Challenges and opportunities in awake craniotomy for brain tumor surgery in low and lower-middle income countries: A narrative review and perspective.

BACKGROUND: Low- (LIC) and Lower-Middle Income Countries (LMIC) are presented with unique challenges and opportunities when performing awake craniotomy (AC) for brain tumors. These circumstances arise from factors that are financial, infrastructural, educational, personnel, and socio-cultural in nature. METHODS: We performed a systematic narrative review of series on AC for intra-axial brain tumors in LIC/LMIC using PRISMA guidelines, focusing on the challenges and opportunities in these settings. The PubMed, Scopus, and Web of Science databases were searched. RESULTS: After initially identifying 74 studies, inclusion-exclusion criteria were applied, leaving a total of 14 studies included in the review. These involved 409 patients who underwent AC in LIC/LMIC. These series were from India, Ghana, Nigeria, Iran, Pakistan, Morocco, the Philippines, and Egypt. The most common pathology encountered were gliomas (10-70%). Most studies (11/14, 78.5%) reported on their technique of cortical-subcortical mapping. All reported on motor mapping and 8 of these performed language mapping. The most common outcomes reported were seizure and neurologic deficits, and longest follow-up was at 1 year. Challenges noted were lack of equipment and trained personnel, need for validated tests for the local setting, and sociocultural factors. Opportunities identified were volume for training, technique innovation, and international collaboration. CONCLUSION: There are numerous challenges and opportunities that arise when performing AC in LIC/LMIC. A collaborative approach towards harnessing the opportunities, and seeking creative solutions to address the challenges, would provide an ideal mechanism towards advancing neurosurgical care and specialty worldwide.

Case report: when art is faced with brain surgery: acute change in creative style in a painter after glioma resection.

Background: Strong interactions between art and health are well-known. While advances in brain surgery resulted in an improved preservation of sensorimotor, visuospatial, language and cognitive functions, creative abilities received less attention. However, creativity may represent a critical issue to resume an optimal quality of life, especially in artists. Here, a unique case of sudden change in creative style in a painter who underwent glioma resection is described. This prompts to explore further creative thinking and its clinical implications in routine practice. Methods: A 36-year-old right-handed woman experienced inaugural seizures, allowing the discovery of a right frontal lesion. The patient was a professional painter and did not complain about any decline in her creativity. The preoperative neurological examination was normal. Results: Surgery was achieved with a maximal tumor resection through a frontal lobectomy. A WHO grade II oligodendroglioma was diagnosed. A regular surveillance was performed without adjuvant oncological treatment. The patient did not exhibit postoperative functional deterioration and she returned to normal activities including painting during 15 years. Remarkably, even though her creative activity was judged by the patient herself to be rich and satisfying, her style drastically changed from surrealism and mysticism to cubism whereas she was not able to explain why. Conclusion: This is the first report of acute modification of the painting style following frontal lobectomy for a low-grade glioma, supporting that brain resective surgery may impact creativity. While neglected for many decades, this complex human ability should be evaluated more regularly in neurosurgical practice, particularly in artists.

Multivariate mapping of low-resilient neurocognitive systems within and around low-grade gliomas.

