Neurological Disorders PDF

12937C26.pgs 1/22/03 1:56 PM Page 697 chapter Neurological Disorders 26 On the afternoon of June 16, 1783, Dr. Samuel Johnson, the famed English lexicographer, sat for his portrait in the studio of Miss Frances Reynolds, the sadly untalented sister of Sir Joshua Reynolds. Despite his 73 years...

12937C26.pgs 1/22/03 1:56 PM Page 697 chapter Neurological Disorders 26 On the afternoon of June 16, 1783, Dr. Samuel Johnson, the famed English lexicographer, sat for his portrait in the studio of Miss Frances Reynolds, the sadly untalented sister of Sir Joshua Reynolds. Despite his 73 years and marked obesity, Johnson afterwards walked the considerable distance from the studio to his home. He went to sleep at his usual hour in the evening and awoke according to his account around 3 a.m. on June 17. To his surprise and horror, he found that he could not speak. He immediately tested his mental faculties by successfully composing a prayer in Latin verse. Next he tried to loosen his powers of speech by drinking some wine, violating his recently acquired habits of temperance. The wine only put him back to sleep. Upon reawakening after sunrise, Johnson still could not speak. He found, however, that he could understand others and that he could write. His penmanship and composition were somewhat defective. . . . Johnson proceeded to summon his physicians, Drs. Brocklesby and Heberden, who came and examined him. They prescribed blisters on each side of the throat up to the ear, one on the head, and one on the back, along with salts of hartshorn [ammonium carbonate]. Heberden, who was one of London’s leading doctors, predicted a speedy recovery. His confidence proved quite justified: the therapeutic regimen was so efficacious that Johnson’s speech began returning within a day or two. Recovery proceeded smoothly over the next month, and even the mild disorders in writing lessened. Johnson finally was left with a slight but stable dysarthria [difficulty articulating words] until he succumbed to other causes later in the next year. (Rosner, 1974, p. 1) D r. Johnson’s case has been described and discussed a number of times because he was an interesting and celebrated person, the author of the first English dictionary, and because his transitory illness was never fully explained. His aphasia provides an example of almost complete loss of a specific function (speech) and seemingly rapid and almost complete recovery. The story also contains a testimony to the knowledge and insight of his doctors, because their prediction of the outcome was correct. There are, however, many questions that the critical reader may wish to ask. How much weight should self-testimony be accorded? Did Johnson in fact experience a stroke or some 697 12937C26.pgs 698 1/22/03 P A RT V 1:56 PM PLASTICITY Page 698 AND DISORDERS other brain disorder? His claiming to have discovered, when alone in the middle of the night, that he could not speak is not unreasonable, because he was known to have the habit of talking to himself. But, because he was an eccentric, we might also wonder if the speechlessness was faked for some purpose or if its cause was psychological. If his disorder was real, what was it and where was it? Some neurologists have thought that the lesion must have been very small or was only a transitory blood clot. Others have speculated that, because he could not speak for a time but could still think, compose Latin verse, and write, he might normally have had the functions of speech in both hemispheres. Obviously, Dr. Johnson’s case provides substance for much speculation. In this chapter we will describe the examination given to a patient by a neurologist, and then we will survey a number of common neurological disorders, including vascular disorders, epilepsy, tumors, headaches, infections, and disorders of the spinal cord. The Neurological Examination People suspected of having some disorder of the nervous system are usually examined by a neurologist, a physician specializing in the treatment of such disorders. The neurologist takes a history from the patient, makes a general assessment of the patient’s condition, and perhaps recommends additional tests (for example, an EEG or a brain scan) that seem to be indicated by the history or the initial examination. At the end of this initial assessment, the neurologist writes a case summary. The Patient’s History The neurologist’s first step is to ask the patient about the problem. Information is also collected about the patient’s background, with particular attention paid to any history of disease, accidents, and the occurrence of symptoms such as headache, loss of consciousness, and sleep disturbances. Family background is reviewed as well, because many diseases, such as epilepsy, have a high familial incidence. While the history is being taken, the neurologist observes the patient’s behavior, assessing mental status, watching facial features for abnormalities or asymmetries, listening for speech abnormalities, and observing posture. The patient’s state of awareness is described with adjectives such as alert, drowsy, stuporous, confused, and so forth. Any evidence of delusions and hallucinations is reported. Facial expression and behavior reveal whether the patient is agitated, anxious, depressed, apathetic, or restless. The neurologist may test some simple aspects of memory by reciting a series of digits and asking the patient to repeat it. In addition, the neurologist may look to see whether the patient is leftor right-handed and ask about the history of handedness in the family, because handedness can be a clue to which hemisphere controls speech. A number of simple tests for speech may be given, such as asking the meaning of words, having rhymes or words repeated (for example, “la-la,” “ta-ta”), having objects named, and having the patient read and write. 12937C26.pgs 1/22/03 1:56 PM Page 699 CHAPTER 26 NEUROLOGICAL DISORDERS The Physical Examination The neurologist uses a number of tools in the course of the physical examination. They include (1) a measuring tape to measure head and body size, the size of skin lesions, and so on; (2) a stethoscope to listen to the sounds of the heart and blood vessels and an otoscope to examine the auditory canal and eardrum; (3) a flashlight to elicit pupillary reflexes; (4) tongue blades to elicit the gag reflex and abdominal and plantar reflexes; (5) a vial of coffee to assess smell and vials of salt and sugar to assess taste; (6) a 256-Hz tuning fork to test vibratory sensation and hearing; (7) a cotton wisp to elicit the corneal reflex and to test sensitivity to light touch, plastic tubes to test temperature sensations, and pins to test pain sensation; (8) a hammer to elicit muscle stretch reflexes, such as the knee-jerk reflex; (9) some coins and keys to test the recognition of objects through touch; and (10) a blood-pressure cuff to measure blood pressure. One of the most important parts of the neurological examination is the study of the head. Its general features such as size and shape are assessed, and a detailed examination is made of the sensory and motor functioning of its 12 sets of cranial nerves. Cranial-nerve malfunctions discovered in this part of the examination can be important clues to the location and nature of nervous system damage. The motor system in other parts of the body is examined to assess muscle bulk, tone, and power; to test for the occurrence