Objective: To characterize factors that contribute to symptomatic narcolepsy and excessive daytime sleepiness in neuromyelitis optica and multiple sclerosis.

Methods: Japanese university hospitals. Methods: Case study. Methods: Seven Japanese patients whose initial diagnoses were multiple sclerosis and who were exhibiting excessive daytime sleepiness. Methods: Lesions on magnetic resonance imaging, cerebrospinal fluid hypocretin-1 levels, and serum anti-aquaporin 4 (AQP4) antibody titer.

Results: Bilateral and symmetrical hypothalamic lesions associated with marked or moderate hypocretin deficiency were found in all 7 cases. Four of these patients met the International Classification of Sleep Disorders 2 narcolepsy criteria. Three patients, including 2 patients with narcolepsy, were seropositive for anti-AQP4 antibody and diagnosed as having neuromyelitis optica-related disorder.

Conclusions: Since AQP4 is highly expressed in the hypothalamic periventricular regions, an immune attack on AQP4 may be partially responsible for the bilateral and hypothalamic lesions and hypocretin deficiency in narcolepsy/excessive daytime sleepiness associated with autoimmune demyelinating diseases.