The "onco-functional balance" in surgery for diffuse low-grade glioma: integrating the extent of resection with quality of life

Object-oriented hand dexterity and grasping abilities, from the animal quarters to the neurosurgical OR: a systematic review of the underlying neural correlates in non-human, human primate and recent findings in awake brain surgery

Introduction

The sensorimotor integrations subserving object-oriented manipulative actions have been extensively investigated in non-human primates via direct approaches, as intracortical micro-stimulation (ICMS), cytoarchitectonic analysis and anatomical tracers. However, the understanding of the mechanisms underlying complex motor behaviors is yet to be fully integrated in brain mapping paradigms and the consistency of these findings with intraoperative data obtained during awake neurosurgical procedures for brain tumor removal is still largely unexplored. Accordingly, there is a paucity of systematic studies reviewing the cross-species analogies in neural activities during object-oriented hand motor tasks in primates and investigating the concordance with intraoperative findings during brain mapping. The current systematic review was designed to summarize the cortical and subcortical neural correlates of object-oriented fine hand actions, as revealed by fMRI and PET studies, in non-human and human primates and how those were translated into neurosurgical studies testing dexterous hand-movements during intraoperative brain mapping.

Methods

A systematic literature review was conducted following the PRISMA guidelines. PubMed, EMBASE and Web of Science databases were searched. Original articles were included if they: (1) investigated cortical activation sites on fMRI and/or PET during grasping task; (2) included humans or non-human primates. A second query was designed on the databases above to collect studies reporting motor, hand manipulation and dexterity tasks for intraoperative brain mapping in patients undergoing awake brain surgery for any condition. Due to the heterogeneity in neurosurgical applications, a qualitative synthesis was deemed more appropriate.

Results

We provided an updated overview of the current state of the art in translational neuroscience about the extended frontoparietal grasping-praxis network with a specific focus on the comparative functioning in non-human primates, healthy humans and how the latter knowledge has been implemented in the neurosurgical operating room during brain tumor resection.

Discussion

The anatomical and functional correlates we reviewed confirmed the evolutionary continuum from monkeys to humans, allowing a cautious but practical adoption of such evidence in intraoperative brain mapping protocols. Integrating the previous results in the surgical practice helps preserve complex motor abilities, prevent long-term disability and poor quality of life and allow the maximal safe resection of intrinsic brain tumors.

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.

CompreTAP: Feasibility and reliability of a new language comprehension mapping task via preoperative navigated transcranial magnetic stimulation

OBJECTIVE

Stimulation-based language mapping approaches that are used pre- and intraoperatively employ predominantly overt language tasks requiring sufficient language production abilities. Yet, these production-based setups are often not feasible in brain tumor patients with severe expressive aphasia. This pilot study evaluated the feasibility and reliability of a newly developed language comprehension task with preoperative navigated transcranial magnetic stimulation (nTMS).

METHODS

Fifteen healthy subjects and six brain tumor patients with severe expressive aphasia unable to perform classic overt naming tasks underwent preoperative nTMS language mapping based on an auditory single-word Comprehension TAsk for Perioperative mapping (CompreTAP). Comprehension was probed by button-press responses to auditory stimuli, hence not requiring overt language responses. Positive comprehension areas were identified when stimulation elicited an incorrect or delayed button press. Error categories, case-wise cortical error rate distribution and inter-rater reliability between two experienced specialists were examined.

RESULTS

Overall, the new setup showed to be feasible. Comprehension-disruptions induced by nTMS manifested in no responses, delayed or hesitant responses, searching behavior or selection of wrong target items across all patients and controls and could be performed even in patients with severe expressive aphasia. The analysis agreement between both specialists was substantial for classifying comprehension-positive and -negative sites. Extensive left-hemispheric individual cortical comprehension sites were identified for all patients. Apart from one case presenting with transient worsening of aphasic symptoms, pre-existing language deficits did not aggravate if results were used for subsequent surgical planning.

