What is a Multiple Sleep Latency Test ?

This is a specialized sleep study that is typically done as a follow up to a sleep study. It is usually done in isolation and involves spending the better part of the day in one of the Children’s Sleep Laboratories.

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Who needs it?

This is typically done as a follow on in patients with excessive sleepiness as in suspected narcolepsy or hypersomnia. This study is not typically done in a patient with excessive sleepiness related to obstructive sleep apnea syndrome.

How is it done?

This involves the patient being asked to relax and allow themselves to sleep. If sleep is not achieved within 20 minutes then the patient takes a break for 2 hours and the cycle is repeated 4 to 5 times. If the patient does achieve sleep within 20 minutes, then the patient is allowed to sleep for a maximum of 15 minutes and is then woken up. If the patient does sleep, then the sleep is watched closely to see if the patient attains REM sleep.


This test is usually performed to check Continuous Postive Airway Pressure (CPAP) compliance or to ensure
optimal treatment of sleep apnea. This test is most commonly requested by doctors for patients who are
required to have a CDL license renewed by the Department of Transportation (DOT) or another agency that
has their employees operating large equipment. A MWT is a series of 4 controlled sessions approximately 40 minutes long every 2 hours.
During the session, the patient sits upright in a darkened room and tries to remain alert. The
parameters recorded will help determine the patient’s level of alertness.
A standard MWT records the following parameters:

  • EEG (Electroencephalogram) – monitors brain activity to identify sleep stages
  • EOG (Electrooculogram) – records eye movement
  • EMG (Electromyogram) – records muscle activity for monitoring muscle tone
  • EKG (Electrocardiogram) – monitors heart activity