Narcolepsy sleep disorder symptoms and causes

Narcolepsy is a neurological sleep disorder most often characterized by excessive daytime sleepiness. Narcoleptics do not need more sleep than non-narcoleptics; rather, narcoleptics have difficulty controlling when to sleep and when to wake. Narcoleptics often have trouble staying asleep during the night and staying awake during the day (National Institute of Neurological Disorders and Stroke [NINDS], 2011).

About 70% of narcoleptics experience cataplexy, a sudden, temporary loss of muscle tone, often triggered by strong emotions like laughter. A minority experience dream-like hallucinations as they fall asleep and wake up.

Symptoms usually start between 12 – 25 years of age [1]. Narcolepsy without cataplexy as rare, occurring in 1.37 per 100,000 person-years. Narcolepsy with cataplexy is even more rare, occurring in 0.74 per 100,000 person-years. Narcolepsy with cataplexy occurs in 0.02 – 0.05% of the population [2].

Narcolepsy sleep disorderThe cause of narcolepsy is not entirely understood. Some reports indicate a potential environmental trigger like Streptococcus pyogenes or seasonal influenza infection. The infection may cause the immune system to mistakenly destroy neurons in the hypothalamus that produce hypocretin (orexin), a neurotransmitter involved in controlling sleep-wake cycles and appetite. Narcoleptics with cataplexy often have little to no hypocretin in their cerebrospinal fluid and experience weight gain.

Certain individuals are more likely to develop narcolepsy. Nearly 100% of narcoleptics carry the human leukocyte antigen (HLA) DQB1*0602 subtype, but only a minority of those that carry the HLA subtype develop narcolepsy [3].

While there is no cure for narcolepsy, treatment usually involves behavioral and drug therapies with such medicines as Modafinil. Drug therapies may come with side effects like nausea, headache, and nervousness.

The diagnosis of narcolepsy may involve a series of tests: polysomnogram (PSG), multiple sleep latency tests (MSLT), levels of hypocretin in the cerebrospinal fluid, and HLA typing.

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