Navigated transcranial magnetic stimulation mapping of the motor cortex for preoperative diagnostics in pediatric epilepsy

A Comprehensive Overview of the Current Status and Advancements in Various Treatment Strategies against Epilepsy

Epilepsy affects more than 70 million individuals of all ages worldwide and remains one of the most severe chronic noncommunicable neurological diseases globally. Several neurotransmitters, membrane protein channels, receptors, enzymes, and, more recently noted, various pathways, such as inflammatory and mTORC complexes, play significant roles in the initiation and propagation of seizures. Over the past two decades, significant developments have been made in the diagnosis and treatment of epilepsy. Various pharmacological drugs with diverse mechanisms of action and other treatment options have been developed to control seizures and treat epilepsy. These options include surgical treatment, nanomedicine, gene therapy, natural products, nervous stimulation, a ketogenic diet, gut microbiota, etc., which are in various developmental stages. Despite a plethora of drugs and other treatment options, one-third of affected individuals are resistant to current medications, while the majority of approved drugs have severe side effects, and significant changes can occur, such as pharmacoresistance, effects on cognition, long-term problems, drug interactions, risks of poor adherence, specific effects for certain medications, and psychological complications. Therefore, the development of new drugs and other treatment options that have no or minimal adverse effects is needed to combat this deadly disease. In this Review, we comprehensively summarize and explain all of the treatment options that have been approved or are in developmental stages for epilepsy as well as their status in clinical trials and advancements.

Developmental models of motor-evoked potential features by transcranial magnetic stimulation across age groups from childhood to adulthood

To derive the maturation of neurophysiological processes from childhood to adulthood reflected by the change of motor-evoked potential (MEP) features. 38 participants were recruited from four groups (age mean in years [SD in months], number (males)): children (7.3 [4.2], 7(4)), preadolescents (10.3 [6.9], 10(5)), adolescents (15.3 [9.8], 11(5)), and adults (26.9 [46.2], 10(5)). The navigated transcranial magnetic stimulation was performed on both hemispheres at seven stimulation intensity (SI) levels from sub- to supra-threshold and targeted to the representative cortical area of abductor pollicis brevis muscle. MEPs were measured from three hand- and two forearm-muscles. The input-output (I/O) curves of MEP features across age groups were constructed using linear mixed-effect models. Age and SI significantly affected MEP features, whereas the stimulated side had a minor impact. MEP size and duration increased from childhood to adulthood. MEP onset- and peak-latency dropped in adolescence, particularly in hand muscles. Children had the smallest MEPs with the highest polyphasia, whereas I/O curves were similar among preadolescents, adolescents, and adults. This study illustrates some of the changing patterns of MEP features across the ages, suggesting developing patterns of neurophysiological processes activated by TMS, and to motivate studies with larger sample size.

Navigated Transcranial Magnetic Stimulation Motor Mapping and Diffusion Tensor Imaging Tractography for Diencephalic Tumor in Pediatric Patients

Background. In deep-seated brain tumors, adequate preoperative planning is mandatory to assess the best surgical corridor to obtain maximal safe resection. Functional diffusor tensor imaging (DTI) tractography based on navigated transcranial magnetic stimulation (nTMS) motor mapping has proven to be a valid preoperative examination method in adults. The aim of this paper is to present the application of nTMS and functional DTI tractography in a series of pediatric diencephalic tumors. Material and methods. Three patients affected by thalamic (one) and thalamopeduncular tumor (two) were successfully examined with nTMS motor mapping and DTI tractography between October 2020 and October 2021 (F:M 3:0, mean age 12 years ± 0.8). Cortical representation of leg, hand and mouth were determined in the affected hemisphere and the positive stimulation spots were set as seeds point for tractography. Results. Mapping of the motor cortex and tracts reconstruction for leg and hand were successful in all patients, while facial function was properly mapped in one patient only. In all cases, the procedure was well tolerated and no adverse events were recorded. Spatial relationships between tumor and functional tissue guided the surgical planning. Extent of the resection varied from 96.1% to 100% with a postoperative new motor deficit in one patient. Conclusions. nTMS and DTI fiber tracking is a feasible, effective and well-tolerated method to identify motor pathway in deep-seated lesion in pediatric population.