Accumulating evidence suggests that the brain exhibits a remarkable capacity for functional compensation in response to neurological damage, a resilience potential that is deeply rooted in the malleable features of its underlying anatomo-functional architecture. This propensity is particularly exemplified by diffuse low-grade gliomas (DLGGs), a subtype of primary brain tumour. However, functional plasticity is not boundless, and surgical resections directed at structures with limited neuroplasticity may lead to incapacitating impairments. Yet, maximizing DLGG resections offers substantial oncological benefits, especially when the resection extends beyond the tumour margins (i.e., supra-tumour or supra-total resection). In this context, the primary objective of this study was to identify which cerebral structures were associated with less favourable cognitive outcomes after surgery, while accounting for intra-tumour and supra-tumour features of the surgical resections. To reach this objective, we leveraged a unique cohort of 400 DLGG patients who underwent surgery with awake cognitive mapping. Patients benefited from a neuropsychological assessment consisting of 18 subtests administered before and 3 months post-surgery. We analysed changes in performance and applied topography-focused and disconnection-focused multivariate lesion-symptom mapping (LSM) using support vector regressions with an attempt to capture resected cortico-subcortical structures less amenable to full cognitive compensations. The observed changes in performance were of a limited magnitude suggesting an overall recovery (13/18 tasks fully recovered despite a mean resection extent of 92.4%). Nevertheless, LSM analyses revealed that a lack of recovery in picture naming was linked to damage in the left inferior temporal gyrus and inferior longitudinal fasciculus. Similarly, for semantic fluency abilities, an association was established with damage to the left precuneus/posterior cingulate. For phonologic fluency abilities, the left dorso-medial frontal cortex and the frontal aslant tract were implicated. Moreover, difficulties in spatial exploration were associated with injury to the right dorsomedial prefrontal cortex and its underlying connectivity. An exploratory analysis suggested that supra-tumoral resections were associated with a less pronounced recovery following specific resection patterns, such as supra-tumour resections of the left uncinate fasciculus (picture naming), the left corticostriatal tract and the anterior corpus callosum (phonologic fluency), the hippocampus and para-hippocampus (episodic memory), and the right frontal-mesial areas (visuospatial exploration). Collectively, these patterns of results shed new light on both low-resilient neural systems and the prediction of cognitive recovery following glioma surgery. Furthermore, they indicate that supra-tumour resections were only occasionally less well-tolerated from a cognitive viewpoint. In doing so, they have deep implications for surgical planning and rehabilitation strategies.

The Alcatraz-Strategy: a roadmap to break the connectivity barrier in malignant brain tumours.

In recent years, the discovery of functional and communicative cellular tumour networks has led to a new understanding of malignant primary brain tumours. In this review, the authors shed light on the diverse nature of cell-to-cell connections in brain tumours and propose an innovative treatment approach to address the detrimental connectivity of these networks. The proposed therapeutic outlook revolves around three main strategies: (a) supramarginal resection removing a substantial portion of the communicating tumour cell front far beyond the gadolinium-enhancing tumour mass, (b) morphological isolation at the single cell level disrupting structural cell-to-cell contacts facilitated by elongated cellular membrane protrusions known as tumour microtubes (TMs), and (c) functional isolation at the single cell level blocking TM-mediated intercellular cytosolic exchange and inhibiting neuronal excitatory input into the malignant network. We draw an analogy between the proposed therapeutic outlook and the Alcatraz Federal Penitentiary, where inmates faced an impassable sea barrier and experienced both spatial and functional isolation within individual cells. Based on current translational efforts and ongoing clinical trials, we propose the Alcatraz-Strategy as a promising framework to tackle the harmful effects of cellular brain tumour networks.

Predictors of cognition after glioma surgery: connectotomy, structure-function phenotype, plasticity.

Determining preoperatively the maximal extent of resection that would preserve cognitive functions is the core challenge of brain tumor surgery. Over the last decade, the methodological framework to achieve this goal has been thoroughly renewed: the population-level topographically-focused voxel-based lesion-symptom mapping has been progressively overshadowed by machine learning (ML) algorithmics, in which the problem is framed as predicting cognitive outcomes in a patient-specific manner from a typically large set of variables. However, the choice of these predictors is of utmost importance, as they should be both informative and parsimonious. In this perspective, we first introduce the concept of connectotomy: instead of parametrizing resection topography through the status (intact/resected) of a huge number of voxels (or parcels) paving the whole brain in the cartesian 3D-space, the connectotomy models the resection in the connectivity space, by computing a handful number of networks disconnection indices, measuring how the structural connectivity sustaining each network of interest was hit by the resection. This connectivity-informed reduction of dimensionality is a necessary step for efficiently implementing ML tools, given the relatively small number of patient-examples in available training datasets. We further argue that two other major sources of interindividual variability must be considered to improve the accuracy with which outcomes are predicted: the underlying structure-function phenotype and neuroplasticity, for which we provide an in-depth review and propose new ways of determining relevant predictors. We finally discuss the benefits of our approach for precision surgery of glioma.

Functional and oncological outcomes after right hemisphere glioma resection in awake versus asleep patients: a systematic review and meta-analysis.

