OBJECTIVE:Approximately one-third of patients with epilepsy develop drug-resistant epilepsy (DRE). Extratemporal lobe epilepsy (ETLE) represents 30%-40% of focal epilepsy cases. ETLE poses significant challenges in localization and treatment because these patients often have diffuse and complex epileptogenic networks. Laser interstitial thermal therapy (LITT) has emerged as a minimally invasive alternative for localizable DRE, yet data for its use in the pediatric ETLE population remain limited. This study aimed to evaluate the safety and efficacy of LITT in pediatric ETLE and identify predictive factors for favorable seizure outcomes. METHODS:This retrospective study reviewed pediatric patients who underwent LITT for ETLE at a single National Association of Epilepsy Centers level 4 epilepsy center from 2015 to 2023. Patients with prior LITT for temporal lobe epilepsy, hypothalamic hamartomas, or corpus callosotomies were excluded. Preoperative evaluations included noninvasive testing (e.g., video-EEG, MRI, PET, magnetoencephalography) and invasive monitoring with stereo-EEG. The primary study endpoints were 1) International League Against Epilepsy (ILAE) classification at 12 months after the index LITT or additional surgical intervention for the treatment of seizures, and 2) procedure-related complications. Secondary analyses examined imaging concordance with the final ablation location, total ablation volume, and perioperative metrics. RESULTS:Twenty-nine patients underwent an index LITT procedure for ETLE. At 12 months, 14 patients (48.3%) achieved a good outcome (ILAE class 1-3), and 12 (41.4%) were seizure free (ILAE class 1). There were 6 patients (20.7%) who required additional surgery within 12 months. Concordant PET with the final LITT ablation volume independently predicted seizure outcome (p = 0.04). The total ablation volume ranged from 0.66 to 8.45 cm3, and was not statistically different between groups. In the perioperative period, 3 patients developed transient steroid-responsive LITT-related edema, while no permanent neurological deficits, hematomas, surgical site infections, or deaths occurred. CONCLUSIONS:This study demonstrated that LITT is a safe and effective treatment option for pediatric ETLE and may achieve acceptable rates of seizure freedom with a minimally invasive approach. Concordance between noninvasive imaging (particularly PET) with LITT targets was associated with favorable outcomes, underscoring the importance of thorough preoperative evaluations to determine appropriate ablation candidates. Future multicenter prospective studies are warranted to further refine patient selection criteria and optimize treatment paradigms.

OBJECTIVE:We describe a safe, informative, and easy-to-implement approach for presurgical mapping of visual working memory (VWM) with stereo-electroencephalography (SEEG). METHODS:Twenty-four patients with drug-resistant epilepsy, 11-23 years of age, performed a single-probe change detection VWM task, during SEEG monitoring. High-gamma modulations (HGMs) and connectivity modulations (weighted phase lag index) were computed for encoding, retention, recall, and response phases compared to a rest phase. Effects of lesioning sites with significant HGM on neuropsychological outcomes were analyzed. RESULTS:Validity of our VWM task was evident by picture vocabulary scores covarying positively with increasing consistency and negatively with increasing maximum latency of the response times, respectively. VWM task elicited specific patterns of cortical HGMs during each phase: bilateral frontoparietal augmentation during encoding, replaced by widespread suppression during retention, followed by diffuse bilateral augmentation during the recall and response phases. Distinct neural circuits were also observed during each phase of the VWM task: left-lateralized phonological loop during encoding, short-range bilateral frontal connectivity during retention, and interhemispheric peri-Rolandic hubs during recall and response phases. Lesioning sites with significant high-gamma augmentation was associated with declines in domains directly relevant to VWM including working memory (slope -6.18, p < .001), visuospatial (-1.17, p = .031), picture vocabulary (-1.45, p < .001), and letter-word identification (-6.39, p = .004), whereas lesioning sites with significant high-gamma suppression, particularly in recall and response phases, affected domains sharing resources for neural computations with working memory, but not directly related to VWM including processing speed (-16.04, p = .049), calculation (-19.12, p = .020), and verbal comprehension (-9.09, p = .020). SIGNIFICANCE:Our observations extend theoretical models of VWM by providing phase-specific engagement of neural subsystems, particularly of phonological loop during encoding of even visually-cued stimuli and spatial rehearsal mechanisms during retention. Clinically, adverse neuropsychological outcomes from lesioning of VWM sites during epilepsy surgery support wider adoption of VWM mapping during presurgical evaluation of patients with drug-resistant epilepsy.

