How is Narcolepsy Diagnosed?
Night and Day Testing
A person with the symptoms of narcolepsy needs to have testing done in a sleep lab. First they will be required to spend a night being monitored in the lab in order to rule out other sleep disorders and also to detect the timing of REM sleep. In the morning, they will be awakened and will continue to stay at the lab for daytime testing. This daytime test is called a Multiple Sleep Latency Test (MSLT). During this test the individual will take 4 or 5 twenty minute naps at two hours intervals. For example, 8am, 10am, 12pm, 2pm & 4pm. The sleep lab technicians will determine how long it takes for the individual to fall asleep during these naps. At the end of the day, an average is taken across all of the naps.
A person with severe daytime sleepiness will have an average sleep onset of less than 5 minutes. Normal people fall asleep between 10 and 20 minutes on average across all of the naps.
Anyone with severe daytime sleepiness may be asked to take this test. However, the difference between narcoleptics and others is that a person with narcolepsy will not only fall asleep in less than 5 minutes, but they will also have REM sleep on at least two of the naps. Others with severe daytime sleepiness (such as those with sleep apnea) can fall asleep in less than 5 minutes, however they will not have two naps with REM sleep.