The right hemisphere has been underestimated by being considered as the non-dominant hemisphere. However, it is involved in many functions, including movement, language, cognition, and emotion. Therefore, because lesions on this side are usually not resected under awake mapping, there is a risk of unfavorable neurological outcomes. The goal of this study is to compare the functional and oncological outcomes of awake surgery (AwS) versus surgery under general anesthesia (GA) in supratentorial right-sided gliomas. A systematic review of the literature according to PRISMA guidelines was performed up to March 2023. Four databases were screened. Primary outcome to assess was return to work (RTW). Secondary outcomes included the rate of postoperative neurological deficit, postoperative Karnofsky Performance Status (KPS) score and the extent of resection (EOR). A total of 32 articles were included with 543 patients who underwent right hemisphere tumor resection under awake surgery and 294 under general anesthesia. There were no significant differences between groups regarding age, gender, handedness, perioperative KPS, tumor location or preoperative seizures. Preoperative and long-term postoperative neurological deficits were statistically lower after AwS (p = 0.03 and p < 0.01, respectively), even though no difference was found regarding early postoperative course (p = 0.32). A subsequent analysis regarding type of postoperative impairment was performed. Severe postoperative language deficits were not different (p = 0.74), but there were fewer long-term mild motor and high-order cognitive deficits (p < 0.05) in AwS group. A higher rate of RTW (p < 0.05) was documented after AwS. The EOR was similar in both groups. Glioma resection of the right hemisphere under awake mapping is a safer procedure with a better preservation of high-order cognitive functions and a higher rate of RTW than resection under general anesthesia, despite similar EOR.

Is intraoperative mapping of music performance mandatory to preserve skills in professional musicians? Awake surgery for lower-grade glioma conducted from a meta-networking perspective.

OBJECTIVE: In surgery for lower-grade glioma (LGG) in professional musicians, for whom preserving music ability is essential, a critical question has emerged, namely, is it mandatory to include music performance during awake mapping, as proposed in several reports? In fact, music ability is subserved by a mosaic of interactive cognitive and emotional processes that rest on several networks. Therefore, from a meta-network perspective, the authors investigated whether an integrated multimodal monitoring of these cognitive and emotional functions during stimulation mapping could be efficient in maintaining musical skill. Indeed, it could be difficult for a patient to play a musical instrument in the surgical setting in addition to performing other tasks, such as movement and language. METHODS: An awake mapping-guided resection for LGG without intraoperative music performance was performed in 3 professional musicians. Intraoperative tests were tailored to each patient depending on the critical corticosubcortical circuits surrounding the tumor, including not only sensorimotor or language skills but also higher-order functions with a constant multitasking during the resection. RESULTS: Although music skills were not mapped during surgery, all patients resumed their professional activities, preserving the ability to play music and to perform concerts, to teach and to compose music, or to start learning a new instrument. CONCLUSIONS: A connectome-based resection without intraoperative music performance seems effective in achieving maximal glioma removal while preserving crucial networks subserving musical skills, creativity, and music learning. Neurosurgery should evolve toward a meta-networking approach to better understand higher-order functions mediating complex behavior, such as being a professional musician.

Multimodal study of multilevel pulvino-temporal connections: a new piece in the puzzle of lexical retrieval networks.

Advanced methods of imaging and mapping the healthy and lesioned brain have allowed for the identification of the cortical nodes and white matter tracts supporting the dual neurofunctional organization of language networks in a dorsal phonological and a ventral semantic stream. Much less understood are the anatomical correlates of the interaction between the two streams; one hypothesis being that of a subcortically mediated interaction, through crossed cortico-striato-thalamo-cortical and cortico-thalamo-cortical loops. In this regard, the pulvinar is the thalamic subdivision that has most regularly appeared as implicated in the processing of lexical retrieval. However, descriptions of its connections with temporal (language) areas remain scarce. Here we assess this pulvino-temporal connectivity using a combination of state-of-the-art techniques: white matter stimulation in awake surgery and postoperative diffusion MRI (n = 4), virtual dissection from the Human Connectome Project 3 and 7 T datasets (n = 172) and operative microscope-assisted post-mortem fibre dissection (n = 12). We demonstrate the presence of four fundamental fibre contingents: (i) the anterior component (Arnold's bundle proper) initially described by Arnold in the 19th century and destined to the anterior temporal lobe; (ii) the optic radiations-like component, which leaves the pulvinar accompanying the optical radiations and reaches the posterior basal temporal cortices; (iii) the lateral component, which crosses the temporal stem orthogonally and reaches the middle temporal gyrus; and (iv) the auditory radiations-like component, which leaves the pulvinar accompanying the auditory radiations to the superomedial aspect of the temporal operculum, just posteriorly to Heschl's gyrus. Each of those components might correspond to a different level of information processing involved in the lexical retrieval process of picture naming.

