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What is a MSLT / PSG

Multiple Wake Test (MWT)

This test measures whether you can stay awake during a time when you are normally would not sleep.  This test is conducted during the day, but unlike the MSLT, the patient will attempt stay awake without napping during the daytime.  There will be 4 trials lasting 40 minutes. 


The Maintenance of Wakefulness Test (MWT) is used to measure how alert you are during the day. It shows whether or not you are able to stay awake for a defined period of time. This is an indicator of how well you are able to function and remain alert in quiet times of inactivity. 

The test is based on the idea that your ability to stay awake may be more important to know in some cases than how fast you fall asleep. This is the case when the MWT is used to see how well a sleep disorders patient is able to stay awake after starting treatment. It is also used to help judge whether a patient is too tired to drive or perform other daily tasks. 


Multiple Sleep Latency Test (MSLT)

Used to diagnose Narcolepsy and measure the degree of daytime sleepiness. To ensure accurate results, it is performed on the morning following a Diagnostic Overnight PSG. This test measures how long it takes you to fall asleep. A video camera is used to record movements during sleep. A Multiple Sleep Latency Test or MSLT, is designed to measure the degree of sleep tendency or sleepiness in a given patient. This test is conducted during the day following a routine PSG and features a series of up to 5 naps, each lasting usually less than 30 minutes.


The MSLT is used extensively to test for narcolepsy, to distinguish between physical tiredness and true excessive daytime sleepiness, or to assess whether treatments for breathing disorders are working. Its main purpose is to discover how readily a person will fall asleep in a conducive setting, how consistent or variable this is, and the way they fall asleep in terms of REM sleep and other brain patterns. This can be used to identify and differentiate between various sleep problems.


Preparation: On the day of the test the patient is asked not to consume any stimulants, such as tea, coffee, colas, and chocolate.

  • Often a formal sleep study has been performed the night before.

  • Sometimes urine screening is done to make sure no substances exist in the subject's body that might interfere with sleep.

  • The patient may be asked to fill out a pre-test questionnaire.

  • Electrodes are attached to the patient's head to record brain waves.

  • Electrodes are attached by the eyes to record eye movement.

  • Electrodes are attached to the chin to detect muscle tone.

  • Heart beat may also be monitored.

  • The patient is asked to perform simple tasks to test that the equipment is working properly.

  • The patient is asked to nap for 20 minutes, and then is awakened.

  • The nap process is repeated every 2 hours for a total of four or five times.

  • The patient may be asked to fill out a post-test questionnaire.

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