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Sleep Disorders

Inaccurate sleep study/narcolepsy?

01/30/2008

Question:

I was wondering if the environment of a sleep lab could create a false negative for a sleep disorder such as narcolepsy? I have eds and symptoms that might suggest cataplexy but because the environment of the sleep lab was noisy and i was uncomfortable from the wires. I don`t think I fell asleep in the first 5 minutes which I understand is necessary for a diagnosis of narcolepsy. I won`t have the results for a while but I am worried they the doctor might dismiss the possibility based on the delayed sleep latency.

I understand the cataplexy is unique enough to narcolepsy that it can make the diagnosis easier but since there was no doc present at the testing I never got to describe my symptoms. I do feel weak when I laugh but don`t lose muscle strength/control with that so much as if I am surprised, frustrated, angry, anticipating an event etc. I have also had complete collapses after standing up after napping and of all things, in elevators when they start moving. Can someone have cataplexy where laughter isn`t the primary trigger? I do feel weak and slump to the floor if someone were to tickle me but isn`t that normal?

thanks!

Answer:

This is an interesting question about the reliability of a sleep history and testing for the diagnosis of narcolepsy. I'll address each part of this question after a brief overview of narcolepsy.

Narcolepsy affects about 1 in 2000 people. Narcolepsy is characterized by excessive sleepiness and abnormal intrusions of rapid eye movement (REM) sleep phenomena into awake time. Typically, during REM sleep, our muscles are inactive (except for our breathing muscles and eye muscles) and unable to move. In individuals with narcolepsy, this "paralysis" of muscles may occur during wakefulness (known as cataplexy, usually brought on by strong emotions) or during transitions between sleep and wakefulness (sleep paralysis). In addition, dreams may intrude up in these times as well (known as hypnagogic or hypnopompic hallucinations). Other symptoms of narcolepsy may include poor nighttime sleep and automatic behaviors (performing tasks without being aware of what you are doing or having recall of having done it).

While true cataplexy (brief, sudden, bilateral loss of muscle tone brought on by strong emotions) is considered very strong evidence of narcolepsy, the other symptoms listed may be seen in individuals without narcolepsy. Furthermore, individuals diagnosed with narcolepsy may not have any or have only some of the other associated symptoms, though they are always sleepy. The diagnosis of this condition is usually determined by a Sleep Specialist after taking a thorough history, performing an examination, and obtaining objective testing - a sleep study and a daytime nap study (known as a Multiple Sleep Latency Study or MSLT).

The MSLT is required to make the diagnosis of narcolepsy in patients presenting with sleepiness but no cataplexy and is still recommended as part of the evaluation for those with cataplexy, though is not required. The test is not fool-proof, however, and patients can exhibit sleepiness and dreams during daytime naps (the findings suggestive of narcolepsy) in conditions other than narcolepsy. Likewise, about 15% of patient's with narcolepsy and cataplexy will have normal or borderline normal MSLT results (defined as a sleep onset longer than 8 minutes on average and less than 2 naps with dreaming). To minimize these problems, the MSLT should only be performed by following an extremely strict protocol, which includes a pretest evaluation by a Sleep Specialist, maintaining a sleep diary for 1-2 weeks before the test, and a sleep study the night before the MSLT documenting adequate sleep (and the lack of other sleep disorders). If these guidelines are not adhered to, the test may not be very reliable.

I urge you to get an evaluation and discuss your test results with a Sleep Specialist. After performing a history and physical examination and reviewing your test results, they can determine if a diagnosis can be made or if additional testing is required.

To learn more about Narcolepsy or other sleep disorders, please visit the American Academy of Sleep Medicine website. In addition to information, the website contains a list of Sleep Centers across the country so that you may locate one near you. The Narcolepsy Network also provides information and links to support groups for those with this condition. Good luck and here's to good sleep!

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Response by:

Dennis   Auckley, MD Dennis Auckley, MD
Associate Professor of Medicine
School of Medicine
Case Western Reserve University