Narcolepsy secondary to anti-Ma2 encephalitis: two case reports

Abstract

Recent studies suggest that sleep disorders are present in two-thirds of patients with autoimmune encephalitis. In anti-Ma2 encephalitis, hypersomnia appears to be frequent. However, only few cases of type 1 narcolepsy have been reported to date with anti-Ma2 encephalitis. We report 2 new cases of patients with narcolepsy secondary to anti-Ma2 encephalitis. Patient 1, a 68-year-old man, had narcolepsy type 1, including sleep attacks, cataplexy, abnormal Multiple Sleep Latency Tests and hypocretin-1 deficiency (< 50 ng/L) in the cerebrospinal fluid (CSF), associated with a cerebellar syndrome. Anti-Ma2 antibodies were present in the serum and CSF and antivoltage-gated potassium channel antibodies in the serum. He benefited from a treatment with pitolisant. Patient 2, a 42-year-old man, had narcolepsy type 2, including hypersomnolence, no cataplexy, intermediate CSF levels of hypocretin-1 (138 ng/L), abnormal Multiple Sleep Latency Tests, and a limbic encephalitis presentation. Anti-Ma2 antibodies were present in the serum and CSF, and anti-Ma1 antibodies were in the CSF. For both, repeated polysomnographies were necessary to establish the precise diagnosis of central hypersomnia, emphasizing the importance of carrying out sleep investigations in a tertiary neurology center with sleep medicine expertise in patients with anti-Ma2 encephalitis.

Citation: Brunet de Courssou J-B, Testard P, Sallansonnet-Froment M, et al. Narcolepsy secondary to anti-Ma2 encephalitis: two case reports. J Clin Sleep Med. 2023;19(4):837-841.

Keywords: Ma2; auto-immune encephalitis; hypersomnia; narcolepsy; paraneoplastic; sleep disease.

Figure 1. Sleep studies during night and day showing narcolepsy in 2 patients with anti-Ma2 encephalitis.

The 48-hour procedure starts with a nighttime polysomnography stopped at 6:30 am, followed by 5 MSLT performed at 8:00 am, 10:00 am, 12:00 am, 2:00 pm, 4:00 pm (first line), followed by an 24-hour bed rest monitoring (second line). The x-axis indicates clock time and the y-axis indicates sleep stages (W = wakefulness; R = rapid eye movement sleep [REM] sleep, in red color; 1, 2, and 3 = non-REM N1, N2, and N3 sleep stages). Note the frequent sleep onset in REM periods (REM sleep appearing less than 15 min after sleep onset), whether during the night and during daytime, a feature of narcolepsy. MSLT = Multiple Sleep Latency Test.