Narcolepsy

 | October 1, 2007

Narcolepsy

Narcolepsy is a disorder of sleep/wake regulation whose hallmark is daytime sleepiness. A variety of other symptoms may also be present, but abnormalities of REM sleep seem to underlie each one. Instead of occurring normally — after a steady progression through the other stages of sleep — REM sleep intrudes at unusual and unwelcome times, such as immediately after sleep begins, as soon as a person lies down, or even in the midst of daytime activities.

Willpower or better nighttime sleep habits cannot overcome the profound drowsiness of narcolepsy. As a result, people with narcolepsy often have great trouble completing tasks.

About 1 in 2,000 people has this condition. It affects both sexes and all races equally, and it has a genetic component; having a close relative makes a person 20 to 40 times more likely to have it.

In the late 1990s, researchers discovered that many cases of narcolepsy result from the lack of a brain chemical called hypocretin (sometimes called orexin) that normally maintains wakefulness and helps regulate sleep. People with narcolepsy lose the cells that make hypocretin. The discovery of the gene that makes hypocretin and the location of its production in the brain has spurred research focused on new ways to diagnose and treat this disorder.

Narcolepsy usually becomes apparent during adolescence or young adulthood, although symptoms sometimes appear in early childhood or middle age. On average, it takes five years of symptoms and visits to five physicians before a diagnosis of narcolepsy is made. This is because sleepiness may be the only symptom, or cataplectic attacks (see "Cataplexy") may be misdiagnosed as epilepsy or fainting.

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Symptoms of narcolepsy

Narcolepsy may manifest in any of several ways:

Excessive sleepiness. People with narcolepsy often feel extremely tired and struggle to stay awake during the daytime.

Sleep attacks. A person may suddenly fall asleep for 5 to 10 minutes when relaxing or even while carrying on a conversation. If REM sleep and dreaming occur immediately, the individual sometimes makes conversation that is appropriate to the dream instead of the actual situation.

Cataplexy. In cataplexy, the brain mechanism that paralyzes muscles during REM sleep becomes activated during the day. Thus, you may be fully alert but suffer partial paralysis or a complete muscle collapse, often brought on by laughter, anger, or other strong emotions. Cataplexy may set in several years after daytime sleepiness first appears, although sometimes it's the first symptom of narcolepsy. In mild cataplexy, your knees may buckle, or the muscles of your jaw or neck may become weak and difficult to control. When it's severe, the muscles become completely paralyzed, and you may fall to the ground. You are usually fully awake and aware of what's going on, but unable to talk. Although a few people then fall asleep, most recover spontaneously after several seconds or minutes.

Sleep paralysis. A terrifying feeling of paralysis may occur during the transition between wakefulness and sleep if the REM stage begins before a person is fully asleep. Although muscle control usually returns within a few minutes, such episodes can cause great anxiety.

Hypnagogic hallucinations. When REM dreaming occurs during wakefulness, the vivid and often frightening images, known as hypnagogic hallucinations, are difficult to distinguish from reality. A person may see prowlers or believe that his or her house is on fire. This usually happens just at sleep onset or upon awakening. This condition can be confused with mental illness because its symptoms resemble those of some psychotic disorders.

Disturbed nighttime sleep. Just as sleep intrudes during the day, unwelcome awakenings can occur at night, depriving narcoleptics of restorative rest and exacerbating daytime drowsiness. Some feel as if they have hardly slept at all.

Automatic behavior. Because of their profound sleepiness, people with narcolepsy perform many routine tasks without being fully aware of what they are doing. For example, one man washed and dried the dishes and then stacked them in the refrigerator but had no recollection of doing so.

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Treatments for narcolepsy

Treatment for narcolepsy is geared toward improving wakefulness during the day and preventing REM-related symptoms.

Most people require stimulant medications such as methylphenidate (Ritalin) and dextroamphetamine (Dexedrine) to counter sleep attacks and drowsiness (see Table 5). Because these medications have been abused as recreational drugs and misused as diet pills, drug enforcement agencies often require physicians to provide extensive documentation when they prescribe them. Even with medication, however, people are never as alert as they would be if they didn't have this condition.

Modafinil (Provigil), a once-a-day medication to promote wakefulness, has a different mechanism of action than the older stimulants. It doesn't cause such side effects as euphoria or weight loss, so there's less concern about its misuse or abuse. However, it is less potent.

In most people, antidepressants that suppress REM sleep — such as fluoxetine (Prozac), sertraline (Zoloft), paroxetine (Paxil), clomipramine (Anafranil), or venlafaxine (Effexor) — can also prevent cataplexy and other REM-related symptoms.

Another medication for cataplexy is sodium oxybate (Xyrem), also known as gamma hydroxybutyrate (GHB). This medication helps decrease the number of cataplexy episodes and may improve nighttime sleep and reduce daytime sleepiness as well. Because of its chemical properties, it must be taken at bedtime and again during the middle of the night. Xyrem is tightly regulated because of its potential for misuse; it has been associated with criminal acts such as date rape.

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Review Date: 2007-10-01

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