology_Adams. Several endocrine and menstrual abnormalities (particularly amenorrhea), as well as the use of oral contraceptives, have been postulated as causative factors, but none has been substantiated. Cases have been reported during pregnancy, both those who have symptoms for the first time during pregnancy and a larger group with ongoing pseudotumor who become pregnant. Despite the theoretical appeal of relating the endocrine and other changes of pregnancy to the increased ICP, no suitable connection has been found, and there is no evidence that premature delivery or termination of the pregnancy ameliorates the pseudotumor. Nevertheless, our obstetric colleagues have often recommended delivery when safe for the fetus if the mother’s vision is threatened. Most of the standard medical treatments detailed below have been used with some benefit during pregnancy, as in the series reported by Huna-Baron and Kupersmith.


Neurology_Adams

Neurology_Adams. The mechanism of increased CSF pressure in the idiopathic form of the disorder has remained elusive, but some experience suggests that, in at least some cases, there is a functional obstruction to outflow in the venous sinuses. Karahalios and colleagues and others have found the cerebral venous pressure to be elevated in pseudotumor cerebri; in half of their patients, there was a venous outflow obstruction demonstrated by venography with a pressure gradient across the site of narrowing of the venous sinus. A related finding in some cases, pointed out to us some time ago by Fishman (1984), is one of partial obstruction of the lateral sinuses by enlarged pacchionian granulations (seen during the venous phase of conventional angiography). It is here that the evidence for a venous cause of pseudotumor has been most persuasive. Several authors have proposed that venous hypertension increases the resistance to CSF absorption and is the proximate mechanism underlying pseudotumor. Similarly,


Neurology_Adams

Neurology_Adams. has been most persuasive. Several authors have proposed that venous hypertension increases the resistance to CSF absorption and is the proximate mechanism underlying pseudotumor. Similarly, Farb and colleagues, using sophisticated MRI venography, found venous stenosis in 27 of 29 patients with pseudotumor (and in 4 of 59 control subjects). In both studies and in others similar ones, the nature of the obstruction was not clear, but the fact that in some cases it was bilateral and focal suggests that the stenosis was not simply the passive result of raised ICP. This issue is not yet resolved, as noted below.


Neurology_Adams

Neurology_Adams. Intervention by stenting of a venous sinus at the sites of apparent obstruction has resulted in clinical improvement and a reduction in CSF pressure. For example, 5 of 12 patients treated by Higgins and colleagues became asymptomatic, but this was a population selected by the demonstration of a focal pressure gradient in the lateral sinus during venography. Karahalios and colleagues had similar success in several patients. What is not clear is how prevalent these partial venous obstructions are and what precisely is their nature (if not simply enlarged granulations). In some series, the abnormality has been found in 10 to 25 percent of patients who lack any features of pseudotumor (Leach et al). We have seen an obese patient of short stature who presented with typical pseudotumor cerebri, but who was found to have, in addition, anticardiolipin antibodies that resulted in thrombosis of the right transverse sinus; lysis of the clot led to resolution of the pseudotumor syndrome.


Neurology_Adams

Neurology_Adams. In an attempt to settle the role of the venous stenosis, King and colleagues measured intracranial venous pressure while withdrawing spinal fluid from the cervical subarachnoid space in patients with idiopathic pseudotumor cerebri. Their observation that the intracranial venous pressure drops immediately upon the reduction in CSF pressure supports the notion that the increased venous pressure is secondary. Furthermore, they describe patients with pseudotumor and normal venous pressures in the sagittal and transverse sinuses. The unsatisfactory nature of all the currently offered theories of causation of pseudotumor cerebri are reviewed by Walker, but at the moment our reading of the literature suggests that venous stenosis from granulations or from some as yet undefined functional change, may account for a proportion of what had previously been considered to be idiopathic cases. How the venous changes relate to obesity and sex is also unclear. Perhaps some individuals have a


Neurology_Adams

Neurology_Adams. change, may account for a proportion of what had previously been considered to be idiopathic cases. How the venous changes relate to obesity and sex is also unclear. Perhaps some individuals have a congenital configuration of the venous sinuses that is exaggerated with obesity and elevated systemic venous pressures.


