Chapter 028. Sleep Disorders (Part 10) pot

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 patient's 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 by a blood alcohol level of 0.10 g/dL. More than half of Americans admit to
driving when drowsy. An estimated 250,000 motor vehicle crashes per year are
due to drowsy drivers, thus causing 20% of all serious crash injuries. Drowsy
driving legislation, aimed at improving education of all drivers about the hazards
of driving drowsy and establishing sanctions comparable to those for drunk
driving, is pending in several states. Screening for sleep disorders, provision of an
adequate number of safe highway rest areas, maintenance of unobstructed
shoulder rumble strips, and strict enforcement and compliance monitoring of
hours-of-service policies are needed to reduce the risk of sleep-related
transportation crashes. Evidence for significant daytime impairment [in
association either with the diagnosis of a primary sleep disorder, such as
narcolepsy or sleep apnea, or with imposed or self-selected sleep-wake schedules
(see "Shift-Work Disorder," below)] raises the issue of the physician's
responsibility to notify motor vehicle licensing authorities of the increased risk of
sleepiness-related vehicle accidents. As with epilepsy, legal requirements vary
from state to state, and existing legal precedents do not provide a consistent
interpretation of the balance between the physician's responsibility and the
patient's right to privacy. At a minimum, physicians should document discussions
with the patient regarding the increased risk of operating a vehicle, as well as a
recommendation that driving be suspended until successful treatment or a schedule

modification can be instituted.
The distinction between fatigue and sleepiness can be useful in the
differentiation of patients with complaints of fatigue or tiredness in the setting of
disorders such as fibromyalgia (Chap. 329), chronic fatigue syndrome (Chap.
384), or endocrine deficiencies such as hypothyroidism (Chap. 335) or Addison's
disease (Chap. 336). While patients with these disorders can typically distinguish
their daytime symptoms from the sleepiness that occurs with sleep deprivation,
substantial overlap can occur. This is particularly true when the primary disorder
also results in chronic sleep disruption (e.g., sleep apnea in hypothyroidism) or in
abnormal sleep (e.g., fibromyalgia).
While clinical evaluation of the complaint of excessive sleepiness is usually
adequate, objective quantification is sometimes necessary. Assessment of daytime
functioning as an index of the adequacy of sleep can be made with the multiple
sleep latency test (MSLT), which involves repeated measurement of sleep latency
(time to onset of sleep) under standardized conditions during a day following
quantified nocturnal sleep. The average latency across four to six tests
(administered every 2 h across the waking day) provides an objective measure of
daytime sleep tendency. Disorders of sleep that result in pathologic daytime
somnolence can be reliably distinguished with the MSLT. In addition, the multiple
measurements of sleep onset may identify direct transitions from wakefulness to
REM sleep that are suggestive of specific pathologic conditions (e.g., narcolepsy).
Narcolepsy
Narcolepsy is both a disorder of the ability to sustain wakefulness
voluntarily and a disorder of REM sleep regulation (Table 28-2). The classic
"narcolepsy tetrad" consists of excessive daytime somnolence plus three specific
symptoms 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, often
elicited by emotion (cataplexy); (2) hallucinations at sleep onset (hypnogogic
hallucinations) or upon awakening (hypnopompic hallucinations); and (3) muscle

paralysis upon awakening (sleep paralysis). The severity of cataplexy varies, as
patients may have two to three attacks per day or per decade. Some patients with
objectively confirmed narcolepsy (see below) may show no evidence of cataplexy.
In those with cataplexy, the extent and duration of an attack may also vary, from a
transient sagging of the jaw lasting a few seconds to rare cases of flaccid paralysis
of the entire voluntary musculature for up to 20–30 min. Symptoms of narcolepsy
typically begin in the second decade, although the onset ranges from ages 5–50.
Once established, the disease is chronic without remissions. Secondary forms of
narcolepsy have been described (e.g., after head trauma).
Table 28-2 Prevalence of Symptoms in Narcolepsy
Symptom Prevalence, %

Excessive daytime somnolence 100
Disturbed sleep 87
Cataplexy 76
Hypnagogic hallucinations 68
Sleep paralysis 64
Memory problems 50