MR findings of stereotactic radiofrequency VIM-Thalamotomy

To evaluate the role of the MRI after the stereotactic radiofrequency ventralis intermedius nucleus(VIM) thalamotomy for the treatment of tremor. 156 cases of the postthalamotomy MR findings were analyzed retrospectively. The sagittal T1 weighted image(WI), axial and coronal Proton and T2WI were obtained by using 0.38 T(Resonex Sunnyvale, U. S. A) machine . The interval between thalamotomy and MR examination was from 3 days to 2 months. The MR characteristics and complications related to thalamotomy were reviewed. In 16 cases, a follow-up MR was done 3 to 13 months after the initial MR study. We also reviewed the follow-up MR findings. The mean size of the thalamus lesion was 16 mm. The thalamus lesions were noted as a single layer in 23 cases and as layers of different signal intensity in 100 cases; (2 layers in 84 cases, and 3 or more layers in 16 cases). In 74 cases of the 84 cases with 2 layers, the inner layers was isointense with gray matter on T1WI, hypointense on T2WI, and the outer layer was hypointense on T1WI, hypointense on T2WI. There were extrathalamic lesions that were related to mistargetting of stereotactic radiofrequency. The locations of the extrathalamic lesions were the posterior limb of the interal capsule(119 case), the posterior limb of the internal capsule and the midbrain(39 cases), the posterior limb of the internal capsule and the basal ganglia(11 cases), and the midbraine(9 cases). In 5 cases of the mistargetting, double radiofrequency lesions were visualized because of the repeated coaqulation. The other complications were intracerebral hemorrhage(2 cases), subdural hemorrhage(2 cases), epidural hemorrhage(1 case), and intraventricular hemorrhage(1 case). On the follow up MR studies(16 cases), 2 cases showed the hemosiderin deposition in periphery of the lesion. The MRI was useful for the evaluation of the thalamic lesions and complications after the stereotactic radiofrequency VIM-thalamotomy for the treatment of tumor