Different Course of Narcolepsy Diagnosed by Multiple Sleep Latency Test: A Single Center Experience

Background and Objective Several studies have raised questions about determining the diagnosis of the narcolepsy using multiple sleep latency test (MSLT). In this study, we investigated the diagnostic change in narcolepsy type 1 (NT1) and narcolepsy type 2 (NT2) using MSLT with long-term interval. Methods In this retrospective study, the demographic characteristics, polysomnography (PSG), and MSLT parameters were compared at the baseline between the NT1 and NT 2 patients. Then, MSLT re-tests were conducted with a mean follow-up of 8.48 years in patients with NT 1 and 7.05 years with NT 2. Results Seventy-four patients (58 with NT1 and 16 with NT2) were investigated in this study. At the baseline, demographic data showed a larger body mass index value, more sleep paralysis, and hypnogogic hallucination in NT 1 compared to NT 2. Also, at baseline MSLT, shorter mean sleep latency and higher number of sleep onset rapid eye movement periods (SOREMPs) were observed in the NT 1 than those of the NT 2. On follow-up MSLT, 6.9% (n = 4) patients with NT1 and 50% (n = 8) patients with NT2 did not satisfy the previous diagnosis. Furthermore, in all the groups who had the change in repeated-MSLT, the groups with less than 2 SOREMPs observed to be accompanied by negative MSL at follow-up. Conclusions The result of MSLT was observed not to be stable in the diagnosis of NT 2 at the study.