Eloquent Cortex Research Articles

Enhanced sensitivity of electrocorticography during awake craniotomy using a novel circular grid electrode.

Awake craniotomy with intraoperative functional brain mapping (FBM) bedside neurological testing is an important technique used to optimize resective brain surgeries near eloquent cortex. Awake craniotomy performed with electrocorticography (ECoG) and direct electrical stimulation (DES) for FBM can delineate eloquent cortex from lesions and epileptogenic regions. However, current electrode technology demonstrates spatial limitations. Our group has developed a novel circular grid with the goal of improving spatial recording of ECoG to enhance detection of ictal and interictal activity. This retrospective study was approved by the institutional review board at Mayo Clinic Florida. We analyzed patients undergoing awake craniotomy with ECoG and DES and compared ECoG data obtained using the 22 contact circular grid to standard 6 contact strip electrode. We included 144 cases of awake craniotomy with ECoG, 73 using circular grid and 71 with strip electrode. No significant differences were seen regarding preoperative clinical and demographic data, duration of ECoG recording (p = 0.676) and use of DES (p = 0.926). Circular grid was more sensitive in detecting periodic focal epileptiform discharges (PFEDs) (p = 0.004), PFEDs plus (p = 0.032), afterdischarges (ADs) per case (p = 0.022) at lower minimum (p = 0.012) and maximum (p < 0.0012) intensity stimulation, and seizures (p = 0.048). PFEDs (p < 0.001), PFEDs plus (p < 0.001), and HFOs (p < 0.001) but not ADs (p = 0.255) predicted electrographic seizures. We demonstrate higher sensitivity in detecting ictal and interictal activity on ECoG during awake craniotomy with a novel circular grid compared to strip electrode, likely due to better spatial sampling during ECoG. We also found association between PFEDs and intraoperative seizures.

88 Considering Lateralization and Localization of Neurosurgical Intervention for Predicting Treatment Response to Computerized Cognitive Remediation (CCR) Targeting Attention and Working Memory: A Case Series

Objective:Lateralization and localization of neuropathology helps determine the extent to which eloquent cortex and diseased brain tissue share loci, important information for neurosurgical decision-making, and predicting neurocognitive outcomes. Emerging data suggest that lateralization and localization can inform specific neurorehabilitation approaches following acquired brain injury (ABI). In recent years, computerized cognitive remediation (CCR) of attention and working memory (WM) has been included among treatment guidelines to enhance cognition in post-acute recovery following ABI. Although CCR has shown promise for improving attention and executive functioning in ABI, it is unknown how treatment response may be predicted by locus of ABI. Even less is known about the effects of CCR following neurosurgery. The current study explores neurosurgical lateralization and localization as potential variables for predicting treatment response to CCR.Participants and Methods:Adult patients with a variety of neurological diagnoses (N = 17; ∼47% women) completed a full course of Cogmed Working Memory Training (CWMT) s/p neurosurgical intervention. All participants engaged in 30 sessions of CWMT over eight weeks, as well as neuropsychological (NP) assessment at pre-training baseline, immediate post-training, and at 3-month follow-up. Objective and subjective indices of attention, working memory, executive functioning, and emotional well-being were evaluated at three time-points. Neurosurgical loci included left-hemisphere frontal, temporal, and temporoparietal lobes, as well as right-hemisphere frontal, frontotemporal, and temporal lobes.Results:NP data were reviewed and yielded a clinical impression of cognitive and affective functioning for a cohort of patients with heterogeneous diagnoses (e.g., brain tumor, epilepsy, NPH). Preliminary NP findings suggested that treatment response to CCR for WM was consistent with extant literature on brain-behavior relationships according to lateralization and localization of neurosurgical intervention.Conclusions:Neurosurgical patients experience neurocognitive and affective dysfunction that may respond well to cognitive rehabilitation (CR) that includes CCR. Additionally, it is possible that lateralization and localization of surgical intervention may contribute to individual differences in treatment response. Further neurorehabilitation research is warranted to identify patients most likely to benefit from CCR and better tailor CR modalities to optimize recovery s/p neurological surgery.