Neurology_Adams

Neurology_Adams. Some additional comments about the physiologic changes in CSF flow and pressure in relation to alternative mechanisms of pseudotumor may be informative. Using the method of constant infusion manometrics, Mann and coworkers demonstrated an increased resistance to CSF outflow, in their view, caused by an impaired absorptive function of the arachnoid villi. Other authors have attributed intracranial venous hypertension to raised intraabdominal and cardiac filling pressures, the mechanical result of obesity (Sugerman et al, 1995). On inconclusive evidence, benign intracranial hypertension was in the past attributed to an increase in brain volume secondary to an excess of extracellular fluid or blood volume within the cranium (Sahs and Joynt, Raichle et al). An interesting related finding has been an elevated level of vasopressin in the CSF but not in the blood (Seckl and Lightman). In the goat, this peptide causes a rise in ICP and a reduction in CSF absorption, raising the possibility


Neurology_Adams

Neurology_Adams. been an elevated level of vasopressin in the CSF but not in the blood (Seckl and Lightman). In the goat, this peptide causes a rise in ICP and a reduction in CSF absorption, raising the possibility that the pseudotumor state is caused by an aberration of the transit of water in the cerebrum.


Neurology_Adams

Neurology_Adams. Finally, Jacobson and colleagues have made the observation that serum vitamin A levels (in the form of retinol) are 50 percent higher than expected, in patients with pseudotumor—a difference that is not explained by obesity. Because the levels were considerably lower than in cases of hypervitaminosis A with symptomatic forms pseudotumor (see in the following section), the meaning of these findings is uncertain. Symptomatic Causes of Pseudotumor Cerebri (See Table 29-1)


Neurology_Adams

Neurology_Adams. The main considerations in cases of generalized elevation of ICP and papilledema in the absence of an intracranial mass are, foremost, covert occlusion of the dural venous sinuses and then, a list of less-common conditions, including gliomatosis cerebri, occult arteriovenous malformation, and carcinomatous, infectious, or granulomatous meningitis. Although occlusion of the dural venous sinuses and their large draining veins is sometimes equated with pseudotumor, these cases are not, of course, idiopathic. When papilledema occurs in the context of a persistent headache, particularly if the cranial pain is centered near the vertex or medial parietal areas or if there are seizures, venous occlusion is likely. Venous sinus thrombosis can be detected in most instances by careful attention to the appearance of the superior sagittal and transverse sinuses on the T1-weighted MRI or on the contrast-enhanced CT scan, as discussed in Chap. 33 under “Thrombosis of Cerebral Veins and Venous


Neurology_Adams

Neurology_Adams. to the appearance of the superior sagittal and transverse sinuses on the T1-weighted MRI or on the contrast-enhanced CT scan, as discussed in Chap. 33 under “Thrombosis of Cerebral Veins and Venous Sinuses.” Isolated cortical vein thrombosis on the cerebral convexity does not cause pseudotumor (but does induce seizures).


Neurology_Adams

Neurology_Adams. A large cerebral arteriovenous malformation (AVM), by causing an increase both of venous pressure and cerebral blood volume, can give rise to a pseudotumor syndrome. In a few of our cases, these changes in the physiology of the cerebral circulation were made evident by the appearance of early venous flow on the angiogram or by thrombosis of the superior sagittal sinus.


