Typical complaints of this neurological disease are day fatigue, uncontrollable sleep compulsion, failure of single muscles, for example, of the leg musculature with slumping. These so-called cataplexies are often triggered by strong feeling of excitation, e.g., laughter, joy or annoyance, surprise, or anger.

The nightly sleep is often interrupted by awakening. Peculiar occurrences can happen (at sleep onset) while trying to fall asleep and during the wake up phase. For example, the feeling of not being able to move or experiences similar to having a dream, although one is awake.

The cause of the narcolepsy is not exactly known. Most affected persons will, when given a specific blood test, be confirmed to have a certain blood group character (DR. HLA 2, HLA DQ 1).

This condition can be diagnosed by the relevant symptoms which can occur, even partially or in very light form. The diagnosis is confirmed by an examination in the sleep lab. During this polysomnogram test, typical changes of the sleep can be proved, e.g., a very early occurrence of REM sleep (dream phase).

Usually, an examination is also made during the day, the so-called multiple-sleep-latency-test (MSLT). On this occasion, the REM sleep occurrences are measured during short sleep phases in the day.

In some cases, other tests will be administered to rule out other neurological diseases which cause similar symptoms, for example, some forms of epilepsy. However, in spite of the name resemblance, narcolepsy has nothing to do with epilepsy.