Data-efficient resting-state functional magnetic resonance imaging brain mapping with deep learning.

Resting-state functional MRI (RS-fMRI) enables the mapping of function within the brain and is emerging as an efficient tool for the presurgical evaluation of eloquent cortex. Models capable of reliable and precise mapping of resting-state networks (RSNs) with a reduced scanning time would lead to improved patient comfort while reducing the cost per scan. The aims of the present study were to develop a deep 3D convolutional neural network (3DCNN) capable of voxel-wise mapping of language (LAN) and motor (MOT) RSNs with minimal quantities of RS-fMRI data. Imaging data were gathered from multiple ongoing studies at Washington University School of Medicine and other thoroughly characterized, publicly available data sets. All study participants (n = 2252 healthy adults) were cognitively screened and completed structural neuroimaging and RS-fMRI. Random permutations of RS-fMRI regions of interest were used to train a 3DCNN. After training, model inferences were compared using varying amounts of RS-fMRI data from the control data set as well as 5 patients with glioblastoma multiforme. The trained model achieved 96% out-of-sample validation accuracy on data encompassing a large age range collected on multiple scanner types and varying sequence parameters. Testing on out-of-sample control data showed 97.9% similarity between results generated using either 50 or 200 RS-fMRI time points, corresponding to approximately 2.5 and 10 minutes, respectively (96.9% LAN, 96.3% MOT true-positive rate). In evaluating data from patients with brain tumors, the 3DCNN was able to accurately map LAN and MOT networks despite structural and functional alterations. Functional maps produced by the 3DCNN can inform surgical planning in patients with brain tumors in a time-efficient manner. The authors present a highly efficient method for presurgical functional mapping and thus improved functional preservation in patients with brain tumors.

Specificity of Quantitative Functional Brain Mapping with Arterial Spin-Labeling for Preoperative Assessment.

Arterial spin-labeling is a noninvasive MR imaging technique allowing direct and quantitative measurement of brain perfusion. Arterial spin-labeling is well-established in clinics for investigating the overall cerebral perfusion, but it is still occasionally employed during tasks. The typical contrast for functional MR imaging is blood oxygen level-dependent (BOLD) imaging, whose specificity could be biased in neurologic patients due to altered neurovascular coupling. This work aimed to validate the use of functional ASL as a noninvasive tool for presurgical functional brain mapping. This is achieved by comparing the spatial accuracy of functional ASL with transcranial magnetic stimulation as the criterion standard. Twenty-eight healthy participants executed a motor task and received a somatosensory stimulation, while BOLD imaging and arterial spin-labeling were acquired simultaneously. Transcranial magnetic stimulation was subsequently used to define hand somatotopy. Functional ASL was found more adjacent to transcranial magnetic stimulation than BOLD imaging, with a significant shift along the inferior-to-superior direction. With respect to BOLD imaging, functional ASL was localized significantly more laterally, anteriorly, and inferiorly during motor tasks and pneumatic stimulation. Our results confirm the specificity of functional ASL in targeting the regional neuronal excitability. Functional ASL could be considered as a valid supplementary technique to BOLD imaging for presurgical mapping when spatial accuracy is crucial for delineating eloquent cortex.

