Essential Features
Narcolepsy is a neurological condition characterized by severe and persistent daytime sleepiness, and a number of other unusual symptoms associated with REM sleep abnormalities. The symptoms of narcolepsy include:
Excessive Daytime Sleepiness. Excessive daytime sleepiness in narcolepsy manifests as general sleepiness throughout the day, the need for repeated naps, and unintended lapses into sleep during the day. Such lapses into sleep generally occur during monotonous or sedentary situations (watching T.V., sitting on a bus), but may also take the form of "sleep attacks" or sudden, irresistible lapses into sleep, which can occur in highly unusual situations such as eating, walking or driving. While sleepiness is the core symptoms of narcolepsy, it is important to keep in mind that excessive daytime sleepiness may also be due to a number of other conditions (see assessment of narcolepsy).
Cataplexy. Cataplexy is a sudden, bilateral loss of muscle tone, usually triggered by strong emotions such as laughter, surprise or even anger. Cataplexy may affect local muscle groups resulting in such things as buckling of the knees or facial drooping, or may affect the entire body resulting in collapse to the ground. Episodes usually last several seconds to minutes. Cataplexy is generally not accompanied by a loss of consciousness (as it is often portrayed in movies) but sleep may follow an episode. Cataplexy is a highly specific symptoms of narcolepsy, occurring only very rarely in other conditions. However, cataplexy needs to be differentiated from other similar appearing phenomenon such as seizures or syncope (fainting).
Sleep Paralysis. Sleep paralysis is a temporary inability to move or talk occurring as one is falling asleep or waking up. Episodes may last for several minutes. The experience, while short-lived, can be very frightening to the individual, particularly as they may be accompanied by hypnagogic or hypnopompic hallucinations (see below). It should be noted that while sleep paralysis is common in narcolepsy, it may occur in otherwise healthy individuals from time to time.
Hypnagogic/Hypnopompic Hallucinations. Hypnagogic hallucinations are those that occur as one is falling asleep, while hypnopompic hallucinations occur as one is waking up. Such hallucinations can take the form of abnormal visions, sounds, kinetic or tactile sensations. They may even involve more complex hallucinations such as sensations of floating out of one's body, or the feeling of a figure in the room threatening the dreamer. These hallucinations may accompany sleep paralysis, further contributing to their frightening nature. Such hallucinations are common in narcolepsy, but may occur in otherwise healthy individuals from time to time.
Disrupted Sleep. While sleepiness is a core symptom of narcolepsy, it should also be appreciated that individuals with narcolepsy frequently also experience disrupted nocturnal sleep, usually with frequent brief awakening throughout the night. Nightmares or unusual dreams are another frequent complaint.
Automatic Behaviour. In some cases the daytime sleepiness associated with narcolepsy may manifest as automatic behaviour. This involves carrying out activities in a semiautomatic manner without memory or consciousness, which at times can produce nonsensical results (going into a room and forgetting why one was going there, putting one's purse into the refrigerator etc.).
Other. Individuals with narcolepsy have higher rates of REM Sleep Behaviour Disorder and Obstructive Sleep Apnea, and thus may have symptoms associated with these conditions.
The symptoms of narcolepsy typically begin in adolescence or one's early twenties but it can begin in childhood or later in life. Sleepiness is usually the first symptom to manifest and is generally persistent. Other symptoms such as cataplexy can occur later on and at variable times.
Left untreated, narcolepsy is a seriously impairing illness. Patients struggle to do well in school, keep jobs and socialize. Patients may become socially isolated and commonly develop low confidence and depression.
In the United States the prevalence of narcolepsy has been estimated to be about 1 in 2000. The prevalence of narcolepsy seems to vary markedly dependent on the population studied, being quite rare in Israel for example, but more common in Japan.
