It is a chronic sleep disorder which leads to excessive daylight drowsiness.
It may be due to a genetic factor and unusual signal being released in the brain as a result of absence of the brain chemical called hypocretin/orexin, which controls sleep. It is often seen as the effect of the immune system erroneously working against the production of hypocretin in thr brain.
It results in unexpected attacks of sleep, abrupt loss of muscle tone and hallucinations.
