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Multiple Sleep Latency Test (MSLT) and Guidelines
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Supplemental - Highly Recommended: Parkinson's Disease (PD) Recommendations for use: To determine the presence of excessive daytime sleepiness (EDS) and a narcoleptic phenotype in PD population.
Short Description of Instrument
The Multiple Sleep Latency Test (MSLT) consists of performing a simple daytime polygraphic recording (EEG, EOG and EMG) in a quiet room without noise by turning off the light and closing the door. The patient, who is wearing their street clothes, is then invited in to lie on the bed, close his/her eyes and go to sleep. The patient must have slept more than four hours the previous night.
The MSLT consists of five tests ("naps") separated by two hours at 9:30 am, 11:30 am, 1:30 pm, 3:30 pm and 5:30 pm. The previous night's overnight PSG should be completed between 1.5 and 2.5 hours before the first nap (i.e., between 7:00 and 7:30 am). Once a test is initiated, sleep onset is determined when the waking alpha rhythm disappears for more than 50% of an "epoch" (more than 15 seconds in a 30-second period) and any sleep activity (N1, N2, N3 or REM phase) appears.
Once sleep onset is determined, the patient can sleep for 15 minutes, and the activity of this period is analyzed. If the patient does not fall asleep within 20 minutes at the start of the test, the test is terminated. At the end of the five tests, the mean sleep onset latency is evaluated (sum of the sleep onset latencies of the five tests performed divided by five) and the number of tests in which REM sleep was detected. If the REM phase appears before 15 minutes after sleep onset, then there has been a "REM sleep onset". When interpreting these parameters, the subject needs to be checked to see if they slept more than four hours the previous night and that in the days prior to the test he/she has performed a regular wake/sleep rhythm (by means of a diary or actigraphy).
Comments/Special Instructions
It has been shown that a subgroup of PD patients with EDS show several REM sleep periods during the MSLT, a feature that it is seen in patients with narcolepsy.
Scoring and Psychometric Properties
Scoring: EDS is considered to be present if the mean sleep onset latency is less than eight minutes. EDS is classified as mild (mean latency between five and eight minutes) and severe (less than five minutes). Latencies of more than eight minutes are considered normal. The mean sleep onset latency in healthy subjects aged 21-35 years is ten minutes, 11-12 minutes in subjects aged 30-49 years, and 9 minutes in individuals aged 50-59 years. When assessing the TLMS result, medication taken by the patients should be known, since, for example, the consumption of benzodiazepines decreases sleep latency, and antidepressants reduce the amount of REM sleep.
Strengths: MSLT is an objective method that is considered the gold standard for assessment of EDS by measuring the ability to fall asleep when the subject is instructed to sleep in a soporific situation. MSLT provides objective, reliable, and accurate identification of EDS.
Weaknesses: Actigraphy and polysomnography are required before performing the MSLT. Does not identify the cause of EDS. Requires spending one night and one day at the sleep lab. It is expensive and requires expert technicians and sleep experts.
Key References:
Krahn L, Arand D, Avidan A. Recommended protocols for the Multiple Sleep Latency Test and Maintenance of Wakefulness Test in adults: guidance from the American Academy of Sleep Medicine. J Clin Sleep Med. 2021 Dec 1;17(12):2489-2498.
Littner MR, Kushida C, Wise M, Davila DG, Morgenthaler T, Lee-Chiong T, Hirshkowitz M, Loube DL, Bailey D, Berry RB, Kapen S, Kramer M.  Practice parameters for clinical use of the Multiple Sleep Latency Test and the Maintenance of Wakefulness Test. Sleep. 2005 Jan;28(1):113-21.
Additional References:
Bargiotas P, Lachenmayer ML, Schreier DR, Mathis J, Bassetti CL. Sleepiness and sleepiness perception in patients with Parkinson's disease: a clinical and electrophysiological study. Sleep. 2019 Apr 1;42(4):zsz004.
Rye DB, Bliwise DL, Dihenia B, Gurecki P. FAST TRACK: daytime sleepiness in Parkinson's disease. J Sleep Res. 2000 Mar;9(1):63-9.
Document Last Updated August 2022