Personalized surgery of brain tumors in language areas: the role of preoperative brain mapping in patients not eligible for awake surgery

OBJECTIVE

Awake surgery represents the gold standard for resection of brain tumors close to the language network. However, in some cases patients may be considered not eligible for awake craniotomy. In these cases, a personalized brain mapping of the language network may be achieved by navigated transcranial magnetic stimulation (nTMS), which can guide resection in patients under general anesthesia. Here the authors describe their tailored nTMS-based strategy and analyze its impact on the extent of tumor resection (EOR) and language outcome in a series of patients not eligible for awake surgery.

METHODS

The authors reviewed data from all patients harboring a brain tumor in or close to the language network who were considered not eligible for awake surgery and were operated on during asleep surgery between January 2017 and July 2022, under the intraoperative guidance of nTMS data. The authors analyzed the effectiveness of nTMS-based mapping data in relation to 1) the ability of the nTMS-based mapping to stratify patients according to surgical risks, 2) the occurrence of postoperative language deficits, and 3) the EOR.

RESULTS

A total of 176 patients underwent preoperative nTMS cortical language mapping and nTMS-based tractography of language fascicles. According to the nTMS-based mapping, tumors in 115 patients (65.3%) were identified as true-eloquent tumors because of a close spatial relationship with the language network. Conversely, tumors in 61 patients (34.7%) for which the nTMS mapping disclosed a location at a safer distance from the network were identified as false-eloquent tumors. At 3 months postsurgery, a permanent language deficit was present in 13 patients (7.3%). In particular, a permanent deficit was observed in 12 of 115 patients (10.4%) with true-eloquent tumors and in 1 of 61 patients (1.6%) with false-eloquent lesions. With nTMS-based mapping, neurosurgeons were able to distinguish true-eloquent from false-eloquent tumors in a significant number of cases based on the occurrence of deficits at discharge (p < 0.0008) and after 3 months from surgery (OR 6.99, p = 0.03). Gross-total resection was achieved in 80.1% of patients overall and in 69.5% of patients with true-eloquent lesions and 100% of patients with false-eloquent tumors.

CONCLUSIONS

nTMS-based mapping allows for reliable preoperative mapping of the language network that may be used to stratify patients according to surgical risks. nTMS-guided asleep surgery should be considered a good alternative for personalized preoperative brain mapping of the language network that may increase the possibility of safe and effective resection of brain tumors in the dominant hemisphere whenever awake mapping is not feasible.

Non-pharmacological treatments for pediatric refractory epilepsies

INTRODUCTION

Antiseizure medications (ASMs) are the primary treatment option for epilepsies of wide etiologies, however, about 10-20% of children do not gain sustained seizure control and in this case, it is worth investigating "alternative" therapeutic approaches aside from ASMs. Nowadays, non-pharmacological strategies for epilepsy treatment encompass dietary interventions, neurostimulation-based techniques, and biobehavioral approaches.

AREAS COVERED

A search on PubMed database was conducted. Experimental and clinical studies, as well as meta-analysis and structured reviews on the latest non-pharmacological treatments for drug-resistant epilepsy (DRE) in children, were included. Special attention is given to the efficacy and tolerability outcomes, trying to infer the role novel approaches may have in the future.

EXPERT OPINION

The large heterogeneity of primary clinical outcomes and the unavoidable subjective response of each patient to treatments prevents Researchers from the identification of a single, reliable, approach to treat DRE. The understanding of fine pathophysiologic processes is giving the way to the use of alternative therapies, such as the well-known ketogenic diet, in a "personalized" view of treatment. The goal is to apply the non-pharmacological treatment most suitable for the patient's sake.