Chapter 028. Sleep Disorders (Part 10)

Specific questioning about the occurrence of sleep episodes during normal waking hours, both intentional and unintentional, is necessary to determine the extent of the adverse effects of sleepiness on a patients daytime function. Specific areas to be addressed include the occurrence of inadvertent sleep episodes while driving or in other safety-related settings, sleepiness while at work or school (and the relationship of sleepiness to work and school performance), and the effect of sleepiness on social and family life. Driving is particularly hazardous for patients with increased sleepiness. Reaction time is equally impaired by 24 h of sleep loss as...
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Chapter 028. Sleep Disorders (Part 10) Chapter 028. Sleep Disorders (Part 10) Specific questioning about the occurrence of sleep episodes during normalwaking hours, both intentional and unintentional, is necessary to determine theextent of the adverse effects of sleepiness on a patients daytime function. Specificareas to be addressed include the occurrence of inadvertent sleep episodes whiledriving or in other safety-related settings, sleepiness while at work or school (andthe relationship of sleepiness to work and school performance), and the effect ofsleepiness on social and family life. Driving is particularly hazardous for patientswith increased sleepiness. Reaction time is equally impaired by 24 h of sleep lossas by a blood alcohol level of 0.10 g/dL. More than half of Americans admit todriving when drowsy. An estimated 250,000 motor vehicle crashes per year aredue to drowsy drivers, thus causing 20% of all serious crash injuries. Drowsydriving legislation, aimed at improving education of all drivers about the hazardsof driving drowsy and establishing sanctions comparable to those for drunkdriving, is pending in several states. Screening for sleep disorders, provision of anadequate number of safe highway rest areas, maintenance of unobstructedshoulder rumble strips, and strict enforcement and compliance monitoring ofhours-of-service policies are needed to reduce the risk of sleep-relatedtransportation crashes. Evidence for significant daytime impairment [inassociation either with the diagnosis of a primary sleep disorder, such asnarcolepsy or sleep apnea, or with imposed or self-selected sleep-wake schedules(see Shift-Work Disorder, below)] raises the issue of the physiciansresponsibility to notify motor vehicle licensing authorities of the increased risk ofsleepiness-related vehicle accidents. As with epilepsy, legal requirements varyfrom state to state, and existing legal precedents do not provide a consistentinterpretation of the balance between the physicians responsibility and thepatients right to privacy. At a minimum, physicians should document discussionswith the patient regarding the increased risk of operating a vehicle, as well as arecommendation that driving be suspended until successful treatment or a schedulemodification can be instituted. The distinction between fatigue and sleepiness can be useful in thedifferentiation of patients with complaints of fatigue or tiredness in the setting ofdisorders such as fibromyalgia (Chap. 329), chronic fatigue syndrome (Chap.384), or endocrine deficiencies such as hypothyroidism (Chap. 335) or Addisonsdisease (Chap. 336). While patients with these disorders can typically distinguishtheir daytime symptoms from the sleepiness that occurs with sleep deprivation,substantial overlap can occur. This is particularly true when the primary disorderalso results in chronic sleep disruption (e.g., sleep apnea in hypothyroidism) or inabnormal sleep (e.g., fibromyalgia). While clinical evaluation of the complaint of excessive sleepiness is usuallyadequate, objective quantification is sometimes necessary. Assessment of daytimefunctioning as an index of the adequacy of sleep can be made with the multiplesleep latency test (MSLT), which involves repeated measurement of sleep latency(time to onset of sleep) under standardized conditions during a day followingquantified nocturnal sleep. The average latency across four to six tests(administered every 2 h across the waking day) provides an objective measure ofdaytime sleep tendency. Disorders of sleep that result in pathologic daytimesomnolence can be reliably distinguished with the MSLT. In addition, the multiplemeasurements of sleep onset may identify direct transitions from wakefulness toREM sleep that are suggestive of specific pathologic conditions (e.g., narcolepsy). Narcolepsy Narcolepsy is both a disorder of the ability to sustain wakefulnessvoluntarily and a disorder of REM sleep regulation (Table 28-2). The classicnarcolepsy tetrad consists of excessive daytime somnolence plus three specificsymptoms related to an intrusion of REM sleep characteristics (e.g., muscle atonia,vivid dream imagery) into the transition between wakefulness and sleep: (1)sudden weakness or loss of muscle tone without loss of consciousness, oftenelicited by emotion (cataplexy); (2) hallucinations at sleep onset (hypnogogichallucinations) or upon awakening (hypnopompic hallucinations); and (3) muscleparalysis upon awakening (sleep paralysis). The severity of cataplexy varies, aspatients may have two to three attacks per day or per decade. Some patients withobjectively confirmed narcolepsy (see below) may show no evidence of cataplexy.In those with cataplexy, the extent and duration of an attack m ...