Sabsevitz, David S.

BACKGROUND The authors aimed to evaluate the feasibility/safety of stereo-electroencephalography (SEEG) and SEEG-guided radiofrequency thermocoagulation (RFTC) in patients with drug-resistant epilepsy previously implanted with neuromodulation devices, using a retrospective cohort design evaluating patients treated at the Mayo Clinic Florida Epilepsy Center. OBSERVATIONS Nine patients (mean age 36.3 ± 10.9 years, 33% female) with prior implantation of neuromodulation devices were included. A vagus nerve stimulator was present in 8 of 9 patients, and 4 patients had undergone previous intracranial neuromodulation. Five patients underwent SEEG-RFTC. The mean SEEG monitoring duration was 6.5 ± 2.9 days. No intraoperative or procedural complications occurred, including hardware-related issues. No permanent or significant neurological/cognitive deficits occurred. One patient experienced transient postoperative neurological symptoms attributed to perilesional edema. Seizure reduction ranged from 50% to 75% following SEEG-RFTC. LESSONS SEEG and SEEG-RFTC are feasible in patients who have implanted neuromodulation devices, including intracranial implants. These procedures may be performed without interference with existing hardware and provide meaningful seizure reduction in highly refractory populations. Further studies with larger cohorts and longer follow-up are needed to better define efficacy and patient selection. https://thejns.org/doi/10.3171/CASE26376

OBJECTIVE Protocols for intraoperative mapping during awake craniotomy vary widely. The aim of this study was to evaluate how the number and type of intraoperative neuropsychological paradigms administered via NeuroMapper, a tablet-based platform, during awake glioma surgery affect positive mapping rates, return to work (RTW), and oncological outcomes. Factors associated with the operative duration and early postoperative neurological deficits were of additional interest. METHODS This single-center retrospective study included patients with diffuse low- and high-grade gliomas who underwent awake craniotomy with NeuroMapper-guided mapping between 2018 and 2024. Primary outcomes were RTW, progression-free survival (PFS), and overall survival (OS); operative duration and early postoperative deficits were secondary outcomes. Covariate balancing propensity score (CBPS) analysis was used to address confounding by tumor grade, with all postweighting standardized mean differences < 0.10. A weighted logistic regression model assessed RTW, and CBPS-weighted Cox models assessed PFS and OS. Linear regression was used to analyze intraoperative variables, operative duration, and early postoperative deficits. RESULTS Of 189 patients included in the analysis, 65 had LGG (median age 39 years) and 124 had HGG (median age 56 years). Mapping complexity varied, with 1–6 tasks used (median 4). Weighted multivariate logistic regression analysis identified the following independent predictors of RTW: preoperative Karnofsky Performance Status score ≥ 80 (OR 1.37, p = 0.039), absence of recurrent disease (OR 0.30, p < 0.001), use of 5–6 paradigms (OR 1.54, p = 0.047), positive mapping (OR 2.41, p = 0.017), and subtotal resection (OR 4.43, p = 0.002). Intraoperative seizure, early postoperative deficit, and the resection technique were not significant. IDH mutation status was associated with improved PFS (HR 0.15, p < 0.001), while subtotal resection was associated with worsened PFS (HR 3.00, p < 0.001). Positive mapping was associated with better OS (HR 0.57, p = 0.04). The operative duration was unaffected by mapping variables but was longer in patients with obesity (β = 0.28, p = 0.038). CONCLUSIONS Positive NeuroMapper-guided mapping of more diverse linguistic functions was associated with RTW and longer OS. Additionally, mapping complexity did not prolong surgery times, supporting potential standardization.

Purpose: Subcortical functional brain mapping is a valuable technique, especially involving lesions within or near white matter tracts. Motor and language deficits caused by intraoperative damage to these subcortical fibers are associated with worse outcomes. However, there are variable approaches to performing subcortical functional brain mapping. This systematic review was performed to better understand indications and optimal stimulation parameters. Methods: A systematic review was performed by PRISMA guidelines, using PubMed, Scopus, and Medline databases. Search dates ranged from inception to November 30th, 2024. Studies included adults who underwent subcortical electrical stimulation for functional brain mapping. Results: A total of 55 articles (249 patients, mean age 44.8 years, 114 female) were included. The most common pathology was brain tumor (96.3%), primarily gliomas and metastases, and 24.4% of all cases had a history of epilepsy. The most frequently mapped white matter tracts were the arcuate fasciculus, corticospinal/pyramidal tract, and inferior fronto-occipital fasciculus, involving motor, language, and cognitive functions. Bipolar stimulation (50–60 Hz, 0.5–1 millisecond, 1–10 mA) was preferred over monopolar stimulation. Among 147 patients with outcome data, 89.1% did not suffer permanent adverse outcomes including neurologic deficits, although long-term outcomes were inconsistently reported. Conclusions: The methodologic variability of subcortical functional brain mapping and lack of long-term follow-up reported limits determination of optimal parameter selection for electrical stimulation although common trends are reported. Functional brain mapping approaches may be guided by the tract and network involved. Further studies are needed to develop a standardized approach and more definitive guideline to its performance.