of involuntary muscle movements, such as shaking and tremors; and to assess the status of reflexes. In addition, coordination is examined by having a patient perform such tasks as walking heel to toe in a straight line, touching the neurologist’s finger and his or her own nose repeatedly, making rapid alternating movements of the fingers, tapping the foot as rapidly as possible, and so on. Generally, all the muscles of the body are tested in head-to-foot order, and the status of each is recorded on a standard chart. A sensory examination includes an investigation of sensitivity to painful stimulation, to touch, and to temperature, as well as an analysis of vibration sense, joint-position sense, two-point discrimination, tactile localization, identification of objects, and the ability to identify numbers or letters traced on the skin with a blunt object. These sensory tests allow the functions of individual sensory systems to be assessed and provide information about the location of possible dysfunctions. Vascular Disorders The normal functioning of the central nervous system can be affected by a number of vascular problems, because blood-vessel disease or damage can greatly—even totally—reduce the flow of oxygen and glucose to a brain region. If such interference lasts longer than 10 minutes, all cells in the affected region die. Most disease of the cerebral vascular system develops in the arterial system; disease of venous drainage is uncommon in the central nervous system. Cerebral vascular diseases are among the most common causes of death and chronic disability in the Western world. A common term used in a discussion of cerebral vascular disorder is stroke, also known as cerebral vascular accident. A stroke is the sudden appearance of neurological symptoms as a result of interruption of blood flow. Stroke can 699 12937C26.pgs 700 1/22/03 P A RT V 1:56 PM PLASTICITY Page 700 AND DISORDERS result from a wide variety of vascular disorders, but not all vascular disorders produce stroke. The onset of dysfunction can be insidious, spanning months or even years. Stroke often produces an infarct, an area of dead or dying tissue resulting from an obstruction of the blood vessels normally supplying the area. As you read this paragraph, someone in the United States will suffer a vascular accident. If the flow through small blood vessels, such as capillaries, is interrupted, the effects are more limited than the often-devastating consequences of damage to large vessels. If a stroke or other cerebral vascular disorder occurs in one restricted part of a vessel (and other parts of the system are relatively healthy), the prognosis can be rather good, because vessels in the surrounding areas can often supply blood to at least some of the deprived area. On the other hand, if a stroke affects a region supplied largely by weak or diseased vessels, the effects can be much more serious, because there is no possibility of compensation. In addition, the surrounding weak zones themselves may be at increased risk of stroke. In the long run, a small vascular lesion in a healthy brain will have a good prognosis for substantial recovery of function. In the event of preexisting vascular lesions, the effects of the new lesions may be extremely variable. The lesions can be cumulative and obliterate a functional zone of brain tissue, producing serious consequences. As with other lesions, the behavioral symptoms subsequent to vascular lesions depend on the location of damage. Of the numerous vascular disorders that affect the central nervous system, the most common are ischemia, migraine stroke, cerebral hemorrhage, angiomas, and arteriovenous aneurysms. Cerebral Ischemia Ischemia refers to any of a group of disorders in which the symptoms are caused by vessel blockage preventing a sufficient supply of blood to the brain. In thrombosis, for example, some of the blood in a vessel has coagulated to form a plug or clot that has remained at the place of its formation. An embolism is a clot or other plug brought through the blood from a larger vessel and forced into a smaller one, where it obstructs circulation. An embolism can be a blood clot, a bubble of air, a deposit of oil or fat, or a small mass of cells detached from a tumor. Curiously, embolisms most often affect the middle cerebral artery of the left side of the brain. Reduction in blood flow can also result from other kinds of factors that narrow the vessel. The most common example of such narrowing is a condition marked by thickening and hardening of the arteries, called cerebral arteriosclerosis. When ischemia is temporary, it may be termed cerebral vascular insufficiency or transient ischemia, indicating the variable nature of the disorder with the passage of time. The onset of transient attacks is often abrupt; in many cases, they are experienced as fleeting sensations of giddiness or impaired consciousness. Migraine Stroke Since the late 1800s, physicians have recognized that migraine attacks may lead to infarcts and permanent neurological deficits. Such migraine strokes are relatively rare compared with other types, but they are believed to account for a significant proportion of strokes in young people (under 40 years of age), es- 12937C26.pgs 1/22/03 1:56 PM Page 701 CHAPTER 26 pecially women. The immediate cause of these strokes is probably some form of vasospasm—constriction of blood vessels—but the underlying cause of the vasospasm remains a mystery. The classic migraine stroke is experienced as a transient ischemic attack with a variety of neurological symptoms, including impaired sensory function (especially vision), numbness of the skin (especially in the arms), difficulties in moving, and aphasia. The precise symptoms depend on the vessels affected; however, the posterior cerebral artery is most commonly affected. Cerebral Hemorrhage Cerebral hemorrhage is a massive bleeding into the substance of the brain. The most frequent cause is high blood pressure, or hypertension. Other causes include congenital defects in cerebral arteries, blood disorders such as leukemia, and toxic chemicals. The onset of cerebral hemorrhage is abrupt, and the bleeding may quickly prove fatal. It usually occurs when a person is awake, presumably because the person is more active and thus has higher blood pressure. Prognosis is poor in cerebral hemorrhage, especially if the patient is unconscious for more than 48 hours. Angiomas and Aneurysms Angiomas are congenital collections of abnormal vessels that divert the normal flow of blood. These capillary, venous, or arteriovenous (A-V) malformations are masses of enlarged and tortuous cortical vessels that are supplied by one or more large arteries and are drained by one or more large veins, most often in the field of the middle cerebral artery. Because they create abnormalities in the amount and pattern of blood flow and are inherently weak, angiomas may lead to stroke or to an inadequate distribution of blood in the regions surrounding the vessels. In some cases, they cause arterial blood to flow directly into veins after only briefly, or sometimes not at all, servicing the surrounding brain tissue. Aneurysms are vascular dilations resulting from localized defects in the elasticity of a vessel. They can be visualized as balloonlike expansions of vessels that are usually weak and prone to rupture. Although aneurysms are usually due to congenital defects, they may also develop