Selective Amygdalohippocampectomy

Comparative Efficacy of Neuromodulatory Strategies for Drug-Resistant Epilepsy: A Systematic Review and Meta-Analysis

OBJECTIVE

The study aims to evaluate the efficacy of neuromodulatory strategies for people who have drug-resistant epilepsy (DRE).

METHODS

We searched electronic repositories, including PubMed, Web of Science, Embase, and the Cochrane Library, for randomized controlled trials, their ensuing open-label extension studies, and prospective studies focusing on surgical or neuromodulation interventions for people with DRE. We used seizure frequency reduction as the primary outcome. A single-arm meta-analysis synthesized data across all studies to assess treatment effectiveness at multiple time points. A network meta-analysis evaluated the efficacy of diverse therapies in randomized controlled trials. Grading of Recommendations, Assessment, Development, and Evaluations was applied to evaluate the overall quality of the evidence.

RESULTS

Twenty-eight studies representing 2936 individuals underwent 10 treatments were included. Based on the cumulative ranking in the network meta-analysis, the top 3 neuromodulatory options were deep brain stimulation (DBS) with 27% probability, responsive neurostimulation (RNS) with 22.91%, and transcranial direct current stimulation with 24.31%. In the single-arm meta-analysis, in the short-to-medium term, seizure control is more effective with RNS than with invasive vagus nerve stimulation (inVNS), which in turn is slightly more effective than DBS, though the differences are minimal. However, in the long term, inVNS appears to be less effective than both DBS and RNS. Trigeminal nerve stimulation, transcranial magnetic stimulation, and transcranial alternating current stimulation did not demonstrate significant seizure frequency reduction.

CONCLUSIONS

Regarding long-term efficacy, RNS and DBS outperformed inVNS. While transcranial direct current stimulation and transcutaneous auricular VNS showed promise for treating DRE, further studies are needed to confirm their long-term efficacy.

Minimally Invasive Epilepsy Surgery

Surgery remains a critical and often necessary intervention for a subset of patients with epilepsy. The overarching objective of surgical treatment has consistently been to enhance the quality of life for these individuals, either by achieving seizure freedom or by eliminating debilitating seizure types. This review specifically examines minimally invasive surgical approaches for epilepsy. Contemporary advancements have introduced a range of treatments that offer increased safety and efficacy compared to traditional open resective epilepsy surgeries. This manuscript provides a comprehensive review of these techniques and technologies.

Memory and executive functioning outcomes of selective amygdalohippocampectomy in patients with hippocampal sclerosis: A preliminary study in a developing country

Background

Selective amygdalohippocampectomy (SA) is an effective treatment for drug-resistant cases of epilepsy due to hippocampal sclerosis (HS). However, its neurocognitive outcomes are inconsistent across the previous studies, pointing to potential location-specific confounders. Here, we investigated the neurocognitive outcomes of SA in an Iranian center recently adopting this approach.

Methods

Thirty adults (53.3% of females, age 31.4 ± 6.2 years) with drug-resistant epilepsy due to HS were included in the study. Patients were stratified into surgical (n = 15) and medical (n = 15) treatment groups based on their preferences. Neurocognitive function was assessed before and 6 months after intervention using Wisconsin Card Sorting Test (WCST), Wechsler Adult Intelligence Scale-Revised, and Wechsler Memory Scale- Third Edition (WMS-III). Postintervention performance changes were compared between the two groups, and predictors of worse postoperative outcomes were investigated.

Results

Longitudinal changes of performance in WMS-III and WCST were significantly different between the surgically and medically treated patients. Postoperative WMS-III performance showed an average 25% decline (mean ∆T2-T1 = -25.1%, T = -6.6, P < 0.001), and WCST performance improved by an average of 49% (mean ∆T2-T1 = +49.1%, T = 4.6, P < 0.001). The decline in memory performance was more severe in the left-sided surgery and in patients with higher baseline education (mean ∆T2-T1 = -31.1%, T = -8.9, P < 0.001).

Conclusion

In our center, executive functioning improved or remained stable after SA, but memory functions declined moderately. The left-sided SA and higher education were associated with more severe decline in memory functions, highlighting the need for special considerations for these groups.

White Fiber Correlates of Amygdalohippocampectomy Through the Middle Temporal Gyrus Approach

OBJECTIVE

The white fiber and gross anatomy relevant for performing amygdalohippocampectomy through the middle temporal gyrus approach for mesial temporal sclerosis has been depicted by white fiber dissection.

