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Clinical Director, New York University School of Medicine

Thyroid ophthalmopathy, discussed further on, presents in the similar fashion but without ptosis and is less common than myasthenia. Fortunately, in many cases of undetermined cause, the palsy disappears in a few weeks or months. Sixth Nerve Palsy Infarction of the sixth nerve is a common cause of sixth nerve palsy in diabetics, in which case there is usually pain near the outer canthus of the eye. An idiopathic form that occurs in the absence of diabetes- possibly atherosclerotic, arteritic, or phlebitic- is also well known. An isolated sixth nerve palsy with global headache, and more specifically when the palsy is bilateral, as mentioned below, frequently proves to be caused by neoplasm. In children, the most common tumor involving the sixth nerve is a pontine glioma; in adults, it is a metastatic tumor arising from the nasopharynx. Thus it is essential that the nasopharynx be examined carefully in every case of unexplained sixth nerve palsy, particularly if it is accompanied by sensory symptoms on the side of the face. As the abducens nerve passes near the apex of the petrous bone, it is in close relation to the trigeminal nerve. Both may be implicated by petrositis, manifest by facial pain and diplopia (Gradenigo syndrome). Fractures at the base of the skull and petrous clivus tumors may have a similar effect, and sometimes head injury alone is the only assignable cause, even in the absence of a fracture (as mentioned, fourth nerve palsy is a more common complication of closed cranial injury). Unilateral or bilateral abducens weakness may be a nonspecific sign of increased intracranial pressure from any source- including brain tumor, meningitis, and pseudotumor cerebri; rarely, it may appear after lumbar puncture, epidural injections, or insertion of a ventricular shunt. The type that arises with infarction of the rostral midbrain (pseudo-sixth) was described above. Occasionally the nerve is compressed by a congenitally persistent trigeminal artery. Fourth Nerve Palsy the fourth nerve is particularly vulnerable to head trauma (this was the cause in 43 percent of 323 cases of trochlear nerve lesions collected by Wray from the literature). The reason for this vulnerability has been speculated to be the long crossed course of the nerves. This reflects the relative infrequency of carotid artery aneurysms in the infraclinoid portion of the cavernous sinus, where they could impinge on the sixth nerve. Diabetic infarction of the fourth nerve occurs, but far less frequently than infarction of the third or sixth nerves. Trochlear nerve palsy may also be a false localizing sign in cases of increased intracranial pressure, but again not nearly as often as abducens palsy. Entrapment of the superior oblique tendon is a rare cause (Brown syndrome) in which, in addition to diplopia, there is focal pain at the corner of the orbit; hence it may be mistaken for the Tolosa-Hunt syndrome, discussed further on. Superior oblique myokymia is an unusual but easily identifiable condition, characterized by recurrent episodes of vertical diplopia, monocular blurring of vision, and a tremulous sensation in the affected eye. The problem is usually benign and responds to carbamazepine, but rare instances presage pontine glioma or demyelinating disease. Compression of the fourth nerve by a small looped branch of the basilar artery has been suggested as the cause of the idiopathic variety, analogous to several other better documented vascular compression syndromes affecting cranial nerves. Third Nerve Palsy the third nerve is commonly compressed by aneurysm, tumor, or temporal lobe herniation. In a series of 206 cases of third nerve palsy collected by Wray and Taylor, neoplastic diseases accounted for 25 percent and aneurysms for 18 percent. Of the neoplasms, 25 percent were parasellar meningiomas and 4 percent pituitary adenomas. As emphasized earlier, enlargement of the pupil is a sign of extramedullary third nerve compression because of the peripheral location in the nerve of the pupilloconstrictor fibers. By contrast, as indicated above, infarction of the nerve in diabetics usually spares the pupil, since the damage is situated in the central portion of the nerve. The oculomotor palsy that complicates diabetes (this was the cause in 11 percent of the Wray and Taylor series) develops over a few hours and is accompanied by pain, usually severe, in the forehead and around the eye.

