The third International Classification of Sleep Disorders (ICSD-3) defines narcolepsy as patients with periods of sleep attacks or excessive daytime sleepiness. Neurophysiology tests with unremarkable polysomnography and positive Multiple Sleep Latency Test scores establish the diagnosis of narcolepsy.
Usually, narcolepsy type 1 is differentiated by the presence of immunological pathophysiology and the consequent lower levels of hypocretin-12 and usually narcolepsy type 1 patients have cataplexy and a CSF hypocretin-1 concentration ≤ 110 pg/mL or < 1/3 of mean values obtained in normal volunteers.
However, the normal levels of hypocretin-1 are higher than 200 pg/mL2. Indeed, there is a grey zone between 110 pg/mL and 200 pg/mL that is not discussed in the literature.