Tatum, William O.

Abstract To characterize invasive neuromodulation for insular drug‐resistant epilepsy, we retrospectively evaluated 22 patients treated with responsive neurostimulation (RNS; n = 14) or chronic subthreshold stimulation (CSS; n = 8). Stereoelectroencephalography was performed in 20 cases (91%). Median baseline seizure frequency was 10.5/month. Forty‐one percent had prior epilepsy surgery. At year 3, median seizure reduction (MSR) was 83% ( p = .01, Wilcoxon signed‐rank test), with a responder rate (RR) of 77%; MSR was 92% for CSS and 75% for RNS. There were no significant differences in MSR ( p ≥ .4) or RR ( p > .9) when comparing RNS versus CSS. Three patients achieved seizure freedom by year 3. Patients undergoing combined insular–thalamic stimulation ( n = 5) demonstrated an MSR of 84%, 86%, and 88% at 1, 2, and 3 years; seizure reduction in thalamocortical versus cortical‐only stimulation was not different ( p ≥ .1). Parasagittal lead trajectories achieved closer insular proximity than transopercular trajectories ( p < .0001, Mann–Whitney U ‐test). Median charge density at last follow‐up was 1.3 μC/cm 2 . There were no acute surgical complications and all stimulation‐related side effects resolved with programming adjustments. This study expands the limited literature on insular neuromodulation by demonstrating effectiveness of RNS and CSS, suggesting potential benefit from combined thalamocortical targeting, and defining parasagittal trajectories as a surgical approach for optimal lead proximity.

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

Abstract The objective of the study was to assess the frequency of interictal epileptiform discharges (IEDs) in calcified neurocysticercosis (NCC) and its relationship with calcification burden. Forty‐nine patients with calcified NCC (low‐burden, 1–2 calcifications, n = 24; high‐burden, ≥15 calcifications, n = 25) and seizure history underwent prolonged (8‐h) electroencephalography (EEG), interpreted by epileptologists who were blinded to patient history and calcification category. Clinical seizure outcomes were also assessed. We found that IEDs occurred in 7 of 49 participants (14.3%), with no difference between low‐burden (12.5%) and high‐burden (16.0%) groups ( p = 1.000). All IEDs (spikes and/or sharp waves) in the high‐burden group ( n = 4) were high‐voltage (100–150 μV), whereas those in the low‐burden group ( n = 3) were low or medium voltage (20–70 μV). Among the participants who had IEDs, 5 (71.4%) had seizures in the last year, compared with 14 (33.3%) in the group without IEDs detected ( p = 0.093). Among 19 participants with seizures in the last year, 5 were identified as having drug‐resistant epilepsy (DRE). All five cases of DRE occurred in individuals with 15 or more calcifications (5/25, 20%, vs 0/24, p = 0.023). We conclude that IEDs occur frequently in individuals with calcified NCC. Although calcification burden itself was not associated with the presence of IEDs, drug‐resistant cases and high‐voltage IEDs were concentrated in the high‐burden group, supporting the role of calcified parasites as epileptogenic foci.

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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.

Abstract Objective To measure the relative levels of signal and noise in expert diagnosis of epilepsy. Methods Twenty multinational epileptologists independently reviewed 50 vignettes of adult and pediatric patients presenting with suspected seizure(s) on two separate occasions with a ≥30‐day washout period. Experts provided a diagnosis of epilepsy or non‐epilepsy based on clinical information and, if requested, routine EEG and neuroimaging data. Cases had an established clinical diagnosis of epilepsy or non‐epilepsy based on capture of habitual paroxysmal events on video‐EEG or long‐term clinical follow‐up. Experts' judgments were analyzed to decompose variability into different sources: signal (objective differences between cases), level noise (experts' bias toward over/under‐diagnosis), pattern noise (experts' idiosyncratic reactions to specific case features), and occasion noise (inconsistency across occasions). Results The probability of an expert making a different diagnosis for a given case on two different occasions was 16%. The probability of two different experts making a different diagnosis for the same case was 26%. Signal (case “difficulty”) accounted for 66–69% of total variation, with 31–34% attributable to noise. Level noise was the largest contributor in the absence of EEG/neuroimaging results (23%), while pattern noise dominated when test results were available (24%). Occasion noise contributed relatively little (1%) but was still sufficient to cause diagnostic reversals in 16–22% between occasions. Significance The degree of noise in expert diagnosis of epilepsy is substantial, stemming primarily from physicians' idiosyncratic interpretations of case features and variable dispositions toward over‐ or under‐diagnosis. Strategies to improve reliability are needed, including standardized data collection protocols and structured decision algorithms. For “difficult cases,” where expert reliability and accuracy are lowest, our findings support current clinical practice which favors early referral for video‐EEG monitoring over reliance on diagnostic anchoring. This diagnostic pathway may become more accessible with advances in EEG technology (e.g., wearable devices) and artificial intelligence.