Objective We used electrical stimulation mapping (ESM) of functional responses, after-discharges (ADs), and unwanted electrical stimulation-induced seizures (EIS) to explore differences in cortical excitability in tuberous sclerosis complex (TSC) patients on mTOR inhibitors, TSC patients not on mTOR inhibitors, and drug-resistant epilepsy (DRE) of unknown etiology. Methods In 20 patients with TSC and 10 patients with DRE of unknown etiology, incidence and current thresholds of physiologic (language and motor) and pathologic (ADs, EIS) responses were analyzed using mixed effects models against disease phenotype (TSC vs unknown) and use of mTOR inhibitors. Results Patients with TSC showed a higher incidence and required a lower threshold current to elicit motor responses and ADs compared to those with DRE of unknown etiology. In TSC patients, mTOR inhibitors increased the threshold for motor responses and ADs, and decreased the incidence of face motor responses, language responses, and ADs. Conclusions TSC patients exhibit higher physiologic and pathologic cortical excitability evidenced by a higher incidence and lower current thresholds of ESM responses, which appears to be mitigated by mTOR inhibitors. Significance To our knowledge, this is the first study providing direct intracranial evidence for altered cortical excitability in TSC and the corrective effect of mTOR inhibitors.

PURPOSE:We demonstrate that different regions of the cerebral cortex have different diurnal rhythms of spontaneously occurring high-frequency oscillations (HFOs). METHODS:High-frequency oscillations were assessed with standard-of-care stereotactic electroencephalography in patients with drug-resistant epilepsy. To ensure generalizability of our findings beyond patients with drug-resistant epilepsy, we excluded stereotactic electroencephalography electrode contacts lying within seizure-onset zones, epileptogenic lesions, having frequent epileptiform activity, and excessive artifact. For each patient, we evaluated twenty-four 5-minute stereotactic electroencephalography epochs, sampled hourly throughout the day, and obtained the HFO rate (number of HFOs/minute) in every stereotactic electroencephalography channel. We analyzed diurnal rhythms of the HFO rates with the cosinor model and clustered neuroanatomic parcels in a standard brain space based on similarity of their cosinor parameters. Finally, we compared overlap among resting-state networks, described in the neuroimaging literature, and chronobiological spatial clusters discovered by us. RESULTS:We found five clusters that localized predominantly or exclusively to the left perisylvian, left perirolandic and left temporal, right perisylvian and right parietal, right frontal, and right insular-opercular cortices, respectively. These clusters were characterized by similarity of the HFO rates according to the time of the day. Also, these chronobiological spatial clusters preferentially overlapped with specific resting-state networks, particularly default mode network (clusters 1 and 3), frontoparietal network (cluster 1), visual network (cluster 1), and mesial temporal network (cluster 2). CONCLUSIONS:This is probably the first human study to report clusters of cortical regions with similar diurnal rhythms of electrographic activity. Overlap with resting-state networks attests to their functional significance and has implications for understanding cognitive functions and epilepsy-related mortality.

