Evolution of a surgical technique for posteroventral pallidotomy using CT/MR fusion and intraoperative...

This is a prospective review of 60 posteroventral pallidotomies performed in 48 patients. Twelve patients had bilateral pallidotomies; five of these were staged and seven were performed simultaneously at the one surgical procedure. The report focuses on evolution of a surgical technique originally using the computed tomographic (CT) scan for target acquisition, culminating in a technique of fusing the magnetic resonance (MR) and CT scans. The technique involves macrostimulation with threshold identification of the optic tract and internal capsule. Utilizing the current procedure reproducible accurate lesions were made in the ansa lenticularis and internal pallidum as confirmed on postoperative MR scans. Initial results would indicate a very good effect on motor functions such as rigidity and dyskinesia and moderate to good effect on tremor. Secondary effects were seen on hypokinetic features such as on/off fluctuations, postural stability, gait dysfunction and limb bradykinesia. There was no injury to the internal capsule or optic tract throughout the series. Gait and postural stability were adversely affected in two patients early on in the series before the utilization of the MR/CT fusion technique and before the introduction of the current lesioning technique. There was no other adverse morbidity for the procedure.