Neurology_Adams

Neurology_Adams. Several systemic diseases that are associated with raised CSF protein concentration have given rise to a pseudotumor syndrome, including the Guillain-Barré syndrome, systemic lupus, and spinal tumors, particularly oligodendroglioma. Elevated spinal fluid pressure has been attributed to a blockage of CSF absorption by the proteinaceous fluid in Guillain-Barré syndrome, but this mechanism has never been validated and fails to explain those few instances in which pseudotumor syndromes has been associated with a near-normal protein content of the CSF. This explanation is even less compelling if one recalls that the protein concentration of the fluid in the cerebral spaces is considerably lower than in the spinal ones. Also, as we have pointed out, when calculated correctly, neither the resistance to CSF absorption nor the colloid osmotic effect attributable to an increased protein content in the spinal fluid is adequate to explain the pressure elevation (Ropper and Marmarou). The


Neurology_Adams

Neurology_Adams. resistance to CSF absorption nor the colloid osmotic effect attributable to an increased protein content in the spinal fluid is adequate to explain the pressure elevation (Ropper and Marmarou). The mechanism of this type of pseudotumor syndrome is presently unknown.


Neurology_Adams

Neurology_Adams. In addition to mechanical factors, a number of toxic and metabolic disturbances may give rise to a pseudotumor syndrome. In children, as chronic corticosteroid therapy is withdrawn, there may be a period of headache, papilledema, and elevated ICP with little or no enlargement of the lateral ventricles. Lead toxicity in children may be marked by brain swelling and papilledema. Excessive doses of tetracycline (particularly outdated medication) and vitamin A (particularly in the form of isotretinoin, an oral vitamin A derivative used in the treatment of severe acne) also have been shown to cause intracranial hypertension in children and adolescents. Ingestion of large quantities of bear liver by hunters is another curious source of intoxication with vitamin A underlying pseudotumor. Isolated instances of hypoor hyperadrenalism, myxedema, and hypoparathyroidism have been associated with increased CSF pressure and papilledema, and occasionally the administration of estrogens,


Neurology_Adams

Neurology_Adams. Isolated instances of hypoor hyperadrenalism, myxedema, and hypoparathyroidism have been associated with increased CSF pressure and papilledema, and occasionally the administration of estrogens, phenothiazines, lithium, the antiarrhythmic drug amiodarone, and quinolone antibiotics has the same effect, for reasons not known.


Neurology_Adams

Neurology_Adams. The first step in differential diagnosis is to exclude an underlying tumor or the nontumorous causes of raised ICP, mainly dural venous occlusion, and meningeal inflammation. This can be accomplished by CT and MRI, although it should be borne in mind that certain chronic meningeal reactions (e.g., those caused by sarcoidosis or to tuberculous or carcinomatous meningitis), which give rise to headache and papilledema, may sometimes elude detection by these imaging procedures. In these cases, however, lumbar puncture will disclose the diagnosis. It should be emphasized that the diagnosis of idiopathic pseudotumor cerebri should not be accepted when the CSF content is abnormal.


Neurology_Adams

Neurology_Adams. Careful evaluations of the visual fields and of visual acuity is required soon after the diagnosis of idiopathic pseudotumor is established. Repeated examination of visual function, preferably in collaboration with an ophthalmologist, is essential in detecting early and potentially reversible visual loss. At the same time, it must be acknowledged that measurements of visual acuity (and of confrontation fields) are relatively insensitive means of detecting early visual loss and that abnormalities in these tests indicate that damage to the optic nerve head has already occurred. Quantitative perimetry, using the kinetic Goldmann technique, has been more informative than other methods. The neurologist probably is advised to refer the patient for perimetry as an adjunctive test. Fundus photographs are also a reasonable means of assessing the course of papilledema. A reduction in previously normal acuity to less than 20/20 corrected, enlargement of the blind spot, or the appearance of


Neurology_Adams

Neurology_Adams. are also a reasonable means of assessing the course of papilledema. A reduction in previously normal acuity to less than 20/20 corrected, enlargement of the blind spot, or the appearance of sector field defects, usually inferonasal, are indications for prompt treatment of raised ICP.


