Topological Characteristics Associated with Intraoperative Stimulation Related Epilepsy of Glioma Patients: A DTI Network Study

Background: Awake craniotomy with intraoperative stimulation has been utilized in glioma surgical resection to preserve the quality of life. Epilepsy may occur in 5–20% of cases, leading to severe consequences. This study aimed to discuss the mechanism of intraoperative stimulation-related epilepsy (ISE) using DTI-based graph theoretical analysis. Methods: Twenty patients with motor-area glioma were enrolled and divided into two groups (Ep and nEp) according to the presence of ISE. Additionally, a group of 10 healthy participants matched by age, sex, and years of education was also included. All participants underwent T1, T2, and DTI examinations. Graph theoretical analysis was applied to reveal the topological characteristics of white matter networks. Results: Three connections were found to be significantly lower in at least one weighting in the Ep group. These connections were between A1/2/3truL and A4ulL, A1/2/3truR and A4tR, and A6mL and A6mR. Global efficiency was significantly decreased, while the shortest path length increased in the Ep group in at least one weighting. Ten nodes exhibited significant differences in nodal efficiency and degree centrality analyses. The nodes A6mL and A6mR showed a marked decrease in total four weightings in the Ep group. Conclusions: The hub nodes A6mL and A6mR are disconnected in patients with ISE, causing subsequent lower efficiency of global and regional networks. These findings provide a basis for presurgical assessment of ISE, for which caution should be taken when it involves hub nodes during intraoperative electrical stimulation.

A systematic review of the use of subcortical intraoperative electrical stimulation mapping for monitoring of executive deficits and neglect: what is the evidence so far?

Background Over the past decade, the functional importance of white matter pathways has been increasingly acknowledged in neurosurgical planning. A method to directly study anatomo-functional correlations is direct electrical stimulation (DES). DES has been widely accepted by neurosurgeons as a reliable tool to minimize the occurrence of permanent postoperative motor, vision, and language deficits. In recent years, DES has also been used for stimulation mapping of other cognitive functions, such as executive functions and visuospatial awareness. Methods The aim of this review is to summarize the evidence so far from DES studies on subcortical pathways that are involved in visuospatial awareness and in the following three executive functions: (1) inhibitory control, (2) working memory, and (3) cognitive flexibility. Results Eleven articles reported on intraoperative electrical stimulation of white matter pathways to map the cognitive functions and explicitly clarified which subcortical tract was stimulated. The results indicate that the right SLF-II is involved in visuospatial awareness, the left SLF-III and possibly the right SLF-I are involved in working memory, and the cingulum is involved in cognitive flexibility. Conclusions We were unable to draw any more specific conclusions, nor unequivocally establish the critical involvement of pathways in executive functions or visuospatial awareness due to the heterogeneity of the study types and methods, and the limited number of studies that assessed these relationships. Possible approaches for future research to obtain converging and more definite evidence for the involvement of pathways in specific cognitive functions are discussed.

P03.05 The use of subcortical intraoperative electrical stimulation mapping for assessment of executive functions: A summary of the evidence so far

BACKGROUND Over the past years, the functional subcortical architecture of the brain has been increasingly acknowledged in neurosurgical planning. A method to study anatomo-functional correlations is direct electrical stimulation (DES). DES is widely used by neurosurgeons and considered as a reliable tool to minimize the occurrence of permanent postoperative motor, language and visual deficits. In recent years, DES has also been used for mapping of other cognitive functions, such as executive functions. MATERIAL AND METHODS We systematically summarized the evidence so far from DES studies on subcortical pathways that are involved in the following three executive functions: (1) inhibitory control, (2) working memory and (3) cognitive flexibility. RESULTS We only found twelve articles that reported on intraoperative electrical stimulation of white matter pathways to map executive functions and explicitly clarified which subcortical tract was stimulated. The results indicate that the second branch of the right superior longitudinal fasciculus (SLF-II) is involved in inhibitory control, the first branch of the right superior longitudinal fasciculus (SLF-I) and the third branch of the left superior longitudinal fasciculus (SLF-III) are involved in working memory and the cingulum is involved in cognitive flexibility. CONCLUSION We were unable to draw any specific conclusions, nor unequivocally established the pathways involved in executive functions due to heterogenous study characteristics, methods and tasks, and the limited number of studies that assessed these relationships. Clearly, neurosurgical groups are exploring novel methods to assess cognition during awake neurosurgery, but are far from consensus on indications and protocols, which complicated the comparison and summarization of findings. We will discuss possible approaches for future research to obtain converging and more definite evidence for the involvement of subcortical pathways in specific executive functions.

