No amount of nighttime or daytime sleep produces full alertness. Laughter is the most common precipitant. Anger, embarrassment, excitement, and other forms of emotion also can induce it.
Severe attacks produce complete paralysis of striated muscles, but respiratory muscles are spared.
Twitching around the face or eyelids may accompany the weakness. Consciousness is preserved at the onset but prolonged episodes may be associated with auditory, visual, or tactile hallucinations and may lead directly into REM sleep. Differ from dreams because some awareness of the surroundings is preserved. Diplopia and blurred vision, also common complaints, are probably due to failure of fusion induced by drowsiness. Organic hypersomnias due to thalamic infarction, encephalitis, encephalopathy, tumor.