Neurology_Adams

Neurology_Adams. If intracranial hypertension and papilledema are left untreated or fail to respond to the measures outlined below, there is danger of permanent visual loss from compressive damage to the optic nerve fibers and compression of the central retinal veins. Corbett and associates, who described a group of 57 patients followed for 5 to 41 years, found severe visual impairment in 14, and Wall and George, using refined perimetric methods, reported an even higher incidence of visual loss. Moreover, children with pseudotumor share the same visual risks as adults (Lessell and Rosman). Sometimes, vision is lost abruptly, either without warning or following one or more episodes of monocular or binocular visual obscurations. Treatment of Pseudotumor Cerebri


Neurology_Adams

Neurology_Adams. This has proven difficult and a variety of methods have been proposed. The main concern, as alluded to earlier, is the prevention of visual loss but headache may become disabling enough to require special attention. Most patients with idiopathic intracranial hypertension will be found initially to have no, or minor visual changes aside from the papilledema; the headache and lumbar puncture pressure then guide treatment. Besides symptomatic relief of headaches, the progression of visual loss is the main concern. At least one-fourth of patients have recovered within 6 months after treatment by repeated lumbar punctures and drainage of sufficient CSF to maintain the pressure at normal or near-normal levels (<200 mm H2O). The lumbar punctures have been performed daily or on alternate days at first, and then at longer intervals, according to the level of pressure. While cumbersome and sometimes impractical, evidently, this is sometimes sufficient to restore the balance between CSF


Neurology_Adams

Neurology_Adams. days at first, and then at longer intervals, according to the level of pressure. While cumbersome and sometimes impractical, evidently, this is sometimes sufficient to restore the balance between CSF formation and absorption for at least several months. At the same time, weight loss has been encouraged and the best results have been reported when weight reduction was successful (see further on regarding weight loss).


Neurology_Adams

Neurology_Adams. This approach has been considered the first step in treatment for patients who are not losing visual acuity rapidly. Large doses of acetazolamide in the range of 1 to 5 g/d, are required and the expected side effects of paresthesias and nauseas may not be tolerated. Sustained use of the drug has a risk of kidney stones. Oral hyperosmotic agents—such as glycerol (15 to 60 mg four to six times daily), or furosemide 20 to 80 mg bid—to reduce CSF formation all have their advocates, but they generally have only a short-term impact on vision and headaches.


Neurology_Adams

Neurology_Adams. This is always advised if the patient is markedly overweight but is difficult to accomplish. In two pathologically obese patients, we have resorted to bariatric surgical approaches, which had a beneficial effect on the pseudotumor but left the patient for a time with the gastrointestinal disturbances that commonly complicate these procedures. Sugerman and associates (1999) studied 24 obese women with pseudotumor who had operations and found the results to be satisfactory over several years. Two of our patients developed a sensory polyneuropathy after surgery. The use of bariatric procedures is currently undergoing reevaluation for obesity in general, but in the circumstances of pseudotumor with visual loss, it is a reasonable alternative. The effect of weight loss in less overweight individuals is uncertain.


Neurology_Adams

Neurology_Adams. In patients whose headaches are unresponsive to the usual therapeutic measures—mainly acetazolamide and weight reduction—a treatment method that may have considerable temporary success is a lumbar–peritoneal shunt. Only a few of our patients have undergone this surgical procedure. It has been relatively safe and effective, but because of a tendency for the shunt to become obstructed or to be dislodged in obese patients, sometimes causing back or sciatic pain, the procedure has less appeal than in the past. Burgett et al, who treated 30 patients in this manner, reported success in reducing headache in almost all and in improving vision in 70 percent. Despite its shortcomings, this procedure may be preferable to the optic nerve fenestration described below. We have not had to resort to cranial subtemporal decompression, a procedure that was formerly used when vision was threatened.