Evaluation of a nnU-Net type automated clinical volumetric tumor segmentation tool for diffuse low-grade glioma follow-up.

BACKGROUND AND PURPOSE: Diffuse low-grade gliomas (DLGG) are characterized by a slow and continuous growth and always evolve towards an aggressive grade. Accurate prediction of the malignant transformation is essential as it requires immediate therapeutic intervention. One of its most precise predictors is the velocity of diameter expansion (VDE). Currently, the VDE is estimated either by linear measurements or by manual delineation of the DLGG on T2 FLAIR acquisitions. However, because of the DLGG's infiltrative nature and its blurred contours, manual measures are challenging and variable, even for experts. Therefore we propose an automated segmentation algorithm using a 2D nnU-Net, to 1) gain time and 2) standardize VDE assessment. MATERIALS AND METHODS: The 2D nnU-Net was trained on 318 acquisitions (T2 FLAIR & 3DT1 longitudinal follow-up of 30 patients, including pre- & post-surgery acquisitions, different scanners, vendors, imaging parameters…). Automated vs. manual segmentation performance was evaluated on 167 acquisitions, and its clinical interest was validated by quantifying the amount of manual correction required after automated segmentation of 98 novel acquisitions. RESULTS: Automated segmentation showed a good performance with a mean Dice Similarity Coefficient (DSC) of 0.82±0.13 with manual segmentation and a substantial concordance between VDE calculations. Major manual corrections (i.e., DSC<0.7) were necessary only in 3/98 cases and 81% of the cases had a DSC>0.9. CONCLUSION: The proposed automated segmentation algorithm can successfully segment DLGG on highly variable MRI data. Although manual corrections are sometimes necessary, it provides a reliable, standardized and time-winning support for VDE extraction to asses DLGG growth.

Disruption of the left anterior ventrolateral temporal cortex along with the inferior longitudinal fasciculus impairs the ability to retrieve famous face names: Evidence from three longitudinal case studies.

The cortical distribution of the proper name (PN) retrieval network has been widely studied contrary to its connectional anatomy. Here, we report the case of three patients with a low-grade glioma damaging the mid-to-anterior part of the left temporal lobe. A longitudinal behavioural assessment showed that the surgery caused a long-lasting decline in PN retrieval performances in all patients. Furthermore, a detailed analysis of surgery-related structural disconnections revealed that interruption of the inferior longitudinal fasciculus was the unique common denominator.

Integrating direct electrical brain stimulation with the human connectome.

Neurological and neurodevelopmental conditions are a major public health concern for which new therapies are urgently needed. The development of effective therapies relies on the precise mapping of the neural substrates causally involved in behaviour generation. Direct electrical stimulation (DES) performed during cognitive and neurological monitoring in awake surgery is currently considered the gold standard for the causal mapping of brain functions. However, DES is limited by the focal nature of the stimulation sites, hampering a real holistic exploration of human brain functions at the network level. We used 4137 DES points derived from 612 glioma patients in combination with human connectome data-resting-state functional MRI, n = 1000 and diffusion weighted imaging, n = 284-to provide a multimodal description of the causal macroscale functional networks subtending 12 distinct behavioural domains. To probe the validity of our procedure, we (i) compared the network topographies of healthy and clinical populations; (ii) tested the predictive capacity of DES-derived networks; (iii) quantified the coupling between structural and functional connectivity; and (iv) built a multivariate model able to quantify single subject deviations from a normative population. Lastly, we probed the translational potential of DES-derived functional networks by testing their specificity and sensitivity in identifying critical neuromodulation targets and neural substrates associated with postoperative language deficits. The combination of DES and human connectome data resulted in an average 29.4-fold increase in whole brain coverage compared to DES alone. DES-derived functional networks are predictive of future stimulation points (97.8% accuracy) and strongly supported by the anatomical connectivity of subcortical stimulations. We did not observe any significant topographical differences between the patients and the healthy population at both group and single subject level. Showcasing concrete clinical applications, we found that DES-derived functional networks overlap with effective neuromodulation targets across several functional domains, show a high degree of specificity when tested with the intracranial stimulation points of a different stimulation technique and can be used effectively to characterize postoperative behavioural deficits. The integration of DES with the human connectome fundamentally advances the quality of the functional mapping provided by DES or functional imaging alone. DES-derived functional networks can reliably predict future stimulation points, have a strong correspondence with the underlying white matter and can be used for patient specific functional mapping. Possible applications range from psychiatry and neurology to neuropsychology, neurosurgery and neurorehabilitation.

