When all the classic symptoms are present, making a narcolepsy diagnosis is fairly easy. But if the sleep attacks are isolated and cataplexy is mild or absent, a diagnosis is more difficult to make. In addition to doing a physical exam and asking about the personal and family medical history, the doctor may recommend tests, such as the polysomnogram and the multiple sleep latency test.
Diagnosing narcolepsy (a condition characterized by brief attacks of deep sleep) is relatively easy when all the symptoms are present. But if the sleep attacks are isolated and cataplexy (a sudden loss of muscle tone and strength) is mild or absent, a diagnosis is more difficult.
If a person has possible narcolepsy symptoms, the healthcare provider will do a physical exam and ask about the personal and family medical history. The healthcare provider will also recommend additional tests in order to diagnose narcolepsy.
Two tests used to make a narcolepsy diagnosis are the polysomnogram and the multiple sleep latency test. These are usually performed by a sleep specialist.
The polysomnogram involves continuous recording of sleep brain waves and a number of nerve and muscle functions during nighttime sleep. When tested, people with narcolepsy fall asleep rapidly, enter rapid eye movement (REM) sleep early, and may awaken often during the night. The polysomnogram also helps to detect other possible sleep disorders that could cause daytime sleepiness.
Sleep Latency Test
For the multiple sleep latency test, a person is given a chance to sleep every two hours during normal wake times. Observations are made of the time taken to reach various stages of sleep. This test measures the degree of daytime sleepiness and also detects how soon REM sleep begins. Again, people with narcolepsy fall asleep rapidly and enter REM sleep early.