Narcolepsy is the most common primary hypersomnia, which is caused by loss of hypocretin neurons. Hypocretin in the neurohypothalamus is of crucial role in the maintenance of awakeness. Narcolepsy is characterized by hypnagogic/hypnopompic hallucinations, sleep paralysis and disrupted night sleep in addition to hypersomnia. Cataplexy is the pathognomonic feature of narcolepsy observed in 60-90%...