The level of hypocretin 1 (orexin A) in cerebrospinal fluid and the diagnosis of narcolepsy and other somnolent disorders.

excessive daytime sleepiness, cataplexy, sleep paralysis, and hypnagogic hallucinations (1). A nocturnal polysomnogram, followed by the multiple sleep latency test is suggested for the diagnosis. These tests, performed at a sleep disorders clinic, confirm the daytime sleepiness by showing a short sleep latency of usually less than 5 minutes, as well as an abnormally short latency prior to the first rapid eye movement (REM) period (2). HLA typing also helps the diagnosis. However, the tests often have false-negative and false-