Multiple Sleep Latency Test (MSLT)

Definition
The MSLT is a specialized sleep study that is typically done during the day after a nocturnal polysomnography. It is indicated for patients with excessive daytime sleepiness in which narcolepsy or hypersomnia are suspected and sleep apnea ruled out or treated.

How is the test performed?
For the test, electrodes are placed on the chin, the scalp, the outer edge of the eyelids, and the legs. These electrodes will monitor activities such as brain waves, muscle movements, eye movements, breathing, snoring, heart rate and leg movements while you sleep. An airflow device is placed below the nose, and a pulse oximeter is placed on a finger. The test then consists of 5 timed naps taken at 2-hour intervals. If sleep is not achieved within 15 minutes, the patient takes a break for 2 hours and then the cycle is repeated until the total of 5 naps are attempted. If sleep is achieved within 15 minutes, the patient is allowed to sleep for 20 minutes, then awoken and the cycle repeated. If the patient does get to sleep, the amount of time it takes them to get to REM sleep is also measured.