Multiple Sleep Latency Test

Posted on August 7, 2009 in Latest News

Multiple Sleep Latency Test (MLST) is a nap study done to test the propensity of the person to fall asleep in quite (sleepy) situations during the day. This test is often done following an overnight sleep study. It is the standard way to measure the level of day time sleepiness. It is one of the differential diagnosis tools for narcolepsy and idiopathic hypersomnia.

The MSLT charts brain waves and heartbeat and records eye and chin movements. The study also measures how quickly and how often one enters the rapid-eye-movement (REM) stage of sleep. The test usually begins about two hours after awakening in the morning and continues to late afternoon or early evening. The test is painless and the diagnosis takes about seven hours to complete.

Procedure:

The patient is taken to the screening procedure and all the drugs used by the patient are noted down. The patient submits the sleep diary for at least one week before the MLST. The patient should not smoke for at least 30 minutes before each nap trial. The patient is advised not to have alcohol or caffeine during the procedure.

Generally MSLT is performed immediately following polysomnography recording on the previous night. This helps to access the causes of excessive sleeping during the day. A cool, dark and quiet place is selected where the patient is allowed to rest during testing. Sensors are placed on the head, face, chin and chest of the patient which are in turn connected to a computer for recording.

The patient is asked to lie quietly in bed and try to go to sleep. The test will measure how long it takes the subject to fall asleep. After sleeping for 15 minutes the patient is awakened. Each trial will end if the patient does not fall asleep within 20 minutes and about 5 such trials are recorded at two-hour interval each. Between the nap trials, the patient is asked to stay out of bed so that he remains awake. After the last nap trial, the sensors are removed and the patient is free to go.

The MLST Record:

MLST records the data from the nap study and the chart gives sleep wake times and sleep stages. The technologist looks for and counts the number of times the patient entered REM sleep. MLST report includes the start and end times of each nap or nap opportunity, latency from lights out to the first epoch of sleep, mean sleep latency (arithmetic mean of all naps or nap opportunities), and number of sleep-onset REM periods (defined as greater than 15 sec of REM sleep in a 30-sec epoch).

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