METHODS

Three previously frozen and formalin fixed cerebral hemispheres were studied. The Klingler method of fiber dissection was used to study the anatomy. The primary tools used were hand-made wooden spatulas, forceps, and microscissors. The anatomy of the amygdala and hippocampus and the landmarks for performing the disconnection during epilepsy surgery are presented. The white fibers at risk during the middle temporal gyrus approach were studied.

RESULTS

The white fiber tracts at risk during the middle temporal gyrus approach for epilepsy surgery are the fibers of the inferior frontooccipital fasciculus, temporal extension of the anterior commissure, Meyer loop of the optic radiation, and uncinate fasciculus. On the basis of our anatomic dissections, we present a novel entry point into the temporal horn, potentially minimizing injury to the fibers of the sagittal stratum. We also propose novel landmarks to perform the amygdala disconnection in mesial temporal sclerosis.

CONCLUSIONS

The middle temporal gyrus is a commonly used approach to perform temporal lobectomy and amygdalohippocampectomy for patients with mesial temporal sclerosis. The anatomy relevant to the approach as presented will aid while performing epilepsy surgery.

Scalp-HFO indexes are biomarkers for the lateralization and localization of the epileptogenic zone in preoperative assessment

During the noninvasive evaluation phase for refractory epilepsy, the localization of the epileptogenic zone (EZ) is essential for the surgical protocols. Confirmation of laterality is required when the preoperative evaluation limits the EZ to bilateral anterior temporal lobes or bilateral frontal lobes. High-frequency oscillations (HFOs) are considered to be promising biological markers for the EZ. However, a large number of studies on HFOs stem from intracranial research. There were few quantitative measures for scalp HFOs, so we proposed a new method to quantify and analyze scalp HFOs. This method was called the "scalp-HFO index" (HI) and calculated in both the EZ and non-EZ. The calculation was based on the numbers and spectral power of scalp HFOs automatically detected. We labeled the brain lobes involved in the EZ as regions of interest (ROIs). The HIs based on the ripple numbers (n-HI) and spectral power (s-HI) were significantly higher in the ROI than in the contra-ROI (P = 0.012, P = 0.003), indicating that HIs contributed to the lateralization of EZ. The sensitivity and specificity of n-HI for the localization of the EZ were 90% and 79.58%, respectively, suggesting that n-HI was valuable in localizing the EZ. HI may contribute to the implantation strategy of invasive electrodes. However, few scalp HFOs were recorded when the EZ was located in the medial cortex region.NEW & NOTEWORTHY We proposed the scalp-high-frequency oscillation (HFO) index (HI) as a quantitative assessment method for scalp HFOs to locate the epileptogenic zone (EZ). Our results showed that the HI in regions of interest (ROIs) was significantly higher than in contra-ROIs. Sensitivity and specificity of HI based on ripple rates (n-HI) for EZ localization were 90% and 79.58%, respectively. If the n-HI of the brain region was >1.35, it was more likely to be an epileptogenic region. Clinical application of HIs as an indicator may facilitate localization of the EZ.

Extrapial Hippocampal Resection in Anterior Temporal Lobectomy: Technical Description and Clinical Outcomes in a 62-Patient Case Series

BACKGROUND

Anterior temporal lobectomy (ATL) is the most effective treatment for drug-resistant mesial temporal lobe epilepsy. Extrapial en bloc hippocampal resection facilitates complete removal of the hippocampus. With increasing use of minimally invasive treatments, considering open resection techniques that optimize the integrity of tissue specimens is important both for obtaining the correct histopathological diagnosis and for further study.

OBJECTIVE

To describe the operative strategy and clinical outcomes associated with an extrapial approach to hippocampal resection during ATL.

METHODS

A database of epilepsy surgeries performed by a single surgeon between October 2011 and February 2019 was reviewed to identify all patients who underwent ATL using an extrapial approach to hippocampal resection. To reduce confounding variables for outcome analysis, subjects with prior resections, tumors, and cavernous malformations were excluded. Seizure outcomes were classified using the Engel scale.

RESULTS

The surgical technique is described and illustrated with intraoperative images. A total of 62 patients met inclusion criteria (31 females) for outcome analysis. Patients with most recent follow-up <3 yr (n = 33) and >3 yr (n = 29) exhibited 79% and 52% class I outcomes, respectively. An infarct was observed on postoperative magnetic resonance imaging in 3 patients (1 asymptomatic and 2 temporarily symptomatic). An en bloc specimen in which the subiculum and all hippocampal subfields were preserved was obtained in each case. Examples of innovative research opportunities resulting from this approach are presented.

CONCLUSION

Extrapial resection of the hippocampus can be performed safely with seizure freedom and complication rates at least as good as those reported with the use of subpial techniques.