If these patients are carefully observed as they get on and off an examining table or in and out of bed, they display poor management of the entire axial musculature, moving their bodies without shifting the center of gravity or adjusting their limbs appropriately. The erect posture is assumed in a very awkward manner- with hips and knees only slightly flexed and stiff and a delay in swinging the legs over the side of the bed. Sudarsky and Simon have quantified these defects by means of high-speed cameras and computer analysis. They report a reduction in height of step, an increase in sway, and a decrease in rotation of the pelvis and counterrotation of the torso. Walking is perceptibly slower than normal, the body is held stiffly and moves en bloc, arm swing is diminished, and there is a tendency to fall backwards- features that are reminiscent of the gait in Parkinson disease. It is a frequent feature of the lateral medullary syndrome, in which falling occurs to the side of the infarction. In patients with vestibular neuronitis, falling also occurs to the same side as the lesion. With the Tullio phenomenon (vertigo induced by loud, highpitched sounds or by yawning, due to a spontaneous or traumatic fenestration of the vestibule of the semicircular canal), the toppling is contraversive; with midbrain strokes, the falls tend to be backward. As with the related "frontal gait," described below, patients who have difficulty initiating gait or whose steps are so short as to be ineffective are helped by marching to a cadence or in step with the examiner. Frontal Lobe Disorder of Gait Standing and walking may be severely disturbed by diseases that affect the frontal lobes, particularly their medial parts and their connections with the basal ganglia. This disorder is sometimes spoken of as a frontal lobe ataxia or as an "apraxia of gait" among numerous other labels, since the difficulty in walking cannot be accounted for by weakness, loss of sensation, cerebellar incoordination, or basal ganglionic abnormality. Patients with so-called apraxia of gait do not have apraxia of individual limbs, particularly of the lower limbs; conversely, patients with apraxia of the limbs usually walk normally. More likely, the disorder represents a loss of integration, at the cortical and basal ganglionic levels, of the essential instinctual elements of stance and locomotion that are acquired in infancy and often lost in old age. As a shorthand, they are listed here as "frontal"; in any case, most cases of central gait disorder are accompanied by a degree of frontal lobe dementia. Patients assume a posture of slight flexion with the feet placed farther apart than normal. At times they halt, unable to advance without great effort, although they do much better with a little assistance or with exhortation to walk in step with the examiner or to a marching cadence. Turning is accomplished by a series of tiny, uncertain steps that are made with one foot, the other foot being planted on the floor as a pivot. The initiation of walking becomes progressively more difficult; in advanced cases, the patient makes only feeble, abortive stepping movements in place, unable to move his feet and legs forward; in even more advanced cases, the patient can make no stepping movements whatsoever, as though his feet were glued to the floor. These late phenomena have been referred to colloquially as "magnetic feet" or the "slipping clutch" syndrome (Denny-Brown) and as "gait ignition failure" (Atchison et al). In some patients, difficulty in the initiation of gait may be an early and apparently isolated phenomenon; but invariably, with the passage of time, sometimes of years, the other features of the frontal lobe gait disorder become evident. In an attempt to describe these disorders, Liston and colleagues have separated them into three categories: "ignition apraxia," disequilibrium, and mixed types. They associate trouble starting the gait cycle, shuffling, and freezing with the first type and poor balance with the second. This is a useful restatement of the phenomenology, but most cases in our experience have been of the combined type, and patients of both types are prone to falling. Most patients, while seated or supine, are able to make complex movements with their legs, such as drawing imaginary figures or pedaling a bicycle, and quite remarkably, to simulate the motions of walking, all at a time when their gait is seriously impaired. Eventually, however, all movements of the legs become slow and awkward, and the limbs, when passively moved, offer variable resistance (paratonia, or gegenhalten). Difficulty in turning over in bed is characteristic, and this maneuver may eventually become impossible. These advanced motor disabilities are usually associated with dementia, but the gait and mental disorders need not evolve in parallel, as emphasized below. Grasping, groping, hyperactive tendon reflexes, and Babinski signs may or may not be present. The end result in some cases is a "cerebral paraplegia in flexion" (Yakovlev), in which the patient lies curled up in bed, immobile and mute, with the limbs fixed by contractures in an attitude of flexion. On the basis of success in a small controlled trial conducted by Baezner and colleagues, amantadine 100 mg daily or twice daily may be tried for cases of vascular white matter degeneration with prominent gait difficulty. Gait of the Aged An alteration of gait unrelated to overt cerebral disease is an almost universal accompaniment of aging.

