[Olivopontocerebellar atrophy and Parkinson's disease: diagnostic problems].

Clinical diagnoses of Parkinson's disease (PD) is highly inaccurate. Olivopontocerebellar atrophy (OPCA) is a major source of diagnostic confusion. We have studied the clinical characteristics of 50 patients with PD, 24 patients with OPCA judged by the presence of selective atrophy of the cerebellum and brainstem (diagnosed by CT brain scan) and 30 normal controls of similar age. The typical triad of PD, tremor, rigidity and akinesia, did not distinguish among patients from either group. The presence of severe postural imbalance and reflex myoclonus (in OPCA but not in PD) were the 2 most highly discriminative clinical features.