from hypertension, arteriosclerosis, embolisms, or infections. A characteristic symptom of an aneurysm is severe headache, which may be present for years, because the aneurysm is exerting pressure on the dura mater, which is richly endowed with pain receptors. Treatment of Vascular Disorders Most vascular disorders have no specific treatment, although the most common remedies include drug therapy and surgery. Supportive therapies are useful if they are delivered within 3 hours after a vascular emergency. They include such drugs as anticoagulants to dissolve clots or prevent clotting, vasodilators to dilate the vessels, drugs to reduce blood pressure, and salty solutions or steroids to reduce cerebral edema (the accumulation of fluid in and around damaged tissue). Treatment with anticoagulants is effective only if they are given soon after a blood vessel is blocked. If treatment is delayed more than 3 hours, it is unlikely NEUROLOGICAL DISORDERS 701 12937C26.pgs 702 1/22/03 P A RT V 1:56 PM PLASTICITY Page 702 AND DISORDERS to be helpful. Surgical techniques have improved greatly in recent years but are not always practical. For example, the only certain cure for an aneurysm is total removal, which is usually not feasible. Aneurysms are sometimes painted with various plastic substances to prevent them from rupturing. In regard to cerebral hemorrhage, it may be necessary to perform surgery to relieve the pressure of the blood from the ruptured vessel on the rest of the brain. Traumatic Head Injuries Cases per 100,000 population per year 700 600 500 Male 400 300 200 Female 100 0 Figure 10 26.1 20 30 40 50 Age (years) Incidence rates of head trauma in Olmsted County, Minnesota, 1965–1974. (After Annegers et al., 1980.) Brain injury is a common result of automobile and industrial accidents; cerebral trauma or injury from a blow to the head is the most common form of brain damage in people under the age of 40; and, in one telephone survey in Sweden, cerebral concussion (injury resulting from a violent blow or shock) producing at least brief unconsciousness was reported by 5% of those interviewed. In addition, another 5% or so of the general population are likely to have suffered concussion without obvious unconsciousness, although they would have experienced some confusion about the events surrounding the blow to the head. The two most important factors in the incidence of head injury are age and sex. Children and elderly people are more likely to suffer head injuries from falls than are others, and males between 15 and 30 years of age are very likely to incur brain injuries, especially from automobile and motorcycle accidents (Figure 26.1). A child’s chance of suffering significant closed-head injury before he or she is old enough to drive is 1 in 30. Head injury can affect brain function by causing direct 60 70 80+ damage to the brain; by disrupting blood supply; by inducing bleeding, leading to increased intracranial pressure; by causing swelling, leading to increased intracranial pressure; by opening the brain to infection; and by producing scarring of brain tissue (the scarred tissue becomes a focus for later epileptic seizures). There are two main types of head injury: open-head injury and closed-head injury. Open-Head Injuries Open-head injuries are traumatic brain injuries in which the skull is penetrated, as in gunshot or missile wounds, or in which fragments of bone penetrate the brain substance. In many cases, the injury does not cause the victim to lose consciousness. Open-head injuries tend to produce distinctive symptoms that may undergo rapid and spontaneous recovery. The neurological signs may be highly specific, and the effects of the injuries often closely resemble those of surgical excision of a small area of cortex. The specificity of neurological symptoms subsequent to open-head injuries makes such patients especially good research subjects. Three thorough investigations of World War II (1939–1945) veterans with open-head injuries have been published—by Newcombe, by Luria, and by Teuber and coworkers. 12937C26.pgs 1/22/03 1:56 PM Page 703 CHAPTER 26 NEUROLOGICAL DISORDERS 703 Closed-Head Injuries Closed-head injuries result from a blow to the head, which can subject the brain to a variety of mechanical forces. First, there is damage at the site of the blow, a bruise (contusion) called a coup. Coups are incurred where the brain has been compacted by the bone’s pushing inward, even when the skull is not fractured. Second, the pressure that produces the coup may push the brain against the opposite side of the skull, producing an additional bruise, known as a countercoup (Figure 26.2). Third, the movement of the brain may cause a twisting or shearing of fibers, producing microscopic lesions. These lesions may occur throughout the brain but are most common in the frontal and temporal lobes. In addition, the twisting and shearing may damage the major fiber tracts of the brain, especially those crossing the midline, such as the corpus callosum and anterior commissure. As a result, connection between the two sides of the brain may be disrupted, leading to a disconnection syndrome. Fourth, the bruises and strains caused by the impact may produce bleeding (hemorrhage). Because the blood is trapped within the skull, it acts as a growing mass (hematoma), exerting pressure on surrounding structures. Finally, as Figure Regions of the brain most frequently damaged in closedwith blows to other parts of the body, blows to the brain produce edema, anhead injury (indicated by gray and other source of pressure on the brain tissue. Closed-head injuries resulting blue shading). A blow can produce a from traffic accidents are particularly severe because the head is moving contusion both at the site of impact when the blow is struck, thereby increasing the velocity of the impact, and and at the opposite side of the brain, multiplying the number and severity of small lesions throughout the brain. owing to compression of the brain against the front (A) or the back (B) Computerized tomographic scans of accident victims suffering prolonged of the skull. coma (a loss of consciousness) show diffuse brain injury and enlarged ventricles, signs associated with A variety of mechanical forces poor outcomes. cause closed-head injuries as a Closed-head injuries are commonly accompanied result of a blow to the head. by coma. According to Lezak, the duration of uncon(B) (A) sciousness can serve as a measure of the severity of damage, because it correlates directly with mortality, intellectual impairment, and deficits in social skills. The longer the coma lasts, the greater the possibility of serious impairment and death. Two kinds of behavioral effects result from closedhead injuries: (1) discrete impairment of the specific functions mediated by the cortex at the site of the Impact-site coup or countercoup lesion and (2) more generalized damage (coup) impairments from widespread trauma throughout the brain. Discrete impairment is most commonly associated with damage to the frontal and temporal lobes, which are the areas most susceptible to closed-head Pressure injuries. More general impairment, resulting from resulting from minute lesions and lacerations scattered throughout coup (countercoup) the brain and from tears due to movement of the hemispheres in relation to each other, is characterMovement of the brain may shear nerve fibers, causing microscopic lesions, especially