Prognostic factors of postoperative seizure outcome in patients with temporal lobe epilepsy and normal magnetic resonance imaging

Evidence based noninvasive presurgical evaluation for patients with drug resistant epilepsies

PURPOSE OF REVIEW

To review the current practices and evidence for the diagnostic accuracy and the benefits of presurgical evaluation.

RECENT FINDINGS

Preoperative evaluation of patients with drug-resistant focal epilepsies and subsequent epilepsy surgery leads to a significant proportion of seizure-free patients. Even those who are not completely seizure free postoperatively often experience improved quality of life with better social integration. Systematic reviews and meta-analysis on the diagnostic accuracy are available for Video-electroencephalographic (EEG) monitoring, magnetic resonance imaging (MRI), electric and magnetic source imaging, and functional MRI for lateralization of language and memory. There are currently no evidence-based international guidelines for presurgical evaluation and epilepsy surgery.

SUMMARY

Presurgical evaluation is a complex multidisciplinary and multiprofessional clinical pathway. We rely on limited consensus-based recommendations regarding the required staffing or methodological expertise in epilepsy centers.

Predictors of seizure outcomes in stereo-electroencephalography-guided radio-frequency thermocoagulation for MRI-negative epilepsy

Background

One-third of intractable epilepsy patients have no visually identifiable focus for neurosurgery based on imaging tests [magnetic resonance imaging (MRI)-negative cases]. Stereo-electroencephalography-guided radio-frequency thermocoagulation (SEEG-guided RF-TC) is utilized in the clinical treatment of epilepsy to lower the incidence of complications post-open surgery.

Objective

This study aimed to identify prognostic factors and long-term seizure outcomes in SEEG-guided RF-TC for patients with MRI-negative epilepsy.

Design

This was a single-center retrospective cohort study.

Methods

We included 30 patients who had undergone SEEG-guided RF-TC at Sanbo Brain Hospital, Capital Medical University, from April 2015 to December 2019. The probability of remaining seizure-free and the plotted survival curves were analyzed. Prognostic factors were analyzed using log-rank tests in univariate analysis and the Cox regression model in multivariate analysis.

Results

With a mean time of 31.07 ± 2.64 months (median 30.00, interquartile range: 18.00-40.00 months), 11 out of 30 patients (36.7%) were classified as International League Against Epilepsy class 1 in the last follow-up. The mean time of remaining seizure-free was 21.33 ± 4.55 months [95% confidence interval (CI) 12.41-30.25], and the median time was 3.00 ± 0.54 months (95% CI 1.94-4.06). Despite falling in the initial year, the probability of remaining seizure-free gradually stabilizes in the subsequent years. The patients were more likely to obtain seizure freedom when the epileptogenic zone was located in the insular lobe or with one focus on the limbic system (p = 0.034, hazard ratio 5.019, 95% CI 1.125-22.387).

Conclusion

Our findings may be applied to guide individualized surgical interventions and help clinicians make better decisions.

Clinical characteristics of MRI-negative temporal lobe epilepsy

PURPOSE

To investigate the characteristics of patients with MRI-negative temporal lobe epilepsy (TLE) (1.5 T brain MRI) in comparison with: (i) patients with hippocampal sclerosis (HS)-TLE; (ii) persons with non-HS structural TLE; and (iii) patients with dual pathology.

METHODS

This was a retrospective study. All patients with an electro-clinical diagnosis of TLE were studied at the outpatient epilepsy clinic at Shiraz University of Medical Sciences, Shiraz, Iran, from 2008 until 2020.

RESULTS

Six hundred and forty-one patients were studied [273 (42.6%) HS, 154 (24.0%) non-HS structural TLE, 174 (27.1%) MRI-negative TLE, and 40 (6.2%) dual pathology]. The groups differed significantly. Important dissimilarities included: (i) compared with HS-TLE group, patients with MRI-negative TLE more often had a family history of epilepsy and less often had a history of febrile convulsion; (ii) compared with non-HS structural TLE group, patients with MRI-negative TLE more often had focal to bilateral tonic-clonic seizures, less often had focal seizures with impaired awareness, and more often had a family history of epilepsy; (iii) compared with the dual pathology group, patients with MRI-negative TLE less often were male and less often had a history of febrile convulsion.

