Early onset cerebellar ataxia with retained tendon reflexes comparison with Friedreich's ataxia and olivopontocerebellar atrophy : an evoked potential study.

14 patients with the clinical diagnosis of early onset cerebellar ataxia with retained tendon reflexes (EOCA) were evaluated by multimodal evoked potential (EP) studies. The results were compared with observations made on 10 patients with Friedreich's ataxia (FA) and 16 patients with olivopontocerebellar atrophy (OPCA). Ten patients (71.4) with EOCA had abnormality of at least one of the EP parameters. Brainstem auditory evoked response (BAER) studies were abnormal in 50, followed by abnormalities in posterior tibial somatosensory evoked potential (SSEP) (46.1), visual evoked potential (VEP) and median SSEP (30.8 each). Only the abnormality of posterior tibial SSEP had a positive correlation with the duration of disease. The abnormalities in SSEP were more frequent in EOCA than in OPCA and were comparable to that of FA patients. On the contrary, abnormalities of VEP and BAER in EOCA patients were significantly less common (especially VEP) than in FA patients and were almost comparable to OPCA. Thus, on the basis of conventional evoked potential studies, EOCA patients seem to share some common features of FA and OPCA patients. There was no single EP feature to characterize EOCA as a distinct entity.