PURPOSE:To determine if incorporating neuroanatomic or intersubject variation in the occurrence rate of intracranial high-frequency oscillations improves its diagnostic performance for localization of epileptogenic zone (EZ). METHODS:Five minutes of awake stereo-electroencephalography data from 59 patients were analyzed. High-frequency oscillations were analyzed using three different normalization methods: rate per minute, by neuroanatomic region across the patient population, and patient-wise. Generalized linear mixed effects models were trained in patients with good seizure outcomes after epilepsy surgery (higher confidence in the clinical localization of EZ) and tested in patients with poorer outcomes (validation set approach). RESULTS:The generalized linear mixed model with region-wise normalization across the patient population best localized the EZ (highest area under the curve 0.69), closely followed by the rate per minute (0.68). In the test subgroup, the optimal generalized linear mixed model predicted EZ in individual patients with an accuracy of 0.18 to 0.86, sensitivity of 0.05 to 1.00, and specificity of 0.12 to 0.95. In patients with poorest performance of the generalized linear mixed model, although the electrode contacts within EZ were correctly identified, there was a high number of false positives (model-predicted electrode contacts lying outside clinically ascertained EZ). Model performance varied across neuroanatomic regions, with the highest accuracy in the medial/orbital frontal (0.8), lateral temporal (0.78), and lateral parietal (0.76) regions. CONCLUSIONS:Normalizing the high-frequency oscillation occurrence rate by neuroanatomic region improves its diagnostic performance as an interictal biomarker of EZ location. High-frequency oscillations are more likely to reliably identify electrode contacts within EZ in medial/orbital frontal lobe and temporal neocortex.

OBJECTIVE:Nasal dermoid sinus cysts (NDSCs) with intracranial extension in the form of dermal sinus tracts require careful and complete resection to prevent recurrence. Resection techniques necessitate adequate intracranial exposure, but morbidity associated with historical resection approaches has presented unique multidisciplinary challenges for surgeons treating cysts with intracranial extension. METHODS:The authors primarily employed a transnasal approach through a midline nasal incision, utilizing endoscopic or microscopic access between the lateral cartilages for resection of NDSCs with intracranial extension. A retrospective review was completed for patients treated for NDSCs at the authors' pediatric quaternary referral center from 2017 to 2023. Data collection included demographics, comorbidities, perioperative data, pre and postoperative imaging, surgical outcomes, and complications. RESULTS:Eighteen patients with NDSCs with possible or confirmed intracranial extension were surgically treated from 2017 to 2023. Fifteen were treated with resection performed through a midline transnasal approach with endoscopic assistance, achieving successful total resection while avoiding nasal osteotomy or frontal craniotomy. One patient had a slow cerebrospinal fluid leak from an operative durotomy, successfully treated with a lumbar drain. No other complications occurred. No patients required transfusion. Incision length and postoperative scar burden were less than approaches that used osteotomies or craniotomies and demonstrated excellent cosmetic results. No patients have had cyst recurrence or required reoperation. CONCLUSIONS:A transnasal approach through a midline incision with endoscopic assistance is an effective approach for resection of NDSC with intracranial extension, but utility may vary with cyst size and complexity. This approach leverages appropriate exposure for resection with decreased morbidity and decreased incision length through avoidance of osteotomies.

BACKGROUND AND OBJECTIVES:Epilepsy is a significant cause of morbidity and has negative effects on cognitive and psychosocial development in pediatric and young adult patients. For pediatric patients who have epileptogenic foci that are poorly localized, deep, bilateral, or in eloquent regions and are not candidates for resection, responsive neurostimulation (RNS) may be an option. The study objective was to demonstrate safety and seizure outcomes from RNS in pediatric and young adults with intractable epilepsy with a specific focus on differences between thalamic and nonthalamic RNS lead implantation. METHODS:The authors describe a single institution's experience with RNS in patients with drug-resistant epilepsy who were not candidates for seizure focus resection. An Institutional Review Board-approved retrospective review was conducted of all pediatric and young adult patients who underwent RNS implantation at Cincinnati Children's Hospital Medical Center between 2019 and 2023. RESULTS:In total, 24 patients met the inclusion criteria for the study. Seven had thalamic targets whereas 17 had nonthalamic targets. The mean patient age at the time of surgery was 13.8 years (range 5-30), with a mean follow-up of 13 months. Thirteen patients (54%) had prior surgery for seizure control. The median global seizure percentage reduction was 68% in the nonthalamic group and 80% in the thalamic group, a nonsignificant difference, resulting in a reduction of 74% for all study patients ( P = .816). Two adverse events (8.3%) included a wound infection and a lead repositioning. CONCLUSION:RNS implantation in pediatric and young adult patients with epilepsy seems to be a safe and efficacious modality for lowering seizure burden in cases where resection of epileptogenic foci is not a viable option. Thalamic and nonthalamic RNS targeting both lead to impactful seizure reduction. This study adds to the growing body of evidence suggesting that RNS is appropriate in pediatric and young adult patients.

