Insomnia is a cardinal feature of Morvan’s syndrome and can associate with reversed diurnal rhythms and the syndrome of agrypnia excitata.13 Morvan’s syndrome is rarer in patients with only LGI1 antibodies and, indeed, CASPR2 antibodies often associate more frequently with insomnia and agrypnia.8 Aside from Morvan’s syndrome, insomnia is reported in patients with LGI1 antibodies at rates of 7%–23%.4 8 23 The total number of patients affected by any sleep disturbance, including hypersomnolence and rapid eye movement sleep disorder as well as insomnia, reaches 31%–48%. This evidence concerns the gene LGI1 and rapid eye movement sleep disorder.