Localisation of eloquent cortex using magnetoencephalography and its clinical implications

Objectives This study aimed to localise the eloquent cortex and measure evoked field (EF) parameters using magnetoencephalography in patients with epilepsy and tumours near the eloquent cortex. Methods A total of 41 patients (26 with drug-refractory epilepsy and 15 with tumours), with a mean age of 33 years, were recruited. Visual evoked field (VEF), auditory evoked field (AEF), sensory evoked field (SSEF), and motor-evoked field (MEF) latencies, amplitudes, and localisation were compared with those of a control population. Subgroup analyses were performed based on lobar involvement. Evoked Field parameters on the affected side were compared with those on the opposite side. The effect of distance from the lesion on nearby and distant evoked fields was evaluated. Results AEF and VEF amplitudes and latencies were reduced bilaterally (p < 0.05). Amplitude in the ipsilateral SSEF was reduced by 29.27% and 2.16% in the AEF group compared to the contralateral side (p = 0.02). In patients with temporal lobe lesions, the SSEF amplitude was reduced bilaterally (p < 0.02), and latency was prolonged compared with controls. The MEF amplitude was reduced and latency was prolonged in patients with frontal lobe lesions (p = 0.01). EF displacement was 32%, 57%, 21%, and 16% for AEF, MEF, VEF, and SSEF respectively. Patients in the epilepsy group had distant EF abnormalities. Conclusions EF amplitude was reduced and latency was prolonged in the involved hemisphere. Distant EF amplitudes were more affected than latencies in epilepsy. Amplitude and distance from the lesion had negative correlation for all EF. EF changes indicated eloquent cortical displacement which may not be apparent on MRI.

A state-of-the-art review on deep learning for estimating eloquent cortex from resting-state fMRI.

Deep learning algorithms have greatly improved our ability to estimate eloquent cortex regions from resting-state brain scans for patients about to undergo neurosurgery. The use of deep learning has the potential to fully automate functional mapping of cortex in this context. We present a highly focused state-of-the-art review on current technology for estimating eloquent cortex from resting-state functional magnetic resonance scans and identify potential paths to meet this goal in the future.

Detection and Mitigation of Neurovascular Uncoupling in Brain Gliomas.

Functional magnetic resonance imaging (fMRI) with blood oxygen level-dependent (BOLD) technique is useful for preoperative mapping of brain functional networks in tumor patients, providing reliable in vivo detection of eloquent cortex to help reduce the risk of postsurgical morbidity. BOLD task-based fMRI (tb-fMRI) is the most often used noninvasive method that can reliably map cortical networks, including those associated with sensorimotor, language, and visual functions. BOLD resting-state fMRI (rs-fMRI) is emerging as a promising ancillary tool for visualization of diverse functional networks. Although fMRI is a powerful tool that can be used as an adjunct for brain tumor surgery planning, it has some constraints that should be taken into consideration for proper clinical interpretation. BOLD fMRI interpretation may be limited by neurovascular uncoupling (NVU) induced by brain tumors. Cerebrovascular reactivity (CVR) mapping obtained using breath-hold methods is an effective method for evaluating NVU potential.

Functional MRI in Neuro-Oncology: State of the Art and Future Directions.

Since its discovery in the early 1990s, functional MRI (fMRI) has been used to study human brain function. One well-established application of fMRI in the clinical setting is the neurosurgical planning of patients with brain tumors near eloquent cortical areas. Clinical fMRI aims to preoperatively identify eloquent cortices that serve essential functions in daily life, such as hand movement and language. The primary goal of neurosurgery is to maximize tumor resection while sparing eloquent cortices adjacent to the tumor. When a lesion presents in the vicinity of an eloquent cortex, surgeons may use fMRI to plan their best surgical approach by determining the proximity of the lesion to regions of activation, providing guidance for awake brain surgery and intraoperative brain mapping. The acquisition of fMRI requires patient preparation prior to imaging, determination of functional paradigms, monitoring of patient performance, and both processing and analysis of images. Interpretation of fMRI maps requires a strong understanding of functional neuroanatomy and familiarity with the technical limitations frequently present in brain tumor imaging, including neurovascular uncoupling, patient compliance, and data analysis. This review discusses clinical fMRI in neuro-oncology, relevant ongoing research topics, and prospective future developments in this exciting discipline.

