A prospective randomized comparison of CT and MRI pre-operative localization for pallidotomy.

OBJECTIVE During the pallidotomy procedure, is pre-operative localization with MRI more accurate than CT and does it result in a significant difference in surgical outcome? METHODS Twenty-four Parkinson's Disease patients received a unilateral pallidotomy for their motor symptoms. Dyskinesia was scored pre- and six weeks postoperatively. All patients had a pre-operative CT scan and MRI to calculate the target co-ordinates. Patients were then randomly selected to proceed with either the CT or MRI coordinates. The final position for the lesion was determined with intraoperative macrostimulation and impedance measurements. The percentage improvement of dyskinesia was noted for each patient and the two groups compared by the Mann-Whitney test. The distance from the final target to the MRI and CT pre-operative co-ordinates were calculated for each patient. The mean distance for each modality was then compared by Student's t-test. The number of electrode repositionings was also recorded for each patient and the two groups compared by the nonparametric Mann-Whitney test. RESULTS Although the MRI co-ordinates were significantly (p<0.023) closer to the final target, this did not translate into a significant reduction in electrode repositionings. There was no significant difference in the improvement in dyskinesia between the two groups. CONCLUSIONS The pre-operative MRI co-ordinates were significantly (p=0.023) closer to the final target than those from the CT. The potential advantages and disadvantages of both imaging modalities are reviewed. There was no significant difference in surgical outcome using either MRI or CT for pre-operative localization in pallidotomy.