How is narcolepsy diagnosed?

There are several tests and diagnostic criteria available that are used by clinicians to diagnose narcolepsy.

If you suspect you may be suffering from narcolepsy, there is a simple self-test that measures your levels of tiredness.

Epworth Sleepiness Scale

The Epworth Sleepiness Scale in a simple self-test to measure levels of excessive sleepiness. The test outlines certain everyday situations for you to rate how likely you are to doze off or fall asleep. Complete this interactive version below and get results instantly which will give you guidance on your next steps and can be printed out to take to your appointment if you do need to consult your doctor.

Key

What your score means

• If your score is below 10 you have a healthy level of daytime sleepiness in comparison to the general population
• If your score is between 10 and 18 you have an excessive level of daytime sleepiness compared to the general population which may require further attention. You should consider whether you are obtaining adequate sleep, need to improve your sleep hygiene and consult your doctor for further medical help
• If your score is 18 or above you have a very high level of excessive daytime sleepiness and it is vital that you consult your doctor for further medical help

(NB: The Epworth sleep test does not prove or disprove that you have a sleep related problem as many factors contribute to excessive sleepiness, and this is just an indication of whether further investigation is required. Please take notice of the results and consult your doctor if your score is high)

• If after filling out the Epworth Sleepiness Scale, it indicates you may suffer from excessive sleepiness, you would need to consult your doctor who would conduct some further tests. These tests might include:
  
  • Polysomnography measures brain activity, eye movement, muscle movement and heart and breathing rates overnight to study your nocturnal sleep pattern. This is carried out by sleep experts in a specialised sleep centre or sleep clinic. Although the test is not always diagnostic in narcolepsy, it can be important to exclude other potential causes of severe sleepiness.
  • Multiple Sleep Latency Test (MSLT) measures how quickly you can fall asleep when instructed to lie in a dark room and attempt to fall asleep. This is repeated four or five times during the morning and early afternoon  at 2-hour intervals. As well as recording the degree of sleepiness, the MSLT measures the type of sleep achieved. People living with narcolepsy fall into dream sleep abnormally quickly and this is an important diagnostic feature.
  • Maintenance of Wakefulness Test (MWT) measures how able you are to stay awake when in a dark room. Again, this is repeated four times a day at 2-hour intervals. This is more of a research tool and is not generally available.
• Further tests can be carried out to detect levels of a neuropeptide called hypocretin or orexin which is thought to be a key factor in the cause of narcolepsy
  
  • CSF orexin (hypocretin) assay – a sample of the fluid that bathes the brain and spinal cord, known as cerebrospinal fluid (CSF) is taken and measured for levels of hypocretin.
  • Testing for the absence or low levels of hypocretin is thought to be a very specific test for typical narcolepsy

There is a set of criteria that doctors use to determine whether or not a patient is suffering from narcolepsy. Two broad categories are recognised.

• Narcolepsy without typical cataplexy (around one third of all narcolepsy patients)
  
  • Patients have been excessively sleepy for at least 3 months with no other cause identified
  • Patients have not experienced cataplexy attacks
  • Polysomnography and multiple sleep latency test readings usually confirm presence of disturbed sleep-wake cycle and excessive daytime sleepiness
• Narcolepsy with cataplexy:
  
  • Patients experience excessive sleepiness for at least 3 months
  • There is a history of typical cataplexy attacks
  • The diagnosis can be confirmed with a polysomnography and multiple sleep latency test reading or by evidence of reduced levels of hypocretin cells. However, many doctors rely purely on the patient’s history if it is classical for narcolepsy and cataplexy.
  • Disturbed sleep is not due to another sleep disorder or other medical disorder, medication or substance misuse