Stereotactic radiofrequency amygdalohippocampectomy: Does reduction of entorhinal and perirhinal cortices influence good clinical seizure outcome?

The Temporal Lobe Club: Newer Approaches to Treat Temporal Lobe Epilepsy

This brief review summarizes presentations at the Temporal Lobe Club Special Interest Group session held in December 2022 at the American Epilepsy Society meeting. The session addressed newer methods to treat temporal epilepsy, including methods currently in clinical use and techniques under investigation. Brief summaries are provided for each of 4 lectures. Dr Chengyuan Wu discussed ablative techniques such as laser interstitial thermal ablation, radiofrequency ablation, focused ultrasound; Dr Joon Kang reviewed neuromodulation techniques including electrical stimulation and focused ultrasound; Dr Julia Makhalova discussed network effects of the aforementioned techniques; and Dr Derek Southwell reviewed inhibitory interneuron transplantation. These summaries are intended to provide a brief overview and references are provided for the reader to learn more about each topic.

Two-trajectory laser amygdalohippocampotomy: Anatomic modeling and initial seizure outcomes

OBJECTIVE

Laser interstitial thermal therapy (LITT) for mesial temporal lobe epilepsy (mTLE) is typically performed with one trajectory to target the medial temporal lobe (MTL). MTL structures such as piriform and entorhinal cortex are epileptogenic, but due to their relative geometry, they are difficult to target with one trajectory while simultaneously maintaining adequate ablation of the amygdala and hippocampus. We hypothesized that a two-trajectory approach could improve ablation of all relevant MTL structures. First, we created large-scale computer simulations to compare idealized one- vs two-trajectory approaches. A two-trajectory approach was then validated in an initial cohort of patients.

METHODS

We used magnetic resonance imaging (MRI) from the Human Connectome Project (HCP) to create subject-specific target structures consisting of hippocampus, amygdala, and piriform/entorhinal/perirhinal cortex. An algorithm searched for safe potential trajectories along the hippocampal axis (catheter one) and along the amygdala-piriform axis (catheter two) and compared this to a single trajectory optimized over all structures. The proportion of each structure ablated at various burn radii was evaluated. A cohort of 11 consecutive patients with mTLE received two-trajectory LITT; demographic, operative, and outcome data were collected.

RESULTS

The two-trajectory approach was superior to the one-trajectory approach at nearly all burn radii for all hippocampal subfields and amygdala nuclei (p < .05). Two-laser trajectories achieved full ablation of MTL cortical structures at physiologically realistic burn radii, whereas one-laser trajectories could not. Five patients with at least 1 year of follow-up (mean = 21.8 months) experienced Engel class I outcomes; 6 patients with less than 1 year of follow-up (mean = 6.6 months) are on track for Engel class I outcomes.

SIGNIFICANCE

Our anatomic analyses and initial clinical results suggest that LITT amygdalohippocampotomy performed via two-laser trajectories may promote excellent seizure outcomes. Future studies are required to validate the long-term clinical efficacy and safety of this approach.

Rates and predictors of success and failure in repeat epilepsy surgery: A meta-analysis and systematic review

OBJECTIVE

Medically refractory epilepsy is a debilitating disorder that is particularly challenging to treat in patients who have already failed a surgical resection. Evidence regarding outcomes of further epilepsy surgery is limited to small case series and reviews. Therefore, our group performed the first quantitative meta-analysis of the literature from the past 30 years to assess for rates and predictors of successful reoperations.

METHODS

A PubMed search was conducted for studies reporting outcomes of repeat epilepsy surgery. Studies were excluded if they reported fewer than five eligible patients or had average follow-ups < 1 year, and patients were excluded from analysis if they received a nonresective intervention. Outcomes were stratified by each variable of interest, and quantitative meta-analysis was performed to generate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Seven hundred eighty-two patients who received repeat resective epilepsy surgery from 36 studies were included. Engel I outcome was observed in 47% (n = 369) of patients. Significant predictors of seizure freedom included congruent over noncongruent electrophysiology data (OR = 3.6, 95% CI = 1.6-8.2), lesional over nonlesional epilepsy (OR = 3.2, 95% CI = 1.9-5.3), and surgical limitations over disease-related factors associated with failure of the first surgery (OR = 2.6, 95% CI = 1.3-5.3). Among patients with at least one of these predictors, seizure freedom was achieved in 58%. Conversely, the use of invasive monitoring was associated with worse outcome (OR = 0.4, 95% CI = 0.2-0.9). Temporal lobe over extratemporal/multilobe resection (OR = 1.5, 95% CI = 0.8-3.0) and abnormal over normal preoperative magnetic resonance imaging (OR = 1.9, 95% CI = 0.6-5.4) showed nonsignificant trends toward seizure freedom.

SIGNIFICANCE

This analysis supports considering further resection in patients with intractable epilepsy who continue to have debilitating seizures after an initial surgery, especially in the context of factors predictive of a favorable outcome.

