Radiofrequency ablation of the centromedian thalamic nucleus in the treatment of drug-resistant epilepsy

The thalamus: Structure, function, and neurotherapeutics

The complexity and expansive nature of thalamic research has led to numerous interventions for varied disease states. At the same time, this complexity along with siloed areas of study can hinder a comprehensive understanding. The goal of this paper is to give the reader a broader and more detailed perspective on the thalamus. In order to accomplish this goal, the paper begins with a summary of the function, electrophysiology, and anatomy of the normal thalamus. With this foundation, thalamic involvement in neurological diseases is discussed with a focus on epilepsy. Therapeutic interventions in the thalamus for epilepsy as well as movement disorders, psychiatric conditions and disorders of consciousness are described. Lastly limitations in the field and future models of data sharing and cooperation are explored.

Stereoelectroencephalography-Guided Radiofrequency Thermocoagulation: Diagnostic and Therapeutic Implications

Despite recent medical therapeutic advances, approximately one third of patients do not attain seizure freedom with medications. This drug-resistant epilepsy population suffers from heightened morbidity and mortality. In appropriate patients, resective epilepsy surgery is far superior to continued medical therapy. Despite this efficacy, there remain drawbacks to traditional epilepsy surgery, such as the morbidity of open neurosurgical procedures as well as neuropsychological adverse effects. SEEG-guided Radiofrequency Thermocoagulation (SgRFTC) is a minimally invasive, electrophysiology-guided intervention with both diagnostic and therapeutic implications for drug-resistant epilepsy that offers a convenient adjunct or alternative to ablative and resective approaches. We review the international experience with this procedure, including methodologies, diagnostic benefit, therapeutic benefit, and safety considerations. We propose a framework in which SgRFTC may be incorporated into intracranial EEG evaluations alongside passive recording. Lastly, we discuss the potential role of SgRFTC in both delineating and reorganizing epilepsy networks.

Frameless Robot-Assisted Asleep Centromedian Thalamic Nucleus Deep Brain Stimulation Surgery in Patients with Drug-Resistant Epilepsy: Technical Description and Short-Term Clinical Results

INTRODUCTION

This purpose of this work is to give a detailed description of a surgical technique for frameless robot-assisted asleep deep brain stimulation (DBS) of the centromedian thalamic nucleus (CMT) in drug-resistant epilepsy (DRE).

METHODS

Ten consecutively enrolled patients who underwent CMT-DBS were included in the study. The FreeSurfer "Thalamic Kernel Segmentation" module and experience target coordinates were used for locating the CMT, and quantitative susceptibility mapping (QSM) images were used to check the target. The patient's head was secured with a head clip, and electrode implantation was performed with the assistance of the neurosurgical robot Sinovation^®. After opening the dura, the burr hole was continuously flushed with physiological saline to stop air from entering the skull. All procedures were performed under general anesthesia without intraoperative microelectrode recording (MER).

RESULTS

The mean age of the patients at surgery and onset of seizures was 22 years (range 11-41 years) and 11 years (range 1-21 years), respectively. The median duration of seizures before CMT-DBS surgery was 10 years (2-26 years). CMT was successfully segmented, and its position was verified by experience target coordinates and QSM images in all ten patients. The mean surgical time for bilateral CMT-DBS in this cohort was 165 ± 18 min. The mean pneumocephalus volume was 2 cm³. The median absolute errors in the x-, y-, and z-axes were 0.7 mm, 0.5 mm, and 0.9 mm, respectively. The median Euclidean distance (ED) and radial error (RE) was 1.3 ± 0.5 mm and 1.0 ± 0.3 mm, respectively. No significant difference was found between right- and left-sided electrodes regarding the RE nor the ED. After a mean 12-month follow-up, the average reduction in seizures was 61%, and six patients experienced a ≥ 50% reduction in seizures, including one patient who had no seizures after the operation. All patients tolerated the anesthesia operation, and no permanent or serious complications were reported.