Potential surgical therapies for drug-resistant focal epilepsy

Drug-resistant focal epilepsy (DRFE), defined by failure of two antiepileptic drugs, affects 30% of epileptic patients. Epilepsy surgeries are alternative options for this population. Preoperative evaluation is critical to include potential candidates, and to choose the most appropriate procedure to maximize efficacy and simultaneously minimize side effects. Traditional procedures involve open skull surgeries and epileptic focus resection. Alternatively, neuromodulation surgeries use peripheral nerve or deep brain stimulation to reduce the activities of epileptogenic focus. With the advanced improvement of laser-induced thermal therapy (LITT) technique and its utilization in neurosurgery, magnetic resonance-guided LITT (MRgLITT) emerges as a minimal invasive approach for drug-resistant focal epilepsy. In the present review, we first introduce drug-resistant focal epilepsy and summarize the indications, pros and cons of traditional surgical procedures and neuromodulation procedures. And then, focusing on MRgLITT, we thoroughly discuss its history, its technical details, its safety issues, and current evidence on its clinical applications. A case report on MRgLITT is also included to illustrate the preoperational evaluation. We believe that MRgLITT is a promising approach in selected patients with drug-resistant focal epilepsy, although large prospective studies are required to evaluate its efficacy and side effects, as well as to implement a standardized protocol for its application.

Surgical Treatments of Epilepsy

Nearly 30% of epilepsy patients are refractory to medical therapy. Surgical management of epilepsy is an increasingly viable option for these patients. Although surgery has historically been used as a palliative option, improvements in technology and outcomes show its potential in certain subsets of patients. This article reviews the two main categories of surgical epilepsy treatment-resective surgery and neuromodulation. Resective surgery includes temporal lobe resections, extratemporal resections, laser interstitial thermal therapy, and disconnection procedures. We discuss the three main types of neuromodulation-vagal nerve stimulation, responsive neurostimulation, and deep brain stimulation for epilepsy. The history and indications are explored for each type of treatment. Given the myriad types of resection and neuromodulation techniques, patient selection is reviewed in detail, with a discussion on which patients are most likely to benefit from different treatment strategies. We also discuss outcomes with examples of the pertinent landmark trials and their results. Finally, complications and surgical technique are reviewed. As new indications emerge and patient selection is refined, surgical management will continue to evolve as an adjuvant therapy for epileptic patients.

Multiple hippocampal transections for refractory pediatric mesial temporal lobe epilepsy: seizure and neuropsychological outcomes

OBJECTIVE

Temporal lobe epilepsy (TLE) is the most common focal epilepsy across adult and pediatric age groups. It is also the most amenable to surgery, with excellent long-term seizure outcome. Most TLE cases have an epileptogenic zone in the mesial temporal structures, namely the hippocampus. Resecting the dominant hippocampus has been shown to be associated with significant verbal memory deficits, especially in patients with intact verbal memory scores presurgically. Multiple hippocampal transection (MHT) is a relatively new surgical technique designed to interrupt the longitudinal hippocampal circuitry involved in seizure propagation yet preserve the circular fibers involved in memory function. This technique has been used to treat mesial TLE in both dominant- and nondominant-hemisphere cases, almost exclusively in adults. It has been applied to normal and sclerotic hippocampi.

METHODS

In this study, information on 3 pediatric patients who underwent MHT for mesial TLE at Children's Wisconsin between 2017 and 2018 is included. Clinical, electroencephalographic, and neuropsychological features and outcomes are described in detail.

RESULTS

MRI revealed a tumor in the amygdala with a normal hippocampus in 1 patient and hippocampal sclerosis in 2 patients. All patients underwent stereoelectroencephalography confirming the involvement of the hippocampus in seizure onset. MHTs were completed under intraoperative monitoring, with amygdala and temporal tip resection in all patients due to early spread to these regions. All patients had excellent seizure outcomes at 1 year, and 2 of the 3 patients remain seizure free at last follow-up (range 20-36 months), all with stable or improved neuropsychological profiles, including verbal memory.

CONCLUSIONS

MHT is a relatively new surgical procedure designed to preserve essential memory circuitry while disrupting seizure propagation pathways in the hippocampus. A growing body of literature shows good seizure and neuropsychological results, but mainly in adults. This is the first series of MHTs used exclusively in children at one medical center, showcasing excellent seizure control and preservation of neuropsychological functioning. One of the patients is also the first described to have MHT in the setting of an amygdalar tumor abutting the hippocampus, further expanding the pathological setting in which MHT can be used effectively.