in frontal and temporal ized by a loss of complex cognitive functions, includlobes. Blood trapped in the skull (hematoma) and ing reductions in mental speed, concentration, and swelling (edema) cause pressure on the brain. overall cognitive efficiency. The patients generally 26.2 12937C26.pgs 704 Table 1/22/03 P A RT V 1:56 PM PLASTICITY Page 704 AND DISORDERS 26.1 Primary and secondary brain complain of an inability to concentrate or to do things as well as they could before the accident, even though their intelligence rating may still be well above average. In fact, in our Primary (Immediate on Impact) Brain Injuries experience, it seems that bright people are the most affected Macroscopic lesions by closed-head injuries because they are acutely aware of any Contusions underlying the site of impact (coup) loss of cognitive skill that prevents them from returning to Countercoup contusion, frequently in the their former competence level. undersurfaces of the frontal lobes and the tips of Closed-head injuries that damage the frontal and temporal the temporal lobes lobes also tend to have significant effects on personality and Laceration of the brain from depressed skull fracture social behavior. According to Lezak, relatively few victims of Microscopic lesions traffic accidents who have sustained severe head injuries ever Widespread shearing or stretching of fibers resume their studies or return to gainful employment; if they Secondary Consequences of Brain Injury do reenter the work force, they do so at a level lower than that Intracranial hemorrhage before their accidents. Edema in white matter adjacent to focal mass lesions Often, the chronic effects of closed-head injuries are not Diffuse brain swelling—hyperemia accompanied by any obvious neurological signs, and the paIschemic brain damage tients may therefore be referred for psychiatric evaluation. Raised intracranial pressure Thorough psychological assessments are especially useful Brain shift and herniation in these cases for uncovering seriously handicapping cogniSecondary Insult from Extracerebral Events tive deficits that have not yet become apparent. The pathoEffects of multiple or systemic injury or both logical effects of closed-head injury are summarized in Hypoxia Table 26.1. Fat embolism People who once sustain head injuries are more likely to Delayed Effects sustain subsequent head injuries, and there is a strong sugDegeneration of white matter gestion in the literature that the effects of even very mild Disturbed flow of cerebrospinal fluid—hydrocephalus head injuries may be cumulative. For example, it is well established that a boxer will sustain a significant level of brain Source: After Levin et al., 1982. injury—culminating in a condition called traumatic encephalopathy (known more commonly as the “punch-drunk syndrome”)— even though the periods of unconsciousness experienced by the boxer may have been few and of short duration. injury after closed-head trauma Behavioral Assessment in Head Injury Although neuroradiological measures can provide objective indicators of neural status after head injury, behavior is the most important measure of the integrity of the nervous system. In the immediate postinjury period, the two most obvious behavioral symptoms are coma and amnesia. Clinical judgment of the depth of coma was largely subjective and unreliable until the Glasgow Coma Scale (Table 26.2) was designed to provide an objective indicator of the degree of unconsciousness and of recovery from unconsciousness. In this scale, three indices of wakefulness are evaluated: eye opening, motor response, and verbal response. A score of 8 or less is often used as a criterion for severe closed-head injury, with a score ranging from 9 to 12 being a criterion for moderate injury. A shortcoming of the scale as a measure of the severity of brain injury is that as many as 50% of brain injury victims admitted to hospitals have scores ranging from 13 to 15, indicating an absence of coma, and yet later such patients may suffer many of the consequences of head injury. 1/22/03 Table 1:56 PM Page 705 26.2 The Glasgow Coma Scale Response Points None To pain To speech 1 2 3 Spontaneous 4 No response Extension 1 2 Abnormal flexion Withdrawal 3 4 Localizes pain 5 Obeys commands 6 No response Incomprehensible Inappropriate 1 2 3 Confused 4 Oriented 5 Index of wakefulness Eye Opening (E) Not attributable to ocular swelling Pain stimulus is applied to chest or limbs Nonspecific response to speech or shout, does not imply that the patient obeys command to open eyes Eyes are open; does not imply intact awareness Motor Response (M) Flaccid “Decerebrate,” adduction, internal rotation of shoulder, and pronation of the forearm “Decorticate,” abnormal flexion, adduction of the shoulder Normal flexor response; withdraws from pain stimulus with abduction of the shoulder Pain stimulus applied to supraocular region or fingertip causes limb to move to attempt to avoid it Follows simple commands Verbal Response (V) (Self-explanatory) Moaning and groaning, but no recognizable words Intelligible speech (e.g., shouting or swearing), but no sustained or coherent conversation Patient responds to questions in a conversational manner, but the responses indicate varying degrees of disorientation and confusion Normal orientation to time, place, and person Note: The summed Glasgow Coma Scale is equal to E + M + V (3–15 points). Source: After B. Teasdale and B. Jennett, 1974. The length of posttraumatic amnesia is an alternative measure of severity of injury. Even though definitions of posttraumatic amnesia vary (some include the period of coma, whereas others are restricted to the period of anterograde amnesia), there is good evidence that the duration of amnesia is correlated (imperfectly) with later memory disturbance, as illustrated in Figure 26.3. A commonly used scale is as follows: amnesia lasting less than 10 minutes corresponds to very mild injury; amnesia lasting 10 to 60 minutes corresponds to mild injury; amnesia lasting 1 to 24 hours corresponds to moderate injury; amnesia lasting 1 to 7 days corresponds to severe injury; amnesia lasting more than 7 days corresponds to very severe injury. One problem with using amnesia as a measure is that there is no consistent method of measuring it. Researchers evaluate it, variously, by retrospective questioning, by measures of disorientation, or by neuropsychological assessment, and each method yields a different estimate of the severity of amnesia and hence of the extent of injury. (A) Injury Retrograde amnesia Figure 26.3 Acute alterations in memory after closed-head injury. (A) A diagram showing the sequence of alterations. The period of coma and anterograde amnesia are often called the period of posttraumatic amnesia (PTA), although by some definitions PTA is limited to the anterograde amnesia. (B) Histograms showing the distribution of individual scores of story recall by patients in three groups distinguished by the period of PTA. Scores represent recall of the second of two stories. (Part A after Levin et al., 1982; part B after Newcombe, 1987.) Posttraumatic amnesia Coma Anterograde amnesia Preinjury memory (B) Restoration of memory Immediate recall Recall at 30 minutes 20 15 Story recall score 12937C26.pgs 10 5 0 <1 week <1 >1 month month <1 week Period of coma <1 >1 month month 12937C26.pgs 706 1/22/03 P A RT V 1:56 PM PLASTICITY Page 706 AND DISORDERS Recovery