Neurology_Adams

Neurology_Adams. Most authorities eschew the use of corticosteroids and have objected strenuously to their inclusion as a treatment for pseudotumor in previous editions of this book. Nevertheless, with the administration of prednisone (40 to 60 mg/d) we have occasionally observed a gradual recession of papilledema and a lowering of CSF pressure, but such responses were not consistent or sustained and it has been difficult to decide whether this represented the effect of treatment or the natural course of the disease. Greer, who reported on 110 patients, 11 of whom were treated with these agents, decided that they were of no value. Moreover, in patients whose papilledema seems to recede under the influence of corticosteroids, there is always a danger that it will recur when the drug is tapered. Considering the potential for undesirable side effects of corticosteroids, we have used them very sparingly and only for brief periods while preparing the patient for more definitive treatment.


Neurology_Adams

Neurology_Adams. Fenestration of the Optic Nerve Sheath For patients who are losing vision, unilateral fenestration of the optic nerve sheath is a procedure favored by some ophthalmologists. According to Corbett and colleagues, this procedure—which consists of partial unroofing of the orbit and the creation of an intraorbital window opening in the dural–arachnoid sheaths surrounding the optic nerve—effectively preserved or restored vision in 80 to 90 percent of patients. Even when the procedure is performed on only one side, its effect on vision is often bilateral and about two-thirds of patients have some relief of headache as well, although this has been transient in most of our patients.


Neurology_Adams

Neurology_Adams. However, the operation carries a moderately high risk of orbital vascular obstruction and unilateral visual loss, as happened in two of our patients. The causes of visual loss after this operation by various reports have included central retinal artery or vein occlusion, choroidal infarction, optic nerve trauma, hemorrhage into the nerve sheath, and infection. Over the past decades, enthusiasm for the procedure had diminished after publication of several series in which there was visual loss in 2 to 11 percent of patients. Some of these data come from studies of sheath fenestration for ischemic optic neuropathy, a condition not comparable to the disc swelling of pseudotumor. Follow-up studies have indicated that the reduction in ICP was limited to 1 year or less. As a result of recent reexamination of the complications of this procedure, considered to be lower than in the past, there is renewed interest for the procedure over lumbar peritoneal shunting. Relief of Venous Obstruction


Neurology_Adams

Neurology_Adams. Relief of Venous Obstruction In a number of patients, the CSF pressure remains elevated and the papilledema becomes chronic despite one of the above-described treatments. It is the management of this group that is the most difficult and controversial. A careful search should then be made for anatomic and hematologic causes that might underlie cerebral venous dural sinus disease. Sometimes it is useful to treat venous occlusion using interventional vascular techniques. In cases of venous thrombosis antiphospholipid antibody syndrome, sickle cell disease, hormonally induced clotting, and related disorders, medical measures may be tried first, but intravascular thrombolysis remains an option.


Neurology_Adams

Neurology_Adams. The more complex decision to apply stenting to the partial occlusion of the transverse sinus by generous pacchionian granulations should probably be guided by the same principles, that is, failure of medical treatment to adequately control CSF pressure, or relive the threat to vision. In a series of 10 patients with intractably raised CSF pressure and morphologic obstruction in the venous sinuses, Donnet and colleagues were able to provide complete relief by stenting in 6 patients and partial relief in 2 patients, with follow-up ranging from 6 to 36 months. In a summary of published cases and series of patients with pseudotumor cerebri treated by endovascular stenting of venous sinus stenosis, Arac and colleagues concluded that approximately 80 percent were relieved of their main symptoms, and a similar proportion showed resolution, or improvement in papilledema. This is a selected group of patients.


Neurology_Adams

Neurology_Adams. In summary, the clinician is left with only incomplete guidance as to the course of treatment of pseudotumor cerebri. In cases with no visual impairment and with moderate headaches, we have favored aggressive weight reduction, acetazolamide, and repeated lumbar punctures. For more severe cases, we perform careful vascular imaging and correction of venous sinus occlusions as noted above. Failing this, we have advised lumbar drainage to the peritoneum. If vision is imminently threatened, optic sheath fenestration is probably the best course.