CONCLUSION

Employing this new comprehension-based nTMS setup allowed to identify language relevant cortical sites in all healthy subjects and severely aphasic patients who were thus far precluded from classic production-based mapping. This pilot study, moreover, provides first indications that the CompreTAP mapping results may support the preservation of residual language function if used for subsequent surgical planning.

White matter tracts and executive functions: a review of causal and correlation evidence

Executive functions are high-level cognitive processes involving abilities such as working memory/updating, set-shifting and inhibition. These complex cognitive functions are enabled by interactions among widely distributed cognitive networks, supported by white matter tracts. Executive impairment is frequent in neurological conditions affecting white matter; however, whether specific tracts are crucial for normal executive functions is unclear. We review causal and correlation evidence from studies that used direct electrical stimulation during awake surgery for gliomas, voxel-based and tract-based lesion-symptom mapping, and diffusion tensor imaging to explore associations between the integrity of white matter tracts and executive functions in healthy and impaired adults. The corpus callosum was consistently associated with all executive processes, notably its anterior segments. Both causal and correlation evidence showed prominent support of the superior longitudinal fasciculus to executive functions, notably to working memory. More specifically, strong evidence suggested that the second branch of the superior longitudinal fasciculus is crucial for all executive functions, especially for flexibility. Global results showed left lateralization for verbal tasks and right lateralization for executive tasks with visual demands. The frontal aslant tract potentially supports executive functions, however, additional evidence is needed to clarify whether its involvement in executive tasks goes beyond the control of language. Converging evidence indicates that a right-lateralized network of tracts connecting cortical and subcortical grey matter regions supports the performance of tasks assessing response inhibition, some suggesting a role for the right anterior thalamic radiation. Finally, correlation evidence suggests a role for the cingulum bundle in executive functions, especially in tasks assessing inhibition. We discuss these findings in light of current knowledge about the functional role of these tracts, descriptions of the brain networks supporting executive functions and clinical implications for individuals with brain tumours.

Neurocognitive Assessment of Mathematics-Related Capacities in Neurosurgical Patients

A precise neuropsychological assessment is of the utmost importance for neurosurgical patients undergoing the surgical excision of cerebral lesions. The assessment of mathematical abilities is usually limited to arithmetical operations while other fundamental visuo-spatial aspects closely linked to mathematics proficiency, such as the perception of numerical quantities and geometrical reasoning, are completely neglected. We evaluated these abilities with two objective and reproducible psychophysical tests, measuring numerosity perception and non-symbolic geometry, respectively. We tested sixteen neuro-oncological patients before the operation and six after the operation with classical neuropsychological tests and with two psychophysical tests. The scores of the classical neuropsychological tests were very heterogeneous, possibly due to the distinct location and histology of the tumors that might have spared (or not) brain areas subserving these abilities or allowed for plastic reorganization. Performance in the two non-symbolic tests reflected, on average, the presumed functional role of the lesioned areas, with participants with parietal and frontal lesions performing worse on these tests than patients with occipital and temporal lesions. Single-case analyses not only revealed some interesting exceptions to the group-level results (e.g., patients with parietal lesions performing well in the numerosity test), but also indicated that performance in the two tests was independent of non-verbal reasoning and visuo-spatial working memory. Our results highlight the importance of assessing non-symbolic numerical and geometrical abilities to complement typical neuropsychological batteries. However, they also suggest an avoidance of reliance on an excessively rigid localizationist approach when evaluating the neuropsychological profile of oncological patients.

Corticocortical Evoked Potentials in Eloquent Brain Tumor Surgery. A Systematic Review

Eloquent brain tumor surgery involves the delicate task of resecting tumors located in regions of the brain responsible for critical functions, such as language, motor control, and sensory perception. Preserving these functions is of paramount importance to maintain the patient's quality of life. Corticocortical evoked potentials (CCEPs) have emerged as a valuable intraoperative monitoring technique that aids in identifying and preserving eloquent cortical areas during surgery. This systematic review aimed to assess the utility of CCEPs in eloquent brain tumor surgery and determine their effectiveness in improving patient outcomes. A comprehensive literature search was conducted using electronic databases, including PubMed/Medline and Scopus. The search strategy identified 11 relevant articles for detailed analysis. The findings of the included studies consistently demonstrated the potential of CCEPs in guiding surgical decision making, minimizing the risk of postoperative neurological deficits, and mapping functional connectivity during surgery. However, further research and standardization are needed to fully establish the clinical benefits and refine the implementation of CCEPs in routine neurosurgical practice.