Novel Approaches for Treatment of Epilepsy

Epilepsy is a serious neurological disorder on the juncture of psychiatry and neurology. It is characterized by recurrent and episodic seizures which are due to excessive discharge by the brain neurons. The therapeutic response failure of more than one or two antiepileptic drugs (AEDs) is the benchmark of refractory or intractable epilepsy. The aim of the study was to determine new approaches which lead towards the treatment of epilepsy. In order to treat focal mesial temporal lobe epilepsy or neocortical epilepsy in adults and any malformation of cortical development such as focal dysplasia surgical resection remains the gold standard treatment. Disconnection procedures such as corpus callosotomy and multiple subpial transections are the best alternative treatment for that patient whose seizure origin is in eloquent cortex or having generalized epilepsy syndromes. Palliative neuromodulation procedures such as Vagus nerve stimulation (VNS), Responsive neurostimulation (RNS) and Deep brain stimulation (DBS) are best approach to treat intractable epileptic patients who are not suitable candidates of surgery. As the search of better management of epilepsy continues gene therapy and optogenetics gain a momentum in neuroscience.

From cryogenic to on-scalp magnetoencephalography for the evaluation of paediatric epilepsy.

Magnetoencephalography (MEG) is a neurophysiological technique based on the detection of brain magnetic fields. Whole-head MEG systems typically house a few hundred sensors requiring cryogenic cooling in a rigid one-size-fits-all (commonly adult-sized) helmet to keep a thermal insulation space. This leads to an increased brain-to-sensor distance in children, because of their smaller head circumference, and decreased signal-to-noise ratio. MEG allows detection and localization of interictal and ictal epileptiform discharges, and pathological high frequency oscillations, as a part of the presurgical assessment of children with refractory focal epilepsy, where electroencephalography is not contributive. MEG can also map the eloquent cortex before surgical resection. MEG also provides insights into the physiopathology of both generalized and focal epilepsy. On-scalp recordings based on cryogenic-free sensors have demonstrated their use in the field of childhood focal epilepsy and should become a reference technique for diagnosing epilepsy in the paediatric population. WHAT THIS PAPER ADDS: Magnetoencephalography (MEG) contributes to the diagnosis and understanding of paediatric epilepsy. On-scalp MEG recordings demonstrate some advantages over cryogenic MEG.

PRACTICAL ASPECTS OF FUNCTIONAL MRI IN CLINICAL EXAMINATIONS

The eloquent cerebral cortices are involved in movement, sensation, speech, vision, and higher cortical functions. Functional magnetic resonance imaging (fMRI) allows the evaluation of brain function, aiding in neurosurgical planning by mapping eloquent cortical areas. Considering the high cost of the hardware involved, the purpose of this work is to present a more affordable, in-house alternative for these studies that can provide adequate results in a clinical setting. We also present some practical information on how to perform these exams. We describe an affordable in-house hardware solution used by an imaging center, and examples of fMRI paradigms used to evaluate motor and language tasks. The fMRI studies show robust activations in eloquent areas consistent with the tasks performed on the exam. Images of post-processed studies illustrate clinical cases. The fMRI have well-established applications, mapping eloquent cortical areas in patients with brain lesions. In the case of surgical planning, it allows the surgeon to maximize the resection area while minimizing sequelae. More affordable hardware can reduce the cost of these exams, making them more accessible to the general public.

ID: 203253 Electrochemical Characterization of the First FDA-Cleared Thin-Film Electrodes for Recording and Stimulation of Brain Activity

Introduction: Subdural strip and grid (SDE) and stereoelectroencephalography (sEEG) electrodes are essential tools for pre-surgical evaluation of patients suffering from drug resistant epilepsy (DRE). Both device types are used to precisely localize the origin and spread of seizures and the relationship with eloquent cortex. The electrodes must accurately and reliably record brain activity over a wide frequency band needed for seizure event detection and deliver electrical stimulation within safety limits for brain mapping. The ability of the devices to meet these performance criteria is tested using electrochemical evaluation, which is a critical step in the path to commercialization of implantable medical devices. Driven by a constant need to develop new technologies or improve upon existing ones with potential to enhance the tissue/electrode interaction, here we present a thorough electrochemical characterization of two implantable thin-film SDG and sEEG arrays.??

