Autoimmune Cerebellar Ataxias

Autoimmune cerebellar ataxias include a heterogeneous group of disorders characterized by isolated or predominant cerebellar dysfunction caused by immune-mediated mechanisms. The best-characterized autoimmune ataxia is paraneoplastic cerebellar degeneration (PCD) that, depending on the type of cancer, associates with different paraneoplastic antibodies such as Yo antibodies in patients with breast or ovarian cancer, Tr (DNER) antibodies in patients with Hodgkin lymphoma, and SOX1 or voltage-gated calcium channel (VGCC) antibodies in patients with small-cell lung cancer (SCLC). Patients with PCD and SCLC can have concurrent symptoms of Lambert–Eaton myasthenic syndrome (LEMS). Non-paraneoplastic cerebellar ataxias usually associate with glutamic acid decarboxylase (GAD) or mGluR1 antibodies. Patients with autoimmune ataxia respond poorly to immunotherapy even when the associated antibodies are directed against neuronal surface antigens (VGCC, mGluR1). Cerebellar ataxia may occur in patients with dietary gluten sensitivity. The autoimmune pathogenesis of gluten ataxia is unclear. Acute cerebellar ataxia and acute cerebellitis are the most frequent causes of cerebellar dysfunction in children. Whereas the term acute cerebellar ataxia is used to define patients with normal MRI and a benign clinical course, the term acute cerebellitis implies a more severe disorder with MRI inflammatory changes. In these patients the long-term prognosis is less favourable.