Monthly Case

The 27-year-old female patient presents in the outpatient clinic because she abruptly loses muscle strength when she has to laugh or when she trains intensely at the gym. The muscles of the neck are mostly involved, but her muscles in her arms and legs can also be affected so that objects can fall out of her hands or that she falls to the ground. This complaint has been going on for the past ten years. The frequency with which she loses muscle strength varies with the presence of the appropriate triggers. Additionally, she often feels tired during the day although she sleeps well during the night. It can happen that she suddenly falls asleep for ten or 20 minutes during the day even when she does not feel really tired. Over the past decade she had gained around 65 pounds without changing eating habits, now attaining a body-mass-index of 38.7. She has no further complaints. There is no history of a psychiatric disorder or any other diseases.

Because of the excessive daytime sleepiness and an increased propensity to sleep during the day there is a need for further sleep studies in a sleep laboratory which take place for three days. Polysomnography was entirely normal. The Multiple Sleep Latency Test, performed at 9 and 11 a.m. and at 1, 3, and 5 p.m., showed a pathologically short mean sleep latency of 2.6 min and four sleep onset-REM (= SOREM) with a mean latency of 3.7 min.

The patient’s history and the results from the Multiple Sleep Latency Test allow to establish the diagnosis of narcolepsy with cataplexy (= Narcolepsy type I). Narcolepsy with cataplexy leads to excessive daytime sleepiness, often associated with naps even in the absence of tiredness which mostly last less than 20 minutes. Cataplectic attacks correspond to a sudden loss of muscle tone in emotionally connoted situations (laughter, joy, startle), often in circumscribed parts of the body. The substantial weight gain in our patients also has to be considered as a symptom of narcolepsy with cataplexy due to a positive energy balance.

Almost always narcolepsy with cataplexy is due to orexin-deficiency (orexin = hypocretin), a neurotransmitter exclusively produced in the lateral hypothalamus. Conversely, narcolepsy without cataplexy does not represent orexin-deficiency but should be considered a different disease entity. Mechanisms leading to orexin-deficiency are most likely the result of a topographically selective autoimmunologically induced inflammation in the hypothalamus.

Medical treatment of narcolepsy with cataplexy includes gammahydroxybutyrate to ameliorate cataplectic attacks as well as stimulating substances such as modafinil or methylphenidate. With this therapeutic approach our patient has substantially less cataplectic attacks and also excessive daytime sleepiness has improved. Contrary, her weight gain persists which is why she considers liposuction.

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