Minimally Invasive, Endoscopic-Assisted Device for Subdural Electrode Implantation in Epilepsy

Endoscopic Epilepsy Surgery: Systematic Review and Meta-Analysis

Endoscopic epilepsy surgery is a fast emerging minimally invasive alternative to open surgery. The approach minimizes the extent of bone and brain resection and reduces surgical morbidity. This systematic review and meta-analysis sought to evaluate the favorable outcome of seizure improvement in patients undergoing endoscopic epilepsy surgery. The search was conducted by two independent researchers using PubMed and Web of Science until January 2023 to find studies reporting results of patients who underwent endoscopic epilepsy surgery. We extracted data on the clinical profile and outcomes of the patients from the eligible studies. Fifteen studies yielded 340 patients, of which 293 underwent endoscopic epilepsy surgery. The patient cohort consisted of 189 (55.6%) males. A total of 171 (58.3) patients had a favorable outcome of either Engel I or II or > 90% seizure control. Thirteen studies were included in our meta-analysis, and demonstrated improved seizure control after endoscopic epilepsy surgery, with a pooled seizure freedom rate of 58% (95% CI: 0.43-0.71, I 2  = 77.1%, τ 2  = 0.6836). Studies focusing on pediatric populations reported a higher proportion of positive outcomes, with a rate of 73.27% (95% CI: 62-82%, I 2  = 0.0%). In comparison, mixed-age populations showed a lower success rate of 48% (95% CI: 32-65%, I 2  = 79.0%). Furthermore, there was significant difference in treatment outcomes between the pediatric and mixed age groups ( p  = 0.014). The hypothalamic hamartomas (HH) patient population demonstrated a favorable outcome proportion of 61.71% (95% CI: 48.92-73.06%), with a moderate level of heterogeneity ( I 2  = 62.9%, tau 2  = 0.4266). Five patients developed postoperative complications, and there were three deaths. Our findings suggest that endoscopic epilepsy surgery is particularly effective in pediatric populations and among patients with HH, underscoring the importance of considering patient demographics and disease characteristics in clinical decision-making. The heterogeneity across studies necessitates cautious interpretation of the pooled results, advocating for tailored approaches in treatment planning. Prospective trials are required to establish class I evidence for the role of endoscopic epilepsy surgery compared with the recognized open surgical techniques.

"Mail-slot" Technique for Minimally Invasive Placement of Subdural Grid Electrodes: A Single-institution Experience

BACKGROUND

In the management of multi-drug-resistant focal epilepsies, intracranial electrode implantation is used for precise localization of the ictal onset zone. In select patients, subdural grid electrode implantation is utilized. Subdural grid placement traditionally requires large craniotomies to visualize the cortex prior to mapping. However, smaller craniotomies may enable shorter operations and reduced risks. We aimed to compare surgical outcomes between patients undergoing traditional large craniotomies with those undergoing tailored "mini" craniotomies (the "mail-slot" technique) for subdural grid placement.

METHODS

This retrospective cohort study included 23 patients who underwent subdural electrode implantation for epilepsy monitoring between 2014 and 2020. Patients were categorized into mini-craniotomies (n = 9) and traditional large craniotomies (n = 14) groups. Demographics, operative details, and outcomes were reviewed. Craniotomy size and number of electrodes were determined via post hoc radiographs.

RESULTS

Of the 23 patients studied, the mini group had smaller craniotomy sizes (mean: 22.71 cm2 vs. 65.17 cm2, P < 0.001) and higher electrode-to-size ratios (mean: 4.25 vs. 1.71, P < 0.0001). The mini group had slightly fewer total electrodes (mean: 88.67 vs. 107.43, P = 0.047). No significant differences were found in operative duration, blood loss, invasive electroencephalography duration, complications, or Engel scores between the groups. One patient per group required further invasive epilepsy monitoring for localization; all patients underwent therapeutic surgery.

CONCLUSIONS

Our findings suggest that mini-craniotomies for subdural grid placement in epilepsy monitoring offer significant advantages, including smaller craniotomy sizes and shorter operation durations, without compromising safety or efficacy. These results support the trend towards minimally invasive, patient-tailored surgical approaches in epilepsy treatment.

Smaller Knife, Fewer Seizures? Recent Advances in Minimally Invasive Techniques in Pediatric Epilepsy Surgery

Children with drug-resistant epilepsy are at high risk for developmental delay, increased mortality, psychiatric comorbidities, and requiring assistance with activities of daily living. Despite the advent of new and effective pharmacologic therapies, about one in 5 children will develop drug-resistant epilepsy, and most of these children continue to have seizures despite trials of other medication. Epilepsy surgery is often a safe and effective option which may offer seizure freedom or at least a significant reduction in seizure burden in many children. However, despite published evidence of safety and efficacy, epilepsy surgery remains underutilized in the pediatric population. Patient and family fears about the risks of surgery may contribute to this gap. Less invasive surgical techniques may be more palatable to children with epilepsy and their caregivers. In this review, we present recent advances in minimally invasive techniques for the surgical treatment of epilepsy as well as intriguing possibilities for the future. We describe the indications for, benefits of, and limits to minimally-invasive techniques including Stereo-encephalography, laser interstitial thermal ablation, deep brain stimulation, focused ultrasound, stereo-encephalography-guided radiofrequency ablation, endoscopic disconnections, and responsive neurostimulation.

Contribution of Ictal Source Imaging for Localizing Seizure Onset Zone in Patients With Focal Epilepsy

OBJECTIVE

To determine whether seizure onset zone (SOZ) can be localized accurately prior to surgical planning in patients with focal epilepsy, we performed noninvasive EEG recordings and source localization analyses on 39 patients.

METHODS

In 39 patients with focal epilepsy, we recorded and extracted 138 seizures and 1,325 interictal epileptic discharges using high-density EEG. We investigated a novel approach for directly imaging sources of seizures and interictal spikes from high-density EEG recordings, and rigorously validated it for noninvasive localization of SOZ determined from intracranial EEG findings and surgical resection volume. Conventional source imaging analyses were also performed for comparison.

RESULTS

Ictal source imaging showed a concordance rate of 95% when compared to intracranial EEG or resection results. The average distance from estimation to seizure onset (intracranial) electrodes is 1.35 cm in patients with concordant results, and 0.74 cm to surgical resection boundary in patients with successful surgery. About 41% of the patients were found to have multiple types of interictal activities; coincidentally, a lower concordance rate and a significantly worse performance in localizing SOZ were observed in these patients.

CONCLUSION

Noninvasive ictal source imaging with high-density EEG recording can provide highly concordant results with clinical decisions obtained by invasive monitoring or confirmed by resective surgery. By means of direct seizure imaging using high-density scalp EEG recordings, the added value of ictal source imaging is particularly high in patients with complex interictal activity patterns, who may represent the most challenging cases with poor prognosis.