Topological Characteristics Associated with Intraoperative Stimulation Related Epilepsy of Glioma Patients: A DTI Network Study

Purpose Awake craniotomy with intraoperative stimulation has been utilized in glioma surgical resection to preserve life quality. While 5-20% of cases may occur epilepsy during the procedure which leads to severe consequences. The study aimed to discussing the mechanism of intraoperative stimulation-related epilepsy (ISE) with DTI based graph theoretical analysis.Methods 20 patients with motor-area glioma were enrolled and divided into 2 groups (Ep and nEp) according to whether there was ISE. Additionally, a group of 10 healthy participants matched by age, gender and education year were also involved. All participants underwent T1, T2 and DTI. Graph theoretical analysis was applied to reveal topological characteristics of the white matter networks. Results Three connections were found to be significantly lower in at least one weighting in Ep group. They are the connection between A1/2/3truL and A4ulL, A1/2/3truR and A4tR, and A6mL and A6mR. Global efficiency was found to be significantly decreased while the shortest path length increased in Ep group in at least one weighting. Ten nodes exhibited significant difference in the nodal efficiency and degree centrality analysis. The nodes A6mL and A6mR showed markable decrease in total four weightings in Ep group.Conclusion The hub nodes A6mL and A6mR, get disconnected in the patients with ISE, causing subsequent lower efficiency of global and regional network. The findings provide basis for presurgical assessment of ISE, for that caution should be taken when it involves hub nodes during intraoperative electrical stimulation.

Clinical Outcomes of Surgical Management of Primary Brachial Plexus Tumors

Introduction This study evaluates the clinical presentation, tumor characteristics, and clinical outcomes of surgically treated benign and malignant brachial plexus tumors (BPTs). Methods A prospective study of patients with BPTs from June 2015 to August 2020 was conducted. All patients underwent surgical resection with microneurolysis and intraoperative electrical stimulation to preserve the functioning nerve fascicles. Results Fourteen patients with 15 BPTs underwent surgical resection. Mean age was 37.8 ± 12.3 years; with male to female ratio 4:10. The clinical presentations were swelling (100%), pain (84.6%), and paresthesia (76.9%). The lesions involved roots (5/15), trunk (5/15), division (1/15), and cords (4/15). Thirteen patients had benign pathology (8 schwannomas, 3 neurofibromas, 2 lipomas) and two had malignant neurofibrosarcoma. Gross total resection was achieved in all cases except a dumbbell tumor. The mean follow-up period was 24 ± 5 months. Postoperatively, all patients reported improvement in pain and paresthesia with no new sensory deficit. All patients had developed initial motor weakness (Grades 2–4); however, full power (Grade 5) was recovered by 3 to 5 months. Conclusion Total resection can be achieved by appropriate microneural dissection and electrophysiologic monitoring and is potentially curative with preserving function.

Predicting the Extent of Resection in Low-Grade Glioma by Using Intratumoral Tractography to Detect Eloquent Fascicles Within the Tumor

BACKGROUND An early maximal safe surgical resection is the current treatment paradigm for low-grade glioma (LGG). Nevertheless, there are no reliable methods to accurately predict the axonal intratumoral eloquent areas and, consequently, to predict the extent of resection. OBJECTIVE To describe the functional predictive value of eloquent white matter tracts within the tumor by using a pre- and postoperative intratumoral diffusion tensor imaging (DTI) tractography protocol in patients with LGG. METHODS A preoperative intratumoral DTI-based tractography protocol, using the tumor segmented volume as the only seed region, was used to assess the tracts within the tumor boundaries in 22 consecutive patients with LGG. The reconstructed tracts were correlated with intraoperative electrical stimulation (IES)-based language and motor subcortical mapping findings and the extent of resection was assessed by tumor volumetrics. RESULTS Identification of intratumoral language and motor tracts significantly predicted eloquent areas within the tumor during the IES mapping: the positive predictive value for the pyramidal tract, the inferior fronto-occipital fasciculus, the arcuate fasciculus and the inferior longitudinal fasciculus positive was 100%, 100%, 33%, and 80%, respectively, whereas negative predictive value was 100% for all of them. The reconstruction of at least one of these tracts within the tumor was significantly associated with a lower extent of resection (67%) as opposed to the extent of resection in the cases with a negative intratumoral tractography (100%) (P < .0001). CONCLUSION Intratumoral DTI-based tractography is a simple and reliable method, useful in assessing glioma resectability based on the analysis of intratumoral eloquent areas associated with motor and language tracts within the tumor.

