Stereotactic MRI-guided laser interstitial thermal therapy for extratemporal lobe epilepsy

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.

Modeling for neurosurgical laser interstitial thermal therapy with and without intracranial recording electrodes

Laser thermal ablation has become a prominent neurosurgical treatment approach, but in epilepsy patients it cannot currently be safely implemented with intracranial recording electrodes that are used to study interictal or epileptiform activity. There is a pressing need for computational models of laser interstitial thermal therapy (LITT) with and without intracranial electrodes to enhance the efficacy and safety of optical neurotherapies. In this paper, we aimed to build a biophysical bioheat and ray optics model to study the effects of laser heating in the brain, with and without intracranial electrodes in the vicinity of the ablation zone during the LITT procedure. COMSOL Multiphysics finite element method (FEM) solver software was used to create a bioheat thermal model of brain tissue, with and without blood flow incorporation via Penne's model, to model neural tissue response to laser heating. We report that the close placement of intracranial electrodes can increase the maximum temperature of the brain tissue volume as well as impact the necrosis region volume if the electrodes are placed too closely to the laser coupled diffuse fiber tip. The model shows that an electrode displacement of 4 mm could be considered a safe distance of intracranial electrode placement away from the LITT probe treatment area. This work, for the first time, models the impact of intracranially implanted recording electrodes during LITT, which could improve the understanding of the LITT treatment procedure on the brain's neural networks a sufficient safe distance to the implanted intracranial recording electrodes. We recommend modeling safe distances for placing the electrodes with respect to the infrared laser coupled diffuse fiber tip.

Magnetic Resonance-Guided Laser Interstitial Thermal Therapy in the Management of Hypothalamic Hamartomas: A Systematic Review and Meta-Analysis

OBJECTIVE

Magnetic resonance-guided laser interstitial thermal therapy (MRg-LITT) is a promising new technique to ablate epileptic foci in patients with hypothalamic hamartoma (HH). We aim to systematically synthesize all available evidence and determine the effectiveness of MRg-LITT in reducing seizures in patients with HH.

METHODS

We systematically searched MEDLINE (PubMed), Embase (Ovid), Scopus, and Google Scholar for all relevant articles. We used Open[Meta]Analyst to pool the number of seizure-free patients after MRg-LITT treatment in a random-effects model. Risk ratios were calculated, and subgroups were analyzed. Comprehensive meta-analysis was used to assess publication bias via funnel plots, Egger's regression test, and Begg's correlation test. This review complies with the Preferred Reporting Items for Systematic Review and Meta-Analyses guidelines.

RESULTS

After screening the titles, abstracts, and full texts, we included 17 articles in our meta-analysis, which revealed a 77.1% rate of seizure freedom (95% confidence interval 0.696-0.837, P<0.001), with moderate heterogeneity (I2=49.46%). Subgroup analysis by study design and sensitivity analyses excluding 1 study at a time did not impact the results substantially, and we found no evidence of publication bias. Adverse effects included electrolyte imbalances, weight gain, and transient neurologic disturbances.

CONCLUSIONS

MRg-LITT might be a feasible and effective technique for ablation of epileptic foci, leading to seizure freedom in a large proportion of patients with HH. However, there is a paucity of literature on the topic, and prospective clinical trials with larger number of participants comparing MRg-LITT to open surgery are needed.

Magnetic resonance-guided laser interstitial thermal therapy versus open surgical corpus callosotomy for pediatric refractory epilepsy: A systematic review and meta-analysis

PURPOSE

Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) is a novel, minimally invasive alternative to traditional open surgery corpus callosotomy (CC). We aim to compare both approaches in terms of time of hospitalization and surgical procedure, complications, and efficacy outcomes.

METHODS

A systematic search on PubMed, Embase, Web of Science, and Cochrane Library databases was performed for studies directly comparing MRgLITT and open surgery for refractory epilepsy in children.

RESULTS

A total of 240 patients from five studies were included. There was no statistically significant difference observed between the two groups regarding the favorable Engel outcome. (RR 0.89; 95 % CI 0.70-1.14; p = 0.36; I2=0 %) The mean hospital length of stay (LOS) was significantly shorter in the patients who underwent MRgLITT. (MD -2.84 days; 95 % CI [-3.17]-[-2.51] days; p < 0.00001; I2=90 %) The mean operation duration was significantly longer in the intervention group. (MD 1.38 h; 95 % CI 0.64- 2.12 h; p = 0.00002; I2=55 %). The mean blood loss was significantly lower in patients who underwent MRgLITT. (MD -75.15 ml; 95 % CI [-92.82]-[-57.48] ml; p < 0.00001; I2=0 %) CONCLUSION: CC is a valuable option for treating RE, especially in children. The open surgery bears the stigma of an invasive and complicated technique which might justify its underuse. MRgLITT is a great alternative and possibly a way to widen the use of callosotomy in children, however, its cost and availability may be a challenge.

Laser interstitial thermal therapy of a single nodule in a complex epileptic network with multiple periventricular nodular heterotopias

Surgical management of drug-resistant epilepsy (DRE) in patients with multiple periventricular nodular heterotopias (PVNHs) is challenging. Identifying the location of seizure onset within these complex epileptic networks is difficult, and open resection carries risks of injury to surrounding functional white matter tracts such as optic radiations (ORs). The authors demonstrate tractography-assisted laser ablation of a single nodule in a patient with DRE and multiple PVNHs. Following surgery, visual fields were intact, highlighting the benefits of OR tractographic reconstruction. At 12 months postoperatively, the patient remained seizure free, suggesting the potential efficacy of targeting a single heterotopia within complex networks in well-selected cases. The video can be found here: https://stream.cadmore.media/r10.3171/2024.4.FOCVID2417.

