One-third of cases of focal epilepsy are drug refractory, and surgery might provide a cure. Seizure-free outcome after surgery depends on the correct identification and resection of the epileptogenic zone. In patients with no visible abnormality on MRI, or in cases in which presurgical evaluation yields discordant data, invasive stereoelectroencephalography (SEEG) recordings might be necessary. SEEG is a procedure in which multiple electrodes are placed stereotactically in key targets within the brain to record interictal and ictal electrophysiological activity. Correlating this activity with seizure semiology enables identification of the seizure-onset zone and key structures within the ictal network. The main risk related to electrode placement is hemorrhage, which occurs in 1% of patients who undergo the procedure. Planning safe electrode placement for SEEG requires meticulous adherence to the following: 1) maximize the distance from cerebral vasculature, 2) avoid crossing sulcal pial boundaries (sulci), 3) maximize gray matter sampling, 4) minimize electrode length, 5) drill at an angle orthogonal to the skull, and 6) avoid critical neurological structures. The authors provide a validation of surgical strategizing and planning with EpiNav, a multimodal platform that enables automated computer-assisted planning (CAP) for electrode placement with user-defined regions of interest.
Thirteen consecutive patients who underwent implantation of a total 116 electrodes over a 15-month period were studied retrospectively. Models of the cortex, gray matter, and sulci were generated from patient-specific whole-brain parcellation, and vascular segmentation was performed on the basis of preoperative MR venography. Then, the multidisciplinary implantation strategy and precise trajectory planning were reconstructed using CAP and compared with the implemented manually determined plans. Paired results for safety metric comparisons were available for 104 electrodes. External validity of the suitability and safety of electrode entry points, trajectories, and target-point feasibility was sought from 5 independent, blinded experts from outside institutions.
CAP-generated electrode trajectories resulted in a statistically significant improvement in electrode length, drilling angle, gray matter–sampling ratio, minimum distance from segmented vasculature, and risk (p < 0.05). The blinded external raters had various opinions of trajectory feasibility that were not statistically significant, and they considered a mean of 69.4% of manually determined trajectories and 62.2% of CAP-generated trajectories feasible; 19.4% of the CAP-generated electrode-placement plans were deemed feasible when the manually determined plans were not, whereas 26.5% of the manually determined electrode-placement plans were rated feasible when CAP-determined plans were not (no significant difference).
CAP generates clinically feasible electrode-placement plans and results in statistically improved safety metrics. CAP is a useful tool for automating the placement of electrodes for SEEG; however, it requires the operating surgeon to review the results before implantation, because only 62% of electrode-placement plans were rated feasible, compared with 69% of the manually determined placement plans, mainly because of proximity of the electrodes to unsegmented vasculature. Improved vascular segmentation and sulcal modeling could lead to further improvements in the feasibility of CAP-generated trajectories.
ABBREVIATIONSCAP = computer-assisted planning; DBS = deep brain stimulation; DSA = digital subtraction angiography; EEG = electroencephalography; EZ = epileptogenic zone; FOV = field of view; MDT = multidisciplinary team; MRA = MR angiography; MRV = MR venography; ROI = region of interest; SEEG = stereoelectroencephalography.
CardinaleFPeroGQuiliciLPianoMColomboPMoscatoA: Cerebral angiography for multimodal surgical planning in epilepsy surgery: description of a new three-dimensional technique and literature review. World Neurosurg84:358–3672015
CardinaleF, PeroG, QuiliciL, PianoM, ColomboP, MoscatoA, : Cerebral angiography for multimodal surgical planning in epilepsy surgery: description of a new three-dimensional technique and literature review. 84:358–367, 20152581952710.1016/j.wneu.2015.03.028)| false
CardosoMJ, ModatM, WolzR, MelbourneA, CashD, RueckertD, : Geodesic information flows: spatially-variant graphs and their application to segmentation and fusion. 34:1976–1988, 201510.1109/TMI.2015.241829825879909)| false
NowellM, RodionovR, ZomboriG, SparksR, WinstonG, KinghornJ, : Utility of 3D multimodality imaging in the implantation of intracranial electrodes in epilepsy. 56:403–413, 201510.1111/epi.1292425656379)| false
PradosFCardosoMJBurgosNGandini Wheeler-KingshottCAMOurselinS: NiftyWeb: web based platform for image processing on the cloud, presented at the ISMRM 24th Annual Meeting & Exhibition2016. (http://discovery.ucl.ac.uk/1476510/1/Submit-niftyweb.pdf) [Accessed November 29 2017] (Abstract)
PradosF, CardosoMJ, BurgosN, Gandini Wheeler-KingshottCAM, OurselinS: NiftyWeb: web based platform for image processing on the cloud, presented at the ISMRM 24th Annual Meeting & Exhibition, 2016. (http://discovery.ucl.ac.uk/1476510/1/Submit-niftyweb.pdf) [Accessed November 29, 2017] (Abstract))| false
SparksRZomboriGRodionovRNowellMVosSBZuluagaMA: Automated multiple trajectory planning algorithm for the placement of stereo-electroencephalography (SEEG) electrodes in epilepsy treatment. Int J Comput Assist Radiol Surg12:123–1362017
Téllez-ZentenoJF, Hernández-RonquilloL, BuckleyS, ZahagunR, RizviS: A validation of the new definition of drug-resistant epilepsy by the International League Against Epilepsy. 55:829–834, 20142482868310.1111/epi.12633)| false
TropeMShamirRRJoskowiczLMedressZRosenthalGMayerA: The role of automatic computer-aided surgical trajectory planning in improving the expected safety of stereotactic neurosurgery. Int J Comput Assist Radiol Surg10:1127–11402015
TropeM, ShamirRR, JoskowiczL, MedressZ, RosenthalG, MayerA, : The role of automatic computer-aided surgical trajectory planning in improving the expected safety of stereotactic neurosurgery. 10:1127–1140, 20152540830510.1007/s11548-014-1126-5)| false
ZuluagaMARodionovRNowellMAchhalaSZomboriGMendelsonAF: Stability, structure and scale: improvements in multi-modal vessel extraction for SEEG trajectory planning. Int J Comput Assist Radiol Surg10:1227–12372015