Extratemporal resections in pediatric epilepsy surgery-an overview

Seizure Outcome After Surgery for Refractory Epilepsy Diagnosed by 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET/MRI): A Systematic Review and Meta-Analysis

OBJECTIVE

When magnetic resonance imaging (MRI) fails to detect an underlying epileptogenic lesion, the odds of a good outcome after epilepsy surgery are significantly lower (20%-65% compared with 60%-90% if a lesion is detected). We investigated the possible effects of introducing hybrid 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)/MRI into the decision algorithm for patients with lesioned and nonlesioned drug-resistant epilepsy.

METHODS

Three databases were searched from January 1990 to October 2022. We registered the protocol with International Platform of Registered Systematic Review and Meta-analysis Protocols. Studies in which 18F-FDG PET/MRI was conducted with ≥12 months of postsurgical follow-up in patients with refractory epilepsy. Random-effects meta-analysis was used to calculate the proportion of patients with good outcomes. Metaregression was used to investigate sources of heterogeneity.

RESULTS

We identified 8105 studies, of which 23 (1292 patients in total) were included. The overall good postoperative outcome rate was 71% (95% confidence interval 63.6-74.9). Good outcome was associated with the location of the refractory epileptic lesion (temporal lobe or extratemporal; risk ratio 1.27 [95% confidence interval 1.01-1.52], P = 0.009); Length of postoperative follow-up ≥40 months included in the same study accounted for 0.6% of the observed heterogeneity.

CONCLUSIONS

Seventy-one percent of patients with refractory epilepsy and 18F-FDG PET/MRI epileptogenic lesion features had a good outcome of epilepsy after surgery. Our findings can be incorporated into routine preoperative consultations and emphasize the importance of the complete resection of the temporal lobe epileptogenic zone for 18F-FDG PET/MRI detection when safe and feasible.

Surgical Outcome in Extratemporal Epilepsies Based on Multimodal Pre-Surgical Evaluation and Sequential Intraoperative Electrocorticography

Objective: to present the postsurgical outcome of extratemporal epilepsy (ExTLE) patients submitted to preoperative multimodal evaluation and intraoperative sequential electrocorticography (ECoG). Subjects and methods: thirty-four pharmaco-resistant patients with lesional and non-lesional ExTLE underwent comprehensive pre-surgical evaluation including multimodal neuroimaging such as ictal and interictal perfusion single photon emission computed tomography (SPECT) scans, subtraction of ictal and interictal SPECT co-registered with magnetic resonance imaging (SISCOM) and electroencephalography (EEG) source imaging (ESI) of ictal epileptic activity. Surgical procedures were tailored by sequential intraoperative ECoG, and absolute spike frequency (ASF) was calculated in the pre- and post-resection ECoG. Postoperative clinical outcome assessment for each patient was carried out one year after surgery using Engel scores. Results: frontal and occipital resection were the most common surgical techniques applied. In addition, surgical resection encroaching upon eloquent cortex was accomplished in 41% of the ExTLE patients. Pre-surgical magnetic resonance imaging (MRI) did not indicate a distinct lesion in 47% of the cases. In the latter number of subjects, SISCOM and ESI of ictal epileptic activity made it possible to estimate the epileptogenic zone. After one- year follow up, 55.8% of the patients was categorized as Engel class I–II. In this study, there was no difference in the clinical outcome between lesional and non lesional ExTLE patients. About 43.7% of patients without lesion were also seizure- free, p = 0.15 (Fischer exact test). Patients with satisfactory seizure outcome showed lower absolute spike frequency in the pre-resection intraoperative ECoG than those with unsatisfactory seizure outcome, (Mann– Whitney U test, p = 0.005). Conclusions: this study has shown that multimodal pre-surgical evaluation based, particularly, on data from SISCOM and ESI alongside sequential intraoperative ECoG, allow seizure control to be achieved in patients with pharmacoresistant ExTLE epilepsy.

Surgical Treatments of Epilepsy

Nearly 30% of epilepsy patients are refractory to medical therapy. Surgical management of epilepsy is an increasingly viable option for these patients. Although surgery has historically been used as a palliative option, improvements in technology and outcomes show its potential in certain subsets of patients. This article reviews the two main categories of surgical epilepsy treatment-resective surgery and neuromodulation. Resective surgery includes temporal lobe resections, extratemporal resections, laser interstitial thermal therapy, and disconnection procedures. We discuss the three main types of neuromodulation-vagal nerve stimulation, responsive neurostimulation, and deep brain stimulation for epilepsy. The history and indications are explored for each type of treatment. Given the myriad types of resection and neuromodulation techniques, patient selection is reviewed in detail, with a discussion on which patients are most likely to benefit from different treatment strategies. We also discuss outcomes with examples of the pertinent landmark trials and their results. Finally, complications and surgical technique are reviewed. As new indications emerge and patient selection is refined, surgical management will continue to evolve as an adjuvant therapy for epileptic patients.

Forecasting Seizure Freedom After Epilepsy Surgery Assessing Concordance Between Noninvasive and StereoEEG Findings

BACKGROUND

Accurate localization of the probable Epileptogenic Zone (EZ) from presurgical studies is crucial for achieving good prognosis in epilepsy surgery.

OBJECTIVE

To evaluate the degree of concordance at a sublobar localization derived from noninvasive studies (video electroencephalography, EEG; magnetic resonance imaging, MRI; 18-fluorodeoxyglucose positron emission tomography FDG-PET, FDG-PET) and EZ estimated by stereoEEG, in forecasting seizure recurrence in a long-term cohort of patients with focal drug-resistant epilepsy.

METHODS

We selected patients with a full presurgical evaluation and with postsurgical outcome at least 1 yr after surgery. Multivariate Cox regression analysis for seizure freedom (Engel Ia) was performed.