Current role of magnetic resonance imaging on assessing and monitoring the efficacy of phototherapy

Phototherapy, also known as photobiological therapy, is a non-invasive and highly effective physical treatment method. Its broad use in clinics has led to significant therapeutic results. Phototherapy parameters, such as intensity, wavelength, and duration, can be adjusted to create specific therapeutic effects for various medical conditions. Meanwhile, Magnetic Resonance Imaging (MRI), with its diverse imaging sequences and excellent soft-tissue contrast, provides a valuable tool to understand the therapeutic effects and mechanisms of phototherapy. This review explores the clinical applications of commonly used phototherapy techniques, gives a brief overview of how phototherapy impacts different diseases, and examines MRI's role in various phototherapeutic scenarios. We argue that MRI is crucial for precise targeting, treatment monitoring, and prognosis assessment in phototherapy. Future research and applications will focus on personalized diagnosis and monitoring of phototherapy, expanding its applications in treatment and exploring multimodal imaging technology to enhance diagnostic and therapeutic precision and effectiveness.

Negative MRI and a seizure onset zone close to eloquent areas in FCD type II: Application of MRg-LiTT after a SEEG re-evaluation in pediatric patients with a previous failed surgery

OBJECTIVE

Negative MRI and an epileptogenic zone (EZ) adjacent to eloquent areas are two main issues that can be encountered during pre-surgical evaluation for epilepsy surgery. Focal Cortical Dysplasia type II (FCD type II) is the most common aetiology underlying a negative MRI. The objective of this study is to present three cases of pediatric patients exhibiting negative MRI and a seizure onset zone close to eloquent areas, who previously underwent traditional open surgery or SEEG-guided radiofrequency thermocoagulations (RF-TC). After seizure seizure recrudescence, pre-surgical SEEG was re-evaluated and Magnetic Resonance-guided laser interstitial thermal therapy (MRg-LiTT) was performed. We discuss the SEEG patterns, the planning of laser probes trajectories and the outcomes one year after the procedure.

METHODS

Pediatric patients who underwent SEEG followed by MRg-LiTT for drug-resistant epilepsy associated with FCD type II at our Centre were included. Pre-surgical videoEEG (vEEG), stereoEEG (sEEG), and MRI were reviewed. Post-procedure clinical outcome (measured by Engel score) and complications rates were evaluated.

RESULTS

Three patients underwent 3 MRg-LiTT procedures from January 2022 to June 2022. Epileptogenic zone was previously studied via SEEG in all the patients. All the three patients pre-surgical MRI was deemed negative. Mean age at seizure onset was 47 months (21-96 months), mean age at MRg-LiTT was 12 years (10 years 10 months - 12 years 9 months). Engel class Ia outcome was achieved in patients #2 and #3, Engel class Ib in patient #1. Mean follow-up length was of 17 months (13 months - 20 months). Complications occurred in one patient (patient #2, extradural hematoma).

CONCLUSIONS

The combined use of SEEG and MRg-LiTT in complex cases can lead to good outcomes both as a rescue therapy after failed surgery, but also as an alternative to open surgery after a successful SEEG-guided Radiofrequency Thermocoagulation (RF-TC). Specific SEEG patterns and a previous good outcome from RF-TC can be predictors of a favourable outcome.

Stereoelectroencephalography-guided laser ablation in neocortical epilepsy: Electrophysiological correlations and outcome

OBJECTIVE

We aimed to study the correlation between seizure outcomes in patients with drug-resistant epilepsy (DRE) who underwent laser interstitial thermal therapy (LITT) and stereoelectroencephalographic electrophysiologic patterns with respect to the extent of laser ablation.

METHODS

We retrospectively analyzed 16 consecutive DRE patients who underwent LITT. A seizure onset zone (SOZ) was obtained from multidisciplinary patient management conferences and again was confirmed independently by two epileptologists based on conventional analysis. SOZs were retrospectively divided into localized, lobar and multilobar, and nonlocalized onset types. A posteriori-predicted epileptogenic zone (PEZ) was identified using the previously developed "EZ fingerprint" pipeline. The completeness of the SOZ and PEZ ablation was compared and correlated with the duration of seizure freedom (SF).

RESULTS

Of 16 patients, 11 had an a posteriori-identified PEZ. Three patients underwent complete ablation of SOZ with curative intent, and the other 13 with palliative intent. Of three patients with complete ablation of the SOZ, two had concordant PEZ and SOZ and achieved 40- and 46-month SF without seizure recurrence. The remaining patient, without any PEZ identified, had seizure recurrence within 1 month. Six of 13 patients with partial ablation of the SOZ and PEZ achieved mean seizure freedom of 19.8 months (range = 1-44) with subsequent seizure recurrence. The remaining seven patients had partial ablation of the SOZ without the PEZ identified or ablation outside the PEZ with seizure recurrence within 1-2 months, except one patient who had 40-month seizure freedom after ablation of periventricular heterotopia.

SIGNIFICANCE

Only complete ablation of the well-restricted SOZ concordant with the PEZ was associated with long-term SF, whereas partial ablation of the PEZ might lead to SF with eventual seizure recurrence. Failure to identify PEZ and ablation limited to the SOZ often led to 1-2 months of SF.

