Preliminary diagnosis of narcolepsy can occur with the presence of excessive daytime sleepiness and cataplexy. Others tests for narcolepsy generally seek to confirm this preliminary diagnosis and devise a treatment program.
Diagnosing narcolepsy usually begins with the patient providing a detailed sleep history, including a questionnaire that gauges the patient’s level of sleepiness and how likely the patient is to fall asleep in certain situations. Patients may also be asked to keep a sleep journal, or a record of their sleep patterns over a week or two.
Some narcolepsy patients may be asked to undergo a test called an overnight polysomnogram, which monitors signals during sleep through the use of electrodes placed on the patient’s head. Additionally, a multiple sleep latency test can be used to measure the onset and sleep and how quickly REM sleep occurs. A hypocretin test may be used to test for low levels of hypocretin, a brain chemical that regulates REM sleep. To conduct this test, doctors will perform a spinal tap to remove a sample of spinal fluid. Finally, genetic blood tests can be used to look for a genetic mutation common in narcolepsy patients.