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What is the Multiple Sleep Latency Test?

The Multiple Sleep Latency Test (MSLT) checks for excessive daytime sleepiness by measuring how quickly you fall asleep in a quiet environment during the day. Also known as a daytime nap study, the MSLT is used to diagnose narcolepsy and  hypersomnia.

How to prepare for the Multiple Sleep Latency Test? (One to Two weeks before the MSLT)

  • Keep a sleep diary for two weeks and attempt to maintain a regular sleep schedule, this will allow the doctor to see your sleep patterns.
  • This may help identify other factors that could be causing daytime sleepiness. 
  • Decreased the use of caffeine 
  • If you are on any medications, your doctor will help you to determine when you can use your medications before the MSLT. 
  •  Some medications may need to be discontinued for a weeks before the MSLT.

(Once you have finished these steps, you will be ready for the MSLT.)

Procedure (During the test)  

  • A sleep technologist will place sensors on Patient head (C3-C4, O1- O2, A1 – A2 & Ground), face (LOC & ROC) and chin (Chin EMG). These sensors are connected to a computer.
  • The sensors show when patient is asleep and awake, and used to determine the onset of REM sleep.
  • Calibration is conducted in the following manner:
  • Eyes —open closed(3- 4 times)
  • Asked to Look Right, Left , Up & Down(3-4 times)
  • Make the Chin Tight & Loose (3 to 4 Times)
  • Instructions will be given to take a nap –During each nap  ,Once the lights off, attempt to fall asleep 
  • Each nap is  in a dark and quiet sleep environment
  • Patient will be awakened after sleeping 15 minutes. 
  • If patient does not fall asleep within 20 minutes, the nap trial will end.


Instructions for Patient (During the day)

The MSLT is a full-day test that consists of 4 to 5 scheduled naps separated by two-hour breaks.

This test is always done following a sleep study that measures your sleep quality and duration.

Cell phone must be turned off during testing. 

No radio or TV may be on during the testing period

Between naps, the patient is instructed to not fall asleep, lie down or even sit in bed: 

   The patient can sit in a chair outside, the testing room read, listen to music

What is to be avoided/ what can you take?

  • Caffeine (coffee, colas, tea, chocolates) are not allowed during the day of the testing, but patient can have juices.
  • Can have food

How is Multiple Sleep Latency Test results scored?

  • A doctor  will review the data, note when you fell asleep during each nap, (Sleep latency –  in between Light Off to  Sleep onset time  
  • Look at sleep stages and determine whether you entered REM sleep.
  • Patients with narcolepsy – have two or more REM sleep stages during an MSLT.
  • People with hypersomnia fall asleep easily but do not reach REM sleep during the nap trial.

The night before your MSLT you will have a sleep study.( Sleep at least 6 hours during the sleep study.  )

Gold cup electrodes Used EEG Electrodes – 7 Electrodes used 

Some Electrodes placed on Right hemisphere on the Head (C4, O2 & A2) & some electrodes placed on the Left hemisphere on the Head (C3 , O1 & A2) & ground placed on forehead 

EOG Electrodes: (4 gold cup electrodes used) 

EOG electrodes are placed 1 cm out and 1 cm up or down from the outer canthus of both eyes

Chin EMG : (2 Electrodes) : 

There are two Electrode used for MSLT Test , one electrodes used for Right side of chin muscle & Second one used for Left side of Chin Muscles 

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