Dopa-responsive parkinsonism phenotype of spinocerebellar ataxia type 2

We report on 2 brothers, Patients 1 and 2, who presented with a similar clinical syndrome consisting of resting tumor, bradykinesia, rigidity, and dysarthria at the ages of 40 and 43 years, respectively. An excellent response to levodopa therapy was observed throughout the disease course. No gait or limb ataxia, slow saccades, or decreased tendon reflexes were detected, but unsteadiness of gait with propulsion developed recently in Patient 1 approximately 25 years after disease onset. Magnetic resonance imaging demonstrated mild atrophy of the pons and cerebellum in Patient 1 and cerebellar atrophy in Patient 2. Expanded CAG repeats, numbering 36, in one allele of the ataxin-2 gene were identified in Patient 1 only; his brother was not available for this investigation. With [^99mTc]TRODAT-1 single photon emission computed tomography of the brain, a significant bilateral and asymmetrical reduction of striatal dopamine transporters was found in Patient 1 compared to healthy controls. This bilateral reduction of striatal dopamine transporters resembled that observed in a set of controls with Parkinson's disease who had asymmetrical impairment. These results suggest that patients with familial parkinsonism who present with typical Parkinson's disease should be screened for the genetic defect of spinocerebellar ataxia type 2. The presynaptic impairment of nigrostriatal function is very likely to be the reason for levodopa responsiveness.