The exact cause of narcolepsy isn't known. Genetics may play a role. Other factors, such as infection, may contribute to the development of narcolepsy.

Normal sleep pattern vs. narcolepsy

The normal process of falling asleep begins with a phase called non-rapid eye movement (NREM) sleep. During this phase, your brain waves slow considerably. After an hour or so of NREM sleep, your brain activity changes, and REM sleep begins. Most dreaming occurs during REM sleep.

In narcolepsy, however, you may suddenly enter into REM sleep without first experiencing NREM sleep, both at night and during the day. Some of the characteristics of REM sleep, such as sudden lack of muscle tone, sleep paralysis and vivid dreams, occur during other sleep stages in people with narcolepsy.

The role of brain chemicals

Hypocretin (hi-po-KREE-tin) is an important chemical in your brain that helps regulate wakefulness and REM sleep. People with narcolepsy have low levels of this neurochemical in their spinal fluid. It's particularly low in those who experience cataplexy. Exactly what causes the loss of hypocretin-producing cells in the brain isn't known, but experts suspect it's due to an autoimmune reaction.

Oct. 24, 2012