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What Is An Polysomnogram (PSG) with MSLT?

A polysomnogram (PSG) is a sleep study that helps determine whether or not you have a sleep disorder.  While you sleep, sleep patterns and behaviors such as brain waves, heart rate and breathing, eye and leg movements, and the oxygen level in your blood are recorded.  A PSG can be done at night or during the day and a trained sleep technologist supervises the sleep study.

The multiple sleep latency test (MSLT) determines excessive daytime sleepiness by measuring how quickly you fall asleep in a quiet situations during the day, and how quickly and how often you enter REM sleep.  The MSLT is sometimes referred to as the daytime nap study and is used to diagnose narcolepsy or idiopathic hypersomnia.  It is always a follow-up test to the overnight PSG which is used to rule out other sleep disorders such as sleep apnea, restless leg syndrome and parasomnias.

man with one eye open in bed, humorous

When you arrive for your sleep study, a Registered Polysomnographic Technologist (RPSGT) or Registered  Respiratory Therapist (RRT) will be at the site to greet you and show you to your room. After you make yourself comfortable, your technologist will take a brief history, explain the study process, and answer any questions you may have prior to applying the sensors.  This procedure is completely painless and generally takes about 40 minutes to make sure everything is placed correctly.

What To Expect

Applying the Sensors

First, the technologist will use stickers to affix leads on your chest and abdomen. 

Next, your head will be marked and measured with a paper ruler and a grease pencil.  This is done because each electrode on your head needs to be in a precise location.  Once this is complete, a prep solution will be applied to clean the scalp for the electrodes. 

Electrodes are then placed on the surface of your scalp with a small amount of paste.  The prep, paste, and tape are hypoallergenic.

Next, Velcro belts will be placed around your chest and abdomen. You'll also have a nasal cannula (similar to an oxygen cannula) to monitor your breathing. You will not receive oxygen during your PSG.

This process is completely painless and generally takes about 40 minutes to make sure everything is placed correctly.


Once you are fitted with the sensors, you are free to stay in your room where you can relax, watch TV, enjoy high-speed internet, catch up on phone calls or read until Lights Out at 11pm.  You may bring your own food/snacks. 

Your technologist will monitor your sleep throughout the study and will be available to answer questions and ensure you’re comfortable. 

In the morning, the technologist will remove some of the sensors used the night before and will explain the multiple sleep latency test (MSLT), during which you will have 5 half hour naps with the first one beginning at about 8:00am.  In between naps, you can relax, catch up on phone calls or read.  Lunch is provided; please notify us of any special dietary needs when you arrive.

All Done, Now What?

When the study is done, the technologist will remove all the wires and sensors.

At your follow-up appointment, you will receive your sleep study results and discuss them with your provider.

Preparing For Your Sleep Test

Sleep Insights offers a relaxing environment with private, hotel-like rooms and at certain locations, a shower may be available.
If you have any questions please contact us, call our Rochester office (585) 385.6070 or your local site.

  • Set Time Aside

    If you are having a PSG with MSLT, this will be an overnight test. Plan on being at our sleep center from approximately 7:00-9:00 pm until 5:00-7:00 am the next morning.

    If you are having just an MSLT, plan on being at our sleep center from approximately 8:00 am until 5:00 pm for daytime testing.

  • Wash and Dry Your Hair

    Wash and dry your hair thoroughly but do not use conditioners or other hair products.

  • Hair Accessories

    Remove any hair weaves or extensions. We cannot do testing with either of these. 

  • Acrylic or Applied Nails

    If you have acrylic nails or applied ("fake") nails an index fingernail needs to be removed for the oxygen reading. If you have gel nail polish, the polish from one of the index fingers will need to be removed. Regular nail polish is fine. The oximeter does not read through acrylic or applied nails, nor gel polish.

  • What Should I Wear?

    Wear comfortable, loose-fitting, two-piece clothing. You must wear pajamas or two-piece clothing for the test.

  • Medications

    Bring – and take – all of your normally scheduled medications unless otherwise directed by your doctor or the staff at Sleep Insights.

  • Special Requirements and Guests

    Notify us of any special needs prior to your arrival.  If you are supervising a child or older patient who is having a sleep test, we have rooms equipped with an additional bed.  Please let us know in advance if you need special accommodations.

    Guests are not permitted to stay in the room without prior permission.

  • Smoking

    Smoking, vaping and the use of alcohol are not permitted in the building or on the premises at any time.

  • No-Show

    Cancellations must be made by at least 12 noon the day before your study, or if your study is on a Saturday or Sunday, by noon on the Friday before. 

    Failure to show up for your scheduled procedure will result in a $100.00 no-show charge.