Unilateral cerebellar lesions influence arm movements bilaterally.

Limb ataxia is seen as a sign of ipsilateral cerebellar dysfunction. However, imaging studies have shown a bilateral cerebellar activation during unilateral hand movements. We questioned whether unilateral cerebellar lesions affect pointing movements not only of the ipsilateral hand but also of the contralateral hand. Horizontal saccadic pointing movements of 10 patients with unilateral cerebellar infarctions (infarctions of the posterior inferior or superior cerebellar artery) were compared with those of 19 controls. The movements were recorded with an infrared video motion analysis system. The peak velocity, time lag, and dysmetria of the ipsilateral and contralateral hands were calculated. Patients with cerebellar infarctions had significantly slower movements not only for the ipsilateral but also for the contralateral arm. The time lag of these movements in patients was also significantly larger for both arms. In contrast, there was no significant difference in dysmetria at the endpoints. These findings indicate that both ipsilateral and contra-lateral movements of patients with unilateral cerebellar lesions are slightly impaired.