RADIOLOGIC CORRELATES OF REACTION-TIME MEASUREMENTS IN OLIVOPONTOCEREBELLAR ATROPHY

We measured simple visual and auditory reaction time (RT) and movement time (MT) in 32 patients with olivopontocerebellar atrophy (OPCA) in comparison to 32 control subjects. In addition, we followed 2 approach es to radiologic assessment by computed tomographic scans: subjective (by inspection of films) and objective (by measurement of 4 radiologic ratios at the level of the posterior fossa and 1 ratio at the suprate ntorial level). All OPCA patients had various degrees of cerebellar at rophy and lengthened RT and MT in comparison to their controls. There were no significant differences in RT and MT performances in patients with mild-moderate versus those with severe cerebellar atrophy as asse ssed by inspection of their films. OPCA patients with severe versus mi ld-moderate atrophy evaluated by 3 measures, i.e., brainstem, brachium pontis and fourth ventricle ratios, presented few significantly lengt hened RT and MT performances. In contrast, patients with severe atroph y revealed by the midbrain ratio had significantly lengthened RT and M T performances compared to those with mild-moderate atrophy assessed b y this ratio on 7 of 8 measures; the 8th measure showed a borderline s ignificant difference. This could be explained by the fact that atroph y at the midbrain level is the only one which involves dopaminergic, n oradrenergic and glutamatergic structures and pathways.