If the initial medical exam and at-home monitoring with self-reported sleep logs indicate potential narcolepsy, doctors then rely on two sleep tests that are performed at a sleep center to look for the cause of the symptoms and determine whether you have narcolepsy or another sleep disorder, explains Shelley Hershner, MD, an assistant professor of neurology and the director of the Collegiate Sleep Clinic at the University of Michigan in Ann Arbor.Polysomnogram For a polysomnogram the patient stays overnight at the sleep center while technicians record data about their brain activity, heart rate, blood pressure, and eye movements. The test can help determine whether your sleep cycle is normal — going into nonrapid eye movement (NREM) and then progressing into REM after an hour or more — or if it indicates narcolepsy (you fall asleep quickly and go right into REM sleep, and then have trouble staying asleep throughout the night).Multiple Sleep Latency Test (MSLT) This full-day sleep test is done on the day after the polysomnogram, and it’s designed to measure how sleepy you are during daytime. It determines how quickly you fall asleep during the day after a full night’s sleep (the previous night in the lab), and it also measures how quickly a person falls asleep and enters REM sleep during a daytime nap.The sleep test takes place over the course of a day. You will be asked to take five scheduled naps with two-hour breaks in between. During each of the scheduled naps you lie in a dark, quiet, and comfortable room and try to sleep. Then, technicians will measure how long it takes you to fall asleep. If you fall asleep, they wake you up after 15 minutes; if you do not fall asleep after 20 minutes, the technician will stop that nap session, per the AASM.Before the sleep test, your doctor will likely order blood and urine tests to screen for substances that can cause false positives.In rare cases your doctor might additionally order a test to measure the levels of the brain hormone hypocretin-1 in the fluid that surrounds the brain and spinal cord, known as a spinal tap or lumbar puncture, according to NINDS. Unless you have another serious medical condition that affects hypocretin levels, low levels are nearly always an indicator of type 1 narcolepsy, though narcolepsy cannot be diagnosed by this test alone.RELATED: Common Myths and Misunderstandings About Narcolepsy
