Narcolepsy: clinical approach to etiology, diagnosis, and treatment

Narcolepsy is a neurologic disorder characterized by excessive daytime sleepiness and manifestations of disrupted rapid eye movement sleep stage. The pathologic hallmark is loss of hypocretin neurons in the hypothalamus likely triggered by environmental factors in a susceptible individual. Patients with narcolepsy, in addition to excessive daytime sleepiness, can present with cataplexy, sleep paralysis, sleep fragmentation, and hypnagogic/hypnopompic hallucinations. Approximately 60% to 90% of patients with narcolepsy have cataplexy, characterized by sudden loss of muscle tone. Only 15% of patients manifest all of these symptoms together. Narcolepsy can be misdiagnosed as a psychiatric disorder or even epilepsy. An appropriate clinical history, polysomnogram, Multiple Sleep Latency Test, and, at times, cerebrospinal fluid hypocretin levels are necessary for diagnosis. The treatment of narcolepsy is aimed toward the different symptoms that the patient manifests. Excessive daytime sleepiness is treated with amphetamine-like or non-amphetamine-like stimulants. Cataplexy is treated with sodium oxybate, tricyclic antidepressants, or selective serotonin and norepinephrine reuptake inhibitors. Sleep paralysis, hallucinations, and fragmented sleep may be treated with benzodiazepine hypnotics or sodium oxybate. Patients with narcolepsy should avoid sleep deprivation, sleep at regular hours, and, if possible, schedule routine napping.