Neurology_Adams

Neurology_Adams. We have been impressed with the persistence of a complex migraineor tension-like headache in some patients whose CSF pressure has been adequately reduced by repeated lumbar punctures, shunting, or optic nerve fenestration. After it has been confirmed that the pressure is not elevated, these headaches may be treated in a manner similar to the usual types of chronic headaches, as outlined in Chap. 9, especially with topiramate, which has the potential benefit of facilitating weight reduction. A recent review of the subject of surgical treatment, extensively referenced, has been given by Brazis. He was unable to conclude that any one approach was superior. These disorders, in which air enters the ventricular system or the subarachnoid spaces, are discussed in relation to cranial injury, and the postoperative state (see Chap. 34). In the case of pneumocranium, the collection of air may act as a mass that compresses adjacent brain tissue, and requires relief by aspiration.


Neurology_Adams

Neurology_Adams. INTRACRANIAL HYPOTENSION (SEE ALSO “LOW-PRESSURE AND SPINAL PUNCTURE HEADACHE” IN CHAP. 9)


Neurology_Adams

Neurology_Adams. After lumbar puncture, this syndrome is usually attributable to a lowering of ICP by leakage of CSF through the needle track into the paravertebral muscles. The headache may last for days or, rarely, weeks. Most characteristic is the relation of the cranial pain to upright posture, and its relief within moments after assuming the recumbent position. Actually, the syndrome includes more than headache. There may be pain at the base of the skull posteriorly and in the back of the neck and upper thoracic spine, mild stiffness of the neck and shoulders, and nausea and vomiting. At times, the signs of meningeal irritation are so prominent as to raise the question of postlumbar puncture meningitis, although lack of fever usually excludes this possibility. In addition to a low or unmeasurable CSF pressure if another spinal tap is performed (the CSF pressure is found to be in the range of 0 to 60 mm H2O), there are occasionally a few to a dozen white cells in the CSF, which may further raise


Neurology_Adams

Neurology_Adams. pressure if another spinal tap is performed (the CSF pressure is found to be in the range of 0 to 60 mm H2O), there are occasionally a few to a dozen white cells in the CSF, which may further raise concern of meningitis. In the infant or young child, stiffness of the neck may be accompanied by irritability, unwillingness to move, and refusal of food. If the headache is protracted, recumbency still reduces it, but a feeling of dull pressure may remain, which the patient continues to report as pain. Many patients also report that shaking the head produces a cephalic pain. Occasionally, there will be unilateral or bilateral sixth nerve palsy or a self-audible bruit from turbulence in the intracranial venous system. Hearing loss is a far less common complication (see Chap. 2). A rare syndrome that has been attributed to sagging of the frontal lobes in low CSF pressure situations (“brain-sagging syndrome”) has been described by Wicklund and coworkers. Patients are apathetic and


Neurology_Adams

Neurology_Adams. syndrome that has been attributed to sagging of the frontal lobes in low CSF pressure situations (“brain-sagging syndrome”) has been described by Wicklund and coworkers. Patients are apathetic and disinhibited and have prominent daytime somnolence, which the authors liken to frontotemporal dementia.


Neurology_Adams

Neurology_Adams. It has been recognized that low CSF pressure is associated on the MRI with variable dural enhancement by gadolinium (Fig. 29-6) and, when the syndrome is protracted and severe, there may be small subdural effusions (see in the following text). In older patients taking warfarin, a subdural hematoma may be found. The use of a 22to 24-gauge needle and the performance of a single clean (atraumatic) tap seemingly reduce the likelihood of a postlumbar puncture headache, as discussed in Chap. 2. A period of enforced recumbency, although widely practiced as a means of preventing headache, probably does not lessen its incidence (Carbaat and van Crevel). The ingestion of large volumes of fluids, the infusion of 1,000 to 2,000 mL of 5 percent glucose, and various forms of caffeine (see further on) are usually recommended, but are of uncertain benefit.


