French consensus. Type 1 and type 2 Narcolepsy: Investigations and follow-up

Abstract

In the new international classification of sleep disorders (ICSD-3), narcolepsy is differentiated into two distinct pathologies: type 1 narcolepsy (NT1) and type 2 narcolepsy (NT2). NT1 is characterised by periods of an irrepressible need to sleep, cataplexy (a sudden loss of muscle tone triggered by emotion) and in some cases the presence of symptoms such as hypnagogic hallucinations, sleep paralysis and disturbed night-time sleep. Its physiopathology is based on the loss of hypocretin neurons in the hypothalamus, seemingly connected to an auto-immune process. By definition, cataplexy is absent and the hypocretin levels in the CSF are normal in NT2. Confirming the diagnosis requires polysomnography and multiple sleep latency tests. The choice of further investigations is based on the presence or absence of typical cataplexy. Further investigations include HLA typing, lumbar puncture to measure the hypocretin level in the CSF, or even brain imagery in the case of narcolepsy suspected to be secondary to an underlying pathology. In this consensus we propose recommendations for the work-up to be carried out during diagnosis and follow-up for patients suffering from narcolepsy.

Keywords: Biomarker; Cataplexy; Hypocretin/orexine; Narcolepsy; Somnolence.