Diagnosis and surgical treatment of refractory and apparent nonlesional focal epilepsy is challenging. Morphometric MRI voxel-based and other postprocessing methods can help to localize the epileptogenic zone and thereby support the planning of further invasive electroencephalography (EEG) diagnostics, and maybe resective epilepsy surgery.
The authors developed an algorithm to implement regions of interest (ROI), based on postprocessed MRI data, into a neuronavigation tool. This was followed by stereotactic ROI-guided implantation of depth electrodes and ROI-navigated resective surgery. Data on diagnostic yield, histology, and seizure outcome were collected and evaluated.
Fourteen consecutive patients with apparently nonlesional epilepsy were included in this study. Reevaluation of the MR images with the help of MRI postprocessing analysis led to the identification of probable subtle lesions in 11 patients. Additional information obtained by SPECT imaging and MRI reevaluation suggested possible lesions in the remaining 3 patients. The ROI-guided invasive implantation of EEG yielded interictal and ictal activity in 13 patients who were consequently referred to resective surgery. Despite the apparently negative MRI findings, focal cortical dysplasia was found in 64% of the patients (n = 9). At the last available outcome, 8 patients (57%) were completely seizure free (International League Against Epilepsy Class 1).
The results demonstrate the feasibility and usefulness of a robust and straightforward algorithm for implementation of MRI postprocessing-based targets into the neuronavigation system. This approach allowed the stereotactic implantation of a low number of depth electrodes only, which confirmed the seizure-onset hypothesis in 90% of the cases without causing any complications. Furthermore, the neuronavigated ROI-guided lesionectomy helped to perform resective surgery in this rather challenging subgroup of patients with apparent nonlesional epilepsy.
ABBREVIATIONSEEG = electroencephalography; ETLE = extratemporal lobe epilepsy; FCD = focal cortical dysplasia; FLAIR = fluid-attenuated inversion recovery; iEEG = invasive EEG; ILAE = International League Against Epilepsy; ISAS = ictal-interictal SPECT analysis by SPM; MAP = morphometric analysis program; ROI = region of interest; rROI = resection ROI; SISCOM = subtraction ictal SPECT coregistered to MRI; SPM = statistical parametric mapping; TLE = temporal lobe epilepsy.
Correspondence Daniel Delev, Department of Neurosurgery, University of Freiburg, University Medical Centre, Breisacherstr. 64, 79106 Freiburg, Germany. email: firstname.lastname@example.org.INCLUDE WHEN CITING Published online June 16, 2017; DOI: 10.3171/2016.12.JNS161676.
Drs. Delev and Quesada contributed equally to this work.
Disclosures Dr. Elger has received support in the form of honoraria and consultation fees from Bial, Eisai, Novartis, Pfizer, Desitin, and UCB; he also received federal funding from the DFG (Deutsche Forschungsgemeinschaft). Dr. Surges has served as a consultant to Bial and has received speakers fees from Cyberonics, Eisai, Novartis, and UCB Pharma.
HuppertzHJ, WellmerJ, StaackAM, AltenmüllerDM, UrbachH, KröllJ: Voxel-based 3D MRI analysis helps to detect subtle forms of subcortical band heterotopia. 49:772–785, 200810.1111/j.1528-1167.2007.01436.x18047585)| false
MoraceRDi GennaroGPicardiAQuaratoPPSparanoAMasciaA: Surgery after intracranial investigation with subdural electrodes in patients with drug-resistant focal epilepsy: outcome and complications. Neurosurg Rev35:519–5262012
MoraceR, Di GennaroG, PicardiA, QuaratoPP, SparanoA, MasciaA, : Surgery after intracranial investigation with subdural electrodes in patients with drug-resistant focal epilepsy: outcome and complications. 35:519–526, 201210.1007/s10143-012-0382-522434511)| 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
WangZIJonesSERisticAJWongCKakisakaYJinK: Voxel-based morphometric MRI post-processing in MRI-negative focal cortical dysplasia followed by simultaneously recorded MEG and stereo-EEG. Epilepsy Res100:188–1932012
WangZI, JonesSE, RisticAJ, WongC, KakisakaY, JinK, : Voxel-based morphometric MRI post-processing in MRI-negative focal cortical dysplasia followed by simultaneously recorded MEG and stereo-EEG. 100:188–193, 201210.1016/j.eplepsyres.2012.02.01122391138)| false
WellmerJParpaleyYvon LeheMHuppertzHJ: Integrating magnetic resonance imaging postprocessing results into neuronavigation for electrode implantation and resection of subtle focal cortical dysplasia in previously cryptogenic epilepsy. Neurosurgery66:187–1952010
WellmerJ, ParpaleyY, von LeheM, HuppertzHJ: Integrating magnetic resonance imaging postprocessing results into neuronavigation for electrode implantation and resection of subtle focal cortical dysplasia in previously cryptogenic epilepsy. 66:187–195, 20102002354910.1227/01.NEU.0000359329.92781.B7)| false
WellmerJvon OertzenJSchallerCUrbachHKönigRWidmanG: Digital photography and 3D MRI-based multimodal imaging for individualized planning of resective neocortical epilepsy surgery. Epilepsia43:1543–15502002
WellmerJ, von OertzenJ, SchallerC, UrbachH, KönigR, WidmanG, : Digital photography and 3D MRI-based multimodal imaging for individualized planning of resective neocortical epilepsy surgery. 43:1543–1550, 20021246025710.1046/j.1528-1157.2002.30002.x)| false
WieserHGBlumeWTFishDGoldensohnEHufnagelAKingD: ILAE Commission Report. Proposal for a new classification of outcome with respect to epileptic seizures following epilepsy surgery. Epilepsia42:282–2862001
WieserHG, BlumeWT, FishD, GoldensohnE, HufnagelA, KingD, : ILAE Commission Report. Proposal for a new classification of outcome with respect to epileptic seizures following epilepsy surgery. 42:282–286, 20011124060410.1046/j.1528-1157.2001.4220282.x)| false