Early implementation of stereoelectroencephalography in children: a multiinstitutional case series

Retained Intracerebral Depth Electrode after Stereotactic Electroencephalography Monitoring: A Case Report

Stereotactic electroencephalography (SEEG) is an increasingly popular surgical modality for localizing the epileptogenic zone. Robot-guided stereotactic electrode placement has been covered in Japan by National Health Insurance since 2020. However, several surgical devices, such as the anchor bolt (a thin, hollow, metal shaft that serves as a guide screw or fixing for each electrode), have not been approved. A 14-year-old female who underwent SEEG for intractable epilepsy and required additional surgery to remove a retained depth electrode from the skull after the SEEG monitoring was finished. She had uncontrolled focal seizures consisting of nausea and laryngeal constriction at the onset. After a comprehensive presurgical evaluation, robot-guided stereotactic electrode implantation was performed to evaluate her seizures by SEEG. Nine depth electrodes were implanted through the twist drill hole. The electrodes were sutured to her skin for fixation without anchor bolts. When we attempted to remove the electrodes after 8 days of SEEG monitoring, one of the electrodes was retained. The retained electrode was removed through an additional skin incision and a small craniectomy under general anesthesia. We confirmed narrowing of the twist drill hole pathway in the internal table of the skull due to osteogenesis, which locked the electrode. This complication might be avoided if an anchor bolt had been used. This case report prompts the approval of the anchor bolts to avoid difficulty in electrode removal. Moreover, approval of a depth electrode with a thinner diameter and more consistent hardness is needed.

Comparison of outcomes after stereoelectroencephalography and subdural grid monitoring in pediatric tuberous sclerosis complex

OBJECTIVE

Patients with tuberous sclerosis complex (TSC) epilepsy present with unique clinical challenges such as early seizure onset and high rates of intractability and multifocality. Although there are numerous studies about the safety and efficacy of stereoelectroencephalography (SEEG), this topic has not been studied in TSC patients who have distinct epilepsy profiles. The authors investigated subdural grid (SDG) and SEEG monitoring to determine whether these procedures lead to similar seizure and safety outcomes and to identify features unique to this pediatric population.

METHODS

TSC patients who underwent SDG or SEEG placement and a second epilepsy surgery during the period from 2007 to 2021 were included in this single-center retrospective cohort analysis. Various patient, hospitalization, and epilepsy characteristics were collected.

RESULTS

A total of 50 TSC patients were included in this study: 30 were included in the SDG cohort and 20 in the SEEG cohort. Baseline weekly seizure count did not significantly differ between the 2 groups (p = 0.412). The SEEG group had a greater mean baseline number of antiepileptic drugs (AEDs) (3.0 vs 2.0, p = 0.003), higher rate of previous surgical interventions (25% vs 0%, p = 0.007), and larger proportion of patients who underwent bilateral monitoring (50% vs 13.3%, p = 0.005). Despite this, there was no significant difference in seizure freedom between the SDG and SEEG cohorts. The mean reduction in seizure count was 84.9% and 47.8% of patients were seizure free at last follow-up (mean 79.4 months). SEEG trended toward being a safer procedure than SDG monitoring, with a shorter mean ICU stay (0.7 days vs 3.9 days, p < 0.001), lower blood transfusion rate (0% vs 13.3%, p = 0.140), and lower surgical complication rate (0% vs 10%, p = 0.265).

CONCLUSIONS

In the comparison of the SDG and SEEG cohorts, the SEEG group included patients who appeared to receive more aggressive management and have a higher rate of multifocality, more prior surgical interventions, more AEDs at baseline, and a higher rate of bilateral invasive monitoring. Despite this, the SEEG cohort had similar seizure outcomes and a trend toward increased safety. Based on these findings, SEEG appears to allow for monitoring of a wider breadth of TSC patients given its minimally invasive nature and its relative simplicity for monitoring numerous regions of the brain.

Stereoelectroencephalography before 2 years of age

OBJECTIVE

Stereoelectroencephalography (SEEG) is a widely used technique for localizing seizure onset zones prior to resection. However, its use has traditionally been avoided in children under 2 years of age because of concerns regarding pin fixation in the immature skull, intraoperative and postoperative electrode bolt security, and stereotactic registration accuracy. In this retrospective study, the authors describe their experience using SEEG in patients younger than 2 years of age, with a focus on the procedure’s safety, feasibility, and accuracy as well as surgical outcomes.

METHODS

A retrospective review of children under 2 years of age who had undergone SEEG while at Children’s Hospital of Philadelphia between November 2017 and July 2021 was performed. Data on clinical characteristics, surgical procedure, imaging results, electrode accuracy measurements, and postoperative outcomes were examined.

RESULTS

Five patients younger than 2 years of age underwent SEEG during the study period (median age 20 months, range 17–23 months). The mean age at seizure onset was 9 months. Developmental delay was present in all patients, and epilepsy-associated genetic diagnoses included tuberous sclerosis (n = 1), KAT6B (n = 1), and NPRL3 (n = 1). Cortical lesions included tubers from tuberous sclerosis (n = 1), mesial temporal sclerosis (n = 1), and cortical dysplasia (n = 3). The mean number of placed electrodes was 11 (range 6–20 electrodes). Bilateral electrodes were placed in 1 patient. Seizure onset zones were identified in all cases. There were no SEEG-related complications, including skull fracture, electrode misplacement, hemorrhage, infection, cerebrospinal fluid leakage, electrode pullout, neurological deficit, or death. The mean target point error for all electrodes was 1.0 mm. All patients proceeded to resective surgery, with a mean follow-up of 21 months (range 8–53 months). All patients attained a favorable epilepsy outcome, including Engel class IA (n = 2), IC (n = 1), ID (n = 1), and IIA (n = 1).

CONCLUSIONS

SEEG can be safely, accurately, and effectively utilized in children under age 2 with good postoperative outcomes using standard SEEG equipment. With minimal modification, this procedure is feasible in those with immature skulls and guides the epilepsy team’s decision-making for early and optimal treatment of refractory epilepsy through effective localization of seizure onset zones.

Subdural electrodes versus stereoelectroencephalography for pediatric epileptogenic zone localization: a retrospective cohort study

OBJECTIVE

The objective of this study was to compare the relative safety and effectiveness of invasive monitoring with subdural electrodes (SDEs) and stereoelectroencephalography (sEEG) in pediatric patients with drug-resistant epilepsy.

METHODS

A retrospective cohort study was performed in 176 patients who underwent invasive monitoring evaluations at UPMC Children’s Hospital of Pittsburgh between January 2000 and September 2021. To examine differences between SDE and sEEG groups, independent-samples t-tests for continuous variables and Pearson chi-square tests for categorical variables were performed. A p value < 0.1 was considered statistically significant.

RESULTS

There were 134 patients (76%) in the SDE group and 42 (24%) in the sEEG group. There was a difference in the proportion with complications (17.9% in the SDE group vs 7.1% in the sEEG group, p = 0.09) and resection (75.4% SDE vs 21.4% sEEG, p < 0.01) between SDE and sEEG patients. However, there was no observable difference in the rates of postresection seizure freedom at 1-year clinical follow-up (60.2% SDE vs 75.0% sEEG, p = 0.55).

CONCLUSIONS

These findings reveal a difference in rates of surgical complications and resection between SDEs and sEEG. Larger prospective, multi-institutional pediatric comparative effectiveness studies may further explore these associations.