Multiple Sleep Latency Test (MSLT) &MAINTENANCE OF WAKEFULNESS TEST

(MWT)

Prepared By: Syed Irshad Murtaza Technologist Neurophysiology Dept

AKUH Karachi Date: 10-12-2013

Multiple Sleep Latency Test (MSLT)The MSLT (Multiple sleep latency test) is an

examination to test reasons for fatigue during the daytime or a compulsive tendency to fall asleep.

It is a series of recordings to monitor a person's sleep patterns.

MSLT is a nap study which is used to see how quickly a person falls asleep in quiet situations during the day time.

It is the standard way to measure the level of daytime sleepiness & is helpful to rule out the other differential diagnosis of other pathological abnormalities.

MSLT• It also measures how quickly and how often a

person enters the REM stage of sleep• It can be used to test for narcolepsy (sudden

and uncontrollable onsets of sleep) .• To distinguish between physical tiredness and

true excessive daytime sleepiness.• Its main purpose is to serve as an objective

measurement of sleepiness.

What is Narcolepsy ?• Narcolepsy is a neurological condition affecting

the area of the brain that controls waking and sleeping cycles.

Narcolepsy is characterized by sudden & uncontrollable attacks of sleep at irregular & unexpected times. Its main features are as followings,

• Excessive daytime sleepiness (EDS)• Cataplexy• Hypnagogic/Hypnoponpic hallucinations.• Sleep paralysis

The cells that produce the small peptides, HO, reside in the hypothalamus, an area deep in the brain. Recent rodent studies indicate that these cells connect to brain regions that are involved in sleep and wakefulness, including the locus coeruleus, raphe nuclei, tuberomammillary nucleus and pontine reticular formation, among others. This evidence suggests that, normally, HO helps the sleep and wakefulness areas carry out their jobs. And HO-related abnormalities may impair their function

MSLT Findings in Narcolepsy•Normally sleep latency should at least be ≥8 min. Latency

prior to this period after lights out is to be considered as early sleep latency in adults, which is regardless to prior disturbed sleep, fatigability, jet lag, shift duty, drugs etc.

Mean sleep latency, which is calculated with all the onset latencies of the sequential naps to obtain.

• To calculate for the Mean Sleep Latency, one would add up all of the Sleep Latencies then divide by the number of naps.

• Sleep onset REM period (SOREMP) of ≥ 2 nap which is obtained within ≤ 20 minutes of the sleep time is

considerable for the diagnosis of narcolepsy.

How to perform MSLT

• The MSLT is a series of 5 naps taken at 2 hour intervals, starting at approximately 8-9:00 A.M.

• This is done the following day after a polysomnogram (PSG) (with normal findings) where a recording of the electrical activity of many physical variables that occur during sleep.

• There are very rare cases reported to be having the presence of obstructive sleep apnea and narcolepsy simultaneously in the same subject.

Recommendations for MSLT• The first nap trial should be started between

1.5-03 hours after waking up from the overnight PSG.

• For the MSLT to be accurate, subject should have had a total sleep time of at least six hours during the overnight sleep study.

• The MSLT determines how long it takes a person to fall asleep at preset times throughout the day.

Recommendations• Four or five segments are to be recorded. • The patient is put to sleep at 2 hours interval of

each nap.• Each segments is allowed to last 20 minutes if

there is no sleep recorded, or a maximum of 15 minutes after the first epoch of sleep.

• It is recommended to record the sleep with continuity for 20 minutes. The time starts from the first drowsy if subject gets asleep, otherwise to be scored from light off, if doesn’t get asleep.

MSLT and its findings.• The MSLT also counts sleep-onset REM periods

(SOREMPS).

• This is when a person enters REM sleep very soon after falling asleep.

• In normal individuals it usually begins about 90 minutes after falling asleep.

• People with narcolepsy often have two or more SOREMPs in a nap trial.

The MSLT may be used to see if a person has idiopathic hypersomnia. Patients with idiopathic hypersomnia fall asleep easily but don’t have SOREMPS .

Calculation for Mean Sleep Latency• Add all of the sleep latencies• (including No Sleep of 20 minutes)• and divide by the number of naps• Example• Nap #1: 6.0 minutes• Nap #2: 3.0 minutes• Nap #3: 0.0 minutes• Nap #4: 20.0 minutes• Nap #5: 2.5 minutes• 31.5 minutes ÷ 5 = 6.3 minutes• Mean Sleep Latency = 6.3min

Standard parameters & Montage• F3-A2• F4-A1• C3 – A2 • C4 – A1 • O1 – A2• O2-A1• EOG left, EOG right• Sub-mental (Chin) EMG• EKG, and pulse oximetry.• Nasal, Chest and abdominal sensors.

Objective of the Study• The objective is to identify the latency of sleep or

time elapsed from lights out of the first epoch of sleep.

• This latency is defined as the point in the polysomnogram (PSG) at which sleep occupies 50% or more of the epoch.

• A 50% reduction of alpha activity along with slow rolling eyes movements and a subtle reduction in muscle tone indicate stage1.

• REM sleep latency is defined as the time from the beginning of sleep to the onset of REM.

