The Latest on Lasers: Improving the Outcome of MRg-LITT Amygdalohippocampotomy

SEEG Radiofrequency Thermocoagulation and Memory: For Now, Avoid the Trap of Overpromising and Underdelivering

Neuropsychological Outcomes After Stereo-EEG Radiofrequency Thermocoagulation Cockle E, Malpas CB, Coleman H, McIlroy A, Laing J, Kwan P, Hunn M, Gutman M, Harb C, Meade C, D'Souza WJ, Halliday AJ, Bulluss K, Vogrin SJ, Alpitsis R, O'Brien TJ, Rayner G, Neal A. Neurology . 2024;103(11):e209815. doi:10.1212/WNL.0000000000209815. Epub 2024 Nov 18. PMID: 39556777. Background and objectives: Stereo-EEG-guided radiofrequency thermocoagulation (RFTHC) has been proposed as relatively safe from a cognitive perspective; however, there is a lack of evidence based on neuropsychological assessments supporting this. This study is the first prospective evaluation of neuropsychological outcomes associated with stereo-EEG-guided RFTHC in patients with focal drug-resistant epilepsy. Methods: This cohort study involved prospective recruitment of consecutive patients undergoing stereo-EEG from 2 Australian centers. A comprehensive neuropsychological assessment was administered before implantation and 3 months after RFTHC (M  = 104.51 days, SD = 29.25). Outcomes across cognitive domains were assessed at a group level with repeated measures t tests. Factorial repeated measures analyses of variance compared memory and language outcomes according to whether dominant mesial temporal lobe (mTL) structures were coagulated. Reliable change indices (RCIs) were computed to explore psychometrically reliable changes at an individual level. Results: The sample comprised 39 patients who underwent stereo-EEG (M  = 37.08 ± 9.67 years, range = 17-56 years, 54% female). Nineteen (49%) had a language dominant epileptogenic zone (EZ), 16 (41%) a non-dominant EZ, and 4 (10%) a bilateral EZ. All patients underwent RFTHC with a mean of 11.87 (SD = 6.82, range = 2-29) coagulation sites. Ten patients (26%) had RFTHC within the dominant mTL. At a group level, RFTHC was not associated with a significant decline on any neuropsychological measures (all comparisons p  > 0.05). Subgroup analyses revealed a decline in delayed verbal recall after RFTHC of dominant mTL structures (F (1,37) = 4.46, p  = 0.04, ηp 2 = 0.11, 95% CI [0–0.30]; medium to large effect), although it did not remain statistically significant after correction for false discovery rate. No statistically significant group differences were observed on visual memory or language measures post-RFTHC (all comparisons p  > 0.05). RCI revealed that after RFTHC within the dominant mTL, 20% of patients experienced a decline in verbal memory and 10% in visual memory. By contrast, 7% declined in verbal memory and 10% in visual memory post-RFTHC outside the dominant mTL. Discussion: While these findings support the current view that RFTHC is cognitively benign for most cases, the results raise the question of a verbal memory decline after coagulation of the dominant mTL. Individualized neuropsychological counseling before stereo-EEG is essential to avoid unanticipated deficits.

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

OBJECTIVE

This study evaluated the therapeutic effects of open and minimally invasive surgeries in patients with drug-resistant epilepsy.

METHODS

This study systematically searched electronic databases, including PubMed, Web of Science, Embase, and the Cochrane Library, for randomized controlled trials, subsequent open-label expansion studies, prospective studies and retrospective studies on surgical procedures for patients with drug-resistant epilepsy. The main outcome was seizure-free status. A one-arm meta-analysis integrating data from all studies was performed to evaluate the treatment outcomes at multiple time points.

RESULTS

A total of 62 studies were included, representing 5958 individuals who received five treatment regimens. The analysis results indicate that anterior temporal lobectomy (ATL) and selective amygdalohippocampectomy is still the best choice for treating drug-resistant mesial temporal lobe epilepsy in adult epilepsy patients. During the overall follow-up period, the seizure free rates for ATL, selective amygdalohippocampectomy, laser interstitial thermal therapy, radiofrequency thermocoagulation, and gamma knife surgery were 62%, 70%, 58%, 47%, and 57%, respectively.

CONCLUSIONS

Among the five surgical methods included in this study, ATL and selective amygdala hippocampal resection seem to have more advantages in postoperative epilepsy control compared to laser interstitial hyperthermia, radiofrequency thermocoagulation, and gamma knife surgery. Each surgical treatment method has its unique focus, and when choosing a specific method, it is necessary to consider the patient's specific situation, the type and location of epileptic seizures, and possible side effects. Treating physician will develop personalized treatment plans based on these factors to maximize treatment effectiveness and reduce risks.

Lobectomy vs. MRgLITT in Temporal Lobe Epilepsy (TLE): A Pilot Study Investigating Vestibulo-Spatial Functions

Background: About 65 million people worldwide are affected by epilepsy, with temporal lobe epilepsy being the most common type resistant to drugs and often requiring surgical treatment. Although open surgical approaches, such as temporal lobectomy, have been the method of choice for decades, minimally invasive MRgLITT has demonstrated promising results. However, it remains unknown whether patients who underwent one of these two approaches would show better performance on vestibulo-spatial tasks. Methods: Twenty-seven patients were included in three different groups: (1) MRgLITT (37.0 ± 15.1 years, two females), (2) R-OP (44 ± 15.7 years, five females) and (3) No-OP (43 ± 11.2 years, three females)-with no significant differences in age, disease duration and number of medications. Groups were compared on their performance in three vestibular-dependent tests: (1) clinical balance test (CBT), (2) triangle completion test (TCT) and (3) rotational memory (RM) test. Results: Significantly better performance of MRgLITT patients, in comparison to the other two groups (R-OP and No-OP), was found for the TCT. The other tests revealed no significant differences between the groups. Conclusions: Patients who underwent MRgLITT performed significantly better on the vestibular-dependent spatial orientation task (TCT) compared to those who underwent temporal lobectomy (R-OP) and non-operated patients. Speculations about reasons for such an effect-including minimal invasiveness with less "collateral damage", influence of operated side, timing of surgery, sample heterogeneity and others-need to be assessed in detail in larger-scale, prospective longitudinal studies.

