IGLON5 and insomnia measurement: Sleep disorders were prevalent among the cohort (28 patients, 29%) and included central sleep apnea (12, 12%), insomnia (10, 10%), REM sleep disorder (10, 5 of whom were IgLON5‐IgG positive), hypersomnia (6, 6%), and narcolepsy/cataplexy (3, 2 of whom had Ma2‐IgG).