Hashimoto's encephalopathy (HE) presents with a variety of neurologic and neuropsychiatric features. Sixteen percentages of HE patients show cerebellar ataxia as a main neurological feature. The clinical features, treatments, laboratory features, brain images, and serum anti-NH2-terminal of α-enolase autoantibodies (anti-NAE Abs), which is a useful diagnostic marker of HE, were investigated in 8 patients. They presented with pure cerebellar ataxia and fulfilled the diagnostic criteria for HE based on the presence of anti-thyroid antibodies and responsiveness to immunotherapy, and were compared with clinical features in other autoimmune cerebellar ataxia associated with anti-GAD, anti-gliadin or anti-Yo. All autoimmune cerebellar ataxic patients presented with truncal ataxia, while nystagmus was absent in HE patients. Most of ataxic form of HE patients had insidious onset mimicking spinocerebellar degeneration, but brain magnetic resonance imaging showed no or mild atrophy of the cerebellum in all patients. Ataxic form of HE patients demonstrated an absence of nystagmus and tended to show a better response to immunotherapy. When a pure cerebellar ataxic patient who presents with truncal ataxia without nystagmus and cerebellar atrophy on brain MRI, HE should be considered as a differential diagnosis and anti-NAE Abs should be examined for the screening of this disease.