from Head Injury Although it is often stated that recovery from head trauma may continue for 2 to 3 years, there is little doubt that the bulk of the cognitive recovery takes place in the first 6 to 9 months. Recovery of memory functions appears to be somewhat slower than recovery of general intelligence, and the final level of memory performance is lower than that of other cognitive functions. Levin and his colleagues suggested that people with brainstem damage, as inferred from oculomotor disturbance, have a poorer cognitive outcome, and it is probably true of people with initial dysphasias or hemipareses as well. Although the prognosis for significant recovery of cognitive functions is good, there is less optimism about the recovery of social skills or normal personality, areas that often change significantly. The results of numerous studies support the conclusion that the quality of life—in regard to social interactions, perceived stress levels, and enjoyment of leisure activities—is significantly reduced after closed-head injury and that this reduction is chronic. There have been few attempts to develop tools to measure changes in psychosocial adjustment in brain-injured people; so we must rely largely on subjective descriptions and self-reports, which provide little information about the specific causes of these problems. Table 26.3 Factors that may precipitate seizures in susceptible persons Hyperventilation Sleep Sleep deprivation Sensory stimuli Flashing lights Reading, speaking, coughing Laughing Sounds: music, bells Trauma Hormonal changes Menses Puberty Adrenal steroids Adrenocorticotrophic hormone (ACTH) Fever Emotional stress Drugs Phenothiazines Analeptics Tricyclic antidepressants Alcohol Excessive anticonvulsants Source: After Pincus and Tucker, 1974. Epilepsy In epilepsy, a person suffers recurrent seizures of various types that register on an electrogram and are associated with disturbances of consciousness. Epileptic episodes have been called convulsions, seizures, fits, and attacks, but none of these terms on its own is entirely satisfactory, because the character of the episodes can vary greatly. Epileptic seizures are common; 1 person in 20 will experience at least one seizure in his or her lifetime. The prevalence of multiple seizures is much lower, however—about 1 in 200. Epileptic seizures are classified as symptomatic seizures if they can be identified with a specific cause, such as infection, trauma, tumor, vascular malformation, toxic chemicals, very high fever, or other neurological disorders. They are called idiopathic seizures if they appear to arise spontaneously and in the absence of other diseases of the central nervous system. Table 26.3 summarizes the great variety of circumstances that appear to be able to precipitate seizures. Although the range of these circumstances is striking, a consistent feature is that the brain is most epileptogenic when it is relatively inactive and the patient is sitting still. Although epilepsy has long been known to run in families, its incidence is lower than a one-gene genetic model would predict. What is more likely is that certain genotypes have a predisposition to seizure problems given certain environmental circumstances. The most remarkable clinical feature of epileptic disorders is the widely varying length of intervals between attacks—from minutes to hours to weeks or even years. In fact, it is almost impossible to describe a basic set of symptoms to be expected in all or even most people with the disorder. At the same time, three particular symptoms are found in many types of epilepsy: 12937C26.pgs 1/22/03 1:56 PM Page 707 CHAPTER 26 1. An aura, or warning, of impending seizure. This aura may take the form of a sensation—an odor or a noise—or it may simply be a “feeling” that the seizure is going to occur. 2. Loss of consciousness. Ranging from complete collapse in some people to simply staring off into space in others, loss of consciousness is often accompanied by amnesia in which the victim forgets the seizure itself and the period of lost consciousness. 3. Movement. Seizures commonly have a motor component, although the characteristics vary considerably. Some people shake during an attack; others exhibit automatic movements, such as rubbing the hands or chewing. A diagnosis of epilepsy is usually confirmed by EEG. In some epileptics, however, seizures are difficult to demonstrate in this way except under special circumstances (for example, in an EEG recorded during sleep). Moreover, not all persons with an EEG suggestive of epilepsy actually have seizures. In fact, some estimates suggest that as many as 4 people in 20 have abnormal EEG patterns, which is many more than the number of people thought to suffer from epilepsy. Several schemes for classifying epilepsy have been published through the years. Four commonly recognized types of seizures are: focal seizures, generalized seizures, and akinetic and myoclonic seizures. Focal Seizures A focal seizure begins in one place and then spreads. In a Jacksonian focal seizure, for example, the attack begins with jerking movements in one part of the body (for example, a finger, a toe, or the mouth) and then spreads to adjacent parts. If the attack begins with a finger, the jerks might spread to other fingers, then the hand, the arm, and so on, producing the so-called Jacksonian march. Hughlings Jackson hypothesized in 1870 that such seizures probably originate from the point (focus) in the neocortex representing the region of the body where the movement is first seen. He was later proved correct. Complex partial seizures, another type of focal seizure, originate most commonly in the temporal lobe and somewhat less frequently in the frontal lobe. Complex partial seizures are characterized by three common manifestations: (1) subjective experiences that presage the attack such as forced, repetitive thoughts, sudden alterations in mood, feelings of déjà vu, or hallucinations; (2) automatisms, which are repetitive stereotyped movements such as lip smacking or chewing or activities such as undoing buttons; and (3) postural changes, as when the person assumes a catatonic, or frozen, posture. Generalized Seizures Generalized seizures are bilaterally symmetrical without focal onset. One subtype, the grand mal attack, is characterized by loss of consciousness and by stereotyped motor activity. This kind of seizure typically comprises three stages: (1) a tonic stage, in which the body stiffens and breathing stops; (2) a clonic stage, in which there is rhythmic shaking; and (3) a postseizure, also called postictal, depression, during which the patient is confused. About 50% of these seizures are preceded by an aura. NEUROLOGICAL DISORDERS 707 12937C26.pgs 708 1/22/03 P A RT V 1:56 PM PLASTICITY Page 708 AND DISORDERS The petit mal attack is a loss of awareness during which there is no motor activity except for blinking, turning the head, or rolling the eyes. These attacks are of brief duration, seldom exceeding about 10 seconds. The EEG recording of a petit mal seizure has a typical pattern known as the three-per-second spike and wave. Akinetic and Myoclonic Seizures Akinetic seizures are ordinarily seen only in children. Usually an affected child collapses suddenly and without warning. These seizures are often of very short duration, and the child may get up after only a few seconds. The fall can be dangerous, however, and it is commonly