Narcolepsy is a sleep disorder that causes uncontrollable sleepiness and frequent daytime sleeping.

The exact cause of narcolepsy is unknown. Studies using gene markers show that the disorder may be genetic. A small group of neurons in the brain has been implicated in producing transitions from sleep to wakefulness and vice-versa. People with narcolepsy may have fewer of these neurons, or these neurons may have been damaged.

The disorder may be aggravated by conditions that cause insomnia, such as disruption of work schedules.

Narcolepsy is characterized by episodes of frequent, uncontrollable daytime sleeping, usually preceded by drowsiness. Sometimes, the person may start dreaming immediately upon falling asleep. The episodes usually occur after meals, but falling asleep may occur while working or driving a vehicle, having a conversation, being in any non-stimulating situation, or being in situations where there is little movement (sedentary situations).

There is a brief period of sleep, and the person awakens feeling refreshed. However, the person may again become uncontrollably sleepy a short time later.

Narcolepsy may also be associated with cataplexy, a brief episode of severe loss of muscle tone in various muscles. Generalized weakness may occur for a few moments during the transition between sleep and wakefulness (sleep paralysis). Many people with narcolepsy also have dreamlike hallucinations in the transition between sleep and wakefulness.

• Persistent drowsiness (hypersomnia -- excessive daytime sleepiness)
• Difficulty for a young adult to stay awake during classes or work
• A sudden, uncontrollable need to sleep during the day (sleep attack)
  • May occur several times during a day
  • Usually happens after eating, but may occur at any time
  • Each sleep episode lasts about 15 minutes
• Awake and refreshed feeling after each episode
• Hallucinations, visual (sight) or auditory (hearing) may come before sleep, or occur during the sleep episode
• Sudden loss of muscle tone (cataplexy)
  • May be associated with emotional reactions such as laughter or anger
  • May be similar in appearance to seizures
• Temporary inability to use muscles (sleep paralysis)
  • Occurs immediately upon awakening
  • Occurs at the onset of drowsiness

Examination and tests are used to rule out disorders that may cause similar symptoms, including sleepiness that results from seizures, sleep apnea, insomnia, restless leg syndrome, other sleep disorders, or other medical, psychiatric, or neurological (nervous system) diseases.

The diagnosis is confirmed by sleep studies (polysomnogram), particularly a study called the Multiple Sleep Latency Test (MSLT). During MSLT, the time it takes to fall asleep during daytime nap opportunities is measured .

Tests to rule out other disorders may include:

• Lab tests (variable, depending on the suspected cause)
• ECG (measures the heart's electrical activity)
• Monitoring of breathing
• EEG (brain activity measurements)
• Recording of the amount of sleep
• Sleep lab study -- recording of observed sleep cycle, including episodes of REM sleep (the part of the cycle where dreaming occurs)
• Blood tests -- determines the presence of narcolepsy-related genes, or medical illnesses associated with excessive sleepiness

Recently, patients with narcolepsy have been found to have low levels of hypocretin (a protein made by the brain) in their spinal fluid. More research will determine how useful this test is in diagnosing narcolepsy.

There is no known cure for narcolepsy. Treatment is aimed at control of the symptoms.

Lifestyle adjustments and learning to cope with the emotional and other effects of the disorder may improve functioning in work and social activities. Planned naps can help regulate daytime sleep and reduce the number of unplanned, sudden sleep attacks. It is important to tell teachers and supervisors about this condition so that those affected are not punished for being "lazy" at school or work.

Eating light or vegetarian meals during the day and avoiding heavy meals prior to important activities may help reduce the odds of an attack after daytime meals. If possible, schedule a brief nap (10 to 15 minutes) after meals.

Prescription medications may be necessary, including stimulants such as dextroamphetamine (Dexedrine, DextroStat) and methylphenidate (Ritalin). Modafinil (Provigil) is a new, less powerful type of stimulant that is believed to have less abuse potential than other stimulants. It has recently been found to be effective in maintaining wakefulness.

Antidepressant medications such as imipramine can help to reduce the number of episodes of cataplexy, but they usually do not reduce the number of sleeping episodes.

Patients with narcolepsy may have driving restrictions placed on them. These restrictions vary from state to state.

Narcolepsy is a chronic, life-long condition. It is not a fatal illness, but it may be dangerous if episodes occur during driving, operating machinery, or similar activities. Narcolepsy is usually controllable with treatment. Treating other underlying sleep disorders can improve symptoms of narcolepsy markedly.

• Injuries and accidents, if attacks occur during activities
• Impairment of functioning at work
• Impairment of social activities
• Side effects of medications used to treat the disorder

Call your health care provider if symptoms suggestive of narcolepsy occur.

Call your health care provider if narcolepsy does not respond to treatment, or if other symptoms develop.

There is no known prevention for narcolepsy. Treatment may reduce the number of attacks. Avoid situations that aggravate the condition if you are prone to attacks of narcolepsy.