Posterior Cingulate Epilepsy: A Systematic Review

SUMMARY

In this review, authors discuss epilepsy originating from posterior cingulate regions, a challenging entity to diagnose and most likely underrecognized. A systematic review of posterior middle and posterior cingulate epilepsy cases was conducted to present a summary of current knowledge about this localization-based type of epilepsy. The literature search identified 32 articles, for a total of 69 patients (34 with posterior middle cingulate epilepsy [pMCE] and 35 with posterior cingulate epilepsy [PCE]). Most patients were children and young adults with drug-resistant lesional epilepsy with high seizure burden. In both groups, most patients reported auras, mainly sensory, but various types were reported, including autonomic, behavioral, and cognitive manifestations. Most pMCE and PCE showed motor manifestations (mainly respectively asymmetric tonic posturing and automotor features). Impaired awareness during seizures was more frequently reported in PCE than in pMCE. As for ictal scalp EEG, epileptogenic abnormalities were poorly lateralized and did not localize the seizure onset zone. An ictal temporal involvement was only observed in PCE. Interictal EEG findings were nonspecific. As for other presurgical noninvasive investigations, data are limited, and no studies have adequately assessed their value. Partly explained by our inclusion criteria, most patients underwent a surgical procedure (either lesionectomy or resection of epileptogenic zone as defined by intracranial EEG study results), which overall yielded good outcomes.

Stereoelectroencephalography-guided radiofrequency ablation of the epileptogenic zone as a treatment and predictor of future success of further surgical intervention

OBJECTIVE

Stereoelectroencephalography (SEEG)-guided radiofrequency ablation (RFA) is increasingly being used as a treatment for drug-resistant localization-related epilepsy. The aim of this study is to analyze the successes and failures using RFA and how response correlates with surgical epilepsy treatment outcomes.

METHODS

We retrospectively reviewed 62 patients who underwent RFA via SEEG electrodes. After excluding five, the remaining 57 were classified into subgroups based on procedures and outcomes. Forty patients (70%) underwent a secondary surgical procedure, of whom 32 were delayed: 26 laser interstitial thermal therapy (LITT), five resection, one neuromodulation. We determined the predictive value of RFA outcome upon subsequent surgical outcome by categorizing the delayed secondary surgery outcome as success (Engel I/II) versus failure (Engel III/IV). Demographic information, epilepsy characteristics, and the transient time of seizure freedom after RFA were calculated for each patient.

RESULTS

Twelve of 49 patients (24.5%) who had RFA alone and delayed follow-up achieved Engel class I. Of the 32 patients who underwent a delayed secondary surgical procedure, 15 achieved Engel class I and nine Engel class II (24 successes), and eight were considered failures (Engel class III/IV). The transient time of seizure freedom after RFA was significantly longer in the success group (4 months, SD = 2.6) as compared to the failure group (.75 months, SD = 1.16; p < .001). Additionally, there was a higher portion of preoperative lesional findings in patients in the RFA alone and delayed surgical success group (p = .03) and a longer time to seizure recurrence in the presence of lesions (p < .05). Side effects occurred in 1% of patients.

SIGNIFICANCE

In this series, RFA provided a treatment during SEEG-guided intracranial monitoring that led to seizure freedom in ~25% of patients. Of the 70% who underwent delayed surgery, longer transient time of seizure freedom after RFA was predictive of the results of the secondary surgeries, 74% of which were LITT.

Magnetic resonance-guided laser interstitial thermal therapy for drug-resistant epilepsy: A systematic review and individual participant data meta-analysis

Magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has emerged as a popular minimally invasive alternative to open resective surgery for drug-resistant epilepsy (DRE). We sought to perform a systematic review and individual participant data meta-analysis to identify independent predictors of seizure outcome and complications following MRgLITT for DRE. Eleven databases were searched from January 1, 2010 to February 6, 2021 using the terms "MR-guided ablation therapy" and "epilepsy". Multivariable mixed-effects Cox and logistic regression identified predictors of time to seizure recurrence, seizure freedom, operative complications, and postoperative neurological deficits. From 8705 citations, 46 studies reporting on 450 MRgLITT DRE patients (mean age = 29.5 ± 18.1 years, 49.6% female) were included. Median postoperative seizure freedom and follow-up duration were 15.5 and 19.0 months, respectively. Overall, 240 (57.8%) of 415 patients (excluding palliative corpus callosotomy) were seizure-free at last follow-up. Generalized seizure semiology (hazard ratio [HR] = 1.78, p = .020) and nonlesional magnetic resonance imaging (MRI) findings (HR = 1.50, p = .032) independently predicted shorter time to seizure recurrence. Cerebral cavernous malformation (CCM; odds ratio [OR] = 7.97, p < .001) and mesial temporal sclerosis/atrophy (MTS/A; OR = 2.21, p = .011) were independently associated with greater odds of seizure freedom at last follow-up. Operative complications occurred in 28 (8.5%) of 330 patients and were independently associated with extratemporal ablations (OR = 5.40, p = .012) and nonlesional MRI studies (OR = 3.25, p = .017). Postoperative neurological deficits were observed in 53 (15.1%) of 352 patients and were independently predicted by hypothalamic hamartoma etiology (OR = 5.93, p = .006) and invasive electroencephalographic monitoring (OR = 4.83, p = .003). Overall, MRgLITT is particularly effective in treating patients with well-circumscribed lesional DRE, such as CCM and MTS/A, but less effective in nonlesional cases or lesional cases with a more diffuse epileptogenic network associated with generalized seizures. This study identifies independent predictors of seizure freedom and complications following MRgLITT that may help further guide patient selection.

