Disorders of Sleep and Wakefulness
Narcolepsy and sleep apnoea are the commonest causes of persistent daytime sleepiness. There are approximately 20 000 people with narcolepsy in the United Kingdom, 100 000 in the United States. The diagnosis of narcoleptic syndrome is established by the history of recurrent daily short sleep attacks in combination with cataplexy, brief episodes of loss of muscle tone and paralysis. Narcolepsy often results from monotony, and cataplexy is usually due to a sudden increase in alertness, with laughter or surprise. About one-half of all subjects also have sleep paralysis, and many describe vivid dreams at sleep onset, or even during wakefulness. In classic cases, the diagnosis is obvious from the history, and also from the finding of at least two sleep-onset REM periods during a multiple sleep latency test (MSLT). The MSLT gives an index of daytime drowsiness, with measurement of the time of sleep onset at 2-h intervals on five occasions throughout the day.
KeywordsAnorexia Nervosa Cluster Headache Daytime Drowsiness Obstructive Sleep Apnoea Sleep Onset
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