Autoimmune Cerebellar Ataxia: Etiology and Clinical Characteristics of a Case Series from China.

Autoimmune cerebellar ataxia (ACA) is an important and potentially treatable cause of sporadic cerebellar syndrome, but studies with large sample size are limited. This study reported a large ACA series in China and described its etiology and clinical characteristics. We reviewed all ACA patients from our hospital (2013-2021) and analyzed their clinical and paraclinical features, treatment, and outcome. ACA subtypes investigated included paraneoplastic cerebellar degeneration (PCD), primary autoimmune cerebellar ataxia (PACA), anti-glutamate decarboxylase (GAD)-associated cerebellar ataxia, opsoclonus-myoclonus syndrome (OMS), Miller Fisher syndrome (MFS), and ACA-associated with autoimmune encephalitis. A total of 127 patients were identified and 40.9% were male. The median onset age was 47.0 years. Gait ataxia was the most prevalent feature followed by limb ataxia, dizziness, and dysarthria/dysphagia. Extracerebellar manifestations included pyramidal signs (28.3%) and peripheral neuropathy/radiculopathy (15.0%). ACA subtypes were PCD (30.7%), PACA (37.8%), ACA associated with autoimmune encephalitis (12.6%), anti-GAD-associated ACA (8.7%), MFS (7.1%), and OMS (3.1%). Neuronal antibodies were positive in 67.7% of patients. Brain magnetic resonance imaging was unremarkable (55.7%) or showed atrophy (18.3%) or abnormal signal intensity (26.1%, most of which was extracerebellar). Although most patients received immunotherapy, the modified Rankin scale at last follow-up was ≤ 2 in only 47.3% patients. Thirteen patients died and 24 relapsed. Compared with PACA, PCD patients were older and had poorer outcome. This study illustrates the heterogeneity in the clinical features of ACA and suggests the importance of neuronal antibody testing in ACA diagnosis. PCD and PACA are the dominant ACA subtypes, and the former has a less favorable prognosis.