Intraoperative computed tomography for intracranial electrode implantation surgery in medically refractory epilepsy

Abstract

A pproximAtely one-third of newly diagnosed epilepsy cases are refractory to medical management, and patients in these cases may be appropriate candidates for surgical intervention. 9,15 The patients often undergo intracranial electroencephalography (EEG) monitoring via implanted subdural and/or depth electrodes to identify a seizure onset zone. Subdural electrode strips and grids are sometimes implanted through bur holes or ObJect Accurate placement of intracranial depth and subdural electrodes is important in evaluating patients with medically refractory epilepsy for possible resection. Confirming electrode locations on postoperative CT scans does not allow for immediate replacement of malpositioned electrodes, and thus revision surgery is required in select cases. Intraoperative CT (iCT) using the Medtronic O-arm device has been performed to detect electrode locations in deep brain stimulation surgery, but its application in epilepsy surgery has not been explored. In the present study, the authors describe their institutional experience in using the O-arm to facilitate accurate placement of intracranial electrodes for epilepsy monitoring. MethODS In this retrospective study, the authors evaluated consecutive patients who had undergone subdural and/or depth electrode implantation for epilepsy monitoring between November 2010 and September 2012. The O-arm device is used to obtain iCT images, which are then merged with the preoperative planning MRI studies and reviewed by the surgical team to confirm final positioning. Minor modifications in patient positioning and operative field preparation are necessary to safely incorporate the O-arm device into routine intracranial electrode implantation surgery. The device does not obstruct surgeon access for bur hole or craniotomy surgery. Depth and subdural electrode locations are easily identified on iCT, which merge with MRI studies without difficulty, allowing the epilepsy surgical team to intraoperatively confirm lead locations. reSultS Depth and subdural electrodes were implanted in 10 consecutive patients by using routine surgical techniques together with preoperative stereotactic planning and intraoperative neuronavigation. No wound infections or other surgical complications occurred. In one patient, the hippocampal depth electrode was believed to be in a suboptimal position and was repositioned before final wound closure. Additionally, 4 strip electrodes were replaced due to suboptimal positioning. Postoperative CT scans did not differ from iCT studies in the first 3 patients in the series and thus were not obtained in the final 7 patients. Overall, operative time was extended by approximately 10-15 minutes for O-arm positioning, less than 1 minute for image acquisition, and approximately 10 minutes for image transfer, fusion, and intraoperative analysis (total time 21-26 minutes). cONcluSiONS The O-arm device can be easily incorporated into routine intracranial electrode implantation surgery in standard-sized operating rooms. The technique provides accurate 3D v...

SEEG assistant: a 3DSlicer extension to support epilepsy surgery

“…Our localization tool accurately segments contact positions with an error less than 0.5 mm [ 21 ] which is directly comparable to the image resolution of the testing CBCT scanner and in line with that reported elsewhere [ 19 ]. Of note, Hebb and colleagues reported a smaller localization error but used a standard CT scanner with higher resolution while we used a CBCT intra operative mobile scanner which has been proven to provide equivalent final accuracy [ 14 ].…”

“…in cases of non-planar trajectories where artefacts may merge neighboring contacts into a single group of indistinguishable voxels. In recent years, several techniques for the localization of intracranial EEG electrodes have been proposed [ 14 – 18 ]. Most of the approaches aim to simplify the manual extraction of contact coordinates for grid/strips or for Deep Brain Stimulation (DBS) electrodes by fusing opportunely thresholded post-implant datasets with pre-implant MRIs [ 19 , 20 ].…”

O-Arm Stereotactic Imaging in Deep Brain Stimulation Surgery Workflow: A Utility and Cost-Effectiveness Analysis

“…The O-arm was designed to provide information on anatomic structures with high X-ray attenuation, such as bony anatomy and metallic objects, and can be applied in DBS surgery using a fiducial-based registration for intraoperative stereotactic imaging [18,[20][21][22][23][24]. In 2015, Lee et al [25] showed that the Medtronic O-arm device could be used to obtain postoperative stereotactic images merged with the preoperative planning MRI studies, which could be used to confirm the final lead position. The use of the O-arm device required some minor modifications in the positioning of the patient to incorporate the device into routine DBS surgery workflow but did not obstruct surgical access [25].…”

“…In 2015, Lee et al [25] showed that the Medtronic O-arm device could be used to obtain postoperative stereotactic images merged with the preoperative planning MRI studies, which could be used to confirm the final lead position. The use of the O-arm device required some minor modifications in the positioning of the patient to incorporate the device into routine DBS surgery workflow but did not obstruct surgical access [25]. Recently, improvements to reduce the partial volume artifacts in the use of the O-arm for intraoperative localization of the DBS leads have been achieved using high-resolution reconstruction of O-arm data, without requiring an increase in the radiation dose [26][27][28].…”

Deep Brain Stimulation: Expanding Applications

“…Advances in intraoperative electrode positioning using computed tomography provided by devices like Medtronic's O-arm and novel electrode implant trajectories may be techniques that assist in bringing the effectiveness of ANT DBS up to the required levels. 79 , 80) These new techniques may be especially effective for targeting the ANT because of the sequestered location of the nucleus and heterogenic local cellular composition.…”