Visit your GP immediately if you think that you have narcolepsy. When you see your GP, take a sleep diary with you and/or a completed Epworth sleepiness questionnaire (see below).
In order to diagnose narcolepsy, your GP will take a close look at your medical and family history. They will ask you about your sleeping habits and any other symptoms that you are having.
The symptoms of narcolepsy usually first appear during the teenage years, and are often mistakenly attributed to 'typical teenage behaviour'. For example, if a pupil falls asleep in class, it may be assumed that they are staying up too late at night and that they are not getting enough sleep.
Ruling out other conditions
Narcolepsy is sometimes a difficult condition to diagnose. Its symptoms can often be attributed to other conditions, such as anaemia (a condition that causes a reduced number of oxygen carrying red blood cells) or epilepsy (a condition that causes repeated seizures or fits).
Therefore, in order to make a correct diagnosis, your GP may carry out several tests to help rule out any other conditions that may be causing your excessive daytime sleepiness. For example, you may require a blood test or an X-ray.
Some medical conditions that can cause excessive daytime sleepiness include:
- head trauma
- stroke – a serious medical condition caused by the blood supply to the brain being disturbed
- inflammatory conditions – any condition that causes inflammation (swelling)
- neurodegenerative conditions – disorders of the nervous system
Excessive daytime sleepiness can also sometimes be caused by the side effects of certain prescription medicines and those bought over-the-counter (OTC).
Sleep analysis
To confirm a suspected case of narcolepsy, you will usually have an in-depth analysis of your sleep patterns. In order to do this, your GP will refer you to a specialist in sleep disorders. Your sleep can be analysed in a number of ways, some of which are outlined below.
Epworth sleepiness scale
The Epworth sleepiness scale is a questionnaire that can help analyse the situations that make you feel sleepy. Your GP will use the results of your completed questionnaire to help them decide whether you to refer you to a sleep specialist.
In filling out the questionnaire, you are asked to rank your likelihood of falling asleep in situations such as sitting and reading, watching television or being a passenger in a car. The specialist will look at your answers to determine whether you are unusually drowsy or whether your sleep pattern is fairly normal.
A score of 10 or below indicates that you have a level of daytime sleepiness that is equal to the general population. However, a score of 18 or above indicates that you have a high level of daytime sleepiness. If this is the case, it is likely that your GP will refer you to a sleep specialist for further investigation.
Polysomnography
Polysomnography is an investigation of your sleep, which is carried out at a specialist sleep centre.
The study usually involves staying overnight at the sleep centre in order to measure your sleeping patterns. During your night time sleep, several different parts of your body will be carefully monitored.
Specialist nurses will place a series of electrodes (small metallic discs) and bands on the surface of your skin and around parts of your body. Electrodes and bands will be placed:
- on your face and scalp (electrodes)
- above the lip (electrodes)
- around the chest (bands)
- around your abdomen (bands)
Sensors will also be placed on your legs and an oxygen sensor will be attached to your finger.
The tests that will be carried out during polysomnography include:
- electro-encephalography (EEG) – this monitors your brain waves
- electromyography (EMG) – this monitors your muscle tone
- recordings of thoracic-abdominal movements – movements in your chest and abdomen
- recordings of your oro-nasal airflow – the airflow through your mouth and nose
- rulse oximetry – this measures your heart rate and blood oxygen levels
- electrocardiography (ECG) – this monitors your heart
- Sound and video recording
After you have slept, a specialist will analyse your test results to see whether you have normal brain wave activity, breathing patterns and muscle and eye movement.
Multiple sleep latency test
A multiple sleep latency test measures how long it takes for you to fall asleep during the day. You may have this test after having a polysomnogram.
If you have a multiple sleep latency test, you will usually be asked to have several naps throughout the day and a specialist will analyse how quickly and easily you fall asleep. If you have narcolepsy, you will usually fall asleep easily and enter rapid eye movement (REM) sleep very quickly.
Narcolepsy with cataplexy
If your GP thinks you may have narcolepsy with cataplexy (temporary muscle weakness), you will be referred to a specialist centre in order to confirm the diagnosis. A diagnosis of narcolepsy with cataplexy will be based on the following criteria:
- you are have excessive daytime sleepiness (EDS), which has happened daily for at least three months
- you have a history of cataplexy (sudden episodes of muscle weakness on both sides of your body that last for less than two minutes and are triggered by emotions)
- your symptoms are not caused by a different sleep condition or medical disorder
Narcolepsy with cataplexy can sometimes be confused with other conditions, such as:
- narcolepsy without cataplexy
- sleep apnoea – a condition that causes interruptions to breathing during sleep
- hypersomnia – an excessive need to sleep
- chronic sleep deprivation – not sleeping for long periods of time
