Narcolepsy is a clinical syndrome characterized by excessive sleepiness, cataplexy, hypnogogic hallucinations, and sleep paralysis. Cataplexy is the abrupt onset of muscle weakness precipitated by emotions such as laughter and anger. Hypnogogic hallucinations may be visual or auditory and occur just prior to sleep onset. Sleep paralysis describes the inability to move for several minutes on awakening. The cataplexy, hallucinations and sleep paralysis represent the occurrence of rapid eye movement (REM) sleep manifestations at inappropriate times.
Narcolepsy affects 1 per 2,000 individuals in the general population. There is a genetic tendency with the risk of narcolepsy in an immediate family member of 1 per 100. Rarely, narcolepsy is triggered by infection or head injury. The human leukocyte antigen HLA DQB1*O602 is the genetic marker for narcolepsy in almost all individuals. Exciting new research is beginning to elucidate the abnormalities in the brain that may predispose a person to narcolepsy.
Excessive sleepiness is treated with stimulants (methylphenidate and amphetamines). Recently a new stimulant, modafinil (Provigil), was approved by the FDA, the first in 25 years. Modafinil has less side effects than the other stimulants and frequently is effective in a single daily dose. Cataplexy is treated with a tricyclic anti-depressant (protriptyline, imipramine or clomipramine) or one of the SSRI anti-depressants (fluoxetine).
