Extraoperative mapping

OBJECTIVE: Extraoperative electrical cortical stimulation (ECS) facilitates defining the seizure onset zone (SOZ) and eloquent cortex. The clinical relevance of stimulation-induced afterdischarges (ADs) is not well defined. METHODS: Fifty-five patients who underwent intracranial electroencephalogram evaluations with ECS were retrospectively identified. ADs were identified in these recordings and categorized by pattern, location, and association with stimulation-induced seizures...

BACKGROUND: Electrocorticography (ECoG) language mapping is often performed extraoperatively, frequently involves offline processing, and relationships with direct cortical stimulation (DCS) remain variable. We sought to determine the feasibility and preliminary utility of an intraoperative language mapping approach guided by real-time visualization of electrocorticograms. METHODS: A patient with astrocytoma underwent awake craniotomy with intraoperative language mapping, utilizing a dual iPad stimulus presentation system coupled to a real-time neural signal processing platform capable of both ECoG recording and delivery of DCS...

PURPOSE: 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. METHODS: 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...

BACKGROUND: Aggressive resection without compromising the patient's neurological status remains a significant challenge in treating intracranial gliomas. Our current study aims to evaluate the efficacy and safety of extra-operative stimulation and mapping via implanted subdural electrodes with or without depth (EOCSM), offering an alternative approach when awake mapping is contraindicated. METHODS: Fifty-one patients undergoing EOCSM for glioma resection in our institution formed the sample study of our current retrospective study...

BACKGROUND: Stereoelectroencephalography (sEEG) facilitates electrical sampling and evaluation of complex deep-seated, dispersed, and multifocal locations. Granger causality (GC), previously used to study seizure networks using interictal data from subdural grids, may help identify the seizure-onset zone from interictal sEEG recordings. OBJECTIVE: To examine whether statistical analysis of interictal sEEG helps identify surgical target sites and whether surgical resection of highly ranked nodes correspond to favorable outcomes...

The infiltrative character of supratentorial lower grade glioma makes it possible for eloquent neural pathways to remain within tumoural tissue, which renders complete surgical resection challenging. Neuromodulation-Induced Cortical Prehabilitation (NICP) is intended to reduce the likelihood of premeditated neurologic sequelae that otherwise would have resulted in extensive rehabilitation or permanent injury following surgery. This review aims to conceptualise current approaches involving Repetitive Transcranial Magnetic Stimulation (rTMS-NICP) and extraoperative Direct Cortical Stimulation (eDCS-NICP) for the purposes of inducing cortical reorganisation prior to surgery, with considerations derived from psychiatric, rehabilitative and electrophysiologic findings related to previous reports of prehabilitation...

NeuroPace responsive neurostimulation (RNS® ) therapy was used in a case of intractable focal epilepsy with bifrontal transmantle heterotopia subserving peculiar homotopic motor distribution in a 16-year-old, right-handed male with intractable seizures. Brain MRI demonstrated bifrontal transmantle heterotopia extending from the central sulcus to subjacent lateral ventricles along with polymicrogyria along the overlying cortex suspected to be the motor cortex. Functional MRI demonstrated homotopic distribution of finger and foot motor function (deeper) within the polymicrogyria...

OBJECTIVE: Resective surgery in language-dominant ventral occipitotemporal cortex (vOTC) carries the risk of causing impairment to reading. Because it is not on the lateral surface, it is not easily accessible for intraoperative mapping, and extensive stimulation mapping can be time-consuming. Here the authors assess the feasibility of using task-based electrocorticography (ECoG) recordings intraoperatively to help guide stimulation mapping of reading in vOTC. METHODS: In 11 patients undergoing extraoperative, intracranial seizure mapping, the authors recorded induced broadband gamma activation (70-150 Hz) during a visual category localizer...

Intraoperative functional language mapping is vital to minimize the risks associated with surgical removal of the seizure onset zone in selected patients with epilepsy. In children, this method has been reported extraoperatively by the placement of invasive electrodes to map the language area and monitor epileptic activity. It is difficult from a technical standpoint to perform an awake craniotomy and language mapping in young children under 10 years of age. Here we report a 9-year-old boy suffering from drug-resistant non-lesional epilepsy who underwent extraoperative and intraoperative electrical stimulation with successful identification of Broca's language area...

OBJECTIVE: We clarified the clinical and mechanistic significance of physiological modulations of high-frequency broadband cortical activity associated with spontaneous saccadic eye movements during a resting state. METHODS: We studied 30 patients who underwent epilepsy surgery following extraoperative electrocorticography and electrooculography recordings. We determined whether high-gamma activity at 70-110 Hz preceding saccade onset would predict upcoming ocular behaviors...

