What is a MSLT, you ask?

So your doctor ordered a MSLT…what in the world is that?

A MSLT is a Multiple Sleep Latency Test performed in a sleep center.  It is a series of nap sessions that are scheduled two hours apart.  During each nap session you are given 20 minutes to fall asleep.  If you don’t fall asleep, the session ends.  If you do fall asleep, you are allowed to sleep for 15 minutes before the sleep technician wakes you up.   You may have four or five nap sessions, depending on what happens during your naps (see below for more details).  Between naps, you can watch TV, read a book, work on the computer, etc.  You won’t be allowed to have any caffeine during the day of the MSLT and if you take any stimulant medication (Adderall, Provigil, etc.) your physician will ask you to stop taking it for a couple of days before the test.  At our lab, we provide a continental breakfast and let you choose a lunch from one of the restaurants near us.

According to American Academy of Sleep Medicine (AASM) guidelines, a MSLT must follow an overnight study.   Basically, your time commitment is one overnight study (at our lab that begins between 8:15 and 8:45 p.m.) followed by a day of napping (at our lab studies end around 3:00 p.m. when four naps are done and around 5:00 p.m. when 5 naps are done).  Not so terrible, right?  The downsides are that you will most likely need to miss a day of work and you will have wires attached to your head for the duration of the day.  (The wires are electrodes that measure your brain waves.  The brain waves tell the sleep technician what stage of sleep you are in).

So what’s the point?  A MSLT is performed when a doctor suspects narcolepsy or to prove excessive daytime tiredness.  Narcolepsy is diagnosed when REM sleep occurs in two or more nap sessions and other diagnostic symptoms are present (sleep paralysis, vivid dreams when waking up or falling asleep, weakness with strong emotion).   Because two nap sessions with REM sleep are required for a diagnosis of narcolepsy, you may need to stay for a 5th nap session if you have REM sleep in only one of the first four nap sessions.  We need to give you every opportunity to have a second REM session to confirm the presence of narcolepsy.  This is usually the only situation in which you would need to stay for a 5th nap.  The sleep technician is not permitted to tell you if you fell asleep, if REM sleep was present, or anything else about what you did during the nap session.  Excessive daytime sleepiness may need to be confirmed before your insurance will cover prescribed stimulant medication such as Provigil.  The most reliable indicator of sleepiness is how long it takes you to fall asleep during each nap session (called the mean sleep onset latency).

A few days after the MSLT, your physician will go over the results with you in his/her office and make appropriate recommendations.

And that is a MSLT.  Naps, free lunch…could it get any better?

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About Jessica

The Sleep Center is a physician-owned, diagnostic sleep facility in beautiful Scottsdale, Arizona. I am Jessica, a registered nurse at the sleep center, exploring every avenue of sleep medicine and sharing my discoveries with you.
This entry was posted in Sleep Disorders, Sleep Testing Procedures. Bookmark the permalink.

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