Stereotactic Laser Ablation for Medically Intractable Epilepsy: The Next Generation of Minimally Invasive Epilepsy Surgery

Epilepsy is a common, disabling illness that is refractory to medical treatment in approximately one-third of patients, particularly among those with mesial temporal lobe epilepsy. While standard open mesial temporal resection is effective, achieving seizure freedom in most patients, efforts to develop safer, minimally invasive techniques have been underway for over half a century. Stereotactic ablative techniques, in particular, radiofrequency (RF) ablation, were first developed in the 1960s, with refinements in the 1990s with the advent of modern computed tomography and magnetic resonance-based imaging. In the past 5 years, the most recent techniques have used MRI-guided laser interstitial thermotherapy (LITT), the development of which began in the 1980s, saw refinements in MRI thermal imaging through the 1990s, and was initially used primarily for the treatment of intracranial and extracranial tumors. The present review describes the original stereotactic ablation trials, followed by modern imaging-guided RF ablation series for mesial temporal lobe epilepsy. The developments of LITT and MRI thermometry are then discussed. Finally, the two currently available MRI-guided LITT systems are reviewed for their role in the treatment of mesial temporal lobe and other medically refractory epilepsies.

Thalamotemporal alteration and postoperative seizures in temporal lobe epilepsy

Objective

There are competing explanations for persistent postoperative seizures after temporal lobe surgery. One is that 1 or more particular subtypes of mesial temporal lobe epilepsy (mTLE) exist that are particularly resistant to surgery. We sought to identify a common brain structural and connectivity alteration in patients with persistent postoperative seizures using preoperative quantitative magnetic resonance imaging and diffusion tensor imaging (DTI).

Methods

We performed a series of studies in 87 patients with mTLE (47 subsequently rendered seizure free, 40 who continued to experience postoperative seizures) and 80 healthy controls. We investigated the relationship between imaging variables and postoperative seizure outcome. All patients had unilateral temporal lobe seizure onset, had ipsilateral hippocampal sclerosis as the only brain lesion, and underwent amygdalohippocampectomy.

Results

Quantitative imaging factors found not to be significantly associated with persistent seizures were volumes of ipsilateral and contralateral mesial temporal lobe structures, generalized brain atrophy, and extent of resection. There were nonsignificant trends for larger amygdala and entorhinal resections to be associated with improved outcome. However, patients with persistent seizures had significant atrophy of bilateral dorsomedial and pulvinar thalamic regions, and significant alterations of DTI‐derived thalamotemporal probabilistic paths bilaterally relative to those patients rendered seizure free and controls, even when corrected for extent of mesial temporal lobe resection.

Interpretation

Patients with bihemispheric alterations of thalamotemporal structural networks may represent a subtype of mTLE that is resistant to temporal lobe surgery. Increasingly sensitive multimodal imaging techniques should endeavor to transform these group‐based findings to individualize prediction of patient outcomes. Ann Neurol 2015;77:760–774

Real-time magnetic resonance-guided stereotactic laser amygdalohippocampotomy for mesial temporal lobe epilepsy

BACKGROUND

Open surgery effectively treats mesial temporal lobe epilepsy, but carries the risk of neurocognitive deficits, which may be reduced with minimally invasive alternatives.

OBJECTIVE

To describe technical and clinical outcomes of stereotactic laser amygdalohippocampotomy with real-time magnetic resonance thermal imaging guidance.

METHODS

With patients under general anesthesia and using standard stereotactic methods, 13 adult patients with intractable mesial temporal lobe epilepsy (with and without mesial temporal sclerosis [MTS]) prospectively underwent insertion of a saline-cooled fiberoptic laser applicator in amygdalohippocampal structures from an occipital trajectory. Computer-controlled laser ablation was performed during continuous magnetic resonance thermal imaging followed by confirmatory contrast-enhanced anatomic imaging and volumetric reconstruction. Clinical outcomes were determined from seizure diaries.

RESULTS

A mean 60% volume of the amygdalohippocampal complex was ablated in 13 patients (9 with MTS) undergoing 15 procedures. Median hospitalization was 1 day. With follow-up ranging from 5 to 26 months (median, 14 months), 77% (10/13) of patients achieved meaningful seizure reduction, of whom 54% (7/13) were free of disabling seizures. Of patients with preoperative MTS, 67% (6/9) achieved seizure freedom. All recurrences were observed before 6 months. Variances in ablation volume and length did not account for individual clinical outcomes. Although no complications of laser therapy itself were observed, 1 significant complication, a visual field defect, resulted from deviated insertion of a stereotactic aligning rod, which was corrected before ablation.

CONCLUSION

Real-time magnetic resonance-guided stereotactic laser amygdalohippocampotomy is a technically novel, safe, and effective alternative to open surgery. Further evaluation with larger cohorts over time is warranted.

MRI-guided stereotactic amygdalohippocampectomy: a single center experience

BACKGROUND

This paper presents our experience of stereotactic radiofrequency amygdalohippocampectomy performed for intractable mesial temporal lobe epilepsy.

METHODS

The article describes the cases of 61 patients who were treated during the period from 2004 to 2010. Mean postoperative follow-up was 5.3 years. Neuropsychological results were obtained for a subset of 31 patients.