recommended that the children wear football helmets until the seizures can be controlled by medication. Myoclonic spasms are massive seizures that basically consist of a sudden flexion or extension of the body and often begin with a cry. Treatment of Epilepsy The treatment of choice for epilepsy is an anticonvulsant drug such as diphenylhydantoin (DPH, Dilantin), phenobarbital, or one of several others. Although the mechanism by which these drugs act is uncertain, they presumably inhibit the discharge of abnormal neurons by stabilizing the neuronal membrane. If medication fails to alleviate the seizure problem satisfactorily, surgery can be performed to remove the focus of abnormal functioning in patients with focal seizures. Tumors Figure 26.4 Frontal section showing a meningioma arising in the dura mater and compressing the right cerebral hemisphere. Notice that the tumor has not infiltrated the brain. (From Zacks, © 1971; reprinted with permission.) Meningioma A tumor, or neoplasm, is a mass of new tissue that persists and grows independently of its surrounding structures and has no physiological use. Brain tumors grow from glia or other support cells rather than from neurons. The rate at which tumors grow varies widely, depending on the type of cell that gave rise to them. Tumors account for a relatively high proportion of neurological disease; after the uterus, the brain is the most common site for them. Tumors that are not likely to recur after removal are called benign, and tumors that are likely to recur after removal—often progressing and becoming a threat to life—are called malignant. Although there are good reasons for distinguishing between benign and malignant tumors, the benign tumor may be as serious as the malignant one, because benign tumors in the brain are often inaccessible to the surgeon. The brain is affected by many types of tumors, and no region of the brain is immune to tumor formation. Tumors can affect behavior in a number of ways. A tumor may develop as a distinct entity in the brain, a so-called encapsulated tumor, and put pressure on the other parts of the brain (Figure 26.4). Encapsulated tumors are also sometimes cystic, which means that they produce a fluid-filled cavity in the brain, usually lined with the tumor cells. Because the skull is of fixed size, any increase in its contents compresses the brain, resulting in dysfunctions. In contrast with encapsulating tumors, so-called infiltrating tumors are not clearly marked off 12937C26.pgs 1/22/03 1:56 PM Page 709 CHAPTER 26 from the surrounding tissue; they may either destroy normal cells and occupy their place or surround existing cells (both neurons and glia) and interfere with their normal functioning (Figure 26.5). The general symptoms of brain tumors, which result from increased intracranial pressure, include headache, vomiting, swelling of the optic disk (papilledema), slowing of the heart rate (bradycardia), mental dullness, double vision (diplopia), and, finally, convulsions, as well as functional impairments due to damage to the brain where the tumor is located. Brain tumors are distinguished on the basis of where they originate: they can be gliomas, meningiomas, or metastatic tumors. Glioma is a general term for the roughly 45% of brain tumors that arise from glial cells and infiltrate the brain substance. Gliomas, ranging from the relatively benign to the highly malignant, vary considerably in their response to treatment. Meningiomas are growths attached to the meninges, the protective outer layer of the brain. They grow entirely outside the brain, are well encapsulated, and are the most benign of all brain tumors. But, even though meningiomas do not invade the brain, they are often multiple and disturb brain function by putting pressure on the brain, often producing seizures as a symptom. Although most meningiomas lie over the hemispheres, some develop between them and are therefore more difficult to remove. If meningiomas are removed completely, they tend not to recur. When they are present, however, it is not uncommon for these tumors to erode the overlying bone of the skull. Metastasis is the transfer of disease from one organ or part to another not directly connected with it. Thus, a metastatic tumor in the brain is one that has become established by a transfer of tumor cells from some other region of the body, most often a lung or a breast. Indeed, it is not uncommon for the first indication of lung cancer to be evidence of a brain tumor. Metastases to the brain are usually multiple, making treatment complicated, and prognosis poor. The most straightforward treatment of brain tumors is surgery, which is also the only way to make a definite histological diagnosis. If feasible, tumors are removed, but, as with tumors elsewhere in the body, success depends on early diagnosis. Radiation therapy is useful for treating certain types of tumors. Chemotherapy has not yet been very successful in the treatment of brain tumors, partly because of the difficulty of getting drugs to pass the blood–brain barrier and enter the tumor. Headaches Headache is so common among the general population that rare indeed is the person who has never suffered one. Headache may constitute a neurological disorder in itself, as in migraine; it may be secondary to neurological disease such as tumor or infection; or it may result from psychological factors, especially stress, as in tension headaches. The pain-sensitive structures within the skull that can produce the headache include the dura mater; the large arteries of the brain; the venous sinuses; and the branches of the 5th, 9th, and 10th cranial nerves and the 1st and 3rd cervical nerves. Pain can be elicited in these structures by pressure, displacement, or inflammation. There are a number of different kinds of headache, including migraine, headache associated with neurological disease, muscle-contraction headaches, and nonmigrainous vascular headaches. NEUROLOGICAL DISORDERS Ventricles Figure 26.5 709 Glioblastoma Frontal section showing a glioblastoma (a malignant type of glia-derived tumor) in the right cerebral hemisphere. Note the displacement of the ventricular system and the invasion of brain tissue (dark area). (From Bannister, © 1978; reprinted with permission.) 12937C26.pgs 710 1/22/03 P A RT V 1:56 PM PLASTICITY Page 710 AND DISORDERS Migraine Figure 26.6 The development of a migraine scotoma as described by Karl Lashley. A person first sees a small patch of lines in the center of the visual field, as shown near the small “x” in the center of the left-hand photograph. Information from the world is no longer visible in that part of the visual field. The striped area spreads progressively outward, leaving a white area where the stripes had been before. Within 15 to 20 minutes, the visual field is almost completely blocked by the scotoma. Normal vision returns shortly thereafter. X = Fixation point Migraine (derived from the Greek hemi and kranion, meaning “half of skull”) is perhaps the most common neurological disorder, afflicting some 5% to 20% of the population at some time in their lives. The World Federation of Neurology defines migraine as a “familial disorder characterized by recurrent attacks of headache widely variable in intensity, frequency, and duration. Attacks are commonly unilateral and are usually associated with anorexia, nausea, and vomiting. In some cases they are preceded by, or associated