Improvement with corticosteroids and azathioprine in GAD65-associated cerebellar ataxia

High levels of antibodies to the 65-kd isoform of glutamic acid decarboxylase (GAD65) are observed in some cases of sporadic, progressive cerebellar ataxia and suggest a potential autoimmune etiology.1-3 Few studies have examined immunotherapy in GAD65-associated ataxia.1,4 We describe a patient with GAD65 ataxia who responded to IV methylprednisolone (IVMP) but not to plasma exchange. Oral azathioprine has provided a sustained clinical remission. A 70-year-old man with type 2 diabetes mellitus and unremarkable family history presented with 9 months of progressive ataxia, beginning with left hemiataxia and dysarthria. He later developed right hemiataxia, progressive gait instability, dysmetria, spasticity, worsening dysarthria, and dysphagia with 5- to 10-kg weight loss. On exam he had loud, scanning, dysarthric speech, gaze-evoked nystagmus, saccadic intrusions, dysmetric saccades, spastic tone and bilateral Babinski signs, marked left greater than right limb ataxia with gross action tremor, dysmetria, and dysdiadokinesia (video). He was unable to stand or walk because of ataxia and received a gastrostomy tube for dysphagia and aspiration. His score on the International Cooperative Ataxia Rating Scale (ICARS) was 78 of …