Cerebellar Autoimmune Diseases

Autoimmune cerebellar ataxias (ACA) encompass a heterogeneous group of disorders characterized by isolated or predominant cerebellar dysfunction caused by immune-mediated mechanisms. ACA include well-characterized entities with a clear trigger and/or association with specific neuronal antibodies, such as paraneoplastic cerebellar degeneration (PCD), cerebellar ataxia associated with glutamic acid decarboxylase antibodies (GAD), gluten ataxia (GA), or postinfectious cerebellar ataxia, as well as patients with suspected immune-mediated cerebellar ataxia but in the absence of malignancy and/or without known pathogenic antibodies. The best characterized autoimmune ataxia is PCD that, depending on the type of cancer, associates with different onconeural antibodies. Non-paraneoplastic ACA usually associate with GAD antibodies. GA is probably overdiagnosed as gliadin antibodies are not specific for the disease. Patients with ACA respond poorly to immunotherapy even when the associated antibodies are directed against neuronal surface antigens. However, a better prognosis is expected when immune-mediated therapeutic interventions are delivered during early stages when the cerebellar reserve still is preserved.