Robotic Instruments Inside the MRI Bore: Key Concepts and Evolving Paradigms in Imaging-enhanced Cranial Neurosurgery

Intraoperative MRI has been increasingly used to robotically deliver electrodes and catheters into the human brain using a linear trajectory with great clinical success. Current cranial MR guided robotics do not allow for continuous real-time imaging during the procedure because most surgical instruments are not MR-conditional. MRI guided robotic cranial surgery can achieve its full potential if all the traditional advantages of robotics (such as tremor-filtering, precision motion scaling, etc.) can be incorporated with the neurosurgeon physically present in the MRI bore or working remotely through controlled robotic arms. The technological limitations of design optimization, choice of sensing, kinematic modeling, physical constraints, and real-time control had hampered early developments in this emerging field, but continued research and development in these areas over time has granted neurosurgeons far greater confidence in using cranial robotic techniques. This article elucidates the role of MR-guided robotic procedures using clinical devices like NeuroBlate and Clearpoint that have several thousands of cases operated in a "linear cranial trajectory" and planned clinical trials, such as LAANTERN for MR guided robotics in cranial neurosurgery using LITT and MR-guided putaminal delivery of AAV2 GDNF in Parkinson's disease. The next logical improvisation would be a steerable curvilinear trajectory in cranial robotics with added DOFs and distal tip dexterity to the neurosurgical tools. Similarly, the novel concept of robotic actuators that are powered, imaged, and controlled by the MRI itself is discussed in this article, with its potential for seamless cranial neurosurgery.

Withdrawal of antiseizure medications after MRI-Guided laser interstitial thermal therapy in extra-temporal lobe epilepsy

PURPOSE

This study investigated the success rate of antiseizure medications (ASMs) withdrawal following MRI Guided Laser Interstitial Thermal Therapy (MRg-LITT) for extra-temporal lobe epilepsy (ETLE), and identified predictors of seizure recurrence.

METHODS

We retrospectively assessed 27 patients who underwent MRg-LITT for ETLE. Patients' demographics, disease characteristics, and post-surgical outcomes were evaluated for their potential to predict seizure recurrence associated with ASMs withdrawal.

RESULTS

The median period of observation post MRg-LITT was 3 years (range 18 - 96 months) and the median period to initial ASMs reduction was 0.5 years (range 1-36 months). ASMs reduction was attempted in 17 patients (63%), 5 (29%) of whom had seizure recurrence after initial reduction. Nearly all patient who relapsed regained seizure control after reinstitution of their ASMs regimen. Pre-operative seizure frequency (p = 0.002) and occurrence of acute post-operative seizures (p = 0.01) were associated with increased risk for seizure recurrence post ASMs reduction. At the end of the observation period, 11% of patients were seizure free without drugs, 52% were seizure free with drugs and 37% still experienced seizures despite ASMs. Compared with pre-operative status, the number of ASMs was reduced in 41% of patients, unchanged in 55% of them and increased in only 4% of them.

CONCLUSIONS

Successful MRg-LITT for ETLE allows for ASMs reduction in a significant portion of patients and complete ASMs withdrawal in a subset of them. Patients with higher pre-operative seizure frequency or occurrence of acute post operative seizures exhibit higher chances relapse post ASMs reduction.

Seizure onset patterns predict outcome after stereo-electroencephalography-guided laser amygdalohippocampotomy

OBJECTIVE

Stereotactic laser amygdalohippocampotomy (SLAH) is an appealing option for patients with temporal lobe epilepsy, who often require intracranial monitoring to confirm mesial temporal seizure onset. However, given limited spatial sampling, it is possible that stereotactic electroencephalography (stereo-EEG) may miss seizure onset elsewhere. We hypothesized that stereo-EEG seizure onset patterns (SOPs) may differentiate between primary onset and secondary spread and predict postoperative seizure control. In this study, we characterized the 2-year outcomes of patients who underwent single-fiber SLAH after stereo-EEG and evaluated whether stereo-EEG SOPs predict postoperative seizure freedom.

METHODS

This retrospective five-center study included patients with or without mesial temporal sclerosis (MTS) who underwent stereo-EEG followed by single-fiber SLAH between August 2014 and January 2022. Patients with causative hippocampal lesions apart from MTS or for whom the SLAH was considered palliative were excluded. An SOP catalogue was developed based on literature review. The dominant pattern for each patient was used for survival analysis. The primary outcome was 2-year Engel I classification or recurrent seizures before then, stratified by SOP category.

RESULTS

Fifty-eight patients were included, with a mean follow-up duration of 39 ± 12 months after SLAH. Overall 1-, 2-, and 3-year Engel I seizure freedom probability was 54%, 36%, and 33%, respectively. Patients with SOPs, including low-voltage fast activity or low-frequency repetitive spiking, had a 46% 2-year seizure freedom probability, compared to 0% for patients with alpha or theta frequency repetitive spiking or theta or delta frequency rhythmic slowing (log-rank test, p = .00015).

SIGNIFICANCE

Patients who underwent SLAH after stereo-EEG had a low probability of seizure freedom at 2 years, but SOPs successfully predicted seizure recurrence in a subset of patients. This study provides proof of concept that SOPs distinguish between hippocampal seizure onset and spread and supports using SOPs to improve selection of SLAH candidates.

Laser Interstitial Thermal Therapy for Epilepsy

Laser interstitial thermal therapy is an important new technique with a diverse use in epilepsy. This article gives an up-to-date evaluation of the current use of the technique within epilepsy, as well as provides some guidance to novice users appropriate clinical cases for its use.

Seizure outcome of pediatric magnetic resonance-guided laser interstitial thermal therapy versus open surgery: A matched noninferiority cohort study

OBJECTIVE

Minimally invasive magnetic resonance-guided laser interstitial thermal therapy (MRgLITT) has been proposed as an alternative to open epilepsy surgery, to address concerns regarding the risk of open surgery. Our primary hypothesis was that seizure freedom at 1 year after MRgLITT is noninferior to open surgery in children with drug-resistant epilepsy (DRE). The secondary hypothesis was that MRgLITT has fewer complications and shorter hospitalization than surgery. The primary objective was to compare seizure outcome of MRgLITT to open surgery in children with DRE. The secondary objective was to compare complications and length of hospitalization of the two treatments.

