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Narcolepsy is a chronic disorder of unknown etiology. Its usual onset is during the second or third decade of life, and it rarely occurs before age five or after age 50. The disorder is seen with equal frequency in men and women. The case described includes the cardinal features of narcolepsy: excessive daytime somnolence, sleep paralysis, hypnagogic hallucinations (vivid dream-like hallucination at sleep onset) and cataplexy. However, patients rarely experience the full tetrad.

Sleep paralysis and hypnagogic hallucinations occur when REM-associated atonia and vivid dream-like visual hallucinations, respectively, intrude into the transition between wakefulness and sleep. During sleep paralysis, the patient is conscious but unable to move the limbs. Hypnagogic hallucinations occur at sleep onset. Hypnopompic hallucinations occur on awakening.

Diagnosis. The diagnosis of narcolepsy is based on an overnight polysomnogram, which evaluates for sleep apnea, periodic limb movements of sleep or other causes of disturbed nocturnal sleep, and a multiple sleep latency test (MSLT) performed the following day. Positive MSLT results are required to confirm the diagnosis. This test consists of a series of four to five nap trials that objectively measure severity of daytime sleepiness. The primary parameters of interest are sleep latency and the presence of sleep-onset REM. Sleep latency refers to the amount of time that it takes a patient to fall asleep. A sleep latency period of less than five minutes is indicative of a pathologic sleepy state, and a sleep latency period of five to 10 minutes suggests pathologic sleepiness. Sleep-onset REM refers to REM sleep that occurs within 10 minutes after sleep onset.

An average sleep latency of less than 10 minutes and sleep-onset REM in at least two nap trials are required to establish the diagnosis. Because sleep-onset REM can occur with REM-sleep deprivation from sleep apnea, sleep-wake schedule disturbances or drug or alcohol withdrawal, an overnight polysomnogram is used to help exclude such causes. A two-week period of alcohol or drug abstinence is required before an MSLT; abstinence may be confirmed with a drug screen before the study.

Treatment. Attempts to treat narcolepsy are often unsuccessful. Excessive daytime sleepiness and cataplexy are particularly difficult to treat. The mainstay of treatment for excessive daytime sleepiness is a combination of several planned daily naps and central nervous system stimulants, such as pemoline (Cylert), methylphenidate or amphetamine sulfate. To avoid development of tolerance to these agents, weekly drug vacations of one to two days.

Cataplexy, sleep paralysis and hypnagogic hallucinations may be treated with tricyclic antidepressants, such as clomipramine, imipramine (Tofranil), nortriptyline and protriptyline, and serotonin reuptake inhibitors, such as fluoxetine (Prozac). Use of these drugs for this indication.