P300 and cerebral blood flow before and after TRH in olivopontocerebellar atrophy.

Ten cases of olivopontocerebellar atrophy (OPCA) (mean age 56 +/- 9 years) and 8 healthy controls (mean age 58 +/- 9 years) were studied. The P300 was measured with a Synax 1100 evoked potential recorder and the regional cerebral blood flow was measured using the stable xenon computed tomography method. The P300 latency was significantly longer in the OPCA group than in the healthy control group. The P300 latency after the intravenous infusion of thyrotropin releasing hormone (TRH) in the OPCA group was significantly shorter than that before the intravenous infusion of TRH. The blood flows in all the measured areas (the cerebellar cortex, the cerebellar white matter, the brainstem, the thalamus, the basal ganglia, the frontal lobe cortex and the frontal lobe white matter) were significantly lower in the OPCA group than in the healthy control group. The blood flows in the cerebellar cortex and in the frontal lobe cortex after the intravenous infusion of TRH were significantly higher than those before the intravenous infusion of TRH. The prolongation of P300 latency in the OPCA group suggests that subclinical disturbance in recognition function is present in OPCA and may be related to the blood flow decrease outside the cerebellum.