METHODS

This retrospective multicenter cohort study included children with DRE treated with MRgLITT or open surgery with 1-year follow-up. Exclusion criteria were corpus callosotomy, neurostimulation, multilobar or hemispheric surgery, and lesion with maximal dimension > 60 mm. MRgLITT patients were propensity matched to open surgery patients. The primary outcome was seizure freedom at 1 year posttreatment. The difference in seizure freedom was compared using noninferiority test, with noninferiority margin of -10%. The secondary outcomes were complications and length of hospitalization.

RESULTS

One hundred eighty-five MRgLITT patients were matched to 185 open surgery patients. Seizure freedom at 1 year follow-up was observed in 89 of 185 (48.1%) MRgLITT and 114 of 185 (61.6%) open surgery patients (difference = -13.5%, one-sided 97.5% confidence interval = -23.8% to ∞, p_{Noninferiority}  = .79). The lower confidence interval boundary of -23.8% was below the prespecified noninferiority margin of -10%. Overall complications were lower in MRgLITT compared to open surgery (10.8% vs. 29.2%, respectively, p < .001). Hospitalization was shorter for MRgLITT than open surgery (3.1 ± 2.9 vs. 7.2 ± 6.1 days, p < .001).

SIGNIFICANCE

Seizure outcome of MRgLITT at 1 year posttreatment was inferior to open surgery. However, MRgLITT has the advantage of better safety profile and shorter hospitalization. The findings will help counsel children and parents on the benefits and risks of MRgLITT and contribute to informed decision-making on treatment options.

Beyond Resection: Neuromodulation and Minimally Invasive Epilepsy Surgery

Epilepsy is a common neurological disease impacting both patients and healthcare systems. Approximately one third of patients have drug-resistant epilepsy (DRE) and are candidates for surgical options. However, only a small percentage undergo surgical treatment due to factors such as patient misconception/fear of surgery, healthcare disparities in epilepsy care, complex presurgical evaluation, primary care knowledge gap, and lack of systemic structures to allow effective coordination between referring physician and surgical epilepsy centers. Resective surgical treatments are superior to medication management for DRE patients in terms of seizure outcomes but may be less palatable to patients. There have been major advancements in minimally invasive surgeries (MIS) and neuromodulation techniques that may allay these concerns. Both epilepsy MIS and neuromodulation have shown promising seizure outcomes while minimizing complications. Minimally invasive methods include Laser Interstitial Thermal Therapy (LITT), RadioFrequency Ablation (RFA), Stereotactic RadioSurgery (SRS). Neuromodulation methods, which are more palliative, include Vagus Nerve Stimulation (VNS), Deep Brain Stimulation (DBS), and Responsive Neurostimulation System (RNS). This review will discuss the role of these techniques in varied epilepsy subtypes, their effectiveness in improving seizure control, and adverse outcomes.

The endoscopic anterior transmaxillary temporal pole approach for mesial temporal lobe epilepsies: a feasibility study

OBJECTIVE

In mesial temporal lobe epilepsy (MTLE), the ideal surgical approach to achieve seizure freedom and minimize morbidity is an unsolved question. Selective approaches to mesial temporal structures often result in suboptimal seizure outcomes. The authors report the results of a pilot study intended to evaluate the clinical feasibility of using an endoscopic anterior transmaxillary (eATM) approach for minimally invasive management of MTLEs.

METHODS

The study is a prospectively collected case series of four consecutive patients who underwent the eATM approach for the treatment of MTLE and were followed for a minimum of 12 months. All participants underwent an epilepsy workup and surgical care at a tertiary referral comprehensive epilepsy center and had medically refractory epilepsy. The noninvasive evaluations and intracranial recordings of these patients confirmed the presence of anatomically restricted epileptogenic zones located in the mesial temporal structures. Data on seizure freedom at 1 year, neuropsychological outcomes, diffusion tractography, and adverse events were collected and analyzed.

RESULTS

By applying the eATM technique and approaching the far anterior temporal lobe regions, mesial-basal resections of the temporal polar areas and mesial temporal structures were successfully achieved in all patients (2 with left-sided approaches, 2 with right-sided approaches). No neurological complications or neuropsychological declines were observed. All 4 patients achieved Engel class Ia outcome up to the end of the follow-up period (19, 15, 14, and 12 months). One patient developed hypoesthesia in the left V2 distribution but there were no other adverse events. The low degree of white matter injury from the eATM approach was analyzed using high-definition fiber tractography in 1 patient as a putative mechanism for preserving neuropsychological function.

CONCLUSIONS

The described series demonstrates the feasibility and potential safety profile of a novel approach for medically refractory MTLE. The study affirms the feasibility of performing efficacious mesial temporal lobe resections through an eATM approach.

Volume-Based Radiofrequency Thermocoagulation for Pediatric Insulo-Opercular Epilepsy: A Feasibility Study

BACKGROUND

Stereotactic ablation surgeries including radiofrequency thermocoagulation (RFTC) and laser interstitial thermal therapy are recent less invasive treatment methods for insular epilepsy. Volume-based RFTC after stereoelectroencephalography was first proposed by a French group as a more effective method for seizure relief in insular epilepsy patients than stereoelectroencephalography-guided RFTC.

OBJECTIVE

To describe the feasibility and technical details about volume-based RFTC in patients with insulo-opercular epilepsy.

METHODS

We successfully treated 3- and 6-year-old patients with medically refractory insulo-opercular epilepsy with volume-based RFTC, in which the target volume of coagulation was flexibly designed by combining multiple spherical models of 5-mm diameter which is smaller than reported previously.

RESULTS

The insula was targeted by oblique trajectory from the frontoparietal area in one case, and the opercular cortex was targeted by perpendicular trajectories from the perisylvian cortex in the other case. The use of the small sphere model required more trajectories and manipulations but enabled more exhaustive coagulation of the epileptogenic zone, with 70% to 78% of the planned target volume coagulated without complications, and daily seizures disappeared after RFTC in both patients.