RESULTS

A total of 74 patients were included, 62.2% were in Engel class Ia with a mean follow-up of 2.8 + 2.4 yr after surgery. In the multivariate analysis for Engel Ia vs >Ib, complete resection of the EZ found in stereoEEG (hazard ratio, HR: 0.24, 95%CI: 0.09-0.63, P = .004) and full concordance between FDG-PET and stereoEEG (HR: 0.11, 95%CI: 0.02-0.65, P = .015) portended a more favorable outcome. Most of our results were maintained when analyzing subgroups of patients.

CONCLUSION

The degree of concordance between noninvasive studies and stereoEEG may help to forecast the likelihood of cure before performing resective surgery, particularly using a sublobar classification and comparing the affected areas in the FDG-PET with EZ identified with stereoEEG.

Detection of epileptogenic focus using advanced dynamic statistical parametric mapping with magnetoencephalography in a patient with MRI-negative focal cortical dysplasia type IIB

Advanced dynamic statistical parametric mapping (AdSPM) with magnetoencephalography (MEG) was used to identify MRI-negative epileptogenic lesions in this report. A 15-year-old girl had MRI-negative and pharmacology-resistant focal-onset epilepsy. She experienced two types of seizures. Type I consisted of her arousal from sleep, staring, and a forced head-turning movement to the left, followed by secondary generalization. Type II began with an aura of dizziness followed by staring and postictal headache with fatigue. Scalp video-electroencephalography (EEG) captured two type I seizures originating from the right frontocentral region. MEG showed scattered dipoles over the right frontal region. AdSPM identified the spike source at the bottom of the right inferior frontal sulcus. Intracranial video-EEG captured one type I seizure, which originated from the depth electrode at the bottom of the sulcus and correlated with the AdSPM spike source. Accordingly, the patient underwent resection of the middle and inferior frontal gyri, including the AdSPM-identified spike source. Histopathological examination revealed that the patient had focal cortical dysplasia type IIB. To date, the patient has been seizure free for 2 years while receiving topiramate treatment. This is the first preliminary report to identify MRI-negative epilepsy using AdSPM. Further investigation of AdSPM would be valuable for cases of MRI-negative focal epilepsy.

Clinical Value of Machine Learning in the Automated Detection of Focal Cortical Dysplasia Using Quantitative Multimodal Surface-Based Features

Objective: To automatically detect focal cortical dysplasia (FCD) lesion by combining quantitative multimodal surface-based features with machine learning and to assess its clinical value.

Methods: Neuroimaging data and clinical information for 74 participants (40 with histologically proven FCD type II) was retrospectively included. The morphology, intensity and function-based features characterizing FCD lesions were calculated vertex-wise on each cortical surface and fed to an artificial neural network. The classifier performance was quantitatively and qualitatively assessed by performing statistical analysis and conventional visual analysis.

Results: The accuracy, sensitivity, specificity of the neural network classifier based on multimodal surface-based features were 70.5%, 70.0%, and 69.9%, respectively, which outperformed the unimodal classifier. There was no significant difference in the detection rate of FCD subtypes (Pearson’s Chi-Square = 0.001, p = 0.970). Cohen’s kappa score between automated detection outcomes and post-surgical resection region was 0.385 (considered as fair).

Conclusion: Automated machine learning with multimodal surface features can provide objective and intelligent detection of FCD lesion in pre-surgical evaluation and can assist the surgical strategy. Furthermore, the optimal parameters, appropriate surface features and efficient algorithm are worth exploring.

18F-FDG PET and high-resolution MRI co-registration for pre-surgical evaluation of patients with conventional MRI-negative refractory extra-temporal lobe epilepsy

PURPOSE

Epilepsy that originates outside of the temporal lobe can present some of the most challenging problems for surgical therapy, especially for patients with conventional magnetic resonance imaging (MRI)-negative refractory extra-temporal lobe epilepsy (ETLE). This study aimed to evaluate the clinical value of pre-surgical ¹⁸F-fluoro-deoxy-glucose positron emission tomography (¹⁸F-FDG PET) and high-resolution MRI (HR-MRI) co-registration in patients with conventional MRI-negative refractory ETLE, and compare their surgical outcomes.

METHODS

Sixty-seven patients with conventional MRI-negative refractory ETLE were prospectively included for pre-surgical ¹⁸F-FDG PET and HR-MRI examinations. Under the guidance of ¹⁸F-FDG PET and HR-MRI co-registration, HR-MRI images were re-read. Based on the image result changes from first reading to re-reading, patients were divided into three groups: Change-1 (lesions of subtle abnormality could be identified in re-read), Change-2 (non-specific abnormalities reported in the first reading were considered as lesions on HR-MRI re-read) and No-change. Post-surgical follow-ups were conducted for up to 59 months.

RESULTS

Visual analysis of ¹⁸F-FDG PET showed focal or regional abnormality in 46 patients (68.6%), while the abnormal rate increased to 94.0% (P < 0.05) by co-registration. Of the 67 patients, 46.3% of them were identified as Change-1, and 11.9% as Change-2 after co-registration and HR-MRI re-read. Patients with Change-1 and -2 were more likely to be recommended to receive surgical resection (P < 0.001). In the 17 post-surgical patients, 88% had good outcomes, whereas 11.7% had poor outcomes during our study period.

CONCLUSION

Pre-surgical evaluation by co-registration of ¹⁸F-FDG PET and HR-MRI could improve the identification of the epileptogenic onset zone (EOZ), and may further guide the surgical decision-making and improve the outcome of the refractory ETLE with normal conventional MRI; therefore, it should be recommended as a standard procedure for pre-surgical evaluation of these patients.