CONCLUSION

Patients with MRI-negative TLE are not a homogenous group of people and it is not necessarily a distinct entity from other forms of TLE either. With the emergence of advanced imaging technologies, the underlying pathologies of MRI-negative TLE may be revealed.

Short and long term prediction of seizure freedom in drug-resistant focal epilepsy surgery

BACKGROUND

The selection of candidates for drug-resistant focal epilepsy surgery is essential to achieve the best post-surgical outcomes.

OBJECTIVE

To develop two prediction models for seizure freedom in the short and long-term follow-up and from them to create a risk calculator in order to individualize the selection of candidates for surgery and future therapies in each patients.

METHODS

A sample of 64 consecutive patients who underwent epilepsy surgery at two Cuban tertiary health institutions between 2012 and 2020 constituted the basis for the prediction models. Two models were obtained through the novel methodology, based on biomarker selection reached by resampling methods, cross-validation and high-accuracy index measured through the area under the receiving operating curve (ROC) procedure.

RESULTS

The first, to pre-operative model included five predictors: epilepsy type, seizures per month, ictal pattern, interictal EEG topography and normal or abnormal magnetic resonance imaging,. it's precision was 0.77 at one year, and with four years and more 0.63. The second model including variables from the trans-surgical and post-surgical stages: the interictal discharges in the post-surgical EEG, incomplete or complete resection of the epileptogenic zone, the surgical techniques employed and disappearance of the discharge in post-resection electrocorticography; the precision of this model was 0.82 at one year, and with four years and more 0.97.

CONCLUSIONS

The introduction of trans-surgical and post-surgical variables increase the prediction of the pre-surgical model. A risk calculator was developed using these prediction models, which could be useful as an accurate tool to improve the prediction in epilepsy surgery.

Identifying important factors for successful surgery in patients with lateral temporal lobe epilepsy

OBJECTIVE

Lateral temporal lobe epilepsy (LTLE) has been diagnosed in only a small number of patients; therefore, its surgical outcome is not as well-known as that of mesial temporal lobe epilepsy. We aimed to evaluate the long-term (5 years) and short-term (2 years) surgical outcomes and identify possible prognostic factors in patients with LTLE.

METHODS

This retrospective cohort study was conducted between January 1995 and December 2018 among patients who underwent resective surgery in a university-affiliated hospital. Patients were classified as LTLE if ictal onset zone was in lateral temporal area. Surgical outcomes were evaluated at 2 and 5 years. We subdivided based on outcomes and compared clinical and neuroimaging data including cortical thickness between two groups.

RESULTS

Sixty-four patients were included in the study. The mean follow-up duration after the surgery was 8.4 years. Five years after surgery, 45 of the 63 (71.4%) patients achieved seizure freedom. Clinically and statistically significant prognostic factors for postsurgical outcomes were the duration of epilepsy before surgery and focal cortical dysplasia on postoperative histopathology at the 5-year follow-up. Optimal cut-off point for epilepsy duration was eight years after the seizure onset (odds ratio 4.375, p-value = 0.0214). Furthermore, we propose a model for predicting seizure outcomes 5 years after surgery using the receiver operating characteristic curve and nomogram (area under the curve = 0.733; 95% confidence interval, 0.588-0.879). Cortical thinning was observed in ipsilateral cingulate gyrus and contralateral parietal lobe in poor surgical group compared to good surgical group (p-value < 0.01, uncorrected).

CONCLUSIONS

The identified predictors of unfavorable surgical outcomes may help in selecting optimal candidates and identifying the optimal timing for surgery among patients with LTLE. Additionally, cortical thinning was more extensive in the poor surgical group.

Stereoelectroencephalography-based research on the value of drug-resistant temporal lobe epilepsy auras: A retrospective single-center study

PURPOSE

To explore the localization value of drug-resistant temporal lobe epilepsy (TLE) aura for preoperative evaluation, based on stereoelectroencephalography (SEEG), and its prognostic value on the surgical outcome.

METHODS

The data of patients with drug-resistant TLE who had SEEG electrodes implanted during preoperative evaluation at the First Affiliated Hospital of the University of Science and Technology of China (Hefei, China) were retrospectively analyzed. The patients were divided into aura-positive and aura-negative groups according to the presence of aura in seizures. To explore the clinical features of aura, we evaluated the localizing and prognostic values of aura for the outcome of anterior temporal lobectomy based on SEEG.

