MSLT Scores

Minutes	Sleepiness
0–5	Severe
5–10	Troublesome
10–15	Manageable
15–20	Excellent

The Multiple Sleep Latency Test (MSLT) is a sleep disorder

Sleep disorder

A sleep disorder, or somnipathy, is a medical disorder of the sleep patterns of a person or animal. Some sleep disorders are serious enough to interfere with normal physical, mental and emotional functioning...

 diagnostic tool. It is used to measure the time elapsed from the start of a daytime nap period to the first signs of sleep, called sleep latency. The test is based on the idea that the sleepier people are, the faster they will fall asleep.

The MSLT can be used to test for narcolepsy

Narcolepsy

Narcolepsy is a chronic sleep disorder, or dyssomnia, characterized by excessive sleepiness and sleep attacks at inappropriate times, such as while at work. People with narcolepsy often experience disturbed nocturnal sleep and an abnormal daytime sleep pattern, which often is confused with insomnia...

, to distinguish between physical tiredness and true excessive daytime sleepiness

Excessive daytime sleepiness

Excessive daytime sleepiness is characterized by persistent sleepiness, and often a general lack of energy, even after apparently adequate night time sleep...

, or to assess whether treatments for breathing disorders are working. Its main purpose is to serve as an objective measure of sleepiness.

The test consists of four or five 20-minute nap opportunities that are scheduled two hours apart. The test is often performed after an overnight sleep study. During the test, data such as the patient's brain waves, EEG, muscle activity, and eye movements are monitored and recorded. The entire test normally takes about 7 hours.

The MSLT is used extensively to test sleepiness in a number of research protocols.

History

The Multiple Sleep Latency Test was created in 1977 by sleep pioneers William C. Dement

William C. Dement

William Charles Dement is a pioneering US sleep researcher, and founder of the Sleep Research Center, the world's first sleep laboratory, at Stanford University. He is a leading authority on sleep, sleep deprivation, and the diagnosis and treatment of sleep disorders such as sleep apnea and...

 and Mary Carskadon

Mary Carskadon

Mary A. Carskadon, Ph.D., is a Professor in the Department of Psychiatry and Human Behavior at the Warren Alpert Medical School of Brown University. She is also the Director of the at E.P. Bradley Hospital. She is considered to be an expert on sleep and circadian rhythms during childhood and...

. It developed out of repeating a project done in 1970 by Dr. Dement called the 90-minute day. They informally called the 0–5 minute range the twilight zone due to its indication of extreme physical and mental impairment.

Typical procedure

Preparation: On the day of the test the patient is asked not to consume any stimulants, such as tea, coffee, colas, and chocolate.

• Often a formal sleep study has been performed the night before.
• Sometimes urine screening is done to make sure no substances exist in the subject's body that might interfere with sleep.
• The patient may be asked to fill out a pre-test questionnaire.
• Electrodes are attached to the patient's head to record brain waves.
• Electrodes are attached by the eyes to record eye movement.
• Electrodes are attached to the chin to detect muscle tone.
• Heart beat may also be monitored.
• The patient is asked to perform simple tasks to test that the equipment is working properly.
• The patient is asked to nap for 20 minutes, and then is awakened.
• The nap process is repeated every 2 hours for a total of four or five times.
• The patient may be asked to fill out a post-test questionnaire.

A clinical neurophysiologist, neurologist

Neurologist

A neurologist is a physician who specializes in neurology, and is trained to investigate, or diagnose and treat neurological disorders.Neurology is the medical specialty related to the human nervous system. The nervous system encompasses the brain, spinal cord, and peripheral nerves. A specialist...

 or sleep specialist

Sleep medicine

Sleep medicine is a medical specialty or subspecialty devoted to the diagnosis and therapy of sleep disturbances and disorders. From the middle of the 20th century, research has provided increasing knowledge and answered many questions about sleep-wake functioning. The rapidly evolving field has...

will review the results and inform the patient or the patient's primary care physician of the interpretation of the test result in the context of the clinical problem.

External links

• Mary Carskadon's page on the MSLT http://www.sleepforscience.org/contentmgr/showdetails.php/id/203