Diffuse low-grade glioma: What is the optimal linear measure to assess tumor growth?

Background

Radiological follow-up of diffuse low-grade gliomas (LGGs) growth is challenging. Approximative visual assessment still predominates over objective quantification due to the complexity of the pathology. The infiltrating character, diffuse borders and presence of surgical cavities demand LGG-based linear measurement rules to efficiently and precisely assess LGG evolution over time.

Methods

We compared optimized 1D, 2D, and 3D linear measurements with manual volume segmentation as a reference to assess LGG tumor growth in 36 patients with LGG (340 magnetic resonance imaging scans), using the clinically important mean tumor diameter (MTD) and the velocity diameter expansion (VDE). LGG-specific progression thresholds were established using the high-grade gliomas-based RECIST, Macdonald, and RANO criteria, comparing the sensitivity to identify progression/non-progression for each linear method compared to the ground truth established by the manual segmentation.

Results

3D linear volume approximation correlated strongly with manually segmented volume. It also showed the highest sensitivity for progression detection. The MTD showed a comparable result, whereas the VDE highlighted that caution is warranted in the case of small tumors with multiple residues. Novel LGG-specific progression thresholds, or the critical change in estimated tumor volume, were increased for the 3D (from 40% to 52%) and 2D methods (from 25% to 33%) and decreased for the 1D method (from 20% to 16%). Using the 3D method allowed a ~5-minute time gain.

Conclusions

While manual volumetric assessment remains the gold standard for calculating growth rate, the 3D linear method is the best time-efficient standardized alternative for radiological evaluation of LGGs in routine use.

Functional Magnetic Resonance Imaging and Diffusion Tensor Imaging-Tractography in Resective Brain Surgery: Lesion Coverage Strategies and Patient Outcomes

Diffusion tensor imaging (DTI)-tractography and functional magnetic resonance imaging (fMRI) have dynamically entered the presurgical evaluation context of brain surgery during the past decades, providing novel perspectives in surgical planning and lesion access approaches. However, their application in the presurgical setting requires significant time and effort and increased costs, thereby raising questions regarding efficiency and best use. In this work, we set out to evaluate DTI-tractography and combined fMRI/DTI-tractography during intra-operative neuronavigation in resective brain surgery using lesion-related preoperative neurological deficit (PND) outcomes as metrics. We retrospectively reviewed medical records of 252 consecutive patients admitted for brain surgery. Standard anatomical neuroimaging protocols were performed in 127 patients, 69 patients had additional DTI-tractography, and 56 had combined DTI-tractography/fMRI. fMRI procedures involved language, motor, somatic sensory, sensorimotor and visual mapping. DTI-tractography involved fiber tracking of the motor, sensory, language and visual pathways. At 1 month postoperatively, DTI-tractography patients were more likely to present either improvement or preservation of PNDs (p = 0.004 and p = 0.007, respectively). At 6 months, combined DTI-tractography/fMRI patients were more likely to experience complete PND resolution (p < 0.001). Low-grade lesion patients (N = 102) with combined DTI-tractography/fMRI were more likely to experience complete resolution of PNDs at 1 and 6 months (p = 0.001 and p < 0.001, respectively). High-grade lesion patients (N = 140) with combined DTI-tractography/fMRI were more likely to have PNDs resolved at 6 months (p = 0.005). Patients with motor symptoms (N = 80) were more likely to experience complete remission of PNDs at 6 months with DTI-tractography or combined DTI-tractography/fMRI (p = 0.008 and p = 0.004, respectively), without significant difference between the two imaging protocols (p = 1). Patients with sensory symptoms (N = 44) were more likely to experience complete PND remission at 6 months with combined DTI-tractography/fMRI (p = 0.004). The intraoperative neuroimaging modality did not have a significant effect in patients with preoperative seizures (N = 47). Lack of PND worsening was observed at 6 month follow-up in patients with combined DTI-tractography/fMRI. Our results strongly support the combined use of DTI-tractography and fMRI in patients undergoing resective brain surgery for improving their postoperative clinical profile.