Diagnosis and Precautions• To be diagnosed as Narcoleptic, the patient

would have to demonstrate a Mean Sleep Latency (an average of all the sleep latencies) of 5 minutes or less and demonstrate at least 2 Sleep Onset REM Periods (SOREMP).

The absence of sleep on a nap opportunity is recorded as a sleep latency of 20 minutes

• Precautions• Smoking should be stopped at least 30 minutes

before each nap trial.

Precautions prior to MSLT• Patient will not be allowed to have any drinks

with caffeine during the study. • Patient will also not be able to see any bright

sunlight. • Vigorous physical activity should be avoided during the

day .• Any stimulating activities by the patient should end at

least 15 minutes prior to each nap opportunity. • A light breakfast is recommended at least 1 hour prior to

the first trial, and a light lunch is recommended immediately after the termination of the second noon trial.

Case discussion (1st recording)

Case discussion (1st recording)

Case discussion (1st recording)

Interpretation (Case discussion) This is MSLT preceded by Prolong PSG which is normal.

During this MSLT 5 naps were recorded at two hours interval, each nap was terminated at 20 minutes. Onset sleep latency during each nap was 30,30,30,90 and 120 seconds respectively. The mean sleep latency was 1 minute. During MSLT three Sleep onset REM periods (SOREM) were noted. Sleep onset REM period latency of each nap was 1, 3 & 4 minutes respectively. The mean SOREM latency was 2.6 minutes.

Conclusion: (case discussion)Severe abnormal MSLT study the findings are suggestive of

narcolepsy.

• The Maintenance of Wakefulness Test (MWT) is an evaluation used as a quantitative polysomnographic (PSG) measurement of daytime wakefulness/somnolence during soporific (dreamy) circumstances. It shows whether or not a subject is able to stay awake for a defined period of time. This is an indicator of how well one is able to function and remain alert in quiet times of inactivity

Standardization of MWT• The MWT is a series of nap studies during the

day in which the subject is asked to stay awake and not fall asleep. How well they can perform that task relates to their degree of daytime sleepiness.”

• MWT- the Maintenance of wakefulness test is some times used in place or in addition to the MSLT as an assessment of daytime somnolence.

• It is a modification of the MSLT performed in a similar manner, with recordings obtained at two hour intervals following nighttime PSG.

Objective of MWTThe MWT is used to see how well a sleepdisorders 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.

This can show if treatment is helping a patient overcome sleepiness.

Factors affecting the Study• The test isolates you from outside factors that can influence the

ability to fall asleep. These factors include the following:• Temperature (too hot or too cold)• Light• Noise• Activity• Other factors that can still affect the study include the following:• Anxiety• Tension• Depression• Age• Caffeine• Drugs and medications• Amount of sleep prior to the study

• F3-A2• F4-A1• C3 – A2 • C4 – A1 • O1 – A2• O2-A1• EOG left, EOG right• Sub-mental (Chin) EMG• EKG, and pulse oximetry.• Nasal, Chest and abdominal sensors.

• 4-trial MWT 20-minute (AASM Guidelines recommendation is 40 min)

protocol is recommended at 2hour intervals.• First trial begins 1.5 to 3 hours after the patient’s usual

wake-up time.• Room should be maximally insulated from external light.• Light source should be positioned slightly behind• patient’s head (out of field of vision)• Room temperature should be set based on the patient’s

comfort level.• Patient should be seated in bed, with the back & head

supported by a bedrest/bolster pillow such that the neck is not uncomfortably flexed or extended.

Procedure &Patient instructions• The MWT varies from the MSLT in the

recording conditions and the instruction to the patient.

• The recording is performed with the patient sitting in a chair in a dark room.

• The patient is instructed to sit quietly with eyes open and remain awake during the recording to assess an individual’s capability not be overwhelmed by sleepiness- that’s is the underlying functioning of the wakefulness system is assessed

Instructions to patients• ‘Please sit still and remain awake for as long

as possible. Look directly ahead of you, and do not look directly at the light.’ Patients should be disallowed from using extraordinary measures such as slapping the face, pinching or singing.

• Trials are ended after 20 minutes if no sleep

occurs, or after unequivocal sleep.• The first occurrence of sustained sleep is

defined as 3 consecutive 30 s epochs of stage 1 or any single 30 s epoch of another sleep stage (II, III, IV, or REM).

• The MWT has proved useful in evaluating

treatment effects in patients with narcolepsy and sleep related breathing disorders.

• • MWT often reveals improvement in treated

patients who continue to physiological sleepy.

The major drawback in the use of Maintenance of wakefulness test is that it has lack of normative data.

• AASM Practice Parameter: Practice Parameters for• Clinical Use of the Multiple Sleep Latency Test and the

Maintenance of Wakefulness Test, Sleep, Vol. 28, No. 1,2005.

• Electroencephalography, Basic principles, clinical applications, and Related fields, by Ernst Niedermeyer, 4TH Edi, vol 2 page 872-3

• Aldrich MS. Narcolepsy. N Engl J Med 1990;323:389-94.

• Thorpy MJ, Goswami M. Treatment of narcolepsy. In: Thorpy MJ.

• http://www.hus.fi/hus-kuvantaminen

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