The figures for major congenital malformations, compiled by Kalter and Warkany, are somewhat higher. What is most important for the neurologist is the fact that the nervous system is involved in most of these infants with major malformations. A perusal of the following pages makes it evident that there is a great variety of structural defects of the nervous system in early life; in fact, every part of the brain, spinal cord, nerves, and musculature may be affected. Furthermore, certain principles are applicable to the entire group of developmental brain disorders. First, the abnormality of the nervous system is frequently accompanied by an abnormality of some other structure or organ (eye, nose, 850 cranium, spine, ear, and heart), which relates them chronologically to a certain period of embryogenesis. Conversely, the presence of these malformations of nonnervous tissues suggests that an associated abnormality of the nervous system is developmental in nature. This principle is not inviolable; in certain maldevelopments of the brain, which must have originated in the embryonal period, all other organs are normal. One can only assume that in this instance the brain was more vulnerable than any other organ to prenatal as well as natal influences. Perhaps this occurs because the nervous system, of all organ systems, requires the longest time for its development and maturation, during which it is susceptible to disease. Second, a maldevelopment of whatever cause should be present at birth and remain stable thereafter, i. Again, this principle requires qualification- the abnormality may have affected parts of the brain that are not functional at birth, so that an interval of time must elapse postnatally before the defect can express itself. Third, for an abnormality to be characterized as developmental, birth should have been nontraumatic and the pregnancy uncomplicated by infection or other injurious event. Conversely, the occurrence of a traumatic birth is not proof of a causative relationship between the injury (or infection) and the abnormality, because a defective nervous system may itself interfere with the birth or the gestational process. Fourth, if the congenital abnormality has occurred in other members of the family of the same or previous generations, it is usually genetic- although, as noted above, this does not exclude the possible adverse effects of exogenous agents. Fifth, many of the teratologic conditions that cause birth defects pass unrecognized because they end in spontaneous abortions. Sixth, low birth weight and gestational age, indicative of premature birth, increase the risk of mental subnormality, seizures, cerebral palsy, and death. Regarding etiology, which is really the crux of the problem of birth defects, some order and classification have emerged. In general, malformations may be subdivided into four groups: (1) one in which a single mutant gene is responsible (2. It has been stated that true malformations are due to fundamental endogenous disturbances of cytogenesis and histogenesis occurring in the first half of gestation and that exogenous factors, which destroy brain tissue but do not cause malformations, operate in the second half. An exogenous lesion occurring during the embryonal period may not only destroy tissue but also derail the neuronal migrations of normal development. Cephalic and spinal meningocele, meningoencephalocele, Dandy-Walker syndrome, meningomyelocele 2. Other restricted congenital abnormalities (Horner syndrome, unilateral ptosis, anisocoria, etc. Congenital extrapyramidal disorders (double athetosis; erythroblastosis fetalis and kernicterus) E. Mental retardation A textbook on principles of neurology is not the place in which to present a detailed account of all the hereditary and congenital developmental abnormalities that might affect the nervous system. For such details, the interested reader should refer to several excellent monographs. These are supplemented by special atlases of congenital malformations mentioned further on. In this chapter we sketch only the major groups and discuss in detail a few of the more common disease entities. The classification in Table 38-1 adheres to a grouping in accordance with the main presenting abnormality or abnormalities. Represented here are the common problems that lead families to seek consultation with the pediatric neurologist: (1) structural defects of the cranium, spine, and limbs, and of eyes, nose, ears, jaws, and skin; (2) disturbed motor function- taking the form of retarded development or abnormal movements; (3) epilepsy; and (4) mental retardation. One has only to walk through an institution for the mentally retarded to appreciate the remarkable number and diversity of physical disfigurements that attend abnormalities of the nervous system.