CONCLUSION

Volume-based RFTC planned with small multiple sphere models may improve the completeness of lesioning for patients with insulo-opercular epilepsy. Careful planning is necessary to reduce the risks of vascular injuries.

Surgical approaches to refractory central lobule epilepsy: a systematic review on the role of resection, ablation, and stimulation in the contemporary era

OBJECTIVE

Epilepsy originating from the central lobule (i.e., the primary sensorimotor cortex) is a challenging entity to treat given its involvement of eloquent cortex. The objective of this study was to review available evidence on treatment options for central lobule epilepsy.

METHODS

A comprehensive literature search (PubMed/Medline, EMBASE, and Scopus) was conducted for studies (1990 to date) investigating postoperative outcomes for central lobule epilepsy. The primary and secondary endpoints were seizure freedom at last follow-up and postoperative neurological deficit, respectively. The following procedures were included: open resection, multiple subpial transections (MSTs), laser and radiofrequency ablation, deep brain stimulation (DBS), responsive neurostimulation (RNS), and continuous subthreshold cortical stimulation (CSCS).

RESULTS

A total of 52 studies and 504 patients were analyzed. Most evidence was based on open resection, yielding a total of 400 patients (24 studies), of whom 62% achieved seizure freedom at a mean follow-up of 48 months. A new or worsened motor deficit occurred in 44% (permanent in 19%). Forty-six patients underwent MSTs, of whom 16% achieved seizure freedom and 30% had a neurological deficit (permanent in 12%). There were 6 laser ablation cases (cavernomas in 50%) with seizure freedom in 4 patients and 1 patient with temporary motor deficit. There were 5 radiofrequency ablation cases, with 1 patient achieving seizure freedom, 2 patients each with Engel class III and IV outcomes, and 2 patients with motor deficit. The mean seizure frequency reduction at the last follow-up was 79% for RNS (28 patients), 90% for CSCS (15 patients), and 73% for DBS (4 patients). There were no cases of temporary or permanent neurological deficit in the CSCS or DBS group.

CONCLUSIONS

This review highlights the safety and efficacy profile of resection, ablation, and stimulation for refractory central lobe epilepsy. Resection of localized regions of epilepsy onset zones results in good rates of seizure freedom (62%); however, nearly 20% of patients had permanent motor deficits. The authors hope that this review will be useful to providers and patients when tailoring decision-making for this intricate pathology.

Open surgery or laser interstitial thermal therapy for low-grade epilepsy-associated tumors of the temporal lobe: A single-institution consecutive series

Outcomes of treating low-grade epilepsy-associated tumors (LEATs) in the temporal lobe with MRI-guided laser interstitial thermal therapy (MRgLITT) remain poorly characterized. This study aimed to compare the safety and effectiveness of treating temporal lobe LEATs with MRgLITT versus open resection in a consecutive single-institution series. We reviewed all adult patients with epilepsy that underwent surgery for temporal lobe LEATs at our institution between 2002 and 2019, during which time we switched from open surgery to MRgLITT. Surgical outcome was categorized by Engel classification at >12mo follow-up and Kaplan-Meir analysis of seizure freedom. We recorded hospital length of stay, adverse events, and available neuropsychological results. Of 14 total patients, 7 underwent 9 open resections, 6 patients underwent MRgLITT alone, and 1 patient underwent an open resection followed by MRgLITT. Baseline group demographics differed and were notable for preoperative duration of epilepsy of 9.0 years (range 1-36) for open resection versus 14.0 years (range 2-34) for MRgLITT. Median length of stay was one day shorter for MRgLITT compared to open resection (p=<.0001). There were no major adverse events in the series, but there were fewer minor adverse events following MRgLITT. At 12mo follow-up, 50% (5/10) of patients undergoing open resection and 57% (4/7) of patients undergoing MRgLITT were free of disabling seizures (Engel I). When comparing patients who underwent similar procedures in the dominant temporal lobe, patients undergoing MRgLITT had fewer and milder material-specific neuropsychological declines than patients undergoing open resections. In this small series, MRgLITT was comparably safe and effective relative to open resection of temporal lobe LEATs.

Surgical Treatments for Epilepsy

PURPOSE OF REVIEW

More than 20 new antiseizure medications have been approved by the US Food and Drug Administration (FDA) in the past 3 decades; however, outcomes in newly diagnosed epilepsy have not improved, and epilepsy remains drug resistant in up to 40% of patients. Evidence supports improved seizure outcomes and quality of life in those who have undergone epilepsy surgery, but epilepsy surgery remains underutilized. This article outlines indications for epilepsy surgery, describes the presurgical workup, and summarizes current available surgical approaches.

RECENT FINDINGS

Class I evidence has demonstrated the superiority of resective surgery compared to medical therapy for seizure control and quality of life in patients with drug-resistant epilepsy. The use of minimally invasive options, such as laser interstitial thermal therapy and stereotactic radiosurgery, are alternatives to resective surgery in well-selected patients. Neuromodulation techniques, such as responsive neurostimulation, deep brain stimulation, and vagus nerve stimulation, offer a suitable alternative, especially in those where resective surgery is contraindicated or where patients prefer nonresective surgery. Although neuromodulation approaches reduce seizure frequency, they are less likely to be associated with seizure freedom than resective surgery.

SUMMARY

Appropriate patients with drug-resistant epilepsy benefit from epilepsy surgery. If two well-chosen and tolerated medication trials do not achieve seizure control, referral to a comprehensive epilepsy center for a thorough presurgical workup and discussion of surgical options is appropriate. Mounting Class I evidence supports a significantly higher chance of stopping disabling seizures with surgery than with further medication trials.