Procedure-Related Temporal Infarct After Retractorless Transsylvian Selective Amygdalohippocampectomy and Impact on 2-Year Epilepsy Outcome

BACKGROUND

Selective amygdalohippocampectomy (SAH) is designed to treat patients with mesial temporal lobe epilepsy (MTLE).

OBJECTIVE

To determine the volume and impact of temporal lobe infarction after retractorless transsylvian SAH (en bloc resection of the hippocampus) that have not been reported.

METHODS

A retrospective analysis of patients treated with retractorless transsylvian SAH. Infarctions were detected by magnetic resonance imaging (MRI) within the first week after the operation. Neuropsychological testing was performed preoperatively and 6 mo later. Seizure outcome was evaluated 2 yr after epilepsy surgery.

RESULTS

Between 2010 and 2014, a total of 30 patients were included in this study. Analysis of postoperative MRI showed the following: (1) mean removal volume of the hippocampus-parahippocampus was 5.72 cm3, and (2) mean volumes of temporal and insular infarctions were 1.71 and 0.25 cm3, respectively. Twenty-five patients (83.3%) were free of disabling seizures (Engel class I) at 2 yr of outcome. Neuropsychological testing revealed improvement in Perceptual Organization Index (P = .036) and verbal paired associates II (P = .014) after the operation. Neither infarction volume nor removal volume was related to epilepsy outcome in linear regression model.

CONCLUSION

Transsylvian SAH has comparable seizure outcomes but bears inherent risks of vasospasm/vascular injury. Immediate postoperative small infarction volume around resection cavity or along surgical corridor was noticed after retractorless transsylvian SAH, which did not cause neuropsychological deteriorations, in contrast to previous study with the use of self-sustaining rigid retraction system. Further study should be performed to compare procedure-related infarctions and their impacts on neuropsychological outcomes in different selective approaches.

Systematic review and network meta-analysis of resective surgery for mesial temporal lobe epilepsy

OBJECTIVE

To evaluate the effectiveness of anterior temporal lobectomy (ATL) versus selective amygdalohippocampectomy (SAH) on seizure-free outcome in patients with temporal lobe epilepsy, using both direct and indirect evidence from the literature.

METHODS

MEDLINE, Embase and Cochrane databases were searched for original research articles and systematic reviews comparing ATL versus SAH, and ATL or SAH versus medical management (MM). The outcome was seizure freedom at 12 months of follow-up or longer. Direct pairwise meta-analyses were conducted, followed by a random-effect Bayesian network meta-analysis (NMA) combining direct and indirect evidence.

RESULTS

Twenty-eight articles were included (18 compared ATL vs SAH, 1 compared ATL vs SAH vs MM, 8 compared ATL vs MM, and 1 compared SAH vs MM). Direct pairwise meta-analyses showed no significant differences in seizure-free outcome of ATL versus SAH (OR 1.14, 95% CI 0.93 to 1.39; p=0.201), but the odds of seizure-free outcome were higher for ATL versus MM (OR 29.16, 95% CI 10.44 to 81.50; p<0.00001), and SAH versus MM (OR 28.42, 95% CI 10.17 to 79.39; p<0.00001). NMA also showed that the odds of seizure-free outcome were no different in ATL versus SAH (OR 1.15, 95% credible interval (CrI) 0.84-1.15), but higher for ATL versus MM (OR 27.22, 95% CrI 15.38-27.22), and SAH versus MM (OR 23.57, 95% CrI 12.67-23.57). There were no significant differences between direct and indirect comparisons (all p>0.05).

CONCLUSION

Direct evidence, indirect evidence and NMA did not identify a difference in seizure-free outcome of ATL versus SAH.

Drug-Resistant Epilepsy and Surgery

BACKGROUND

Epilepsy is a chronic brain disease that is caused by various factors and characterized by recurrent, episodic and temporary central nervous system dysfunction which results due to excessive discharge of brain neurons. In the past decades, despite the continuous development of antiepileptic drugs, there are still many patients with epilepsy progressing to drugresistant epilepsy. Currently, surgical treatment is one of important way to cure drug-resistant epilepsy.

METHODS

Data were collected from Web of Science, Medline, Pubmed, through searching of these keywords: "surgery" and "drug-resistant epilepsy".

RESULTS

An increasing number of studies have shown that surgery plays an important role in the treatment of drug-resistant epilepsy. Moreover, the comprehensive treatment mainly based on surgery can achieve the remission and even cure of drug-resistant epilepsy.

CONCLUSION

In this review, we discuss the pathogenesis of drug-resistant epilepsy and the comprehensive treatment mainly based on surgery; this review may provide a reference for the clinical treatment of drug-resistant epilepsy.