Identification of Metabolomic Markers in Frozen or Formalin-Fixed and Paraffin-Embedded Samples of Diffuse Glioma from Adults.

The aim of this study was to identify metabolomic signatures associated with the gliomagenesis pathway (IDH-mutant or IDH-wt) and tumor grade of diffuse gliomas (DGs) according to the 2021 WHO classification on frozen samples and to evaluate the diagnostic performances of these signatures in tumor samples that are formalin-fixed and paraffin-embedded (FFPE). An untargeted metabolomic study was performed using liquid chromatography/mass spectrometry on a cohort of 213 DG samples. Logistic regression with LASSO penalization was used on the frozen samples to build classification models in order to identify IDH-mutant vs. IDH-wildtype DG and high-grade vs low-grade DG samples. 2-Hydroxyglutarate (2HG) was a metabolite of interest to predict IDH mutational status and aminoadipic acid (AAA) and guanidinoacetic acid (GAA) were significantly associated with grade. The diagnostic performances of the models were 82.6% AUC, 70.6% sensitivity and 80.4% specificity for 2HG to predict IDH status and 84.7% AUC, 78.1% sensitivity and 73.4% specificity for AAA and GAA to predict grade from FFPE samples. Thus, this study showed that AAA and GAA are two novel metabolites of interest in DG and that metabolomic data can be useful in the classification of DG, both in frozen and FFPE samples.

Awake craniotomy in epilepsy surgery includes previously inoperable patients with preserved efficiency and safety.

Introduction: Whilst awake craniotomy has been widely used historically in epilepsy surgery, the safety and efficacy of this approach in epilepsy surgery has been sparsely investigated in controlled studies. The objective of this study is to investigate the safety and efficacy of awake resection in epilepsy surgery and focuses on the possibility to widen surgical indications with awake surgery. Methods: Fifteen patients operated with awake epilepsy surgery were compared to 30 matched controls undergoing conventional/asleep epilepsy surgery. The groups were compared with regard to neurological complications, seizure control and location of resection. Results: Regarding seizure control, 86% of patients in the awake group reached Engel grade 1-2 compared to 73% in the control group, operated with conventional/asleep surgery, not a statistically significant difference. Neither was there a statistical significant difference regarding postoperative neurological complications. However, there was a significant difference in location of the resection when comparing the two groups. Of the 15 patients operated with awake intraoperative mapping, four had previously been considered as non-operable by epilepsy surgery centres, due to vicinity to eloquent brain regions and predicted risk of post-operative neurological deficits. Discussion: The results show that awake epilepsy surgery yields similar level of seizure control when compared to conventional asleep surgery, with maintained safety in regard to neurological complications. Furthermore, the results indicate that awake craniotomy in epilepsy surgery is feasible and possible in patients otherwise regarded as inoperable with epileptigenic zone in proximity to eloquent brain structures.

Neuromodulation-induced prehabilitation to leverage neuroplasticity before brain tumor surgery: a single-cohort feasibility trial protocol.