Surgical outcomes between temporal, extratemporal epilepsies and hypothalamic hamartoma: systematic review and meta-analysis of MRI-guided laser interstitial thermal therapy for drug-resistant epilepsy

BACKGROUND

Approximately 1/3 of patients with epilepsy have drug-resistant epilepsy (DRE) and require surgical interventions. This meta-analysis aimed to review the effectiveness of MRI-guided laser interstitial thermal therapy (MRgLITT) in DRE.

METHODS

The Population, Intervention, Comparator and Outcome approach and Preferred Reporting Items for Systematic Reviews and Meta-Analyses were followed. PubMed, MEDLINE and EMBASE databases were systematically searched for English language publications from 2012 to Nov 2020. Data on the prevalence outcome using the Engel Epilepsy Surgery Outcome Scale (Class I-IV), and postoperative complications were analysed with 95% CIs.

RESULTS

Twenty-eight studies that included a total of 559 patients with DRE were identified. The overall prevalence of Engel class I outcome was 56% (95% CI 0.52% to 0.60%). Hypothalamic hamartomas (HH) patients had the highest seizure freedom rate of 67% (95% CI 0.57% to 0.76%) and outcome was overall comparable between mesial temporal lobe epilepsy (mTLE) (56%, 95% CI 0.50% to 0.61%) and extratemporal epilepsy (50% 95% CI 0.40% to 0.59%). The mTLE cases with mesial temporal sclerosis had better outcome vs non-lesional cases of mTLE. The prevalence of postoperative adverse events was 19% (95% CI 0.14% to 0.25%) and the most common adverse event was visual field deficits. The reoperation rate was 9% (95% CI 0.05% to 0.14%), which included repeat ablation and open resection.

CONCLUSION

MRgLITT is an effective and safe intervention for DRE with different disease aetiologies. The seizure freedom outcome is overall comparable in between extratemporal and temporal lobe epilepsy; and highest with HH.

TRAIL REGISTRATION NUMBER

The study protocol was registered with the National Institute for Health Research (CRD42019126365), which serves as a prospective register of systematic reviews. It is an international database of prospectively registered systematic reviews with a focus on health-related outcomes. Details about the protocol can be found at https://wwwcrdyorkacuk/PROSPERO/.

Delivering epilepsy care in low-resource settings: the role of technology

INTRODUCTION

The implementation of technology in the field of epileptology has traditionally focused on its use for diagnosis and treatment and has, unsurprisingly, been capital-intensive, making it therefore mainly implementable in advanced high-income countries. Because of technological innovations over the past 20 years there has been almost a paradigm shift, particularly in access to and the potential for implementing relevant technology in lesser developed environments. Nearly 80% of people living with epilepsy live in low and middle-income countries.

AREAS COVERED

The challenge and the purpose of this paper is to discuss how technology can be implemented into lesser-resourced contexts not only cost-effectively but in a cost-saving way while also building capacity and thus sustainability.

EXPERT OPINION

The rate of technological advancement presents the risk of progressive widening of the technology and care gaps between advanced and lesser developed regions. Implementing technology is both about finding relevant appropriate technologies for the individual contexts of a diverse range of countries but also about repurposing low-tech technologies for application in epilepsy care in these areas. Finally exciting advances such as autonomous driving, digital twinning and robotic surgery will likely transform epilepsy care in several lower-resourced settings in the next 5-10 years.

Adopting MR-guided stereotactic laser ablations for epileptic lesions: initial clinical experience and lessons learned

OBJECTIVE

MR-guided laser interstitial thermal therapy (MRgLITT) is a minimally invasive technique for ablating brain lesions under real-time MRI feedback and control of the ablation process. The Medtronic Visualase system was recently approved for use in Europe and Israel. We report our initial technical experience using the system in the first 16 cases in which the system was used to ablate focal epileptogenic lesions.

METHODS

We included all consecutive patients with intractable epilepsy who underwent MRgLITT procedures between 2018 and 2020. We reviewed medical charts and imaging studies of patients. Post-ablation MRIs were used to calculate ablation volumes.

RESULTS

Seventeen MRgLITT procedures were performed in 16 patients. One cooling catheter/laser fiber assemblies were placed per patient. Indications for surgery were intractable epilepsy due to TLE (n = 7), suspected low-grade glioma (n = 4), radiological cortical dysplasia (n = 1), hypothalamic hamartoma (n = 1), and MR-negative foci (n = 3). Ablations were made using 30 to 70% of the maximal energy of the Visualase system. We used serial ablations as needed along the tract of the catheter by pulling back the optic fiber; the length of the lesion ranged between 7.4 and 38.1 mm. Ablation volume ranged between 0.27 and 6.78 mm³. Immediate post-ablation MRI demonstrated good ablation of the epileptic lesion in 16/17 cases. In one case with mesial temporal sclerosis, no ablation was performed due to suboptimal position of the catheter. That patient was successfully reoperated at a later date. Mean follow-up was 14.9 months (± 11.6 months). Eleven patients had follow-up longer than 12 months. Good seizure control (Engel I, A) was achieved in 7/11 patients (63%) and 1/11 (9%) had significant improvement in seizure frequency (Angle IIIa). Three patients (27%) did not experience improvement in their seizure frequency (Engel IV, B), and one of these patients died during the follow-up period from sudden unexpected death of epilepsy (SUDEP). No immediate or delayed neurological complications were documented in any of the cases during the follow-up period.

CONCLUSIONS

MRgLITT is a promising technique and can be used safely as an alternative to open resection in both lesional and non-lesional intractable epilepsy cases. In our local series, the success rate of epilepsy surgery was comparable to recent publications.

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.

