Hypnagogic Hallucinations (Narcolepsy) : Causes, Symptoms, Diagnosis, Treatment, Prevention

Hypnagogic or hypnopompic hallucinations are visual, tactile, auditory, or other sensory events, usually brief but occasionally prolonged, that occur at the transition from wakefulness to sleep (hypnagogic) or from sleep to wakefulness (hypnopompic). The phenomenon is thought to have been first described by the Dutch physician Isbrand Van Diemerbroeck in 1664. The person may hear sounds that are not there and see visual hallucinations. These visual and auditory images are very vivid and may be bizarre or disturbing.