INTRODUCTION:Drug-refractory epilepsy (DRE) affects one-third of children with epilepsy and can be treated with surgery. The surgical target is determined by recording spontaneous seizures during stereoelectroencephalography (sEEG). In adults, induced seizures help define the surgical target and predict favorable outcomes. No studies focus on the safety, tolerability, and yield of electrical stimulation for the induction of seizures (ESIS) in children. METHODS:Stimulation at 1 Hz and 50 Hz was performed prospectively and comprehensively (all gray matter channels) during sEEG in children and young adults with DRE. Induced seizures were categorized as electroclinical habitual, clinical habitual (aura), subclinical and non-habitual. Primary safety outcome was rescue medication use. Tolerability was assessed by questionnaire. Yield was induced seizure rate. RESULTS:Sixty-seven patients (n = 30 female) participated during 70 admissions. Patients were 1-21 years old (mean ± SD, 11.1 ± 5.7). n = 10,135 stimulation trials were performed, requiring 175 ± 61 min per patient. One seizure required rescue medication. Tolerability ratings were favorable and improved from pre- to post-session. At least one induced seizure was obtained in 62/70 (89 %) sessions, representing 283/10,135 trials (2.8 %). Combined, habitual seizures and habitual auras accounted for 58 % of induced seizures; non-habitual seizures were uncommon (12 %). Of those with induced seizures, multiple seizure types occurred in 28/62 (45 %). Seizures were induced at 1 Hz and 50 Hz in 22/67 patients (33 %). SIGNIFICANCE:Seizure stimulation during sEEG is safe, well-tolerated, and high-yield in children at both 1 Hz and 50 Hz. These findings motivate a more systematic utilization of ESIS in pediatric patients.

Introduction We studied effects of duration of epilepsy and location of epileptogenic zone (EZ) on visual naming (VN) and auditory naming (AN) response latencies in pediatric focal drug-resistant epilepsy. We also analyzed temporal profiles of high-gamma modulations (HGMs) during VN and AN in peri-sylvian language areas, with respect to AN and VN response latencies. Methods Kernel density distributions of AN and VN response latencies were k-means clustered, and the resulting groups were compared for relevant outcomes. Response latencies and kernel densities were analyzed as functions of age, age of seizure onset, and duration of epilepsy using linear mixed-effects models. Results Shorter response latencies and higher peak densities (more consistent response times) were associated with shorter duration of epilepsy, older age at seizure onset, localized EZ, and higher proportion of seizure-freedom (80 % vs 41 %). Response latencies shortened with age and age of seizure onset and lengthened with increasing duration of epilepsy. Peak kernel densities, indicating consistency of responses, increased with age and age of seizure onset, and decreased with duration of epilepsy. Epilepsy duration over 5.9 years for AN and over 5.3 years for VN were associated with a higher likelihood of prolonged response latencies. Temporal envelopes for HGM during AN were different in the Broca’s area for patients with short and long response latencies. Also, HGM envelopes during VN were different in the visual cortex for these 2 groups. Conclusion The duration-dependent network dysfunction in refractory epilepsy, interfering with naming, supports early surgical intervention before language function is irreversibly compromised.

Ninety percent of tuberous sclerosis complex (TSC) patients have seizures, with ∼50 % developing drug refractory epilepsy. Surgical intervention aims to remove the seizure onset zone (SOZ). This retrospective study investigated the relationship of SOZ size, ictal pattern, and extent of resection with surgical outcomes. TSC patients undergoing resective/ablative surgery with >1-year follow-up and adequate imaging were included. Preoperative iEEG data were reviewed to determine ictal pattern and SOZ location. For outcomes, an ILAE score of 1-3 was defined as good and 4-6 as poor. Forty-four patients were included (age 117.4 ± 110.8 months). Of these, 59.1 % achieved a good outcome, while 40.9 % had a poor outcome. Size of SOZ was a significant factor (p = 0.009), with the poor outcome group having a larger SOZ (11.9 ± 6.7 electrode contacts) than the good outcome group (7.3 ± 7.2). SOZ number was significant (p = 0.020); >1 SOZ was associated with poor outcome. These results demonstrate extent of SOZ as a predictor of seizure freedom following epilepsy surgery in a mostly pediatric TSC cohort. We hypothesize that these features represent biomarkers of focality of the epileptogenic zone and can be used to sharpen prognosis for epilepsy surgery outcomes in this cohort.