RESULTS

Among forty patients, twenty-seven patients were in the aura-positive group and ten (25.0%) patients had multiple auras. The most common TLE aura was abdominal aura [thirteen (34.2%) patients]. The postoperative seizure frequency was significantly reduced in the preoperative aura-positive patients compared to the preoperative aura-negative patients (P = 0.011). Patients with abdominal (P = 0.029) and single (P = 0.036) auras had better surgical prognoses than aura-negative patients. In the preoperative evaluation, aura-positive patients had a better surgical outcome if the laterality of positron emission tomography-computed tomography (PET-CT) hypometabolism was concordant with the epileptogenic focus identified with SEEG (P = 0.031). A good postoperative epileptic outcome in aura-positive patients was observed among those with hippocampal sclerotic medial temporal lobe epilepsy (P = 0.025).

CONCLUSION

Epileptic aura is valuable for the localization of the epileptogenic focus. Abdominal aura and single aura were good predictors of better surgical outcomes. Among patients with a preoperative diagnosis of hippocampal sclerosis or with laterality of PET-CT hypometabolism concordant with the epileptogenic focus identified using SEEG, those with aura are likely to benefit from surgery.

Decision-making in stereotactic epilepsy surgery

Surgery can cure or significantly improve both the frequency and the intensity of seizures in patients with medication-refractory epilepsy. The set of diagnostic and therapeutic interventions involved in the path from initial consultation to definitive surgery is complex and includes a multidisciplinary team of neurologists, neurosurgeons, neuroradiologists, and neuropsychologists, supported by a very large epilepsy-dedicated clinical architecture. In recent years, new practices and technologies have emerged that dramatically expand the scope of interventions performed. Stereoelectroencephalography has become widely adopted for seizure localization; stereotactic laser ablation has enabled more focal, less invasive, and less destructive interventions; and new brain stimulation devices have unlocked treatment of eloquent foci and multifocal onset etiologies. This article articulates and illustrates the full framework for how epilepsy patients are considered for surgical intervention, with particular attention given to stereotactic approaches.

Postsurgical seizure outcome in temporal lobe epilepsy patients with normal or subtle, nonspecific MRI findings

OBJECTIVE

The authors' objective was to report postsurgical seizure outcome of temporal lobe epilepsy (TLE) patients with normal or subtle, nonspecific MRI findings and to identify prognostic factors related to seizure control after surgery.

METHODS

This was a retrospective study of patients who underwent surgery from 1999 to 2014 at two comprehensive epilepsy centers. Patients with a clear MRI lesion according to team discussion and consensus were excluded. Presurgical information, surgery details, pathological data, and postsurgical outcomes were retrospectively collected from medical charts. Multiple logistic regression analysis was used to assess the effect of clinical, surgical, and neuroimaging factors on the probability of Engel class I (favorable) versus class II-IV (unfavorable) outcome at last follow-up.

RESULTS

The authors included 73 patients (59% were female; median age at surgery 35.9 years) who underwent operations after a median duration of epilepsy of 13 years. The median follow-up after surgery was 30.6 months. At latest follow-up, 44% of patients had Engel class I outcome. Favorable prognostic factors were focal nonmotor aware seizures and unilateral or no spikes on interictal scalp EEG.

CONCLUSIONS

Favorable outcome can be achieved in a good proportion of TLE patients with normal or subtle, nonspecific MRI findings, particularly when presurgical investigation suggests a rather circumscribed generator. Presurgical factors such as the presence of focal nonmotor aware seizures and unilateral or no spikes on interictal EEG may indicate a higher probability of seizure freedom.

Epileptogenic networks in drug-resistant epilepsy with amygdala enlargement: Assessment with stereo-EEG and 7 T MRI

OBJECTIVE

Amygdala enlargement is increasingly described in association with temporal lobe epilepsies. Its significance, however, remains uncertain both in terms of etiology and its link with psychiatric disorders and of its involvement in the epileptogenic zone. We assessed the epileptogenic networks underlying drug-resistant epilepsy with amygdala enlargement and investigated correlations between clinical features, epileptogenicity and morphovolumetric amygdala characteristics.

