neurologic disorders
Narcolepsy
Introduction
Narcolepsy is characterized by chronic excessive daytime sleepiness, often with sudden loss of muscle tone (cataplexy). Other symptoms include sleep paralysis and hypnagogic and hypnopompic hallucinations. Diagnosis is by polysomnography and multiple sleep latency testing. Treatment is withmodafinil,armodafinil,solriamfetol,pitolisant,sodium oxybate, or a combination drug that contains calcium, magnesium, potassium, and sodium oxybates for excessive daytime sleepiness and cataplexy. (See also Approach to the Patient With a Sleep or Wakefulness Disorder .) The cause of narcolepsy is unknown. In Europe, Japan, and the US, incidence is 0.2 to 1.6/1000. Narcolepsy is equally common in both sexes. Narcolepsy is strongly associated with specific human leukocyte antigen (HLA) haplotypes, but the cause is not thought to be genetic. Concordance in twins is low (25%), suggesting a prominent role for environmental factors, which often trigger the disorder. The neuropeptide hypocretin-1 is deficient in cerebrospinal fluid (CSF) of narcoleptic animals and most human patients, suggesting that the cause may be HLA–associated autoimmune destruction of hypocretin-containing neurons in the lateral hypothalamus. Narcolepsy features dysregulation of the timing and control of rapid eye movement (REM) sleep. Therefore, REM sleep intrudes into wakefulness and into the transition from wakefulness to sleep. Many symptoms of narcolepsy result from postural muscle paralysis and vivid dreaming, which characterize REM. There are 2 types: Type 1: Narcolepsy due to hypocretin deficiency and accompanied by cataplexy (momentary muscular weakness or paralysis evoked by sudden emotional reactions) Type 2: Narcolepsy with normal hypocretin levels and without cataplexy TheKleine-Levin syndrome, a very rare disorder in adolescent boys, resembles narcolepsy. The Kleine-Levin syndrome causes episodic hypersomnia (excessive daytime sleepiness) and hyperphagia. Etiology is unclear but may be an autoimmune response to an infection. 