Improving specificity of stimulation-based language mapping in stuttering glioma patients: A mixed methods serial case study

Objective

Stimulation-based language mapping relies on identifying stimulation-induced language disruptions, which preexisting speech disorders affecting the laryngeal and orofacial speech system can confound. This study ascertained the effects of preexisting stuttering on pre- and intraoperative language mapping to improve the reliability and specificity of established language mapping protocols in the context of speech fluency disorders.

Method

Differentiation-ability of a speech therapist and two experienced nrTMS examiners between stuttering symptoms and stimulation-induced language errors during preoperative mappings were retrospectively compared (05/2018-01/2021). Subsequently, the impact of stuttering on intraoperative mappings was evaluated in all prospective patients (01/2021-12/2022).

Results

In the first part, 4.85 % of 103 glioma patients stuttered. While both examiners had a significant agreement for misclassifying pauses in speech flow and prolongations (Κ ≥ 0.50, p ≤ 0.02, respectively), less experience resulted in more misclassified stuttering symptoms. In one awake surgery case within the second part, stuttering decreased the reliability of intraoperative language mapping.Comparison with Existing Method(s): By thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions, the reliability and proportion of stuttering symptoms falsely attributed to stimulation-induced language network disruptions can be improved. This may increase the consistency and specificity of language mapping results in stuttering glioma patients.

Conclusions

Preexisting stuttering negatively impacted language mapping specificity. Thus, surgical planning and the functional outcome may benefit substantially from thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions by trained specialists.

Can we improve electrocorticography using a circular grid array in brain tumor surgery?

Intraoperative electrocorticography (iECoG) is used as an adjunct to localize the epileptogenic zone during surgical resection of brain tumors in patients with focal epilepsies. It also enables monitoring of after-discharges and seizures with EEG during functional brain mapping with electrical stimulation. When seizures or after-discharges are present, they complicate accurate interpretation of the mapping strategy to outline the brain's eloquent function and can affect the surgical procedure. Recurrent seizures during surgery requires urgent treatment and, when occurring during awake craniotomy, often leads to premature termination of brain mapping due to post-ictal confusion or sedation from acute rescue therapy. There are mixed results in studies on efficacy with iECoG in patients with epilepsy and brain tumors influencing survival and functional outcomes following surgery. Commercially available electrode arrays have inherent limitations. These could be improved with customization potentially leading to greater precision in safe and maximal resection of brain tumors. Few studies have assessed customized electrode grid designs as an alternative to commercially available products. Higher density electrode grids with intercontact distances less than 1 cm improve spatial delineation of electrophysiologic sources, including epileptiform activity, electrographic seizures, and afterdischarges on iECoG during functional brain mapping. In response to the shortcomings of current iECoG grid technologies, we designed and developed a novel higher-density hollow circular electrode grid array. The 360-degree iECoG monitoring capability allows continuous EEG recording during surgical intervention through the aperture with and without electrical stimulation mapping. Compared with linear strip electrodes that are commonly used for iECoG during surgery, the circular grid demonstrates significant benefits in brain tumor surgery. This includes quicker recovery of post-operative motor deficits (2.4 days versus 9 days, p = 0.05), more extensive tumor resection (92.0% versus 77.6%, p = 0.003), lesser reduction in Karnofsky Performance scale postoperatively (-2 versus -11.6, p = 0.007), and more sensitivity to recording afterdischarges. In this narrative review, we discuss the advantages and disadvantages of commercially available recording devices in the operating room and focus on the usefulness of the higher-density circular grid.

Long-Term Tumor Control Following Targeted Alpha Therapy (TAT) of Low-Grade Gliomas (LGGs): A New Treatment Paradigm?

