Autoantibodies to glutamic acid decarboxylase (GAD) are associated with multiple neurological disorders. Most commonly are cerebellar ataxia and stiff-person syndrome. The classic clinical presentation of patients with anti-GAD65 Ab cerebellar ataxia is a subacute or chronic progressive pancerebeller syndrome. An essentially unilateral cerebellar ataxia associated with anti-GAD65 Ab has not yet been reported.

The patient is a 44-year-old male with a previous history of type 2 Diabetes and primary generalized epilepsy. He presented with progressive coordination difficulty primarily involving his left side over ~6 years.   He reported no clear coordination difficulties involving the right limbs. His focused neurologic exam was significant for asymmetric left-sided cerebellar features, including dysmetria with finger to nose and heel to shin, as well as left hand and foot dysdiadochokinesia.  His gait was mildly ataxic and he had difficulties with tandem gait.

MRI Brain without contrast showed asymmetric atrophy of the left cerebellar hemisphere, peduncle, and vermis. Both serum and CSF anti-GAD antibodies were positive.  In addition, oligoclonal bands were present in the CSF.  The workup for malignancy was negative, including normal PET scan. The patient was treated with CellCept and symptoms have stabilized.

We report a unique case of hemiataxia and asymmetric cerebeller atrophy associated with anti-GAD Ab. Autoimmune antibody-mediated disease should be considered in the differential diagnosis of asymmetric cerebellar ataxia.