OBJECTIVE:The most common medically resistant epilepsy (MRE) involves the temporal lobe (TLE), and children designated as temporal plus epilepsy (TLE+) have a five-times increased risk of postoperative surgical failure. This retrospective, blinded, cross-sectional study aimed to correlate visual and computational analyses of magnetoencephalography (MEG) virtual sensor waveforms with surgical outcome and epilepsy classification (TLE and TLE+). METHODS:Patients with MRE who underwent MEG and iEEG monitoring and had at least 1 year of postsurgical follow-up were included in this retrospective analysis. User-defined virtual sensor (UDvs) beamforming was completed with virtual sensors placed manually and symmetrically in the bilateral amygdalohippocampi, inferior/middle/superior temporal gyri, insula, suprasylvian operculum, orbitofrontal cortex, and temporoparieto-occipital junction. Additionally, MEG effective connectivity was computed and quantified using eigenvector centrality (EC) to identify hub regions. More conventional MEG methods (equivalent current dipole [ECD], standardized low-resolution brain electromagnetic tomography, synthetic aperture magnetometry beamformer), UDvs beamformer, and EC hubs were compared to iEEG. RESULTS:Eighty patients (38 female, 42 male) with MRE (mean age = 11.3 ± 6.2 years, range = 1.0-31.5) were identified and included. Twenty-five patients (31.3%) were classified as TLE, whereas 55 (68.8%) were TLE+. When modeling the association between MEG method, iEEG, and postoperative surgical outcome (odds of a worse [International League Against Epilepsy (ILAE) class > 2] outcome), a significant result was seen only for UDvs beamformer (odds ratio [OR] = 1.22, 95% confidence interval [CI] = 1.01-1.48). Likewise, when the relationship between MEG method, iEEG, and classification (TLE and TLE+) was modeled, only UDvs beamformer had a significant association (OR = 1.47, 95% CI = 1.13-1.92). When modeling the association between EC hub location and resection/ablation to postoperative surgical outcome (odds of a good [ILAE 1-2] outcome), a significant association was seen (OR = 1.22, 95% CI = 1.05-1.43). SIGNIFICANCE:This study demonstrates a concordance between UDvs beamforming and iEEG that is related to both postsurgical seizure outcome and presurgical classification of epilepsy (TLE and TLE+). UDvs beamforming could be a complementary approach to the well-established ECD, improving invasive electrode and surgical resection planning for patients undergoing epilepsy surgery evaluations and treatments.

Editorial: Magnetic resonance-guided laser interstitial thermal therapy (MRg-LiTT) in the minimally invasive surgical treatment of epilepsy and/or brain neoplasms