Mesial temporal lobe epilepsy: long-term seizure outcome of patients primarily treated with transsylvian selective amygdalohippocampectomy

OBJECTIVE The aim of this study was to present long-term seizure outcome data in a consecutive series of patients with refractory mesial temporal lobe epilepsy primarily treated with transsylvian selective amygdalohippocampectomy (SAHE). METHODS The authors retrospectively analyzed prospectively collected data for all patients who had undergone resective surgery for medically refractory epilepsy at their institution between July 1994 and December 2014. Seizure outcome was assessed according to the International League Against Epilepsy (ILAE) and the Engel classifications. RESULTS The authors performed an SAHE in 158 patients (78 males, 80 females; 73 right side, 85 left side) with a mean age of 37.1 ± 10.0 years at surgery. Four patients lost to follow-up and 1 patient who committed suicide were excluded from analysis. The mean follow-up period was 9.7 years. At the last available follow-up (or before reoperation), 68 patients (44.4%) had achieved an outcome classified as ILAE Class 1a, 46 patients (30.1%) Class 1, 6 patients (3.9%) Class 2, 16 patients (10.4%) Class 3, 15 patients (9.8%) Class 4, and 2 patients (1.3%) Class 5. These outcomes correspond to Engel Class I in 78.4% of the patients, Engel Class II in 10.5%, Engel Class III in 8.5%, and Engel Class IV in 2.0%. Eleven patients underwent a second surgery (anterior temporal lobectomy) after a mean of 4.4 years from the SAHE (left side in 6 patients, right side in 5). Eight (72.7%) of these 11 patients achieved seizure freedom. The overall ILEA seizure outcome since (re)operation after a mean follow-up of 10.0 years was Class 1a in 72 patients (47.0%), Class 1 in 50 patients (32.6%), Class 2 in 7 patients (4.6%), Class 3 in 15 patients (9.8%), Class 4 in 8 patients (5.2%), and Class 5 in 1 patient (0.6%). These outcomes correspond to an Engel Class I outcome in 84.3% of the patients. CONCLUSIONS A satisfactory long-term seizure outcome following transsylvian SAHE was demonstrated in a selected group of patients with refractory temporal lobe epilepsy.

Neuropsychological outcomes following stereotactic laser amygdalohippocampectomy

OBJECTIVE

The objective was to analyze neuropsychological testing data from 15 patients before and after stereotactic laser ablation surgery for temporal lobe epilepsy and to describe the seizure outcomes after stereotactic laser ablation surgery.

METHODS

A retrospective review of 15 patients who underwent stereotactic laser ablation and who also underwent neuropsychological testing before and after surgery was performed. Verbal and visual memory was assessed in all 15 patients using California Verbal Learning Test and Wechsler Memory Scale IV. Naming was assessed in 9 of 15 patients using the Boston Naming Test. Statistical analysis was performed to determine clinically significant changes using previously validated reliable change indices and proprietary Advanced Clinical Solutions software. Seizure outcome data were evaluated using Engel classification.

RESULTS

Postsurgery neuropsychological evaluation demonstrated that all 15 patients experienced at least 1 clinically significant decline in either verbal or visual memory. Ten patients in this series, including five with dominant-hemisphere surgery, demonstrated decline in delayed memory for narrative information (Logical Memory II). By contrast, the Boston Naming Test demonstrated more favorable results after surgery. Two of nine patients demonstrated a clinically significant increase in naming ability, and only one of nine patients demonstrated a clinically significant decline in naming ability. With at least 6months of follow-up after surgery, 33% reported seizure freedom.

CONCLUSION

Stereotactic laser ablation can result in clinically significant and meaningful decline in verbal and visual memory when comparing patients to their own presurgical baseline. Naming ability, conversely, is much less likely to be impacted by stereotactic laser ablation and may improve after the procedure.

Innovations in Functional Neurosurgery and Anesthetic Implications

Functional neurosurgery has undergone rapid growth over the last few years fueled by advances in imaging technology and novel treatment modalities. These advances have led to new surgical treatments using minimally invasive and precise techniques for conditions such as Parkinson's disease, essential tremor, epilepsy, and psychiatric disorders. Understanding the goals and technological issues of these procedures is imperative for the anesthesiologist to ensure safe management of patients presenting for functional neurosurgical procedures. In this review, we discuss the advances in neurosurgical techniques for deep brain stimulation, focused ultrasound and minimally invasive laser-based treatment of refractory epilepsy and provide a guideline for anesthesiologists caring for patients undergoing these procedures.