Interventional MRI-guided deep brain stimulation in pediatric dystonia: first experience with the Clear Point system

Object. The placement of deep brain stimulation (DBS) leads in adults is traditionally performed using physiological confirmation of lead location in the awake patient. Most children are unable to tolerate awake surgery, which poses a challenge for intraoperative confirmation of lead location. The authors have developed an interventional MRI (iMRI)-guided procedure to allow for real-time anatomical imaging, with the goal of achieving very accurate lead placement in patients who are under general anesthesia. Methods. Six pediatric patients with primary dystonia were prospectively enrolled. Patients were candidates for surgery if they had marked disability and medical therapy had been ineffective. Five patients had the DYT1 mutation, and mean age at surgery was 11.0 +/- 2.8 years. Patients underwent bilateral globus pallidus internus (GPi, n = 5) or subthalamic nucleus (STN, n = 1) DBS. The leads were implanted using a novel skull-mounted aiming device in conjunction with dedicated software (ClearPoint system), used within a 1.5-T diagnostic MRI unit in a radiology suite, without physiological testing. The Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS) was used at baseline, 6 months, and 12 months postoperatively. Further measures included lead placement accuracy, quality of life, adverse events, and stimulation settings. Results. A single brain penetration was used for placement of all 12 leads. The mean difference (+/- SD) between the intended target location and the actual lead location, in the axial plane passing through the intended target, was 0.6 +/- 0.5 mm, and the mean surgical time (leads only) was 190 +/- 26 minutes. The mean percent improvement in the BFMDRS movement scores was 86.1% +/- 12.5% at 6 months (n = 6, p = 0.028) and 87.6% +/- 19.2% at 12 months (p = 0.028). The mean stimulation settings at 12 months were 3.0 V, 83 mu sec, 135 Hz for GPi DBS, and 2.1 V, 60 mu sec, 145 Hz for STN DBS). There were no serious adverse events. Conclusions. Interventional MRI-guided DBS using the ClearPoint system was extremely accurate, provided real-time confirmation of DBS placement, and could be Used in any diagnostic MRI suite. Clinical outcomes for pediatric dystonia are comparable with the best reported results using traditional frame-based stereotaxy.