P.114 When functional neuroimaging is ambiguous for language localization: a case for Wada testing

Background: To localize cortical speech areas, methods such as fMRI are commonly used, but the Wada test can also determine whether a region is critical to the particular task. We report a case of a left-handed patient with a left frontal tumour in whom fMRI language paradigms produced both left and right Broca’s and Wernicke’s areas. Methods: All imaging used a 3 Tesla Siemens Skyra scanner. The patient performed five speech tasks: word reading, picture naming, semantic questions, pseudohomophone reading, and word generation. All preprocessing and statistical analyses for functional images were performed using Brain Voyager QX. Results: The fMRI results revealed right hemisphere dominance for language processing. A Wada test was performed in order to confirm whether the regions in the left hemisphere were critical to speech. The patient experienced speech arrest during the Wada test, thus confirming that despite bilateral speech activation, the left hemisphere speech regions are required for speech production. Conclusions: This case emphasizes the importance of preoperative fMRI in assessing the location of eloquent cortices adjacent to a tumour and the Wada test is still warranted for examining necessity of left hemisphere language regions when fMRI fails to show clear left-lateralization.

Analysis of Functional Neuroplastic Changes in the Cortical Language System in Relation to Different Growth Patterns of Glioblastoma.

The interpretation of fMRI data in glioblastoma (GB) is challenging as these tumors exhibit specific hemodynamic processes which, together with malignancy, tumor volume and proximity to eloquent cortex areas, may lead to misinterpretations of fMRI signals. The aim of this study was to investigate if different radiologically defined GB tumor growth patterns may also influence the fMRI signal, activation pattern and functional connectivity differently. Sixty-four patients with left-hemispheric glioblastoma were included and stratified according to their radiologically defined tumor growth pattern into groups with a uniform (U-TGP) or diffuse tumor growth pattern (D-TGP). Task-based fMRI data were analyzed using SPM12 with the marsbar, LI and CONN toolboxes. The percent signal change and the laterality index were analyzed, as well as functional connectivity between 23 selected ROIs. Comparisons of both patient groups showed only minor non-significant differences, indicating that the tumor growth pattern is not a relevant influencing factor for fMRI signal. In addition to these results, signal reductions were found in areas that were not affected by the tumor underlining that a GB is not a localized but rather a systemic disease affecting the entire brain.

Responsive Neurostimulation for the Treatment of Children With Drug-Resistant Epilepsy in Tuberous Sclerosis Complex

BackgroundTo review seizure outcomes in children with tuberous sclerosis complex (TSC) and drug-resistant epilepsy (DRE) treated with the responsive neurostimulation (RNS) System. MethodsWe retrospectively reviewed children (<21 years old) with TSC implanted with the RNS System at Texas Children's Hospital between July 2016 and May 2022. ResultsFive patients meeting the search criteria were identified (all female). The median age of the RNS implantation was 13 years (range: 5 to 20 years). The median epilepsy duration before the RNS implantation was 13 years (range: 5 to 20 years). Surgeries before RNS implantation included vagus nerve stimulator placement (n = 2), left parietal resection (n = 1), and corpus callosotomy (n = 1). The median number of antiseizure medications tried before RNS was 8 (range: 5 to 12). The rationale for the RNS System implantation included seizure onset in eloquent cortex (n = 3) and multifocal seizures (n = 2). The maximum current density for each patient ranged between 1.8 and 3.5 μC/cm2, with an average daily stimulation of 2240 (range: 400 to 4200). There was an 86% median seizure reduction (range 0% to 99%) at a median follow-up duration of 25 months (range: 17 to 25 months). No patient experienced implantation or stimulation-related complications. ConclusionsWe observed a favorable improvement in seizure frequency in pediatric patients with DRE secondary to TSC treated with the RNS System. The RNS System may be a safe and effective treatment for DRE in children with TSC.