Translational Approaches to Electrical Stimulation for Peripheral Nerve Regeneration

Background Achieving functional repair after peripheral nerve injury (PNI) remains problematic despite considerable advances in surgical technique. Therein, questions lie regarding the variable capacity of peripheral nerves to regenerate based on environmental influence. In-depth analyses of multiple therapeutic strategies have ensued to overcome these natural obstacles. Of these candidate therapies, electrical stimulation has emerged a frontrunner. Extensive animal studies have reported the ability of brief intraoperative electrical stimulation (BES) to enhance functional regeneration after PNI. Despite these reports, the exact mechanisms by which BES enhances regeneration and its effects on long nerve lesions are largely unknown. Indeed, clinical translation of this seemingly simple therapeutic has not been so simple, but a few studies performed in humans have yielded highly encouraging results. Objective We aimed to help bridge this translational gap by presenting the latest clinical trials on electrical stimulation for PNIs in combination with relevant etiologies, treatments and nonclinical findings. Methods To do so, a systematic search was performed on PubMed, IEEE, and Web of Science databases up to February 2020 using keywords significant to our study. References of each manuscript were screened for additional manuscripts of relevance to our study. Results We found multiple BES clinical studies reporting enhanced functional recovery or increased nerve regeneration. Although improved outcomes were reported, high variability after BES is seen between and within species likely due to injury severity, location and timeline along with other factors. Conclusion Further clinical studies and introduction of novel delivery platforms are vital to uncover the true regenerative potential of electrical stimulationtherapy.

Current strategies for the treatment of malignant gliomas – experience of the Department of Neurosurgery, Brodno Masovian Hospital in Warsaw

Introduction: Malignant gliomas (HGG) are the most common primary malignant brain tumors arising from glial cells. Between HGG, glioblastoma is the most common and the most malignant histological subtype with only a 27% 2-year survival rate. Current standard medical treatment of malignant gliomas is still not satisfactory, and may need some development and modification. We presented and discussed the achievements of the Department of Neurosurgery at Brodno Masovian Hospital in the treatment of malignant gliomas. Material and methods: We step by step presented and discussed the policy in the treatment of malignant gliomas. We showed all steps starting from preparation of surgery (eg. neuroimaging) and finishing on the presentation the development of perioperative management – from intraoperative electrical stimulation mapping and monitoring which is nowadays already standard method to convection-enhanced delivery (CED) and gamma knife (GK) which are new and promising methods in the treatment of glioblastoma. Results: All surgical methods described in this manuscript were introduced to achieve maximal and safe resection of malignant glioma. CED and GK are the last resort methods for patients with recurrent HGG. Discussion: Department of Neurosurgery at Brodno Masovian Hospital deal with all types of brain tumors, including all types of high grade gliomas. As the first Department in Europe with close cooperation with the Department of Neurosurgery in San Francisco, we have started local infusions of drugs directly to the tumor in the real time of magnetic field, and we think that technology may change all approaches to the treatment of high grade gliomas.

Mapping cognitive and emotional networks in neurosurgical patients using resting-state functional magnetic resonance imaging

Neurosurgery has been at the forefront of a paradigm shift from a localizationist perspective to a network-based approach to brain mapping. Over the last 2 decades, we have seen dramatic improvements in the way we can image the human brain and noninvasively estimate the location of critical functional networks. In certain patients with brain tumors and epilepsy, intraoperative electrical stimulation has revealed direct links between these networks and their function. The focus of these techniques has rightfully been identification and preservation of so-called “eloquent” brain functions (i.e., motor and language), but there is building momentum for more extensive mapping of cognitive and emotional networks. In addition, there is growing interest in mapping these functions in patients with a broad range of neurosurgical diseases. Resting-state functional MRI (rs-fMRI) is a noninvasive imaging modality that is able to measure spontaneous low-frequency blood oxygen level–dependent signal fluctuations at rest to infer neuronal activity. Rs-fMRI may be able to map cognitive and emotional networks for individual patients. In this review, the authors give an overview of the rs-fMRI technique and associated cognitive and emotional resting-state networks, discuss the potential applications of rs-fMRI, and propose future directions for the mapping of cognition and emotion in neurosurgical patients.