Surgery procedures in temporal lobe epilepsies

Temporal lobe epilepsy (TLE) is the most common cause of refractory epilepsy amenable for surgical treatment and seizure control. Surgery for TLE is a safe and effective strategy. The seizure-free rate after surgical resection in patients with mesial or neocortical TLE is about 70%. Resective surgery has an advantage over stereotactic radiosurgery in terms of seizure outcomes for mesial TLE patients. Both techniques have similar results for safety, cognitive outcomes, and associated costs. Stereotactic radiosurgery should therefore be seen as an alternative to open surgery for patients with contraindications for or with reluctance to undergo open surgery. Laser interstitial thermal therapy (LITT) has also shown promising results as a curative technique in mesial TLE but needs to be more deeply evaluated. Brain-responsive stimulation represents a palliative treatment option for patients with unilateral or bilateral MTLE who are not candidates for temporal lobectomy or who have failed a prior mesial temporal lobe resection. Overall, despite the expansion of innovative techniques in recent years, resective surgery remains the reference treatment for TLE and should be proposed as the first-line surgical modality. In the future, ultrasound therapies could become a credible therapeutic option for refractory TLE patients.

A Systematic Review of Minimally Invasive Procedures for Mesial Temporal Lobe Epilepsy: Too Minimal, Too Fast?

BACKGROUND

Cortico-amygdalohippocampectomy (CAH) is effective for mesial temporal lobe epilepsy (mTLE). Concerns regarding surgical morbidity have generated enthusiasm for more minimally invasive interventions. A careful analysis of current data is warranted before widespread adoption of these techniques.

OBJECTIVE

To systematically review the use of laser interstitial thermal therapy (LITT), stereotactic radiosurgery (SRS), radiofrequency thermocoagulation (RF-TC), and focused ultrasound for mTLE.

METHODS

Major online databases were searched for prospective observational studies, randomized clinical trials, and retrospective studies (>50 patients), including mTLE patients. Outcomes of interest were seizure freedom (Engel I), complications and re-operation rates, and neuropsychological and quality-of-life (QoL) data.

RESULTS

Nineteen publications were identified. At ≥6 mo postoperatively, LITT (9/19) Engel I outcomes ranged from 52% to 80%. SRS (3/19) has a latency period (52%-67%, 24-36 mo postoperatively) and the radiosurgery vs. open surgery for epilepsy (ROSE) trial reported inferiority of SRS compared to CAH. RF-TC (7/19) demonstrated variable seizure freedom rates (0%-79%) and high re-operation rates (0%-90%). Twelve studies reported neuropsychological outcomes but QoL (4/19) was not widely reported, and few studies (3/19) assessed both. Study quality ranged from fair to good.

CONCLUSION

Based on nonrandomized data, LITT has compelling evidence of efficacy; however, comparisons to surgical resection are lacking. SRS has a latency period and is inferior to CAH (ROSE trial). RF-TC is a less resource-intensive alternative to LITT; however, comparisons of efficacy are limited. Additional studies are needed before minimally invasive procedures can supplant standard surgery.

Alterations Functional Connectivity in Temporal Lobe Epilepsy and Their Relationships With Cognitive Function: A Longitudinal Resting-State fMRI Study

Background: Cognitive impairments in temporal lobe epilepsy (TLE) patients has been described as a chronically progressive feature of the disease. However, how severe recurrent seizures modify neuronal circuits in the human brain and subsequently degrade cognitive function, remains largely unknown. Here, we aimed to investigate longitudinal alterations by functional magnetic resonance imaging (fMRI) in TLE patients and to assess how those alterations are related to cognitive function performance.

Methods: Sixteen TLE patients and 20 normal controls (NCs) were recruited for a study to observe longitudinal alterations in resting-state functional connectivity (FC) and to estimate alertness, orientation, and executive function both at baseline and at a follow-up time ~3 years later.