RESULTS

At their last postsurgical visit, 43 (70.5%) patients were Engel class I, six (9.8%) class II, nine (14.8%) class III, and three (4.9%) class IV. The surgery was complicated by four intracranial hematomas. One of them caused acute hydrocephalus and was treated by shunting and resolved without sequelae, while another caused transitory aphasia. The remaining hematomas were asymptomatic. There were two cases of meningitis which required antibiotic treatment. One patient committed suicide due to postoperative depression. After the procedure, we performed open epilepsy surgery and rethermolesions in three and two patients, respectively (8.2%). Patients showed increases in their mean full scale, verbal, and performance intelligence quotient (IQ) scores of 4, 3, and 4 IQ points, respectively (P<0.05). Five (17.2%), four (13.8%), and four (13.3%) patients improved their full scale, verbal, and performance IQ scores, respectively. No significant changes were found in memory performance, with a mean increase of 1, 3, and 0 memory quotient points in global, verbal, and visual memory, respectively (P<0.05). Global memory improved in three (10.3%) patients, verbal memory in one (3.4%), and one patient (3.3%) showed deterioration in visual memory.

CONCLUSION

Stereotactic radiofrequency amygdalohippocampectomy offers a safe, effective, and less aggressive treatment modality in cases of well-defined mesial temporal lobe epilepsy. Seizure outcome is comparable with the results of conventional epilepsy surgery and cognitive results could be even better.

Different surgical approaches for mesial temporal epilepsy: resection extent, seizure, and neuropsychological outcomes

BACKGROUND

Surgical therapy of intractable mesial temporal lobe epilepsy (MTLE) is an effective and well-established treatment.

OBJECTIVES

We compared two different surgical approaches, standard microsurgical anterior temporal resection (ATL) and stereotactic radiofrequency amygdalohippocampectomy (SAHE) for MTLE, with respect to the extent of resection or destruction, clinical outcomes, and complications.

MATERIAL AND METHODS

75 MTLE patients were included: 41 treated by SAHE (11 right sided, 30 left sided) and 34 treated by ATL (21 right sided, 13 left sided).

RESULTS

SAHE and ATL seizure control were comparable (Engel I in 75.6 and 76.5% 2 years after surgery and 79.3 and 76.5% 5 years after procedures, respectively). The neuropsychological results of SAHE patients were better than in ATL. In SAHE patients, no memory deficit was found. Hippocampal (60.6 ± 18.7%) and amygdalar (50.3 ± 21.9%) volume reduction by SAHE was significantly lower than by ATL (86.0 ± 12.7% and 80.2 ± 20.9%, respectively). The overall rate of surgical nonsilent complications without permanent neurological deficit after ATL was 11.8%, and another 8.8% silent infarctions were found on MRI. The rate of clinically manifest complications after SAHE was 4.9%. The rate of visual field defects after SAHE was expectably less frequent than after ATL.

CONCLUSION

Seizure control by SAHE was comparable to ATL. However, SAHE was safer with better neuropsychological results.

Efficacy and safety of a new robot-assisted stereotactic system for radiofrequency thermocoagulation in patients with temporal lobe epilepsy

The aim of the present study was to evaluate the efficacy and safety of a newly developed robot-assisted frameless stereotactic system for deep electrode implantation and radiofrequency thermocoagulation (RFTC). Deep-electrode implantation was performed in the bilateral mesial temporal lobes of seven patients. Following the implantation of the deep electrodes through the monitored designed path, the epileptogenic zones were determined with the assistance of a robot system. Deep electrode electroencephalograms were recorded prior to and following RFTC. Treatment outcomes were evaluated by computed tomography scans and Engel classification criteria. The procedure was well tolerated by all patients with no patients suffered from severe permanent complications. After follow-ups for 34–62 months, four patients achieved Engel class I, including three patients with Ia classification, two patients were classified as Engel class IVa and one patient was classified as Engel class IVc. Therefore, robot-assisted frameless stereotaxy for deep electrode implantation and RFTC is indicated to be a safe and effective method that may be used effectively in clinical practice.

Limbic networks: clinical perspective

Limbic epilepsy refers to a condition that consists of epileptic seizures that originate in or preferentially involve the limbic system. The majority of cases are medically refractory, necessitating surgical resection when possible. However, even resection of structures thought to be responsible for seizure generation may not leave a patient seizure free. While mesial temporal lobe limbic structures are centrally involved, there is growing evidence that the epileptogenic network consists of a broader area, involving structures outside of the temporal lobe and the limbic system. Information on structural, functional, and metabolic connectivity in patients with limbic epilepsy is available from a large body of studies employing methods such as MRI, EEG, MEG, fMRI, PET, and SPECT scanning, implicating the involvement of various brain regions in the epileptogenic network. To date, there are no consistent and conclusive findings to define the exact boundaries of this network, but it is possible that in the future studies of network connectivity in the individual patient may allow more tailored treatment and prognosis in terms of surgical resection.