Early outcomes of stereoelectroencephalography followed by MR-guided laser interstitial thermal therapy: a paradigm for minimally invasive epilepsy surgery

OBJECTIVEStereoelectroencephalography (sEEG) and MR-guided laser interstitial thermal therapy (MRgLITT) have both emerged as minimally invasive alternatives to open surgery for the localization and treatment of medically refractory lesional epilepsy. Although some data are available about the use of these procedures individually, reports are almost nonexistent on their use in conjunction. The authors’ aim was to report early outcomes regarding efficacy and safety of sEEG followed by MRgLITT for localization and ablation of seizure foci in the pediatric population with medically refractory lesional epilepsy.METHODSA single-center retrospective review of pediatric patients who underwent sEEG followed by MRgLITT procedures was performed. Demographic, intraoperative, and outcome data were compiled and analyzed.RESULTSFour pediatric patients with 9 total lesions underwent sEEG followed by MRgLITT procedures between January and September 2017. The mean age at surgery was 10.75 (range 2–21) years. Two patients had tuberous sclerosis and 2 had focal cortical dysplasia. Methods of stereotaxy consisted of BrainLab VarioGuide and ROSA robotic guidance, with successful localization of seizure foci in all cases. The sEEG procedure length averaged 153 (range 67–235) minutes, with a mean of 6 (range 4–8) electrodes and 56 (range 18–84) contacts per patient. The MRgLITT procedure length averaged 223 (range 179–252) minutes. The mean duration of monitoring was 6 (range 4–8) days, and the mean total hospital stay was 8 (range 5–11) days. Over a mean follow-up duration of 9.3 (range 5.1–16) months, 3 patients were seizure free (Engel class I, 75%), and 1 patient saw significant improvement in seizure frequency (Engel class II, 25%). There were no complications.CONCLUSIONSThese early data demonstrate that sEEG followed by MRgLITT can be used safely and effectively to localize and ablate epileptogenic foci in a minimally invasive paradigm for treatment of medically refractory lesional epilepsy in pediatric populations. Continued collection of data with extended follow-up is needed.

Resting state functional connectivity patterns associated with pharmacological treatment resistance in temporal lobe epilepsy

There are no functional imaging based biomarkers for pharmacological treatment response in temporal lobe epilepsy (TLE). In this study, we investigated whether there is an association between resting state functional brain connectivity (RsFC) and seizure control in TLE. We screened a large database containing resting state functional magnetic resonance imaging (Rs-fMRI) data from 286 epilepsy patients. Patient medical records were screened for seizure characterization, EEG reports for lateralization and location of seizure foci to establish uniformity of seizure localization within patient groups. Rs-fMRI data from patients with well-controlled left TLE, patients with treatment-resistant left TLE, and healthy controls were analyzed. Healthy controls and cTLE showed similar functional connectivity patterns, whereas trTLE exhibited a significant bilateral decrease in thalamo-hippocampal functional connectivity. This work is the first to demonstrate differences in neural network connectivity between well-controlled and treatment-resistant TLE. These differences are spatially highly focused and suggest sites for the etiology and possibly treatment of TLE. Altered thalamo-hippocampal RsFC thus is a potential new biomarker for TLE treatment resistance.SummaryResting State functional magnetic resonance imaging (Rs-fMRI), previously utilized to predict lateralization of seizure foci in temporal lobe epilepsy (TLE), is utilized to determine potential mechanisms and biomarkers for treatment-resistant and well-controlled unilateral TLE. We found significant differences in thalamo-hippocampal functional connectivity between treatment-resistant and well-controlled TLE patients. Differences in functional connectivity were focused to thalamo-hippocampal connections and more pronounced in the hemisphere ipsilateral to seizure foci. Aberrant functional connectivity patterns as measured by Rs-fMRI could thus serve as biomarkers for treatment response in TLE.

Chronic subthreshold cortical stimulation for adult drug-resistant focal epilepsy: safety, feasibility, and technique

OBJECTIVEEpilepsy surgery is effective for lesional epilepsy, but it can be associated with significant morbidity when seizures originate from eloquent cortex that is resected. Here, the objective was to describe chronic subthreshold cortical stimulation and evaluate its early surgical safety profile in adult patients with epilepsy originating from seizure foci in cortex that is not amenable to resection.METHODSAdult patients with focal drug-resistant epilepsy underwent intracranial electroencephalography monitoring for evaluation of resection. Those with seizure foci in eloquent cortex were not candidates for resection and were offered a short therapeutic trial of continuous subthreshold cortical stimulation via intracranial monitoring electrodes. After a successful trial, electrodes were explanted and permanent stimulation hardware was implanted.RESULTSTen patients (6 males) who underwent chronic subthreshold cortical stimulation between 2014 and 2016 were included. Based on radiographic imaging, intracranial pathologies included cortical dysplasia (n = 3), encephalomalacia (n = 3), cortical tubers (n = 1), Rasmussen encephalitis (n = 1), and linear migrational anomaly (n = 1). The duration of intracranial monitoring ranged from 3 to 20 days. All patients experienced an uneventful postoperative course and were discharged home with a median length of stay of 10 days. No postoperative surgical complications developed (median follow-up length 7.7 months). Seizure severity and seizure frequency improved in all patients.CONCLUSIONSThe authors’ institutional experience with this small group shows that chronic subthreshold cortical stimulation can be safely and effectively performed in appropriately selected patients without postoperative complications. Future investigation will provide further insight to recently published results regarding mechanism and efficacy of this novel and promising intervention.

216 Chronic Subthreshold Cortical Stimulation for Adult Drug Resistant Focal Epilepsy: Safety, Feasibility, and Technique

INTRODUCTION Epilepsy surgery, while high successful for lesional epilepsy, can be associated with significant morbidity. The objective was to evaluate the safety profile of chronic subthreshold cortical stimulation in patients with seizure foci not amenable to surgical resection. METHODS Patients underwent intracranial electroencephalography monitoring. Those with seizure foci that were deemed unsafe for resection were offered trial of continuous subthreshold cortical stimulation via intracranial monitoring electrodes. After successful trial, trial electrodes were replaced with permanent stimulation. Patients with permanent implantation prior to February, 2016, reported their seizure severity and life satisfaction before and after stimulation. RESULTS >Eight patients from 2014 to 2016 were included in this study. Age ranged (19-56 years). Intracranial pathologies included: cortical dysplasia (n = 3), encephalomalacia (n = 3), cortical tubers (n = 1), and linear migrational anomaly (n = 1). The duration of intracranial monitoring ranged (3-20 days). All patients experienced were discharged to home (median length of stay: 10 days). No postoperative surgical complications have developed to date (median length of follow-up: 187 days). Patients (n = 4) reported a improvement in seizure severity (worst = 10) from mean 7.5 (SE 0.29) to 1.25 (SE 0.75) and life satisfaction (best = 10) from mean 4.25 (SE 1.03) to 7 (SE 1.1), mean follow-up 8.8 months CONCLUSION Our institutional experience shows that chronic cortical stimulation can be safely and effectively performed in appropriately selected patients without postoperative complications. Future investigation will hopefully provide further insight to recently published results into the efficacy of this novel and promising intervention.