with, neurological and mood disturbances.” There are several types of migraine, including classic migraine, common migraine, cluster headache, and hemiplegic and ophthalmologic migraine. Classic migraine is probably the most interesting form, occurring in about 12% of migraine sufferers, because it begins with an aura, which usually lasts for 20 to 40 minutes. Karl Lashley, arguably the first neuropsychologist, suffered from classic migraine and carefully described his visual aura, which turned out to be common to many migraine sufferers (Figure 26.6). The aura is thought to occur because constriction of one or more cerebral arteries has produced ischemia of the occipital cortex. The results of PET studies have shown that, during the aura, there is a reduction in blood flow in the posterior cortex, and this reduction spreads at the rate of about 2 mm/min, without regard to its location with respect to major blood vessels. Why the reduction in blood flow should spread independently of the major vessels is not known, but its doing so suggests that the vascular changes are secondary to changes in neural function. The actual headache begins as the vasoconstriction reverses (ending the neurological disturbance) and vasodilation takes place. The headache is experienced as an intense pain localized in one side of the head, although it often spreads on that side and sometimes extends to the opposite side as well. A severe headache can be accompanied by nausea and vomiting, and it may last for hours or even days. A significant number of people considered to have classic migraine never suffer the headache but experience the aura. Common migraine is the most frequent type of migraine, occurring in more than 80% of migraine sufferers. There is no clear aura as there is in classic migraine, but there may be a gastrointestinal or other “signal” that an attack is pending. Cluster headache is a unilateral pain in the head or face that rarely lasts longer than 2 hours but recurs repeatedly for a period of weeks or even months before disappearing. Sometimes long periods pass between one series of cluster headaches and the next. The remaining two types of migraine, hemiplegic migraine and ophthalmologic migraine, are relatively rare and include loss of movement of the limbs and eyes, respectively. The frequency of migraine attacks varies from as often as once a week to as seldom as once in a lifetime. In cases in which migraine is frequent, the occur- 12937C26.pgs 1/22/03 1:56 PM Page 711 CHAPTER 26 rence generally decreases with age and usually ceases in middle age. Migraine was generally believed to be rare before adolescence, but in recent years it has been recognized to afflict children as well, although the actual incidence in this population is uncertain. Headache Associated with Neurological Disease Headache is a symptom of many nervous system disorders, usually resulting from the distortion of pain-sensitive structures. Common disorders producing headache include tumor, head trauma, infection, vascular malformations, and severe hypertension (high blood pressure). The characteristics and locations of these headaches vary according to the underlying cause. For example, headache from a brain tumor is almost always located on the same side of the head as the tumor, particularly in the early stages of tumor growth. Headaches induced by brain tumors have no characteristic severity; they may vary from mild to excruciating. Likewise, hypertension headache, although it is nearly always located in the occipital region, is highly variable in severity. Muscle-Contraction Headache The most common headaches are muscle-contraction headaches, also known as tension or nervous headaches. They result from sustained contraction of the muscles of the scalp and neck caused by constant stress and tension, especially if poor posture is maintained for any time. Patients describe their pain as steady, nonpulsing, tight, squeezing, or pressing or as the feeling of having the head in a vise. Some patients complain of a crawling sensation. The headaches may be accompanied by anxiety, dizziness, and bright spots in front of the eyes. In some people, caffeine may exacerbate the headaches, presumably because it exacerbates anxiety. Nonmigrainous Vascular Headaches Headache associated with dilation of the cranial arteries can be induced by a wide variety of diseases and conditions. The most common causes are fever, anoxia (lack of oxygen), anemia, high altitude, physical effort, hypoglycemia (low blood sugar), foods, and chemical agents. In addition, headache may result from congestion and edema of the nasal membranes, often termed vasomotor rhinitis, which is assumed to be a localized vascular reaction to stress. Treatment of Headaches Migraine is treated by specific drugs at the time of an attack and by preventive measures between attacks. In an acute attack, ergotamine compounds, often given in conjunction with caffeine, are useful in alleviating the headache, probably because they produce constriction of the cerebral arteries, thus reducing dilation, which is the source of the pain. In addition, most migraine sufferers find that the headache is reduced in a totally dark room. The most obvious treatment for headache arising from neurological disease is to treat the disease itself. Tension headaches can be relieved by muscle- NEUROLOGICAL DISORDERS 711 12937C26.pgs 712 1/22/03 P A RT V 1:56 PM PLASTICITY Page 712 AND DISORDERS relaxant drugs, minor tranquilizers, the application of heat to the affected muscles, and improvement of posture. They can also be prevented by avoiding the life situations that give rise to stress. Infections Infection is the invasion of the body by disease-producing (pathogenic) microorganisms and the reaction of the tissues to their presence and to the toxins generated by them. Because the central nervous system can be invaded by a wide variety of infectious agents—including viruses, bacteria, fungi, and metazoan parasites—the diagnosis and treatment of infection are important components of clinical neurology. Although infections of the nervous system usually spread from infection elsewhere in the body—especially the ears, nose, and throat—they also may be introduced directly into the brain as a result of head trauma, skull fractures, or surgery. Infections of the nervous system are particularly serious because the affected neurons and glia usually die, leaving permanent lesions. There are a number of processes by which infections kill neural cells. First, infections may interfere with the blood supply to neurons, thus producing thrombosis, hemorrhaging of capillaries, or even the complete choking of larger blood vessels. Second, an infection may disturb glucose or oxygen metabolism in brain cells severely enough to kill them. Third, an infection may alter the characteristics of neural-cell membranes, thus changing the electrical properties of the neurons, or it may interfere with the basic enzymatic processes of neurons, producing any number of abnormal conditions. Fourth, infection leads to the formation of pus, a by-product of the body’s defense against infection. Pus is a fluid composed basically of white blood cells, their by-products, by-products of the infectious microorganisms, and a thin fluid called liquor puris. Pus impairs neuronal functioning in at least two ways: it changes the composition of the extracellular fluids surrounding a neuron, thus