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I-88. The answer is C. (Chap. 26) The parietofrontal area of the brain is responsible for spatial orientation. The major components of the network include the cingulate cortex, posterior parietal cortex, and the frontal eye fields. In addition, subcortical areas in the striatum and thalamus are also important. Together, these systems integrate information to maintain spatial cognition, and a lesion in any of these areas can lead to hemispatial neglect. In neglect syndromes, three behavioral manifestations are seen: Sensory events in the neglected hemisphere have less overall impact; there is a paucity of conscious acts directed toward the neglected hemisphere; and the patient behaves as if the neglected hemisphere is devalued. In Figure I-88, almost all of the As (the target) represented on the left half of the figure are missed. This is an example of a target detection task. Hemianopia alone is not sufficient to cause this finding because the individual can turn his or her head left and right to identify the targets.

Bilateral disorders of the parietofrontal area of the brain can lead to severe spatial disorientation known as Balint’s syndrome. In Balint’s syndrome, there is inability to orderly scan the environment (oculomotor apraxia) and inaccurate manual reaching for objects (optic apraxia). A third finding in Balint’s syndrome is simultanagnosia. Simultanagnosia is the inability to integrate information in the center of the gaze with peripheral information. An example is a target detection test in which only the A’s present in the outer portion of the figure would be indicated. Individuals with this finding also tend to miss the larger objects in a figure and would not be able to accurately identify the target when it was made much larger than the surrounding letters. Construction apraxia refers to the inability to copy a simple line drawing such as a house or star and occurs most commonly in association with parietal lesions. Object agnosia is the inability to name a generic object or describe its use in contrast to anomia when an individual should be able to describe the use of the object even if it cannot be named. The defect in the object agnosia is usually in the territory of the bilateral posterior cerebral arteries.

I-89. The answer is C. (Chap. 27) Shift work sleep disorder is a disorder of the circadian rhythm that is common in any individual who has to commonly work at night. At present, an estimated 7 million individuals in the United States work permanently at night or on rotating shifts. Increasing research devoted to sleep disorders in night shift workers has demonstrated that the circadian rhythm never fully shifts to allow one to perform at full alertness at night. The reason for this is likely multifactorial and includes the fact that most individuals who work at night try to abruptly shift their sleep schedules to a more normal pattern on days when they are not working. Consequently, night shift workers often have chronic sleep deprivation, increased length of time awake before starting work, and misalignment of their circadian phase with the intrinsic circadian phase. The results of this lead to decreased alertness and increased errors during night shifts. In an estimated 5–10% of individuals working night shifts, the excessive sleepiness during the night and insomnia during the day are deemed to be clinically significant. Strategies for treating shift work sleep disorder use a combination of behavioral and pharmacologic strategies. Caffeine does promote wakefulness, but the effects are not long lasting, and

tolerance develops over time. Brief periods of exercise frequently boost alertness and can be used before starting a night shift or during the shift at times of increased sleepiness. Many sleep experts support strategic napping during shifts for no more than 20 minutes at times of circadian nadirs. Naps longer than 20 minutes can lead to sleep inertia during which an individual may feel very disoriented and groggy and experience a decline in motor skills upon abrupt awakening from sleep. Bright lights before and during night shift work may improve alertness, but one must be careful to avoid bright lights in the morning after a night shift because light entrainment is a powerful stimulus of the internal circadian clock. If an individual is exposed to bright light in the morning, it will interfere with the ability to fall asleep during the day. Night shift workers should be encouraged to wear dark sunglasses in the morning on the way home. Sleep during the day is frequently disrupted in night shift workers. Creating a quiet, dark, and comfortable environment is important, and sleep should be a priority for the individual during the day. The only pharmacologic therapy approved by the Food and Drug Administration for treatment of shift work sleep disorder is modafinil 200 mg taken 20–30 minutes before the start of a night shift. Modafinil has been demonstrated to increase sleep latency and decrease attentional failures during night shifts but does not alleviate the feelings of excessive sleepiness. Melatonin is not one of the recommended therapies for shift work sleep disorder. If used, it should be taken 2–3 hours before bedtime rather than right before bedtime to simulate the normal peaks and troughs of melatonin secretion.

