Influence of visual and proprioceptive afferences on tipper limb ataxia inpatients with multiple sclerosis

Our objective was to investigate how cooling of the arm and vision influenc e pointing movements in healthy subjects and patients with cerebellar limb ataxia due to clinically proven multiple sclerosis. An infrared video motio n analysis system was used to record the unrestricted, horizontal pointing movements toward a target under three different conditions involving a movi ng, stationary, or imaginary target; a visual, or acoustic trigger; and vis ion or memory guidance. All three tasks were performed before and after coo ling the arm in ice water. Patients had more hypermetric and slower pointin g movements than controls under all tested conditions. Patients also had si gnificantly larger three-dimensional finger sway paths during the postural phase and larger movement angles of the wrist joint. Memory-guided movement s were the most hypermetric recorded in both groups. Cooling of the limb ha d no effect on amplitude or peak velocity of the pointing movement in eithe r group under all tested conditions, but significantly reduced the three-di mensional finger sway path during the postural phase in patients with limb ataxia. Cooling-induced reduction of the finger sway was largest in those p atients with the largest finger sway before cooling. In conclusion, the coo ling-induced reduction of the proprioceptive afferent inflow, most probably of group I spindle afferents, reduces postural tremor of patients with cer ebellar dysfunction. (C) 1999 Elsevier Science B.V. All rights reserved.