Tumors less than 1 cm in diameter are referred to as microadenomas and are at first confined to the sella. As the tumor grows, it first compresses the pituitary gland; then, as it extends upward and out of the sella, it compresses the optic chiasm; later, with continued growth, it may extend into the cavernous sinus, third ventricle, temporal lobes, or posterior fossa. Recognition of an adenoma when it is still confined to the sella is of considerable practical importance, since total removal of the tumor by transsphenoidal excision or some form of stereotactic radiosurgery is possible at this stage, with prevention of further damage to normal glandular structure and the optic chiasm. Penetration of the diaphragm sellae by the tumor and invasion of the surrounding structures make treatment more difficult. Pituitary adenomas come to medical attention because of endocrine or visual abnormalities. Headaches are present with nearly half of the macroadenomas but are not clearly part of the syndrome. The visual disorder usually proves to be a complete or partial bitemporal hemianopia, which has developed gradually and may not be evident to the patient (see the description of the chiasmatic syndromes on page 206). A small number of patients will be almost blind in one eye and have a temporal hemianopia in the other. This results in a central scotoma on one or both sides (junctional syndrome) in addition to the classic temporal field defect. In 5 to 10 percent of cases, the pituitary adenoma extends into the cavernous sinus, causing some combination of ocular motor palsies. With regard to differential diagnosis, bitemporal hemianopia with a normal sella indicates that the causative lesion is probably a saccular aneurysm of the circle of Willis or a meningioma of the tuberculum sellae. The major endocrine syndromes associated with pituitary adenomas are described briefly in the following pages. Their functional classification can be found in the monograph edited by Kovacs and Asa. A detailed discussion of the diagnosis and management of hormone-secreting pituitary adenomas can be found in the reviews of Klibanski and Zervas and of Pappas and colleagues; recommended also is an article that details the neurologic features of pituitary tumors by Anderson and colleagues. Also worthy of emphasis is the catastrophic syndrome of pituitary apoplexy discussed further on. Amenorrhea-Galactorrhea Syndrome As a rule, this syndrome becomes manifest during the childbearing years. The history usually discloses that menarche had occurred at the appropriate age; primary amenorrhea is rare. A common history is that the patient took birth control pills, only to find, when she stopped, that the menstrual cycle did not re-establish itself. In general, the longer the duration of amenorrhea and the higher the serum prolactin level, the larger the tumor (prolactinoma). The elevated prolactin levels distinguish this disorder from idiopathic galactorrhea, in which the serum prolactin concentration is normal. With large tumors that compress normal pituitary tissue, thyroid and adrenal function will also be impaired. It should be noted that large, nonfunctioning pituitary adenomas also cause modest hyperprolactinemia by distorting the pituitary stalk and reducing dopamine delivery to prolactin-producing cells. Acromegaly this disorder consists of acral growth and prognathism in combination with visceromegaly, headache, and several endocrine disorders (hypermetabolism, diabetes mellitus). The new growth hormone receptor antagonist pegvisomant has been introduced to reduce many of the manifestations of acromegaly (see the editorial by Ho). Cushing Disease Described in 1932 by Cushing, this condition is only about one-fourth as frequent as acromegaly. A distinction is made between Cushing disease and Cushing syndrome, as indicated in Chap. The clinical effects are the same in all of these disorders and include truncal obesity, hypertension, proximal muscle weakness, amenorrhea, hirsutism, abdominal striae, glycosuria, osteoporosis, and in some cases a characteristic mental disorder (page 978). Although Cushing originally referred to the disease as pituitary basophilism and attributed it to a basophil adenoma, the pathologic change may consist only of hyperplasia of basophilic cells or of a nonbasophilic microadenoma.