Results: TLE patients, compared with NCs, showed impaired executive function, intrinsic alertness, and phasic alertness and exhibited lengthened reaction time (RT) in the spatial cue and center cue conditions at baseline. The orienting function of TLE patients was declined at follow-up compared to the baseline. Cross-sectional analysis demonstrated that TLE patients displayed significantly greater positive correlation than NCs between the right dorsolateral prefrontal cortex (DLPFC) and the right inferior parietal lobule (IPL) and right superior frontal gyrus (SFG). Furthermore, among TLE patients, the longitudinal study revealed a decrease in correlation between the right DLPFC and the right SFG compared to the baseline. In addition, there was a significant negative correlation between the longitudinal change in FC and the change in orienting function in TLE subjects.

Conclusions: Abnormal connectivity between the DLPFC and the SFG suggests the potential of longitudinal resting-state fMRI to delineate regions relevant to cognitive dysfunction for disease progression.

Comparison between simultaneously acquired arterial spin labeling and 18F-FDG PET in mesial temporal lobe epilepsy assisted by a PET/MR system and SEEG

Objective

In the detection of seizure onset zones, arterial spin labeling (ASL) can overcome the limitations of positron emission tomography (PET) with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG), which is invasive, expensive, and radioactive. PET/magnetic resonance (MR) systems have been introduced that allow simultaneous performance of ASL and PET, but comparisons of these techniques with stereoelectroencephalography (SEEG) and comparisons among the treatment outcomes of these techniques are still lacking. Here, we investigate the effectiveness of ASL compared with that of SEEG and their outcomes in localizing mesial temporal lobe epilepsy (MTLE) and assess the correlation between simultaneously acquired PET and ASL.

Methods

Between October 2016 and August 2017, we retrospectively studied 12 patients diagnosed with pure unilateral MTLE. We extracted and quantitatively computed values for ASL and PET in the bilateral hippocampus. SEEG findings and outcome were considered the gold standard of lateralization. Finally, the bilateral asymmetry index (AI) was calculated to assess the correlation between PET and ASL.

Results

Our results showed that hypoperfusion in the hippocampus detected using ASL matched the SEEG-defined epileptogenic zone in this series of patients. The mean normalized voxel value of ASL in the contralateral hippocampus was 0.97 ± 0.19, while in the ipsilateral hippocampus, it was 0.84 ± 0.14. Meanwhile, significantly decreased perfusion and metabolism were observed in these patients (Wilcoxon, p < 0.05), with a significant positive correlation between the AI values derived from PET and ASL (Pearson's correlation, r = 0.74, p < 0.05).

Significance

In our SEEG- and outcome-defined patients with MTLE, ASL could provide significant information during presurgical evaluation, with the hypoperfusion detected with ASL reliably lateralizing MTLE. This non-invasive technique may be used as an alternative diagnostic tool for MTLE lateralization.

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ASL has been increasingly used in presurgical evaluations in epilepsy recent years.

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Comparisons of ASL and PET with a PET/MR system using SEEG and treatment outcomes as gold-standard are still lacking.

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Decreased perfusion consistent with hypometabolism and SEEG was observed with ASL.

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ASL offers an effective non-invasive alternative to PET in evaluation of MTLE.

A neuropsychologist's view: Outcome after RF-ablation for mTLE

Concern about postoperative worsening of cognitive functions after temporal lobe epilepsy surgery is an important issue. In this article we review our data on neuropsychological outcome after radiofrequency (RF) ablation of amygdalohippocampal complex (AHC). On a group level we found initial improvement in intelligence domains and unchanged memory scores one year after the surgery. During longitudinal follow-up, we found improvement in both intellectual and memory domains. This improvement was most pronounced up to two years after surgery. On an individual level, no patient worsened in any intellectual domain and most patients improved in memory. We hypothesize that this favorable outcome may be a consequence of minimization of collateral damage and incomplete destruction of target structures. We also summarize our experience with psychiatric complications of the procedure.