I-90. The answer is C. (Chap. 27) This patient complains of symptoms that are consistent with restless legs syndrome (RLS). This disorder affects 1–5% of young to middle-aged individuals and as many as 20% of older individuals. The symptom of RLS is a nonspecific uncomfortable sensation in the legs that begins during periods of quiescence and is associated with the irresistible urge to move. Patients frequently find it difficult to describe their symptoms but usually describe the sensation as deep within the affected limb. Rarely is the sensation described as distinctly painful unless an underlying neuropathy is also present. The severity of the disorder tends to wax and wane over time and tends to worsen with sleep deprivation, caffeine intake, pregnancy, and alcohol. Renal disease, neuropathy, and iron deficiency are known secondary causes of RLS symptoms. In this patient, correcting the iron deficiency is the best choice for initial therapy because this may entirely relieve the symptoms of RLS. For individuals with primary RLS (not related to another medical condition), the dopaminergic agents are the treatment of choice. Pramipexole or ropinirole is recommended as first-line treatment. Although carbidopa/levodopa is highly effective, individuals have a high risk of developing augmented symptoms over time with increasingly higher doses needed to control the symptoms. Other options for treating RLS include narcotics, benzodiazepines, and gabapentin. Hormone replacement therapy has no role in the treatment of RLS.

I-91. The answer is A. (Chap. 27) Narcolepsy is a sleep disorder characterized by excessive sleepiness with intrusion of rapid eye movement (REM) sleep into wakefulness. Narcolepsy affects about one in 4000 individuals in the United States with a genetic predisposition. Recent research has demonstrated that narcolepsy with cataplexy is associated with low or undetectable levels of the neurotransmitter hypocretin (orexin) in the CSF. This neurotransmitter is released from a small number of neurons in the hypothalamus. Given the association of narcolepsy with the major histocompatibility antigen human leukocyte antigen DQB1*0602, it is thought that narcolepsy is an autoimmune process that leads to destruction of the hypocretin-secreting neurons in the hypothalamus. The classic symptom tetrad of narcolepsy is (1) cataplexy, (2) hypnagogic or hypnopompic hallucinations, (3) sleep

paralysis, and (4) excessive daytime somnolence. Of these symptoms, cataplexy is the most specific for the diagnosis of narcolepsy. Cataplexy refers to the sudden loss of muscle tone in response to strong emotions. It most commonly occurs with laughter or surprise but may be associated with anger as well. Cataplexy can have a wide range of symptoms from mild sagging of the jaw lasting for a few seconds to a complete loss of muscle tone lasting several minutes. During this time, individuals are aware of their surroundings and are not unconscious. This symptom is present in 76% of individuals diagnosed with narcolepsy and is the most specific finding for the diagnosis. Hypnagogic and hypnopompic hallucinations and sleep paralysis can occur from any cause of chronic sleep deprivation, including sleep apnea and chronic insufficient sleep. Excessive daytime somnolence is present in 100% of individuals with narcolepsy but is not specific for the diagnosis because this symptom may be present with any sleep disorder as well as with chronic insufficient sleep. The presence of two or more REM periods occurring during a daytime multiple sleep latency test is suggestive but not diagnostic of narcolepsy. Other disorders that may lead to presence of REM during short daytime nap periods include sleep apnea, sleep phase delay syndrome, and insufficient sleep.

