Correlation of electrode position and clinical outcomes in globus pallidus stimulation for dystonia.

BACKGROUND: The correlation between the electrode location and the clinical outcome for internal globus pallidus (GPi) deep brain stimulation (DBS) has not been fully elucidated. OBJECTIVE: The aim of this study was to determine the discrepancies between the theoretical target planned by magnetic resonance imaging (MRI) and the actual electrode location in postoperative MRI, as well as to find the correlation between the final electrode locations and the clinical outcome after GPi DBS. METHODS: Thirty-six patients who underwent GPi DBS for dystonia were included in this retrospective study. The X coordinate was defined as the lateral distance from the midline, the Y coordinate as the anterior distance from the midcommissural point, and the Z coordinate as the inferior distance from the intercommissural line. RESULTS: All coordinates showed a significant difference between theoretical and actual values for all electrode locations (p < 0.05). In particular, greater differences were exhibited for Y than for the X and Z coordinates. There was no significant difference in the accuracy of the localization of the left-side versus the right-side electrode for any coordinates. The patients whose electrodes were located within or near the posteroventral GPi showed better clinical outcomes. CONCLUSIONS: The actual electrode location was slightly more posterior to the theoretically planned target. Electrodes concentrated near the posteroventral GPi tended to yield favorable outcomes.

Long-Term Clinical Outcome of Internal Globus Pallidus Deep Brain Stimulation for Dystonia.

BACKGROUND: GPi (Internal globus pallidus) DBS (deep brain stimulation) is recognized as a safe, reliable, reversible and adjustable treatment in patients with medically refractory dystonia. OBJECTIVES: This report describes the long-term clinical outcome of 36 patients implanted with GPi DBS at the Neurosurgery Department of Seoul National University Hospital. METHODS: Nine patients with a known genetic cause, 12 patients with acquired dystonia, and 15 patients with isolated dystonia without a known genetic cause were included. When categorized by phenomenology, 29 patients had generalized, 5 patients had segmental, and 2 patients had multifocal dystonia. Patients were assessed preoperatively and at defined follow-up examinations postoperatively, using the Burke-Fahn-Marsden dystonia rating scale (BFMDRS) for movement and functional disability assessment. The mean follow-up duration was 47 months (range, 12-84). RESULTS: The mean movement scores significantly decreased from 44.88 points preoperatively to 26.45 points at 60-month follow up (N = 19, P = 0.006). The mean disability score was also decreased over time, from 11.54 points preoperatively to 8.26 points at 60-month follow up, despite no statistical significance (N = 19, P = 0.073). When analyzed the movement and disability improvement rates at 12-month follow up point, no significant difference was noted according to etiology, disease duration, age at surgery, age of onset, and phenomenology. However, the patients with DYT-1 dystonia and isolated dystonia without a known genetic cause showed marked improvement. CONCLUSIONS: GPi DBS is a safe and efficient therapeutic method for treatment of dystonia patients to improve both movement and disability. However, this study has some limitations caused by the retrospective design with small sample size in a single-center.