Narcolepsy is a type of sleep disorder that causes patients to fall asleep suddenly, often at unexpected moments. It is a chronic central nervous system (CNS) disorder triggered by disturbances in the chemicals that regulate sleep-wake cycles in the brain.

Patients with narcolepsy feel drowsy much of the time and generally find it difficult to remain awake for extended periods. Although the exact cause is unknown, researchers believe that a combination of genetics and a trigger (such as a virus) cause the condition to develop. Narcolepsy can strike at any age, but most often develops between the ages of 10 and 25 and affects both sexes equally.

Excessive daytime drowsiness, the main symptom of narcolepsy, may be present for years before the condition is diagnosed. In addition to drowsiness, other symptoms commonly associated with narcolepsy include:

• Cataplexy. A sudden loss of muscle tone that may appear similar to a seizure.
  
  
• Sleep paralysis. A less frequent phenomenon marked by a temporary inability to move.
  
  
• Hypnagogic or hypnopompic hallucinations. Occur when patients are partially awake, causing them to have intense, frightening dreams that they perceive as reality.
  
  
• Automatic behavior. Occurs when patients continue to function as if awake during a sleep episode.

Patients typically seek medical care when they find that overwhelming drowsiness is causing them to fall asleep at inappropriate times or preventing them from functioning effectively. If a physician determines that narcolepsy is a likely diagnosis, the patient may be referred to a sleep specialist. The patient may fill out written evaluations that can reveal the presence of narcolepsy. In most cases, the patient’s sleeping patterns will be observed overnight in a sleep center to identify the specific changes in sleep patterns.

There is no cure for narcolepsy. However, medications and lifestyle changes can help patients to manage their symptoms and to lead full lives. Patients with narcolepsy are encouraged to talk to employers or teachers about their condition and ways to accommodate their needs. They should also take extra precautions to ensure that they are not hurt when a sudden episode of sleep strikes.