ACCELERATION DEFICIT IN PATIENTS WITH CEREBELLAR LESIONS - A STUDY OFKINEMATIC AND EMG-PARAMETERS IN FAST WRIST MOVEMENTS

Slowness of goal-directed movements is a frequent symptom following ce rebellar lesions. So far it has not been demonstrated whether this slo wness represents compensation for impaired braking which is a feature of cerebellar dysfunction with the consequence of hypermetria, or whet her it is an independent part of cerebellar movement disorder. To reso lve this question we tested 18 cerebellar patients in a paradigm where they not only had to perform fast goal-directed wrist flexion movemen ts (amplitudes 5 degrees and 30 degrees) but also wrist flexion moveme nts as fast and large as possible without particular target. In normal s antagonist activity is minimal in large movements without target. Al though subjects were clinically only mildly affected they regularly sh owed a 'slowness of movement' resulting from a reduction of peak accel eration. This in turn was due to the reduced generation of agonist act ivity. Peak velocity was not significantly decreased because the accel eration phase was adequately prolonged. Since these changes were most pronounced in the 'fast' movements without target the compensation hyp othesis should be discarded. The reduction of acceleration must at lea st partially be due to a genuine cerebellar deficiency in the fast gen eration of agonist activity.