Resection frequency map after awake resective surgery for non-lesional neocortical epilepsy involving eloquent areas

Abstract

BackgroundThe resection of eloquent areas is challenging due to postoperative neurological deficits. The purpose of this study was to assess the efficacy and risk of awake brain surgery for non-lesional epilepsy involving the eloquent areas or their adjacent areas and to advocate the generation of a resection frequency map.MethodsWe enrolled 55 patients who underwent awake surgery between 1994 and 2007 for non-lesional epilepsy involving the primary sensori-motor or language areas. All patients underwent two-staged operations including subdural electrode monitoring and awake resective surgery. For each case, the preoperative and postoperative images were spatially normalized and compared on a standard atlas, and the resection map was then computed by summing up each resected area on the atlas.ResultsThe postoperative seizure outcome was Engel class I in 27 patients (49.1%), II in nine (16.4%), III in 14 (25.5%) and IV in five (9.1%). Ten patients (18.2%) experienced postoperative neurological deficits including seven transient (12.7%) and three permanent, but mild ones (5.5%). The neurological complication rate of purely eloquent area resection was 36.8% (7/19). The resection frequency map computed in this study showed that the resection of eloquent areas was tolerable, with the exception of the Broca’s area.ConclusionsAwake resective surgery with intraoperative brain mapping is an effective and safe treatment option for non-lesional epilepsy involving eloquent areas. The resection frequency map can show the resected area of a group as well as individuals and provide an objective measure of neurological risk.Electronic supplementary materialThe online version of this article (doi:10.1007/s00701-011-1074-6) contains supplementary material, which is available to authorized users.

Relationship between cortical resection and visual function after occipital lobe epilepsy surgery

“…Then, we generated the resection frequency map by combining all the ROIs using MATLAB 7.0 software (MathWorks). 11 As a result, 2D axial, coronal, and sagittal images and 3D volume-rendering images were obtained using the MRIcro software.…”

Risk factor analysis of the development of new neurological deficits following supplementary motor area resection

“…The detailed operative methods are described in our previous report. 8 Standard cortical mapping was performed using an Ojemann stimulator, which is a constantcurrent generator that produces a train of biphasic square wave pulses (at a rate of 60 Hz, 1 msec/phase) to minimize the possibility of inducing a seizure. To locate the primary motor cortex, stimuli were applied in 1-mA increments, starting at 1 mA up to a maximum of 10 mA.…”

Response to the authors’ response to Schaller’s comment, “How eloquent is eloquent?”

“…Among the ten patients who developed neurological deficits, seven patients (12.7%) had transient deficits…. Three patients (5.5%) presented with permanent deficits…" [2]. Should I have misunderstood the meaning of this paragraph after repeated reading, then the (real) numbers should have been presented in a clearer manner, probably.…”

“…It has been proposed even to use standardized bilateral implantation protocols where lateralization of ictal onset cannot be clarified by surface EEG recordings [3]. Kim et al have used invasive recordings in the n=55 patients who are representing their final study cohort, and all of them underwent awake craniotomy for resection of their epileptogenic zones with the further help of direct electrical cortical stimulation [2].…”