Intraoperative Cortico-Cortical Evoked Potential

In the surgery management of lesions in areas of the eloquent cortices the preservation of brain functions is required. Intraoperative electrophysiological methods are necessary to preserve the integrity of the functional network, such as motor or language areas. Cortico-cortical evoked potentials(CCEPs)have recently developed as a new intraoperative monitoring method because of advantages of a recording time of approximately 1-2 min, no requirement of patient cooperation, and high reproducibility and reliability of the data. The recent intraoperative CCEP studies have shown that CCEP can map the eloquent areas and white matter pathway, such as the dorsal language pathway, frontal aslant tract, supplementary motor area, and optic radiation. To establish intraoperative electrophysiological monitoring even under general anesthesia, further studies are required.

Efficacy and Quality of Life Outcome of Combined Epilepsy Surgery with RNS Placement (P5-1.002)

<h3>Objective:</h3> Retrospectively review clinical outcomes in patients treated with resection or Laser interstitial Thermal Therapy (LiTT) immediately (≤ 90 days) after implantation of RNS. <h3>Background:</h3> Surgical resection and LiTT are standard treatments for refractory epilepsy, but these options can be limited by eloquent cortex and seizure multifocality. Previous studies have suggested RNS may be used in conjunction with resective surgery (RNS+R) or LiTT (RNS+LiTT) as a new combination of treatments. Besides seizure control, quality of life and psychiatric symptoms including depression and anxiety are considered as important outcome evaluation after epilepsy surgery. <h3>Design/Methods:</h3> 34 patients that had RNS+R or RNS+LiTT at our center were reviewed and 10 were excluded. The decision of dual procedures was made prior to surgery. Patients received RNS+R had both resective surgery and RNS placement in the same procedure. Patients received RNS+LiTT had several weeks gap between the RNS placement and LiTT due to neurosurgical logistics. Clinical follow-ups were performed at 12, 18, 24, 36 and 48 months for evaluation of seizure frequency. Patient health questionnaire-9 (PHQ-9) is used as a depression assessment. Quality of life in epilepsy questionnaire (QOLIE-31) was used as scoring for evaluation of general quality of life. <h3>Results:</h3> Among the 24 patients that had RNS+R or RNS+LiTT, 22 patients (91.6%) showed improved seizure frequency at the last follow up. Fourteen patients had PHQ-9 evaluation and the average score was 5.85±6.29 (mean±SD), among which nine were between 0–4 (minimal depression), one was between 5–9(mild depression), three were between 10–14(moderate depression), one was 15–19(moderately severe depression) and none was 20–27(severe depression). QOLIE-31 done in eight patients showed average score of 65.61 ± 18.09 (mean±SD) in last follow-up visit. <h3>Conclusions:</h3> Our study showed significant seizure control rate of RNS+R or RNS+LiTT therapy in refractory epilepsy patients. It also suggestive for promising psychiatric outcomes and quality of life scoring after surgery. <b>Disclosure:</b> Dr. Pan has nothing to disclose. Dr. Mirza has nothing to disclose. Dr. Agostini has nothing to disclose. Dr. Alick-Lindstrom has nothing to disclose. Dr. Das has received personal compensation for serving as an employee of Concentra. Dr. Das has received personal compensation in the range of $5,000-$9,999 for serving as an Expert Witness for janicek. The institution of an immediate family member of Dr. Das has received research support from NIH. The institution of Dr. Ding has received research support from National Institute of Aging. The institution of Dr. Ding has received research support from NINDS. Dr. Doyle has nothing to disclose. Dr. Dieppa has nothing to disclose. Dr. Hays has nothing to disclose. Dr. Harvey has received personal compensation for serving as an employee of RSC Diagnostics. The institution of Dr. Harvey has received research support from GW Pharmaceuticals. The institution of Dr. Harvey has received research support from Cerevel Pharmaceuticals. The institution of Dr. Harvey has received research support from UCB Pharmaceuticals. The institution of Bradley Lega has received research support from NIH. irina podkorytova has nothing to disclose. Dr. Zepeda Garcia has nothing to disclose. Dr. Perven has nothing to disclose.

