How Is Narcolepsy Diagnosed?
Narcolepsy is a sleep disorder in which someone falls asleep when they do not mean to, often several times a day. These “sleep attacks” tend to occur in the middle of the day, even while driving, eating, working, or talking.
Doctors believe many people with narcolepsy go undiagnosed. The condition may be mistaken for a seizure disorder or a mental health condition.1
Physical exam and medical history
To diagnose narcolepsy, your doctor will ask you about your health and your sleep, then follow with a physical exam. Some questions that your doctor may ask include:2
- Are you sleepy during the day?
- Do you feel rested when you wake up in the morning?
- Do you feel rested when you wake up from a nap?
- When you are falling asleep, do you see, feel, or hear things you know are not there?
- Do you ever find yourself unable to move when you wake up?
- When you laugh or tell a joke, does your face go limp or do your knees buckle?
- Do you have “sleep attacks” or times when falling asleep when you did not mean to?
Your doctor may ask you about a family history of narcolepsy or other health conditions. Only about 10 percent of people with narcolepsy have a family history of the condition. Sometimes, narcolepsy may begin after an upper respiratory infection or autoimmune flare. In rare cases, a head injury, tumor, or stroke leads to narcolepsy.
Sleep lab tests for narcolepsy
Depending on how you answer these questions, your doctor may order a test in a sleep lab. These tests may include actigraphy, polysomnography and a sleep latency test:1,2
- Polysomnography (PSG or sleep study) is an overnight sleep test that records brain and muscle activity, breathing, and eye movements. This test can tell your doctor whether your REM sleep is happening at the right times. It will also tell your doctor if you have other sleep disorders such as sleep apnea or periodic limb movement disorder.
- Multiple sleep latency test (MSLT) is a sleep lab test that measures how quickly someone falls asleep, and when and if they enter REM sleep. The next day after being in the sleep lab, the person is asked to take 5 short naps at least 2 hours apart. Going into REM sleep within 15 minutes on 2 or more naps means you may have narcolepsy.
- Actigraphy is a device worn on your wrist. You may be asked to wear it for 2 weeks before your sleep lab test. It allows your doctor to see your sleep patterns and tell if your sleepiness is caused by not getting enough sleep or a circadian rhythm disorder.
Spinal fluid test
A spinal tap (lumbar puncture) may be needed to see if you have low levels of a neurotransmitter (brain chemical) called hypocretin. Hypocretin is often low in people who have narcolepsy with cataplexy, called Type 1 narcolepsy.1-3
Genetic tests for narcolepsy
It is not used very often but there is a genetic test for narcolepsy. More than 90 percent of people with Type 1 narcolepsy with cataplexy test positive for the gene group DQB1*0602. However, many healthy people who do not have narcolepsy also test positive for DQB1*0602.3