Electromyographical Changes of Anterior Tibial Muscle after Stimulation of Cerebella Dentate Nucleus in Cats

ABSTRACT

Through the use of stereotactic neurosurgical operation, some authors have employed chronic electrical stimulation of the dentate nucleus spasticity and each trial on spastic patients has show marked clinical improvement. We investigated the electrophysiological changes of cats after stereotactic electrical stimulation of the dentate nucleus to elucidate the possibility of clinical application and to evaluate the clinical results. The M-wave is an initial response and the F-wave is a late response in the electromyography of a muscle, which is stimulated by its original controlling nerve itself. There is evidence that the size of the F-wave is dependent on motor neuron excitability and its amplitude is increased significantly at spastic condition. If such a relationship exists, procedures which are carried out to relieve spasticity might be exerted to change the F-wave size and thus it might be possible to use the F-wave as an objective monitor during electrical stimulation of the dentate nucleus. We investigated this possibility in experiments on 10cats weighing between 2.7 Kg and 4.4 Kg. We studied the changes of M and F waves, recorded in EMG, after stereotactic stimulation to cerebellar dentate nucleus in cats. The results were as follows 1) The change of mean value of M-wave amplitude was not significant(control group, 3591+/-1029 microV stimulation group, 3424+/-927 microV, P>0.05). 2) The mean value of F-wave amplitude was significantly reduced about 56.7% after the dentate stimulation(control group, 443.2+/-119 microV stimulation group, 251.3+/-99.4 microV, P<0.05). 3) The F/M ratio also significantly reduced, about 56.8% after the dentate stimulation(control group, 12.5+/-1.9%, stimulation group, 7.1+/-1.2%, P<0.05). Our experimental results demonstrated that the dentate stimulation markedly decreased the size of F-wave amplitude and F/M ration in the experimental cats and we concluded that these electrophysiological changes can be applied as a parameter of clinical evaluation of electrical dentate stimulation for the spasticity.