Narcolepsy and Cataplexy
Michael H. Silber, MD
What causes narcolepsy?
There have been major breakthroughs in understanding the cause of narcolepsy. We know that most cases of narcolepsy in humans are due to a lack of a chemical in the brain called hypocretin. This chemical was unknown before 1998, so this is very new research. Most patients with narcolepsy do not produce hypocretin in a deep part of the brain called the hypothalamus. If you don't produce hypocretin, it would appear that other chemicals that cause alertness cannot function properly.
Research studies have shown that most narcoleptic patients don't have hypocretin in their spinal fluid, and it is possible that this may become a diagnostic test for narcolepsy in the not-too-distant future. What we don't know is why patients with narcolepsy don't produce hypocretin. We think this is probably due to an attack of the body's immune system against the cells that produce it, but this is still speculative. But we are engaged in research projects to try to establish this.
What are the warning signs?
The most important symptom of narcolepsy is sleepiness. Of course, there are many causes of sleepiness, including sleep deprivation, the effect of medications or obstructive sleep apnea , and narcolepsy is not the most common cause. But in any young person who develops sleepiness, narcolepsy has to be considered. Sleepiness is not a specific symptom of narcolepsy.
The most specific symptom is cataplexy, a sudden weakness of the muscles of the body, especially the legs but also the face and neck, that is brought on by strong emotion, especially laughing. Patients with narcolepsy may also have strange dreamlike experiences before falling asleep or waking up in the morning, and they may also have temporary paralysis of the body at the same time. However, these two symptoms are common in the general population and by themselves do not make one a narcoleptic.
Who is affected by narcolepsy?
The frequency of narcolepsy in North America has been quite uncertain. It varies from country to country. It is most common in Japan, and rare in Israel. We embarked on a