Erythromelalgia, first described by Weir Mitchell, is a condition of unknown cause and mechanism in which the feet and lower extremities become red and painful on exposure to warm temperatures for prolonged periods (see page 189). Disturbances of Bladder Function the familiar functions of the bladder and lower urinary tract- the storage and intermittent evacuation of urine- are served by three structural components: the bladder itself, the main component of which is the large detrusor (transitional type) muscle; a functional internal sphincter composed of similar muscle; and the striated external sphincter or urogenital diaphragm. The sphincters assure continence; in the male, the internal sphincter also prevents the reflux of semen from the urethra during ejaculation. For micturition to occur, the sphincters must relax, allowing the detrusor to expel urine from the bladder into the urethra. This is accomplished by a complex mechanism involving mainly the parasympathetic nervous system (the sacral peripheral nerves derived from the second, third, and fourth sacral segments of the spinal cord and their somatic sensorimotor fibers) and to a lesser extent, sympathetic fibers derived from the thorax. The brainstem "micturition centers," with their spinal and suprasegmental connections, may contribute. The detrusor muscle receives motor innervation from nerve cells in the intermediolateral columns of gray matter, mainly from the third and also from the second and fourth sacral segments of the spinal cord (the "detrusor center"). These neurons give rise to preganglionic fibers that synapse in parasympathetic ganglia within the bladder wall. Short postganglionic fibers end on muscarinic acetylcholine receptors of the muscle fibers. There are also betaadrenergic receptors in the dome of the bladder, which are activated by sympathetic fibers that arise in the intermediolateral nerve cells of T10, T11, and T12 segments. These preganglionic fibers pass via inferior splanchnic nerves to the inferior mesenteric ganglia. Th 12 Efferent fibers the storage of urine and the efficient emptying of the bladder is possible only when the spinal segments, together L1 Sympathetic with their afferent and efferent nerve fibers, are connected Mesenteric chain L2 plexuses with the so-called micturition centers in the pontomesencephalic tegmentum. In experimental animals, this center (or L3 centers) lies within or adjacent to the locus ceruleus. A medial L4 region triggers micturition, while a lateral area seems more Superior hypogastric important for continence. These centers receive afferent implexus Pelvic nerves pulses from the sacral cord segments; their efferent fibers (presacral n. In cats, the pontomesenganglia 3 cephalic centers receive descending fibers from anteromedial Sacral constriction Plexus o 3 Vas nerves parts of the frontal cortex, thalamus, hypothalamus, and cere4 bellum, but the brainstem centers and their descending path4 ways have not been precisely defined in humans. Other fibers, from the motor cortex, descend with the corticospinal fibers Postganglionic to the anterior horn cells of the sacral cord and innervate the parasympathetic external sphincter. According to Ruch, the descending pathfibers ways from the midbrain tegmentum are inhibitory and those from the pontine tegmentum and posterior hypothalamus are Int. The pathway that descends with the corticospinal nerve tract from the motor cortex is inhibitory. Thus the net effect of lesions in the brain and spinal cord on the micturition reExternal sphincter flex, at least in animals, may be either inhibitory or facilitaFigure 26-5. Almost all of this information has been inferred from animal experiments; there is little human pathologic material to with adrenergically active drugs as well as the more commonly corroborate the role of central nuclei and cortex in bladder control. What information is available is reviewed extensively by Fowler, the external urethral and anal sphincters are composed of striwhose article is recommended. Incleus of Onuf) in the anterolateral horns of sacral segments 2, 3, creased blood flow was detected in the right pontine tegmentum, and 4. When the bladder was full but subjects were prevented from innervate the anal sphincter. The meaning of these lateralized findings is unclear, the pudendal nerves also contain afferent fibers coursing from but the study supports the presumption that pontine centers are the urethra and the external sphincter to the sacral segments of the involved in the act of voiding. These fibers convey impulses for reflex activities and, the act of micturition is both reflex and voluntary. Some of normal person desires to void, there is first a voluntary relaxation these fibers probably course through the hypogastric plexus, as inof the perineum, followed sequentially by an increased tension of dicated by the fact that patients with complete transverse lesions the abdominal wall, a slow contraction of the detrusor, and an asof the cord as high as T12 may report vague sensations of urethral sociated opening of the internal sphincter; finally, there is a relaxdiscomfort. The bladder is sensitive to pain and pressure; these ation of the external sphincter (Denny-Brown and Robertson). It is senses are transmitted to higher centers along the sensory pathways useful to think of the detrusor contraction as a spinal stretch reflex, described in Chaps. Voluntary Unlike skeletal striated muscle, the detrusor, because of its closure of the external sphincter and contraction of the perineal postganglionic system, is capable of some contractions, imperfect muscles cause the detrusor contraction to subside. The abdominal at best, after complete destruction of the sacral segments of the muscles have no power to initiate micturition except when the despinal cord. Isolation of the sacral cord centers (transverse lesions trusor muscle is not functioning normally.