Technical Implications in Revision Surgery for Deep Brain Stimulation (DBS) of the Thalamus for Refractory Epilepsy

BACKGROUND AND PURPOSE: Implantation of deep brain stimulation (DBS) electrodes in the anterior nucleus of the thalamus (ANT) or the centromedian nucleus (CM), for the treatment of refractory epilepsy, is technically demanding. To enhance the accuracy of electrode placement within the ANT and CM, we analyzed our experience with electrode revision surgery in ANT and CM DBS and investigated the cause of misplacement and verifying methods for accurate placement. METHODS: A retrospective analysis of the medical records of 23 patients who underwent DBS for refractory epilepsy during the period from 2013 to 2016 was performed. RESULTS: Misplacement of the electrode occurred in 1 (25%) of 4 ANT DBS and 2 (14.3%) of 14 patients with CM DBS performed in our institute, and revision surgery was performed in three patients. During this period, we performed three revision surgeries for misplaced electrodes in ANT DBS that were performed at another hospital. Therefore, we performed six revision surgeries (four in ANT, two in CM) for mistargeted DBS electrodes for thalamic DBS. Transventricular lead placement and an anatomical targeting of the ANT was the cause of misplacement in the ANT and intraoperative brain shift was found to be the cause in the CM. For verification of the location of lead placement, magnetic resonance imaging (MRI) was superior to computed tomography and electroencephalography (EEG). CONCLUSIONS: To reduce the rate of electrode misplacement for refractory epilepsy, image-based targeting of the ANT according to individual anatomical variation, and efforts to minimize intraoperative brain shift are essential. To verify the location of the electrode, MRI examination is mandatory in DBS for refractory epilepsy.