Awake Craniotomy Language Mapping in Children With Drug-Resistant Epilepsy due to Focal Cortical Dysplasia

BackgroundLanguage mapping during awake craniotomy can allow for precise resection of epileptogenic lesions, while reducing the risk of damage to eloquent cortex. There are few reports in the literature of language mapping during awake craniotomy in children with epilepsy. Some centers may avoid awake craniotomy in the pediatric age group due to concerns that children are unable to cooperate with such procedures. MethodsWe reviewed pediatric patients from our center with drug-resistant focal epilepsy who underwent language mapping during awake craniotomy and subsequent resection of the epileptogenic lesion. ResultsTwo patients were identified, both female, aged 17 years and 11 years at the time of surgery. Both patients had frequent and disabling focal seizures despite trials of multiple antiseizure medications. Both patients had resection of their epileptogenic lesions with the aid of intraoperative language mapping; in both cases pathology was consistent with focal cortical dysplasia. Both patients had transient language difficulties in the immediate postoperative period but no deficits at six-month follow-up. Both patients are now seizure-free. ConclusionsAwake craniotomy should be considered in pediatric patients with drug-resistant epilepsy in whom the suspected epileptogenic lesion is in close proximity to cortical language areas.

Central quadrantotomy for intractable childhood epilepsy: operative technique and functional neuroanatomy.

Refractory subhemispheric epilepsy has been traditionally treated by resection. The last few decades have seen the emergence of disconnective techniques, for both hemispheric and subhemispheric disease. The aim of this study was to describe the technique for a disconnective surgery for large epileptogenic lesions involving the central (perirolandic cortices), parietal, and occipital lobes. This junctional cortex within the hemisphere (in contrast to anterior and posterior quadrantotomies) presents unique challenges when contemplating a complete disconnection of the region. The surgical technique is achieved through six distinct steps: fronto-central, inferior frontoparietal, lateral temporo-occipital, medial frontal, basal temporo-occipital, and posterior parasagittal callosal disconnections. The functional neuroanatomy of each step is described, along with cadaveric dissections. The authors describe this technique and include a case description of a young girl who presented with childhood-onset intractable epilepsy associated with cognitive stagnation. The postoperative seizure outcome in this patient remains excellent at 2 years' follow-up, with gains in cognition and behavior. Excellent seizure outcomes can be achieved if the network encompassing the entire epileptogenic cortex is disconnected while ensuring preservation of fiber systems that link functionally eloquent uninvolved cortices adjacent to the central quadrant.

Mapping the Central Sulcus Extraoperatively Using Stereoelectroencephalography: A New Application of an Established Method.

Central sulcus localization is undertaken intraoperatively with subdural electrodes through a phase reversal technique using somatosensory evoked potentials from sensorimotor cortices. Extraoperative central sulcus localization using stereoelectroencephalography has not been described previously. Six pediatric patients (aged 12-18 years, 50% females) were investigated with stereoelectroencephalography. Peripheral median and posterior tibial nerve stimulation were performed while recording somatosensory evoked potentials from stereoelectroencephalography electrodes. Central sulcus was successfully localized by this novel method, and this was further supplemented by cortical stimulation data. This is the first report of somatosensory evoked potentials gained using stereoelectroencephalography in primary motor and sensory cortices. This can further supplement other data for safe surgical resection in the eloquent cortex.