Autoimmune cerebellar ataxia

Among the different forms of cerebellar ataxia, autoimmune cerebellar ataxia (ACA) or immune‐mediated cerebellar ataxia (IMCA), which appears to be based on an autoimmune mechanism, has long been considered important from the viewpoint of paraneoplastic syndrome. With the expansion of the concept of immune‐mediated neurological diseases and the identification of many novel autoantibodies, ACA has recently become an important neurological syndrome. Although no definitive diagnostic criteria of ACA exist, Hadjivassilou et al suggested diagnostic criteria for primary ACA in 2020 and Dalmau and Graus showed proposed diagnostic criteria for ACA in 2022. The proposed diagnostic criteria for ACA by Dalmau and Graus emphasize the importance of antibody reliability. In the future, additional studies should be conducted to identify new antibodies associated with ACA and to clarify the importance of each antibody. Moreover, ACA is a disease for which immunological therapeutic intervention is feasible and requires early treatment to maintain cerebellar function. Many cases with ACA have reported the efficacy of immunotherapy. The concept of ACA may have the potential for further expansion and becomes increasingly important in the diagnosis of cerebellar ataxia.