This test helps determine the severity of daytime sleepiness and help diagnose narcolepsy. The term multiple sleep latency test means multiple nap tests during the day. The test is done following an overnight polysomnogram the previous night. The person is given 4-5 opportunities to fall asleep at pre-determined times two hours apart. During this test, the person lies down on a bed in a darkened room. The patient is instructed to try to fall asleep and not to resist sleep. During this test, we measure the time it takes to fall asleep after the lights are turned out and the stages of sleep entered during the nap. In particular, we determine if a person has rapid eye movement sleep (REM sleep) and how long it takes to do so.