I-92. The answer is B. (Chap. 27;

http://www.sleepfoundation.org/site/c.huIXKjM0IxF/b.2417355/k.143E/2002_Sleep_in_America_Pol accessed May 12, 2011) Insomnia is the most common sleep disorder in the population. In the 2002 Sleep in America Poll, 58% of respondents reported at least one symptom of insomnia on a weekly basis, and one-third of individuals experience these symptoms on a nightly basis. Insomnia is defined clinically as the inability to fall asleep or stay asleep, which leads to daytime sleepiness or poor daytime function. These symptoms occur despite adequate time and opportunity for sleep. Insomnia can be further characterized as primary or secondary. Primary insomnia occurs in individuals with an identifiable cause of insomnia and is often a long-standing diagnosis for many years. Within the category of primary insomnia is adjustment insomnia, which is typically of short duration with a well-defined stressor. Secondary causes of insomnia include comorbid medical or psychiatric conditions and can be related to caffeine or illegal and prescribed drugs. Obstructive sleep apnea is thought to affect as many as 10–15% of the population and is currently underdiagnosed in the United States. In addition, because of the rising incidence of obesity, obstructive sleep apnea is also expected to increase in incidence over the coming years. Obstructive sleep apnea occurs when there is ongoing effort to inspire against an occluded oropharynx during sleep. It is directly related to obesity and has an increased incidence in men and in older populations. Narcolepsy affects 1 in 4000 people and is caused by deficit of hypocretin (orexin) in the brain. Symptoms of narcolepsy include a sudden loss of tone in response to emotional stimuli (cataplexy), hypersomnia, sleep paralysis, and hallucinations with sleep onset and waking. Physiologically, there is intrusion or persistence of rapid eye movement sleep during wakefulness that accounts for the classic symptoms of narcolepsy. Restless legs syndrome is estimated to affect 1–5% of young to middle-aged adults and as many as 10–20% of elderly adults. Restless legs syndrome is marked by uncomfortable sensations in the legs that are difficult to describe. The symptoms have an onset with quiescence, especially at night, and are relieved with movement. Delayed sleep phase syndrome is a circadian rhythm disorder that commonly presents with a complaint of insomnia and accounts for as much as 10% of individuals referred to the sleep clinic for evaluation of insomnia. In delayed sleep phase syndrome, the intrinsic circadian rhythm is delayed such that sleep onset occurs much later than normal. When allowed to sleep according to the intrinsic circadian rhythm, individuals with delayed sleep phase syndrome sleep normally and do not experience excessive somnolence. This disorder is most common in adolescence and young adulthood.

I-93. The answer is C. (Chap. 27) Parasomnias are abnormal behaviors or experiences that arise from slow-wave sleep. Also known as confusional arousals, the electroencephalogram during a parasomnia event frequently shows persistence of slow-wave (delta) sleep into arousal. Non–rapid eye movement (NREM) parasomnias may also include more complex behavior, including eating and sexual activity. Treatment of NREM parasomnias is usually not indicated, and a safe environment should be assured for the patient. When injury is likely to occur, treatment with a drug that decreases slow-wave sleep will treat the parasomnia. Typical treatment is a benzodiazepine. There are no typical parasomnias that arise from stage I or stage II sleep. REM parasomnias include nightmare disorder and REM-behavior disorder. REM-behavior disorder is increasingly recognized as associated with Parkinson’s disease and other parkinsonian syndromes. This disorder is characterized by the absence of decreased muscle tone in REM sleep, which leads to the acting out of dreams, sometimes resulting in violence and injury.

I-94. The answer is E. (Chap. 28) (See Figure I-94.) Bitemporal hemianopia is caused by a lesion at the optic chiasm because fibers there decusate into the contralateral optic tract. Crossed fibers are more damaged by compression than uncrossed fibers. This finding is usually caused by symmetric compression in the sellar region by a pituitary adenoma, meningioma, craniopharyngioma, glioma, or aneurysm. These lesions are often insidious and may be unnoticed by the patient. They will escape detection by the physician unless each eye is tested separately. Lesions anterior to the chiasm (retinal injury, optic nerve injury) will cause unilateral impairment and an abnormal pupillary response. Postchiasmic lesions (temporal, parietal, occipital cortex) cause homonymous lesions (similar field abnormalities in both eyes) that vary with location. Occlusion of the posterior cerebral artery supplying the occipital lobe is a common cause of total homonymous hemianopia.

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Date: 2016-04-22; view: 565