What is an MSLT and why is it prescribed?
A multiple sleep latency test (MSLT) is the Gold Standard for testing a patient to make a diagnosis of narcolepsy or idiopathic hypersomnia. The test requires a full day and is a series of four to five, 20-minute naps following an overnight sleep study. You will have the opportunity to take a nap every two hours, beginning when you wake in the morning. If two or more naps containing REM sleep occur, you may test positive for narcolepsy.
How do I prepare for an MSLT and what can I expect during the test?
An MSLT is performed the day after an overnight sleep study is conducted. It will last most of the day. During this non-invasive test, a sleep technologist will place sensors on your head and face. These sensors will help monitor when you are asleep and help to determine when you enter into REM sleep. During the nap trials, you will be asked to try to fall asleep at various increments and data will be collected to see how quickly you fall asleep. If you do fall asleep during the testing, you will be awakened after 15 minutes. This pattern will occur every two hours and will be repeated four to five times.
What do my results indicate?
At the completion of your MSLT, the data collected will be reviewed and interpreted to determine when you fell asleep during the naps and whether you entered REM sleep. Patients with narcolepsy will have at least two REM sleep stages during an MSLT. Those with idiopathic hypersomnia may also fall asleep during testing but will not reach REM sleep. A formal diagnosis will be made by a board-certified sleep medicine physician based on the test’s results.