Narcolepsy is a chronic, neurological disease. It is rare, affecting 20-40 out of 100,000 persons, and presents with excessive daytime sleepiness (EDS), cataplexy (loss of muscle control triggered by emotions), disturbed sleep, hypnagogic hallucinations and sleep paralysis.
Recent observations, suggest that narcolepsy may represent an autoimmune disorder, which arises from a combination of genetic predisposition and such environmental factors as infections and vaccinations eventually leading to a selective loss of hypocretin neurons in the hypothalamus, a structure in the middle of our brain.
The majority of narcolepsy cases are idiopathic (that is of unknown cause) and non sporadic (no family history), about 1-5% are familial or secondary tp a brain disorder. The onset can be at any age, but there is a clear bimodal distribution with peaks at age 15 and 36 years. During the first years after the onset of the first symptoms, there may be progression in severity of the existing symptoms and additional symptoms may develop. Progression of symptoms is unusual after 4-6 years.
The diagnosis is established according to the International Classification of Sleep Disorders revised recently (ICSD-3, 2014), which classifies the disease in two subtypes: Narcolepsy type 1 (NT1) and type 2 (NT2). Both types require the presence of 3 months of EDS. In type 1 there is clear-cut cataplexy (see below) or a proven undetectable amount of hypocretin-1 in the cerebrospinal fluid. In type 2, there is no cataplexy and no proven hypocretin deficiency. The diagnosis is made in a sleep laboratory with polysomnography and a multiple sleep latency test (MSLT) and after exclusion of other causes of EDS.
Another biologic marker is the presence of the HLA DQB1*06:02 type, found in the 90-95% of NT1 and in a large proportion of people with NT2. However, this HLA type is also found in 15-25% of healthy people.
So far narcolepsy cannot be cured. However, there is efficacious treatment.