Correlation of clinical and physiological effects of cerebellar stimulation.

The value of clinical assessment of patients undergoing chronic cerebellar stimulation (CCS) is limited by lack of objective measures but neurophysiological tests can be used to "biocalibrate" the stimulator and may be used to predict effects of CCS. Eighty-seven patients undergoing CCS have been assessed clinically and neurophysiologically over the last 4 years. Somatosensory evoked responses were significantly ( p less than 0.05) reduced in amplitude in 35 patients, cortical somatosensory evoked responses in 44 patients and one or both responses were reduced in 55 patients. There were no clinical or physiological changes in 16 patients. Evoked responses showed significant changes in only 3 patients who did not show clinical improvement. The mean voltage settings were 5.2 volts and most patients were stimulated at 200 herz. These results indicate that significant changes in those somatosensory evoked potentials are a good indication of clinical benefits from CCS but clinical improvement may occur in the absence of any acute effect on evoked responses.