OBJECTIVE The aim of this study was to compare 3 electrode designs—a novel 22-contact circular grid, standard 6-contact strip, and high-density (HD) grid between 32 and 64 contacts—for the detection of epileptiform activity during awake craniotomy. METHODS This study included patients who underwent functional brain mapping with and without direct electrical stimulation during awake craniotomy. Demographic, clinical, and electrocorticography (ECoG) data were collected. RESULTS A total of 194 patients were included, with 264 instances of electrode use: 113 circular grid, 96 strip electrode, and 55 HD grid. The HD grid (15%) was used less to record ECoG during direct electrical stimulation than the circular grid (80%, p < 0.001) and strip electrodes (69%, p < 0.001). Sporadic interictal epileptiform activity was better detected with circular (45%, p < 0.001) and HD (40%, p = 0.006) grids compared with strip electrodes (16%). Spontaneous seizures were recorded more frequently with the circular grid (16%, p = 0.018) compared with the strip electrode (9.4%) and HD grid (1.8%). Afterdischarges were more frequently detected by the circular grid (69%, p = 0.031) and with circular and HD grids (combined) compared with strip electrodes (67% vs 48%, p = 0.024), at lower median intensity (3 mA vs 5 mA, p < 0.001). Multivariable analyses demonstrated circular grids (p < 0.001) to be more sensitive in detecting spontaneous epileptiform activity than strip and HD grid electrodes, and grids (circular and HD) to be better in recording stimulus-induced epileptiform activity (p = 0.01). CONCLUSIONS This study demonstrates a higher rate of detection of epileptiform activity with circular and standard grids when compared with strip electrodes. The standard HD grid was used less during electrical stimulation, demonstrating the importance of both the number of contacts and design array when considering optimal conditions for ECoG and functional brain mapping.

Abstract Objective: Reading is a complex cognitive process requiring the integration of orthographic, phonological, and semantic information. The visual word form area, located in the ventral occipitotemporal cortex, is critically involved in orthographic decoding, and damage to this region is known to cause alexia. In contrast, the contributions of white matter pathways supporting reading are less well understood. Method: We present a unique neurosurgical case undergoing awake brain surgery for resection of a metastasis in the left occipitotemporal cortex. A tubular retractor was used to access the lesion and during the insertion of the retractor the patient underwent careful, continuous neuropsychological testing, including evaluation of reading. fMRI language mapping and diffusion MRI were performed preoperatively. Postoperative neuropsychological testing was completed two weeks after surgery to assess cognitive outcome. Results: The patient developed an alexia with letter-by-letter reading in real time during insertion of the tubular retractor. Stealth imaging enabled localization of the tubular retractor at the exact onset of the alexia and, by correlating this with tractography, showed that the tubular retractor was in the vertical occipital fasciculus (VOF). Conclusions: We present the first detailed case report linking the VOF to the acute onset of alexia observed intraoperatively during awake brain surgery. We discuss the connectomics of reading and possible contributions of the VOF in reading.

Purpose: These American Clinical Neurophysiology Society technical standards suggest best practices for electrical stimulation mapping (ESM) with subdural and stereotactic depth electrodes for seizure induction and mapping of brain function. Methods: A working group was convened from American Clinical Neurophysiology Society membership with expertise in ESM. PubMed searches were performed to identify pertinent peer-reviewed literature. Recurrent meetings reviewed progress, built consensus by discussion, and developed evidence-based recommendations to the extent possible. Recommendations: Stimulators used for ESM should have sufficient dynamic range, ability to interrupt a stimulus train, and ictal disrupt mechanism(s). Charge density should be calculated for the specific electrodes and ESM settings, the maximum safe limits being 52 to 57 μC/cm 2 /phase for subdural electrodes and not established for stereotactic depth electrodes. Subdural ESM for functional mapping is typically performed at 50-Hz pulse frequency, 200- to 300-µs pulse width, 2- to 8-s train duration, and 1- to 20-mA current strength. Stereo ESM is commonly performed using 2 different pulse frequencies: 1 Hz (300–500 µs pulse width, train duration up to 30 s, and often a constant current of 3–5 mA), and 50 Hz (100–500 µs pulse width, train duration 2-8 s, and 0.5–10 mA current intensity). Conclusions: This guideline provides technical standards for the performance of ESM, which will likely evolve over time with advances in technology and additional evidence (also see Graphical Abstract).