Neurology_Adams

Neurology_Adams. The most dependable treatment is a “blood patch” (spinal epidural injection of approximately 20 mL of the patient’s own blood). At least 75 percent of patients are thus relieved of the headache according to Safa-Tisseront and colleagues; they report that after a second injection, improvement occurs in 97 percent. Many patients have transient back or radicular pain (sciatica) following the blood patch. Curiously, the headache is often relieved almost immediately, even if the blood is injected at some distance from the original puncture (although the procedure is usually done at the same level as the previous spinal tap). Moreover, the volume of blood injected, usually about 20 mL, is not related to the chances of success. The mechanism of this rapid improvement, therefore, may not simply be the plugging of a dural leak. A number of patients fail to benefit or have only transient effects; it is then unclear whether repeating the procedure is helpful. The administration of


Neurology_Adams

Neurology_Adams. not simply be the plugging of a dural leak. A number of patients fail to benefit or have only transient effects; it is then unclear whether repeating the procedure is helpful. The administration of caffeine–ergotamine preparations or intravenous caffeine may also have a salutary, although temporary, effect on the orthostatic headache. The addition of analgesic medication is required if the patient must get up to care for himself or to travel. In protracted cases, patience is called for, as most headaches will resolve in 2 weeks or less.


Neurology_Adams

Neurology_Adams. As to mechanism, the pain is presumed to be from tugging on cerebral veins or assuming the upright position. Panullo and colleagues also showed that there is a downward displacement of the upper brainstem and posterior fossa contents when the patient assumes the upright position; but, as pointed out in Chap. 16, only rarely are there associated signs of brain herniation, the exceptions being some of the unusual cases discussed below. Miyazawa and colleagues have proposed that hypovolemia of the CSF, rather than lowered pressure, is the cause of downward displacement of the brain and dilatation of cerebral and spinal epidural veins. They propose that the buoyancy provided by the spinal fluid is lost in these cases.


Neurology_Adams

Neurology_Adams. The same problem of low pressure as that which follows lumbar puncture can occur after straining, a nonhurtful fall, or for no known reason. The cardinal feature is orthostatic headache and only rarely are there other neurologic complaints, such as diplopia from sixth-nerve palsy or a self-audible bruit. In these cases, the CSF pressure is low (60 mm H2O or less) or not measurable; the fluid may contain a few mononuclear cells but is most often normal. A few cases have presented with stupor as a result of downward transtentorial displacement of the diencephalic region (Pleasure et al) or an upper cervical myelopathy caused by downward deformation and displacement of the spinal cord (Miyazaki et al). Some surveys suggest that patients with structural disorders of connective tissue are at greater risk for spontaneous CSF leaks than others. The Marfan and Ehlers-Danlos syndrome as well as autosomal dominant polycystic kidney disease are risk factors as summarized by Schievink.


Neurology_Adams

Neurology_Adams. In many such patients with ostensibly idiopathic low CSF pressure syndromes, there has been a tear in the delicate arachnoid surrounding a nerve root, with continuous leakage of CSF. The site of the leak is difficult to ascertain except when it occurs into the paranasal sinuses (causing CSF rhinorrhea). In a series of 11 patients with spontaneous intracranial hypotension, a putative leak was found by radionuclide cisternography or CT myelography (the preferred procedure by many clinicians) in the cervical region or at the cervicothoracic junction in 5 patients, in the thoracic region in 5, and the lumbar region in 1 (Schievink et al). In the patients who underwent surgical repair, a leaking meningeal diverticulum (Tarlov cyst) was found and could be ligated. This seems to be the most common structural cause, for which reason, we usually undertake a spinal MRI as the first study in obscure cases of leak. A blood patch, as described above, may be useful and should be attempted before