Introduction: Neurosurgery for brain tumors needs to find a complex balance between the effective removal of targeted tissue and the preservation of surrounding brain areas. Neuromodulation-induced cortical prehabilitation (NICP) is a promising strategy that combines temporary inhibition of critical areas (virtual lesion) with intensive behavioral training to foster the activation of alternative brain resources. By progressively reducing the functional relevance of targeted areas, the goal is to facilitate resection with reduced risks of neurological sequelae. However, it is still unclear which modality (invasive vs. non-invasive neuromodulation) and volume of therapy (behavioral training) may be optimal in terms of feasibility and efficacy. Methods and analysis: Patients undertake between 10 and 20 daily sessions consisting of neuromodulation coupled with intensive task training, individualized based on the target site and neurological functions at risk of being compromised. The primary outcome of the proposed pilot, single-cohort trial is to investigate the feasibility and potential effectiveness of a non-invasive NICP protocol on neuroplasticity and post-surgical outcomes. Secondary outcomes investigating longitudinal changes (neuroimaging, neurophysiology, and clinical) are measured pre-NICP, post-NICP, and post-surgery. Ethics and dissemination: Ethics approval was obtained from the Research Ethical Committee of Fundació Unió Catalana d'Hospitals (approval number: CEI 21/65, version 1, 13/07/2021). The results of the study will be submitted to a peer-reviewed journal and presented at scientific congresses. Clinical trial registration: ClinicalTrials.gov, identifier NCT05844605.

Bevacizumab in recurrent WHO grades II-III glioma.

Purpose: The management of recurrent WHO grades II-III (rGII-III) glioma is not well established. This study describes the clinical outcomes in patients who received bevacizumab as rescue treatment. Methods: In this retrospective study, the main inclusion criteria were as follows: adult patients with histologicaly proved rGII-III glioma according 2016 WHO classification treated with bevacizumab from 2011 to 2019, T1 contrast enhancement on MRI. Efficacy was assessed using the high-grade glioma 2017 Response Assessment in Neuro-Oncology criteria. Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method. Results: Eighty-one patients were included (M/F ratio: 1.7, median age at diagnosis: 38 years) among whom 46 (56.8%) had an initial diagnosis of grade II glioma. Previous treatments included at least one surgical intervention, radiotherapy (98.8%), and ≥ 2 chemotherapy lines (64.2%). After bevacizumab initiation, partial response, stable disease, and progressive disease were observed in 27.2%, 22.2%, and 50.6% of patients. The median PFS and OS were 4.9 months (95% confidence interval [CI] 3.7-6.1) and 7.6 months (95% CI 5.5-9.9). Bevacizumab severe toxicity occurred in 12.3%. Twenty-four (29.6%) patients discontinued bevacizumab without radiological progression. Oligodendroglioma and age ≥ 38 years at diagnosis were more frequent in this subgroup (odds ratio = 0.24, 95% CI 0.07-0.84, p = 0.023 and 0.36, 95% CI 0.13-0.99, p = 0.042). Ten of these 24 patients were alive at 12 months and two patients at 8 years after bevacizumab initiation, without any subsequent treatment. Conclusion: Bevacizumab can be an option for heavily pretreated patients with rGII-III glioma with contrast enhancement. In our study, bevacizumab displayed prolonged activity in a subgroup of patients.

Brain Plasticity Profiling as a Key Support to Therapeutic Decision-Making in Low-Grade Glioma Oncological Strategies.

The ability of neural circuits to compensate for damage to the central nervous system is called postlesional plasticity. In diffuse low-grade gliomas (LGGs), a crosstalk between the brain and the tumor activates modulations of plasticity, as well as tumor proliferation and migration, by means of paracrine and electrical intercommunications. Such adaptative mechanisms have a major impact on the benefits and risks of oncological treatments but are still disregarded by current neuro-oncological guidelines. In this review, the authors first aimed to highlight clinical, radiological, and oncological markers that robustly reflect the plasticity potentials and limitations in LGG patients, including the location of the tumor and the degree of critical white matter tract infiltration, the velocity of tumor expansion, and the reactional changes of neuropsychological performances over time. Second, the interactions between the potential/limitations of cerebral plasticity and the efficacy/tolerance of treatment options (i.e., surgery, chemotherapy, and radiotherapy) are reviewed. Finally, a longitudinal and multimodal treatment approach accounting for the evolutive profiles of brain plasticity is proposed. Such an approach integrates personalized predictive models of plasticity potentials with a step-by-step therapeutic decision making and supports onco-functional balanced strategies in patients with LGG, with the ultimate aim of optimizing overall survival and quality of life.