NARCOLEPSY [ back to Glossary Index ]
Narcolepsy is a sleep disorder in which a person who is fully awake will suddenly and involuntarily fall asleep and proceed directly from wakefulness to REM (dream) sleep without first transitioning through the gradually increasing drowsiness, stupor and early stages of non-REM sleep. The disorder affects between 125,000 - 250,000 Americans. Sleep attacks ordinarily last 10-20 minutes. When they are accompanied by episodes of muscle weakness and near total paralysis, doctors speak of "cataplexy." Attacks are frequently triggered any strong emotion such as anger or laughter. When the narcoleptic person wakes up he may feel physically refreshed but emotionally troubled by the hallucinatory quality of the vivid dreams which spring up during the sleep attack. These are called "hypnogogic hallucinations." Approximately 1 out of every 2,000 people (0.05% of the general population) has it. There is currently no cure for it, but narcolepsy can be managed and brought under control with the assistance of a physician at a sleep disorders clinic. Some sufferers refuse to seek help from a doctor out of fear of losing their driver's license.

TBI is a frequent cause of insomnia and other disorders of sleep, but is more rarely a cause of narcolepsy. If narcolepsy is suspected after a TBI, the patient should seek prompt examination from a physician specialist in sleep disorders, given the dangers to the patient and his family. Very recent research by Dr. Seiji Nishino at Stanford University has uncovered an objective, biological marker of the disease which can be detected through a spinal tap. Persons with narcolepsy tend to lack a neuropeptide called orexin, also known as hypocretin, which is completely absent from the cerebrospinal fluid of 80% of narcoleptics. Normals who do not get sleep attacks have the protein. A molecular geneticist named M. Yanagisawa at the Howard Hughes Medical Institute was able to cure narcolepsy in mice by injecting orexin directly into their brains. 90% of human narcoleptics have damage to cells in the lateral hypothalamus which manufacture orexin. Clinical trials of orexin infusion in humans should begin soon.