altering neuronal function; and its presence increases pressure on the brain, disturbing normal functioning. Fifth and finally, infection often causes edema, which leads to compression of the brain tissues, again resulting in dysfunction. Many infections of the nervous system are secondary to infections elsewhere in the body and are accompanied by symptoms of those other infections, including lowered blood pressure and other changes in blood circulation, fever, general malaise, headache, and delirium. In addition, symptoms of cerebral infections include both generalized symptoms of increased intracranial pressure—such as headache, vertigo, nausea, convulsions, and mental confusion—and symptoms specifically associated with the disturbance of particular brain functions. Diagnostic tests for infection include CSF studies in addition to conventional methods of infection identification, such as smear and culture studies. Additionally, CT and other brain scans may be used to diagnose and locate some infectious disorders. Four types of infection can affect the central nervous system: viral infections, bacterial infections, mycotic (fungal) infections, and parasitic infestations. 12937C26.pgs 1/22/03 1:56 PM Page 713 CHAPTER 26 Viral Infections A virus is an encapsulated aggregate of nucleic acid that may be made of either DNA or RNA. Some viruses, such as those causing poliomyelitis and rabies, are called neurotropic viruses, because they have a special affinity for cells of the central nervous system. In contrast, pantropic viruses (such as those that cause mumps and herpes simplex) attack other body tissues in addition to the central nervous system. Most viral infections of the nervous system produce nonspecific lesions affecting widespread regions of the brain, such as lesions due to St. Louis encephalitis, rabies, and poliomyelitis. Bacterial Infections Bacterium is a loose generic name for any microorganism (typically one-celled) that has no chlorophyll and multiplies by simple division. Bacterial infections of the central nervous system result from an infestation of these organisms, usually through the bloodstream. The most common neurological disorders resulting from bacterial infection are meningitis and brain abscess. In meningitis, the meninges are infected by any of a variety of bacteria. Brain abscesses also are produced by a variety of bacteria, secondary to infection elsewhere in the body. An abscess begins as a small focus of purulent (pus-producing) bacteria that cause necrosis (death) of cells in the affected region. As the bacteria multiply and destroy more brain cells, the abscess behaves like an expanding mass (one that is often hollow in the center), producing increasing intracranial pressure. Mycotic Infections Invasion of the nervous system by a fungus is known as a mycotic infection. A fungus is any member of a large group of lower plants (in some taxonomic schemes) that lack chlorophyll and subsist on living or dead organic matter; the fungi include yeasts, molds, and mushrooms. Ordinarily the central nervous system is highly resistant to mycotic infections, but fungi may invade a brain whose resistance has been reduced by diseases such as cancer or tuberculosis. Parasitic Infestations A parasite is an organism that lives on or within another living organism—the host—at the host’s expense. Several kinds of parasites invade the central nervous system and produce diseases, the most important of which are amebiasis and malaria. Amebiasis (also known as amebic dysentery), caused by an infestation of the protozoan ameba Entamoeba histolytica (protozoa are one-celled animals), results in encephalitis and brain abscesses. Malaria is caused by protozoa of the genus Plasmodium, which are transmitted by the bites of infected mosquitoes. Cerebral malaria arises when the plasmodia infect the capillaries of the brain, producing local hemorrhages and the subsequent degeneration of neurons. Treatment of Infections Treatment varies with the type of infection. Viral infections are extremely difficult to treat because there are no specific antidotes, and the only option is to let the disease run its course. Sedatives are sometimes administered to make the NEUROLOGICAL DISORDERS 713 12937C26.pgs 714 1/22/03 P A RT V 1:56 PM PLASTICITY Page 714 AND DISORDERS patient more comfortable. The important exception to this general rule is the treatment of rabies. When a person has had contact with a rabid animal, antirabies vaccine is administered over a period of 2 to 4 weeks to produce immunity before the disease actually develops. Once the disease does develop, rabies is fatal. Bacterial cerebral infections have become less common with the introduction of antibiotic drugs, the usual treatment for these infections. In some cases, it may be necessary to drain abscesses to relieve intracranial pressure or to do spinal taps to remove cerebral spinal fluid and thus reduce the pressure of edema or a buildup of pus. Neither mycotic nor parasitic infections can be treated satisfactorily, although antibiotics are often used to treat associated disorders. Disorders of Motor Neurons and the Spinal Cord A number of movement disorders are produced by damage either to the spinal cord or to cortical projections to the spinal cord. These disorders include myasthenia gravis, a disorder of the muscle receptors; poliomyelitis, a disorder of the motor-neuron cell bodies; multiple sclerosis, a disorder of myelinated motor fibers; paraplegia and Brown-Sequard syndrome, caused by complete transection or hemitransection of the spinal cord, respectively; and hemiplegia, caused by cortical damage. Table 26.4 lists some of the medical terms used in describing movement disorders. Table 26.4 Commonly used terms for movement disorders Apraxia. Inability to carry out purposeful movements or movements on command in the absence of paralysis or other motor or sensory impairments. Usually follows damage to neocortex. Ataxia. Failure of muscular coordination or an irregularity of muscular action. Commonly follows cerebellar damage. Athetosis. A condition in which ceaseless slow, sinuous writhing movements occur, especially in the hands. Due to abnormal function of the extrapyramidal system. Catalepsy. A condition marked by muscular rigidity in which voluntary movements are reduced or absent but posture is maintained. A feature of Parkinson’s disease due to dopamine loss. Cataplexy. Complete loss of movement and posture during which muscle tone is absent but consciousness is spared. Chorea. Literally means dance but refers to the ceaseless occurrence of a wide variety of jerky movements that appear to be well coordinated but are performed involuntarily. Hemiplegia. Complete or partial paralysis to one half of the body. Usually follows damage to the contralateral motor cortex. Palsy. A paralysis of movement that usually refers to persisting movement disorders due to brain damage acquired perinatally. Paralysis. Complete loss of movement or sensation (but more commonly movement) in a part of the body. Usually permanent after damage to motor neurons; temporary after damage to motor cortex (area 4). Paraplegia. Paralysis or paresis of the lower torso and legs. Follows spinal-cord damage. Spasticity. Increase in the tone of certain muscle groups that maintain posture against the force of gravity. If the limb is moved against the rigidity, resistance will initially increase, but then tone will sud