Abstract
Narcolepsy type 1 (NT1) and type 2 (NT2) are two rare neurological diseases, classified as central disorders of hypersomnolence. The pathophysiology of NT1 is well known; it is caused by the selective destruction of hypocretin (Hcrt) neurons, by a highly suspected autoimmune process. On the contrary, little is known about NT2 etiology, sharing with NT1 somnolence and signs of dysregulation of rapid eye movement (REM) sleep, but not cataplexy. Management strategies are rather codified, at least in adults, with a lifelong treatment required in NT1, whereas no pharmacological study focused only on NT2 patients, with sometimes spontaneous improvement or disappearance of their symptoms. We recommend that medications and guidelines in NT2 should be the same as for NT1 (except for cataplexy), but the benefit risk ratio should be reassessed regularly. The main symptom in both diseases is a disabling excessive daytime sleepiness (EDS). First-line medications should be stimulants such as modafinil, armodafinil, or sodium oxybate, second-line methylphenidate and pitolisant, where available, and amphetamines as third-line therapy. Sodium oxybate has the advantage to be also effective to manage the fragmented nocturnal sleep, another common symptom in NT1. We advise to wait a few weeks with a stimulant drug before starting an anticataplectic treatment in NT1, except for severe cataplexy. Furthermore, cataplexy treatment should not be systematic. First-line strategy is the use of sodium oxybate, the only drug approved for cataplexy and EDS in adults. However, antidepressant agents such as venlafaxine are also commonly used, with few adverse effects and a good efficacy, although based on expert consensus only. A clinically relevant tool is required to quantify the severity of narcolepsy, subjective symptoms, and their consequences, to monitor the treatment efficacy, and to finally optimize narcolepsy management. In the future, Hcrt replacement or Hcrt agonists will certainly be options to treat NT1, but for now the different peptides do not cross easily the blood brain barrier. Immune-based therapies are other possibilities in NT1, at disease onset, with already some successful attempts to slow down or stop the autoimmune process.