METHODS

We identified 12 consecutive patients suffering from drug-resistant epilepsy with visually suspected amygdala enlargement and available stereoelectroencephalographic recording. The epileptogenic zone was defined using the Connectivity Epileptogenicity Index. Morphovolumetric measurements were performed using automatic segmentation and co-registration on the 7TAMIbrain Amygdala atlas.

RESULTS

The epileptogenic zone involved the enlarged amygdala in all but three cases and corresponded to distributed, temporal-insular, temporal-insular-prefrontal or prefrontal-temporal networks in ten cases, while only two were temporo-mesial networks. Morphovolumetrically, amygdala enlargement was bilateral in 75% of patients. Most patients presented psychiatric comorbidities (anxiety, depression, posttraumatic stress disorder). The level of depression defined by screening questionnaire was positively correlated with the extent of amygdala enlargement.

CONCLUSIONS

Drug-resistant epilepsy with amygdala enlargement is heterogeneous; most cases implied "temporal plus" networks.

SIGNIFICANCE

The enlarged amygdala could reflect an interaction of stress-mediated limbic network alterations and mechanisms of epileptogenesis.

Temporal lobe epilepsy: A never-ending story

INTRODUCTION

Semiology and anatomo-electroclinical correlations remain invaluable for maintaining the level of excellence in temporal lobe epilepsy (TLE) surgery, in parallel to the constantly evolving technical progress. The aim of this study was to address semiological frequent and not so frequent signs, rarities and red flags in a long follow-up surgical series of patients suffering from TLE.

METHODS

Patients operated within the boundaries of the TL at our center, with presurgical video-EEG recorded seizures and seizure free after a postoperative follow-up of at least 24 months were included. Ictal semiology was systematically described and new red flags were explored by comparing with a second group of patients with the same inclusion criteria but whose outcome had been unfavorable (Engel II-IV).

RESULTS

Sixty-two patients were included, 46 seizure free and 16 with outcome Engel II-IV. Most seizure-free patients had a classical semiological presentation including aura (69.6%, abdominal the most frequent), followed by loss of responsiveness (90.2%) oral automatisms (90.7%), ipsilateral gestural automatisms (53.5%), contralateral upper limb dystonia (37.5%) or immobility (39.1%), and early ipsilateral non-versive head orientation (33.3%). More infrequent presentations were also present in the group of seizure-free patients: ictal language disturbance (13%), maintenance of responsiveness during seizures (9.8%), and contralateral rhythmic non manipulative automatism (6.9%). The presence of an isolated viscerosensory and/or psychic aura was significantly more frequent in the seizure-free group (p = 0.017), as well as oroalimentary automatisms (p = 0.005). Two signs were only present in the group with outcome Engel II-IV, constituting possible red flags (0.06 < p < 0.07): inferior limbs stepping-like automatisms and postictal dysarthria.

CONCLUSION

An adequate clinical exam during seizures and a careful analysis of video recordings allow to recognize infrequent but well-characterized ictal signs that are part of the range of semiology in TLE, together with the most frequent and classical ictal presentations. Special attention to the localization hypothesis must be paid in the absence of oroalimentary automatisms or when the signs classified as possible red flags emerge.

Insular epilepsy surgery: lessons learned from institutional review and patient-level meta-analysis

OBJECTIVE

Insular lobe epilepsy is a challenging condition to diagnose and treat. Due to anatomical intricacy and proximity to eloquent brain regions, resection of epileptic foci in that region can be associated with significant postoperative morbidity. The aim of this study was to review available evidence on postoperative outcomes following insular epilepsy surgery.

METHODS

A comprehensive literature search (PubMed/MEDLINE, Scopus, Cochrane) was conducted for studies investigating the postoperative outcomes for seizures originating in the insula. Seizure freedom at last follow-up (at least 12 months) comprised the primary endpoint. The authors also present their institutional experience with 8 patients (4 pediatric, 4 adult).

