DIFFERENT TYPES OF CEREBELLAR HYPOMETRIA ASSOCIATED WITH A DISTINCT TOPOGRAPHY OF THE LESION IN CEREBELLUM

We recorded ballistic wrist flexion movements in fifteen cerebellar pa tients exhibiting hypometria. The movement and the associated agonist and antagonist EMG activities were analysed. On the basis of the topog raphy of the cerebellar lesion, our patients were divided into three g roups. In the first group including five patients, lesions involved th e efferent dentato-thalamo-cortical pathway and hypometria was associa ted with an imbalance between the rate of rise of the agonist EMG acti vity and the rate of rise of the antagonist EMG activity. Ln the three patients of group II, lesions were located at the level of the middle cerebellar peduncle, disrupting the crossed ponto-cerebellar projecti ons. In these patients, the intensity of the agonist EMG activity was reduced and the duration of the antagonist EMG activity was increased. In the third group including seven patients presenting either a diffu se cerebellar atrophy or a stroke involving a large parenchymatous are a, the agonist-antagonist EMG pattern showed a prolongation of the dur ation of the antagonist burst, Our results show that discrete mechanis ms of cerebellar hypometria are associated with different anatomical l esions. (C) 1998 Elsevier Science B.V.