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Autoimmune encephalitis (AE) can be classified into antibody-defined subtypes, which can manifest with immunotherapy-responsive movement disorders sometimes mimicking non-inflammatory etiologies. In the elderly, anti-leucin-rich-glioma-inactivated-1 (LGI1) and contactin-associated-protein-like-2 (CASPR2) antibody-associated diseases compose a relevant fraction of AE. Patients with LGI1 autoantibodies are known to present with limbic encephalitis and additionally faciobrachial dystonic seizures (FBDS) may occur. However, the clinical spectrum of CASPR2 autoantibody-associated disorders is more diverse including limbic encephalitis, Morvan`s syndrome, peripheral nerve hyperexcitability syndrome, ataxia, pain and sleep disorders. Reports on unusual, sometimes isolated and immunotherapy-responsive movement disorders in CASPR2-autoantibody associated syndromes have caused substantial concern regarding necessity of autoantibody-testing in patients with movement disorders. Therefore, we aimed to systematically assess their prevalence and manifestation in patients with CASPR2 autoimmunity. This international, retrospective cohort study included patients with CASPR2 autoimmunity from participating expert centers in Europe. Patients with ataxia and/or movement disorders were analyzed in detail using questionnaires and video recordings. We recruited a comparator group with anti-leucin-rich-glioma-inactivated-1 (LGI1) encephalitis from the GENERATE network. Characteristics were compared according to serostatus. We identified 164 patients with CASPR2 autoantibodies. Of these, 149 (90.8%) had only CASPR2- and 15 (9.1%) both CASPR2- and LGI1-autoantibodies. Compared to 105 patients with LGI1 encephalitis, patients with CASPR2 autoantibodies more often had movement disorders and/or ataxia (35.6% versus 3.8%; p

This scientific commentary refers to ‘Seronegative autoimmune encephalitis: clinical characteristics and factors associated with outcomes’ by Lee et al. (https://doi.org/10.1093/brain/awac166).