Intraoperative electrocorticography during laser-interstitial thermal therapy predicts seizure outcome in mesial temporal lobe epilepsy

OBJECTIVE

Magnetic resonance-guided laser interstitial thermal therapy (MRLiTT) for treating temporal lobe epilepsy has recently gained popularity. We aimed to investigate the predictive value of pre-and post-MRLiTT epileptiform discharges (EDs) on intraoperative electrocorticography (iECoG) in seizure outcomes for patients with mesial temporal lobe epilepsy (mTLE).

METHODS

We conducted a pilot, prospective single-center cohort study on seven consecutive patients with mTLE that underwent MRLiTT. Pre- and post-MRLiTT iECoG was performed using a 1x8 contact depth electrode along the same trajectory used for the laser catheter.

RESULTS

The responders had a robust reduction in ED frequency compared to pre-MRLiTT iECoG (86% vs 13%, p < 0.01). Clinical characteristics, including risk factors for epilepsy, duration of epilepsy, presence of mesial temporal lobe sclerosis, prior intracranial monitoring, the absolute frequency of pre- or post-MRLiTT EDs, and ablation volume were not significantly associated with responder status.

CONCLUSIONS

This is the first demonstration that intraoperative reduction in EDs during mesial temporal lobe MRLiTT may potentially predict seizure outcomes and may serve as an intraoperative biomarker for satisfactory ablation. However, larger prospective studies are needed to confirm our findings and evaluate the utility of iECoG during MRLiTT.

SIGNIFICANCE

iECoG during mesial temporal lobe MRLiTT may help assess seizure 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.

Extent of parahippocampal ablation is associated with seizure freedom after laser amygdalohippocampotomy

OBJECTIVE

The authors aimed to examine the relationship between mesial temporal subregion ablation volume and seizure outcome in a diverse cohort of patients who underwent stereotactic laser amygdalohippocampotomy (SLAH) for mesial temporal lobe epilepsy (MTLE).

METHODS

Seizure outcomes and pre- and postoperative images were retrospectively reviewed in patients with MTLE who underwent SLAH at a single institution. Mesial temporal subregions and the contrast-enhancing ablation volume were manually segmented. Pre- and postoperative MR images were coregistered to assess anatomical ablation. Postoperative MRI and ablation volumes were also spatially normalized, enabling the assessment of seizure outcome with heat maps.

RESULTS

Twenty-eight patients with MTLE underwent SLAH, 15 of whom had mesial temporal sclerosis (MTS). The rate of Engel class I outcome at 1 year after SLAH was 39% overall: 47% in patients with MTS and 31% in patients without MTS. The percentage of parahippocampal gyrus (PHG) ablated was higher in patients with an Engel class I outcome (40% vs 25%, p = 0.04). Subregion analysis revealed that extent of ablation in the parahippocampal cortex (35% vs 19%, p = 0.03) and angular bundle (64% vs 43%, p = 0.02) was positively associated with Engel class I outcome. The degree of amygdalohippocampal complex (AHC) ablated was not associated with seizure outcome (p = 0.30).

CONCLUSIONS

Although the AHC was the described target of SLAH, seizure outcome in this cohort was associated with degree of ablation for the PHG, not the AHC. Complete coverage of both the AHC and PHG is technically challenging, and more work is needed to optimize seizure outcome after SLAH.

Effects of laser interstitial thermal therapy for mesial temporal lobe epilepsy on the structural connectome and its relationship to seizure freedom

OBJECTIVE

Laser interstitial thermal therapy (LITT) is a minimally invasive surgery for mesial temporal lobe epilepsy (mTLE), but the effects of individual patient anatomy and location of ablation volumes affect seizure outcomes. The purpose of this study is to see if features of individual patient structural connectomes predict surgical outcomes after LITT for mTLE.

METHODS

This is a retrospective analysis of seizure outcomes of LITT for mTLE in 24 patients. We use preoperative diffusion tensor imaging (DTI) to simulate changes in structural connectivity after laser ablation. A two-step machine-learning algorithm is applied to predict seizure outcomes from the change in connectomic features after surgery.

RESULTS

Although node-based network features such as clustering coefficient and betweenness centrality have some predictive value, changes in connection strength between mesial temporal regions predict seizure outcomes significantly better. Changes in connection strength between the entorhinal cortex (EC), and the insula, hippocampus, and amygdala, as well as between the temporal pole and hippocampus, predict Engel Class I outcomes with an accuracy of 88%. Analysis of the ablation location, as well as simulated, alternative ablations, reveals that a more medial, anterior, and inferior ablation volume is associated with a greater effect on these connections, and potentially on seizure outcomes.

SIGNIFICANCE

Our results indicate (1) that seizure outcomes can be retrospectively predicted with excellent accuracy using changes in structural connectivity, and (2) that favorable connectomic changes are associated with an ablation volume involving relatively mesial, anterior, and inferior locations. These results may provide a framework whereby individual pre-operative structural connectomes can be used to optimize ablation volumes and improve outcomes in LITT for mTLE.

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.