CONCLUSIONS

Frameless robot-assisted asleep surgery is a precise and safe approach for placing CMT electrodes in patients with DRE, shortening the surgery time. The segmentation of the thalamic nuclei enables the precise location of the CMT, and the flow of physiological saline to seal the burr holes is a good way to reduce the influx of air. CMT-DBS is an effective method to reduce seizures.

Systematic review and patient-level meta-analysis of radiofrequency ablation for medically refractory epilepsy: Implications for clinical practice and research

BACKGROUND

Radiofrequency thermocoagulation (RF-TC) is a minimally invasive procedure for the treatment of epileptic foci. The aim of this study is to review available evidence on the safety and efficacy of RF-TC for medically refractory epilepsy.

METHODS

A comprehensive literature search (Pubmed/Medline, EMBASE, Cochrane) was conducted for studies with patient-level data on RF-TC for medically refractory epilepsy. Seizure outcome (Engel classification) at last follow-up comprised the primary endpoint. New temporary or permanent post-procedural neurological deficits were the secondary endpoints.

RESULTS

A total of 20 studies (360 patients) were analyzed. Median age at the time of intervention was 29 years (interquartile range (IQR): 21-37) and 57% were males. A lesional MRI was noted in 59% of patients. Median duration of postoperative follow-up was 24 months (IQR: 11-48). The median number of RF-TC lesions per patient was 11 (IQR: 6-19), with bipolar ablation (i.e. between two contiguous contacts) being the most common method (n = 244, 68%). The most common RF-TC location was the mesial temporal structures, without (34%) or with (7%) the temporal neocortex, followed by the insula (13%) and the frontal lobe (12%). Multilobar targets were lesioned in 11% of patients. New neurological deficits developed in 10% of patients (2% remained permanently), with the most common being motor deficits. Among patients with at least 12 months of follow-up (n = 267, 74% of overall cohort), a favorable seizure outcome (Engel I/II class) was achieved in 62% of cases. Patients with a favorable seizure outcome were significantly more likely to have a lesional MRI (71% vs 43% 51%, p < 0.001), have a higher number of RF ablations (15 [IQR 8-31] vs 9 [IQR 4-14], p < 0.001), and undergo monopolar RF-TC (50% vs 30%, p = 0.002).

CONCLUSION

Current evidence supports the promising safety and efficacy profile of RF-TC for medically refractory epilepsy. Randomized controlled trial data are needed to further establish the role of this intervention in preoperative discussions with patients and their families.

Centromedian thalamic deep brain stimulation for drug-resistant epilepsy: single-center experience

OBJECTIVE

Neuromodulation of the centromedian nucleus of the thalamus (CM) has unclear effectiveness in the treatment of drug-resistant epilepsy. Prior reports suggest that it may be more effective in the generalized epilepsies such as Lennox-Gastaut syndrome (LGS). The objective of this study was to determine the outcome of CM deep brain stimulation (DBS) at the authors' institution.

METHODS

Retrospective chart review was performed for all patients who underwent CM DBS at Emory University, which occurred between December 2018 and May 2021. CM DBS electrodes were implanted using three different surgical methods, including frame-based, robot-assisted, and direct MRI-guided. Seizure frequency, stimulation parameters, and adverse events were recorded from subsequent clinical follow-up visits.

RESULTS

Fourteen patients underwent CM DBS: 9 had symptomatic generalized epilepsy (including 5 with LGS), 3 had primary or idiopathic generalized epilepsy, and 2 had bifrontal focal epilepsy. At last follow-up (mean [± SEM] 19 ± 5 months, range 4.1-33 months, ≥ 6 months in 11 patients), the median seizure frequency reduction was 91%. Twelve patients (86%) were considered responders (≥ 50% decrease in seizure frequency), including 10 of 12 with generalized epilepsy and both patients with bifrontal epilepsy. Surgical adverse events were rare and included 1 patient with hardware breakage, 1 with a postoperative aspiration event, and 1 with a nonclinically significant intracranial hemorrhage.

CONCLUSIONS

CM DBS was an effective treatment for drug-resistant generalized and bifrontal epilepsies. Additional studies and analyses may investigate whether CM DBS is best suited for specific epilepsy types, and the relationship of lead location to outcome in different epilepsies.