BACKGROUND: Precise targeting of cortical surface electrodes to epileptogenic regions defined by anatomic and electrophysiological guideposts remains a surgical challenge during implantation of responsive neurostimulation (RNS) devices. OBJECTIVE: To describe a hybrid fluoroscopic and neurophysiological technique for targeting of subdural cortical surface electrodes to anatomic regions with limited direct visualization, such as the interhemispheric fissure. METHODS: Intraoperative two-dimensional (2D) fluoroscopy was used to colocalize and align an electrode for permanent device implantation with a temporary in Situ electrode placed for extraoperative seizure mapping...

To preserve postoperative brain function, it is important for neurosurgeons to fully understand the brain's structure, vasculature, and function. Intraoperative high-frequency electrical stimulation during awake craniotomy is the gold standard for mapping the function of the cortices and white matter; however, this method can only map the "focal" functions and cannot monitor large-scale cortical networks in real-time. Recently, an in vivo electrophysiological method using cortico-cortical evoked potentials (CCEPs) induced by single-pulse electrical cortical stimulation has been developed in an extraoperative setting...

BACKGROUND: The practice of intraoperative electrocorticography (iECoG) to guide resective epilepsy surgery is variable. Limitations of iECoG include variability in recordings from previously unsampled cortex, increased operative time and cost, and a lack of clear benefit to surgical decision-making. OBJECTIVE: To describe a simple technique to supplement extraoperative intracranial recordings with real-time iECoG using the same chronically implanted electrodes that overcome some of these limitations...

Presurgical evaluation and surgery in the pediatric age group are unique in challenges related to caring for the very young, range of etiologies, choice of appropriate investigations, and surgical procedures. Accepted standards that define the criteria for levels of presurgical evaluation and epilepsy surgery care do not exist. Through a modified Delphi process involving 61 centers with experience in pediatric epilepsy surgery across 20 countries, including low-middle- to high-income countries, we established consensus for two levels of care...

Navigated transcranial magnetic stimulation (nTMS) is increasingly applied in language mapping. However, the application mode and task selection of nTMS are not standardized. The aim of this study was to assessed the necessity and validity of multitask nTMS language mapping by comparing results with extraoperative electrical cortical stimulation (eoECS). In this study, sixteen epilepsy surgery patients were examined by nTMS and eoECS language mapping, and the two results were compared. The mapping results were validated with pre- to postoperative language assessments...

PURPOSE: The aim of this retrospective service evaluation was to determine the nature, frequency and clinical value of seizure occurrence during extraoperative direct cortical stimulation for functional mapping in patients undergoing invasive recordings (icEEG) for epilepsy surgery workup. METHODS: We reviewed 145 sequential cases of patients with refractory focal epilepsy who underwent intracranial electrode implantation and extraoperative direct cortical stimulation (CS) for functional mapping...

OBJECTIVE: The authors' goal was to prospectively quantify the impact of resting-state functional MRI (rs-fMRI) on pediatric epilepsy surgery planning. METHODS: Fifty-one consecutive patients (3 months to 20 years old) with intractable epilepsy underwent rs-fMRI for presurgical evaluation. The team reviewed the following available diagnostic data: video-electroencephalography (n = 51), structural MRI (n = 51), FDG-PET (n = 42), magnetoencephalography (n = 5), and neuropsychological testing (n = 51) results to formulate an initial surgery plan blinded to the rs-fMRI findings...

Lower- and higher-order visual cortices in the posterior brain, ranging from the medial- and lateral-occipital to fusiform regions, are suggested to support visual object recognition, whereas the frontal eye field (FEF) plays a role in saccadic eye movements which optimize visual processing. Previous studies using electrophysiology and functional MRI techniques have reported that tasks requiring visual object recognition elicited cortical activation sequentially in the aforementioned posterior visual regions and FEFs...

A key aspect of cognitive control is the management of conflicting incoming information to achieve a goal, termed 'interference control'. Although the role of the right frontal lobe in interference control is evident, the white matter tracts subserving this cognitive process remain unclear. To investigate this, we studied the effect of transient network disruption (by means of direct electrical stimulation) and permanent disconnection (resulting from neurosurgical resection) on interference control processes, using the Stroop test in the intraoperative and extraoperative neurosurgical setting...

This chapter presents a summary of current notions regarding cortical specialization for language and a description of the methods employed for the assessment of that specialization. We distinguish between the "canonical" model of language specialization as it evolved from the early observations of Broca and Wernicke, implicating the inferior frontal gyrus and the posterior temporal cortex of the speech dominant hemisphere (usually the left) and its modern variants that are based on both detailed studies of lesion-symptom correlations and on the results of functional brain mapping methods...