RESULTS

A total of 19 studies with 204 cases (90 pediatric, 114 adult) were identified. The median age at surgery was 23 years, and 48% were males. The median epilepsy duration was 8 years, and 17% of patients had undergone prior epilepsy surgery. Epilepsy was lesional in 67%. The most common approach was transsylvian (60%). The most commonly resected area was the anterior insular region (n = 42, 21%), whereas radical insulectomy was performed in 13% of cases (n = 27). The most common pathology was cortical dysplasia (n = 68, 51%), followed by low-grade neoplasm (n = 16, 12%). In the literature, seizure freedom was noted in 60% of pediatric and 69% of adult patients at a median follow-up of 29 months (75% and 50%, respectively, in the current series). A neurological deficit occurred in 43% of cases (10% permanent), with extremity paresis comprising the most common deficit (n = 35, 21%), followed by facial paresis (n = 32, 19%). Language deficits were more common in left-sided approaches (24% vs 2%, p < 0.001). Univariate analysis for seizure freedom revealed a significantly higher proportion of patients with lesional epilepsy among those with at least 12 months of follow-up (77% vs 59%, p = 0.032).

CONCLUSIONS

These findings may serve as a benchmark when tailoring decision-making for insular epilepsy, and may assist surgeons in their preoperative discussions with patients. Although seizure freedom rates are quite high with insular epilepsy treatment, the associated morbidity needs to be weighed against the potential for seizure freedom.

Surgical Outcomes and EEG Prognostic Factors After Stereotactic Laser Amygdalohippocampectomy for Mesial Temporal Lobe Epilepsy

Objective: To assess the seizure outcomes of stereotactic laser amygdalohippocampectomy (SLAH) in consecutive patients with mesial temporal lobe epilepsy (mTLE) in a single center and identify scalp EEG and imaging factors in the presurgical evaluation that correlate with post-surgical seizure recurrence.

Methods: We retrospectively reviewed the medical and EEG records of 30 patients with drug-resistant mTLE who underwent SLAH and had at least 1 year of follow-up. Surgical outcomes were classified using the Engel scale. Univariate hazard ratios were used to evaluate the risk factors associated with seizure recurrence after SLAH.

Results: The overall Engel class I outcome after SLAH was 13/30 (43%), with a mean postoperative follow-up of 48.9 ± 17.6 months. Scalp EEG findings of interictal regional slow activity (IRSA) on the side of surgery (HR = 4.05, p = 0.005) and non-lateralizing or contra-lateralizing seizure onset (HR = 4.31, p = 0.006) were negatively correlated with postsurgical seizure freedom. Scalp EEG with either one of the above features strongly predicted seizure recurrence after surgery (HR = 7.13, p < 0.001) with 100% sensitivity and 71% specificity.

Significance: Understanding the factors associated with good or poor surgical outcomes can help choose the best candidates for SLAH. Of the variables assessed, scalp EEG findings were the most clearly associated with seizure outcomes after SLAH.

Multi-Head Self-Attention Model for Classification of Temporal Lobe Epilepsy Subtypes

As a long-standing chronic disease, Temporal Lobe Epilepsy (TLE), resulting from abnormal discharges of neurons and characterized by recurrent episodic central nervous system dysfunctions, has affected more than 70% of drug-resistant epilepsy patients across the world. As the etiology and clinical symptoms are complicated, differential diagnosis of TLE mainly relies on experienced clinicians, and specific diagnostic biomarkers remain unclear. Though great effort has been made regarding the genetics, pathology, and neuroimaging of TLE, an accurate and effective diagnosis of TLE, especially the TLE subtypes, remains an open problem. It is of a great importance to explore the brain network of TLE, since it can provide the basis for diagnoses and treatments of TLE. To this end, in this paper, we proposed a multi-head self-attention model (MSAM). By integrating the self-attention mechanism and multilayer perceptron method, the MSAM offers a promising tool to enhance the classification of TLE subtypes. In comparison with other approaches, including convolutional neural network (CNN), support vector machine (SVM), and random forest (RF), experimental results on our collected MEG dataset show that the MSAM achieves a supreme performance of 83.6% on accuracy, 90.9% on recall, 90.7% on precision, and 83.4% on F1-score, which outperforms its counterparts. Furthermore, effectiveness of varying head numbers of multi-head self-attention is assessed, which helps select the optimal number of multi-head. The self-attention aspect learns the weights of different signal locations which can effectively improve classification accuracy. In addition, the robustness of MSAM is extensively assessed with various ablation tests, which demonstrates the effectiveness and generalizability of the proposed approach.

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