Network radiofrequency ablation for drug resistant epilepsy

Radiofrequency ablation (RFA) is a minimally invasive procedure for drug-resistant focal epilepsy. Although well tolerated, seizure outcomes are less favorable than standard resection. RFA is commonly performed following stereoencephalography (sEEG) identification of the seizure onset zone (SOZ). We hypothesized RFA outcomes can improve by adding RFA of seizure spread regions to the SOZ as identified by sEEG, an approach we term network RFA. Four patients underwent network RFA at our institution from 8/2017 to 9/2019. There were two Engel IB outcomes and two Engel III outcomes. The median follow-up length was 25.5 months (range 17-35). No permanent neurological deficits occurred. Etiologies consisted of polymicrogyria (1), mixed malformation of cortical development (MCD) (2), and cryptogenic (1). This study provides descriptive results regarding the efficacy and safety of network RFA. Network RFA can be considered in patients with focal epilepsies with large MCDs that may not be amenable to standard resection.

MR spectroscopic imaging at 3 T and outcomes in surgical epilepsy

For the spectroscopic assessment of brain disorders that require large-volume coverage, the requirements of RF performance and field homogeneity are high. For epilepsy, this is also challenging given the inter-patient variation in location, severity and subtlety of anatomical identification and its tendency to involve the temporal region. We apply a targeted method to examine the utility of large-volume MR spectroscopic imaging (MRSI) in surgical epilepsy patients, implementing a two-step acquisition, comprised of a 3D acquisition to cover the fronto-parietal regions, and a contiguous parallel two-slice Hadamard-encoded acquisition to cover the temporal-occipital region, both with T_R /T_E = 2000/40 ms and matched acquisition times. With restricted (static, first/second-order) B₀ shimming in their respective regions, the Cramér-Rao lower bounds for creatine from the temporal lobe two-slice Hadamard and frontal-parietal 3D acquisition are 8.1 ± 2.2% and 6.3 ± 1.9% respectively. The datasets are combined to provide a total 60 mm axial coverage over the frontal, parietal and superior temporal to middle temporal-occipital regions. We applied these acquisitions at a nominal 400 mm³ voxel resolution in n = 27 pre-surgical epilepsy patients and n = 20 controls. In controls, 86.6 ± 3.2% voxels with at least 50% tissue (white + gray matter, excluding CSF) survived spectral quality inclusion criteria. Since all patients were clinically followed for at least 1 year after surgery, seizure frequency outcome was available for all. The MRSI measurements of the total fractional metabolic dysfunction (characterized by the Cr/NAA metric) in FreeSurfer MRI gray matter segmented regions, in the patients compared with the controls, exhibited a significant Spearman correlation with post-surgical outcome. This finding suggests that a larger burden of metabolic dysfunction is seen in patients with poorer post-surgical seizure control.

Underutilization of epilepsy surgery: Part II: Strategies to overcome barriers

Interventions focused on utilization of epilepsy surgery can be divided into groups: those that improve patients' access to surgical evaluation and those that facilitate completion of the surgical evaluation and treatment. Educational intervention, technological innovation, and effective coordination and communication can significantly improve patients' access to surgery. Patient and public facing, individualized (analog and/or digital) communication can raise awareness and acceptance of epilepsy surgery. Educational interventions aimed at providers may mitigate knowledge gaps using practical and concise consensus statements and guidelines, while specific training can improve awareness around implicit bias. Innovative technology, such as clinical decision-making toolkits within the electronic medical record (EMR), machine learning techniques, online decision-support tools, nomograms, and scoring algorithms can facilitate timely identification of appropriate candidates for epilepsy surgery with individualized guidance regarding referral appropriateness, postoperative seizure freedom rate, and risks of complication after surgery. There are specific strategies applicable for epilepsy centers' success: building a multidisciplinary setup, maintaining/tracking volume and complexity of cases, collaborating with other centers, improving surgical outcome with reduced complications, utilizing advanced diagnostics tools, and considering minimally invasive surgical techniques. Established centers may use other strategies, such as multi-stage procedures for multifocal epilepsy, advanced functional mapping with tailored surgery for epilepsy involving the eloquent cortex, and generation of fresh hypotheses in cases of surgical failure. Finally, improved access to epilepsy surgery can be accomplished with policy changes (e.g., anti-discrimination policy, exemption in transportation cost, telehealth reimbursement policy, patient-centered epilepsy care models, pay-per-performance models, affordability and access to insurance, and increased funding for research). Every intervention should receive regular evaluation and feedback-driven modification to ensure appropriate utilization of epilepsy surgery.

Robot Assisted MRI-Guided LITT of the Anterior, Lateral, and Medial Temporal Lobe for Temporal Lobe Epilepsy

Robotic systems have fundamentally altered the landscape of functional neurosurgery. These allow automated stereotaxy with high accuracy and reliability, and are rapidly becoming a mainstay in stereotactic surgeries such as deep brain stimulation (DBS), stereoelectroencephalography (SEEG), and stereotactic laser ablation/MRI guided laser interstitial thermal therapy (MRgLITT). Robotic systems have been effectively applied to create a minimally invasive approach for diagnostics and therapeutics in the treatment of epilepsy, utilizing robots for expeditious and accurate stereotaxy for SEEG and MRgLITT. MRgLITT has been shown to approach open surgical techniques in efficacy of seizure control while minimizing collateral injury. We describe the use of robot assisted MRgLITT for a minimally invasive laser anterior temporal lobotomy, describing the approach and potential pitfalls. Goals of MRgLITT are complete ablation of the epileptogenic zone and avoiding injury to uninvolved structures. In the middle fossa these include structures such as cranial nerves in the skull base and cavernous sinus and the thalamus. These can be mitigated with careful trajectory planning and control of laser ablation intensity.