Objective: We investigated the role of transverse temporal gyrus and adjacent cortex (TTG+) in facial expressions and perioral movements. Methods: In 31 patients undergoing stereo-electroencephalography monitoring, we describe behavioral responses elicited by electrical stimulation within the TTG+. Task-induced high-gamma modulation (HGM), auditory evoked responses, and resting-state connectivity were used to investigate the cortical sites having different types of responses on electrical stimulation. Results: Changes in facial expressions and perioral movements were elicited on electrical stimulation within TTG+ in 9 (29%) and 10 (32%) patients, respectively, in addition to the more common language responses (naming interruptions, auditory hallucinations, paraphasic errors). All functional sites showed auditory task induced HGM and evoked responses validating their location within the auditory cortex, however, motor sites showed lower peak amplitudes and longer peak latencies compared to language sites. Significant first-degree connections for motor sites included precentral, anterior cingulate, parahippocampal, and anterior insular gyri, whereas those for language sites included posterior superior temporal, posterior middle temporal, inferior frontal, supramarginal, and angular gyri. Conclusions: Multimodal data suggests that TTG+ may participate in auditory-motor integration. Significance: TTG+ likely participates in facial expressions in response to emotional cues during an auditory discourse. (c) 2024 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Purpose Rasmussen encephalitis (RE) is a very rare chronic neurological disorder of unilateral inflammation of the cerebral cortex. Hemispherotomy provides the best chance at achieving seizure freedom in RE patients, but with significant risks and variable long-term outcomes. The goal of this study is to utilize our multicenter pediatric cohort to characterize if differences in pathology and/or imaging characterization of RE may provide a window into post-operative seizure outcomes, which in turn could guide decision-making for parents and healthcare providers. Methods This multi-institutional retrospective review of medical record, imaging, and pathology samples was approved by each individual institution’s review board. Data was collected from all known pediatric cases of peri-insular functional hemispherotomy from the earliest available electronic medical records. Mean follow-up time was 4.9 years. Clinical outcomes were measured by last follow-up visit using both Engel and ILAE scoring systems. Relationships between categorical and continuous variables were analyzed with Pearson correlation values. Results Twenty-seven patients met study criteria. No statistically significant correlations existed between patient imaging and pathology data. Pathology stage, MRI brain imaging stages, and a combined assessment of pathology and imaging stages showed no statistically significant correlation to post-operative seizure freedom rates. Hemispherectomy Outcome Prediction Scale scoring demonstrated seizure freedom in only 71% of patients receiving a score of 1 and 36% of patients receiving a score of 2 which were substantially lower than predicted. Conclusions Our analysis did not find evidence for either independent or combined analysis of imaging and pathology staging being predictive for post peri-insular hemispherotomy seizure outcomes, prompting the need for other biomarkers to be explored. Our data stands in contrast to the recently proposed Hemispherectomy Outcome Prediction Scale and does not externally validate this metric for an RE cohort.

OBJECTIVE:We evaluated changes in cognitive domains after neurosurgical lesioning of cortical sites with significant high-gamma power modulations (HGM) during a visual naming task, although these sites were found language-negative on standard-of-care electrical stimulation mapping (ESM). METHODS:In drug-resistant epilepsy patients who underwent resection/ablation after stereo-electroencephalography (SEEG), we computed reliable change indices (RCIs) from a battery of presurgical and 1-year postsurgical neuropsychological assessments. We modeled RCIs as a function of lesioning even one HGM language site, number of HGM language sites lesioned, and the magnitude of naming-related HGM. The analyses were adjusted for 1-year seizure freedom, operated hemispheres, and the volumes of surgical lesions. RESULTS:In 37 patients with 4455 SEEG electrode contacts (1839 and 2616 contacts in right and left hemispheres, respectively), no ESM language sites were lesioned. Patients with lesioning of even one HGM language site showed significantly lower RCIs for Peabody Picture Vocabulary Test (PPVT), working memory, and verbal learning immediate (VLI) scores. RCI declines with higher number of HGM language sites lesioned were seen in PPVT (slope [β] = -.10), working memory (β = -.10), VLI (β = -.14), and letter-word identification (LWI; β = -.14). No neuropsychological domains improved after lesioning of HGM language sites. Significant effects of the HGM magnitude at lesioned sites were seen on working memory (β = -.31), story memory immediate (β = -.27), verbal learning recognition (β = -.18), LWI (β = -.16), spelling (β = -.49), and passage comprehension (β = -.33). Because working memory was significantly affected in all three analyses, patients with maximal working memory decline were examined post hoc, revealing that all such patients had HGM naming sites lesioned in the posterior quadrants of either hemisphere. SIGNIFICANCE:HGM language mapping should be used as an adjunct to ESM in clinical practice and may help counsel patients/families about postsurgical cognitive deficits.

