CHRONIC THALAMIC-STIMULATION WITH 3-DIMENSIONAL MR STEREOTAXIC GUIDANCE

PURPOSE: To report a method of electrode implantation in the ventralis intermedius nucleus of the thalamus for the treatment of tremor using a 3-D stereotactic MR imaging technique, METHODS: Five patients (thre e men and two women; mean age, 59 years) with medically refractory tre mor had intrathalamic implantation of a stimulating electrode, Stereot actic MR imaging was performed on a 1.5-T unit equipped with an MR-com patible Leksell G stereotactic frame fixed to the patient's head, Calc ulation of the coordinates of the theoretical target was based on the coordinates of the anterior commissure, the posterior commissure, and the midline sagittal plane as determined via stereotactic MR imaging, During the surgical procedure, the best position for the stimulating e lectrode was determined by electrophysiological and clinical studies, Postoperative MR control studies were done in all cases to verify the position of the electrode, RESULTS: Stereotactic MR imaging allowed pr ecise implantation of the stimulating electrode in all patients, Elect rode stimulation produced a 90% reduction of the tremor in two patient s, an 80% and 70% reduction in one patient each, and a persistent micr othalamotomy-like effect in the fifth patient, Examination of the MR c ontrol studies showed that mean error in the positioning of the electr odes was 0.77 +/- 0.6 mm (mean +/- SD) in the x direction and 0.80 +/- 1.02 mm in the y direction, CONCLUSION: Although our series is relati vely small, the precision achieved with stereotactic MR imaging proves that it can be used with confidence for precise functional neurosurgi cal procedures.