Narcolepsy, << NAHR kuh `lehp` see, >> is a disease that causes excessive sleepiness. People with narcolepsy tend to fall asleep several times a day. They also often have trouble staying asleep at night. The disease is a lifelong condition that generally first appears during adolescence. Physicians can treat narcolepsy with medications, but it cannot be cured.
In addition to excessive sleepiness, narcoleptics experience episodes in which their muscles suddenly collapse though they remain awake. This condition, called cataplexy, is brought on by strong emotions, especially laughter and anger. Cataplectic episodes last two minutes or less. Narcoleptics may also experience sleep paralysis and hypnagogic hallucinations. In sleep paralysis, a person suddenly becomes unable to move while falling asleep or waking up. As they fall asleep, people with hypnagogic hallucinations experience vivid, realistic sights and sounds that do not really exist.
Scientists believe the symptoms of narcolepsy are related to REM (R_apid _E_ye _M_ovement) sleep, the phase of sleep during which people dream. The eyes move rapidly in this phase, and the body is paralyzed while dreaming occurs. Narcoleptics experience this same sort of paralysis during cataplectic episodes. Most cases of narcolepsy are caused by the lack of a brain chemical called _hypocretin. Scientists believe the loss of hypocretin may be due to an autoimmune disorder in which the cells that contain the chemical are attacked by the body’s own immune system. Normally, the immune system fights infections.
Not all people who are abnormally sleepy have narcolepsy. But if they also experience cataplexy, they are almost certain to have narcolepsy.
