A Multiple Sleep Latency Test (MSLT) or Maintenance Wakefulness Test (MWT), are 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 30-40 minutes that are timed to start every two hours during the day.
It is important prior to having an MSLT or MWT study that a 1-2 week sleep diary be completed and your Boarded Sleep Specialist Physician be aware of any medications (OTC or otherwise) that you are taking, since many medication can effect the results of this test.
The purpose of the MSLT has two purposes: first, to average the number of minutes that it takes to fall asleep (sleep onset latency) during all the naps and second, to record if REM stage sleep occurs during any of these scheduled napping periods.
The purpose of the MWT is to measure the amount of time it took the patient to fall asleep after being instructed to try to stay wake during the nap periods.
The testing procedure includes essentially the same PSG leads as for a diagnostic overnight study. During the periods between naps, the patient must stay awake and not fall asleep.
This test is particularly useful in helping people with Narcolepsy adjust their medication, diagnose Narcolepsy, objectively quantify the degree of sleepiness in a particular patient, such as an OSA (obstructive sleep apnea) patient who is still sleepy despite CPAP treatment and in diagnosing Idiopathic Hypersomnolence.