BACKGROUND AND OBJECTIVES: Programmable shunt valves (PSVs) used to treat hydrocephalus require specialized valve-specific devices that determine their setting. However, these devices are typically only accessible in major medical centers. This study explores the feasibility of using smartphone magnetometers to assess PSV settings. METHODS: We investigated 2 PSVs, the Codman Certas Plus and Medtronic Strata II, using 3 different smartphones. Free open-source software was used to measure magnetic flux densities of the shunts, and PSV-specific algorithms were developed to interpret these measurements. All measurements were performed ex vivo. RESULTS: We demonstrated that this method could accurately determine PSV settings with 100% accuracy in ex vivo blinded trials. The technique was effective even with a scalp analog simulating different skin thicknesses. CONCLUSION: This proof-of-concept study suggests that smartphones can be used for PSV assessment. However, further development and validation are needed to refine this method for clinical use. This technology could enhance PSV management accessibility, allowing for remote or at-home evaluations by trained individuals or caregivers, thus improving patient care in underserved areas.

OBJECTIVE:Electrical stimulation mapping (ESM) is the clinical standard for functional localization with subdural electrodes (SDE). As stereoelectroencephalography (SEEG) has emerged as an alternative option, we compared functional responses, afterdischarges (ADs), and unwanted ESM-induced seizures (EISs) between the two electrode types.METHODS:Incidence and current thresholds for functional responses (sensory, motor, speech/language), ADs, and EISs were compared between SDE and SEEG using mixed models incorporating relevant covariates.RESULTS:We identified 67 SEEG ESM and 106 SDE ESM patients (7207 and 4980 stimulated contacts, respectively). We found similar incidence of language and motor responses between electrode types; however, more SEEG patients reported sensory responses. ADs and EISs occurred less commonly with SEEG than SDE. Current thresholds for language, face motor, and upper extremity (UE) motor responses and EIS significantly decreased with age. However, they were not affected by electrode type, premedication, or dominant hemispheric stimulation. AD thresholds were higher with SEEG than with SDE. For SEEG ESM, language thresholds remained below AD thresholds up to 26 years of age, whereas this relationship was inverse for SDE. Also, face and UE motor thresholds fell below AD thresholds at earlier ages for SEEG than SDE. AD and EIS thresholds were not affected by premedication.SIGNIFICANCE:SEEG and SDE have clinically relevant differences for functional brain mapping with electrical stimulation. Although evaluation of language and motor regions is comparable between SEEG and SDE, SEEG offers a higher likelihood of identifying sensory areas. A lower incidence of ADs and EISs, and a favorable relationship between functional and AD thresholds suggest superior safety and neurophysiologic validity for SEEG ESM than SDE ESM.

BACKGROUND AND PURPOSE:We analyzed the association of neuropsychological outcomes after epilepsy surgery with the intracranial electrode type (stereo electroencephalography [SEEG] and subdural electrodes [SDE]), and electrical stimulation mapping (ESM) of speech/language. METHODS:Drug-resistant epilepsy patients who underwent comprehensive neuropsychological evaluation before and 1 year after epilepsy surgery were included. SEEG and SDE subgroups were matched by age, handedness, operated hemisphere, and seizure freedom. Postsurgical neuropsychological outcomes (adjusted for presurgical scores) and reliable change indices were analyzed as functions of electrode type and ESM. RESULTS:Ninety-nine patients aged 6-29 years were included with similar surgical resection/ablation volumes in the SEEG and SDE subgroups. Most of the neuropsychological outcomes were comparable between SEEG and SDE subgroups; however, Working Memory and Processing Speed were significantly improved in the SEEG subgroup. Undergoing language ESM was associated with significant improvements in Spelling, Letter-Word Identification, Vocabulary, Verbal Comprehension, Verbal Learning, and Story Memory scores, but a decline in Calculation scores. CONCLUSIONS:Intracranial evaluations with SEEG and SDE are comparable in terms of long-term postsurgical neuropsychological outcomes. Our data suggest that SEEG may be associated with improvements in working memory and processing speed, representing cognitive domains served by spatially distributed networks. Our study also supports wider use of language ESM before epilepsy surgery, preferably using other language tasks in addition to visual naming. Rather than the type of electrode, postsurgical neuropsychological outcomes are driven by whether language ESM was performed or not, with beneficial effects of language mapping.