The median survival time has been reported to vary between 5 and 8 years in low-grade (WHO grade 2) astrocytoma, and between 10 and 15 years for grade 2 oligodendroglioma. Targeted alpha therapy (TAT), using the modified peptide vector [213Bi]Bi/[225Ac]Ac-DOTA-substance P, has been developed to treat glioblastoma (GBM), a prevalent malignant brain tumor. In order to assess the risk of late neurotoxicity, assuming that reduced tumor cell proliferation and invasion should directly translate into good responses in low-grade gliomas (LGGs), a limited number of patients with diffuse invasive astrocytoma (n = 8) and oligodendroglioma (n = 3) were offered TAT. In two oligodendroglioma patients, TAT was applied as a second-line treatment for tumor progression, 10 years after targeted beta therapy using [90Y]Y-DOTA-substance P. The radiopharmaceutical was locally injected directly into the tumor via a stereotactic insertion of a capsule-catheter system. The activity used for radiolabeling was 2-2.5 GBq of Bismuth-213 and 17 to 35 MBq of Actinium-225, mostly applied in a single fraction. The recurrence-free survival times were in the range of 2 to 16 years (median 11 years) in low-grade astrocytoma (n = 8), in which TAT was administered following a biopsy or tumor debulking. Regarding oligodendroglioma, the recurrence-free survival time was 24 years in the first case treated, and 4 and 5 years in the two second-line cases. In conclusion, TAT leads to long-term tumor control in the majority of patients with LGG, and recurrence has so far not manifested in patients with low-grade (grade 2) astrocytomas who received TAT as a first-line therapy. We conclude that targeted alpha therapy has the potential to become a new treatment paradigm in LGG.

Ultra-fast deep-learned CNS tumour classification during surgery

Central nervous system tumours represent one of the most lethal cancer types, particularly among children1. Primary treatment includes neurosurgical resection of the tumour, in which a delicate balance must be struck between maximizing the extent of resection and minimizing risk of neurological damage and comorbidity2,3. However, surgeons have limited knowledge of the precise tumour type prior to surgery. Current standard practice relies on preoperative imaging and intraoperative histological analysis, but these are not always conclusive and occasionally wrong. Using rapid nanopore sequencing, a sparse methylation profile can be obtained during surgery4. Here we developed Sturgeon, a patient-agnostic transfer-learned neural network, to enable molecular subclassification of central nervous system tumours based on such sparse profiles. Sturgeon delivered an accurate diagnosis within 40 minutes after starting sequencing in 45 out of 50 retrospectively sequenced samples (abstaining from diagnosis of the other 5 samples). Furthermore, we demonstrated its applicability in real time during 25 surgeries, achieving a diagnostic turnaround time of less than 90 min. Of these, 18 (72%) diagnoses were correct and 7 did not reach the required confidence threshold. We conclude that machine-learned diagnosis based on low-cost intraoperative sequencing can assist neurosurgical decision-making, potentially preventing neurological comorbidity and avoiding additional surgeries.

Development of an educational method to rethink and learn oncological brain surgery in an "a la carte" connectome-based perspective

BACKGROUND

Understanding the structural connectivity of white matter tracts (WMT) and their related functions is a prerequisite to implementing an "a la carte" "connectomic approach" to glioma surgery. However, accessible resources facilitating such an approach are lacking. Here we present an educational method that is readily accessible, simple, and reproducible that enables the visualization of WMTs on individual patient images via an atlas-based approach.

METHODS

Our method uses the patient's own magnetic resonance imaging (MRI) images and consists of three main steps: data conversion, normalization, and visualization; these are accomplished using accessible software packages and WMT atlases. We implement our method on three common cases encountered in glioma surgery: a right supplementary motor area tumor, a left insular tumor, and a left temporal tumor.

RESULTS

Using patient-specific perioperative MRIs with open-sourced and co-registered atlas-derived WMTs, we highlight the critical subnetworks requiring specific surgical monitoring identified intraoperatively using direct electrostimulation mapping with cognitive monitoring. The aim of this didactic method is to provide the neurosurgical oncology community with an accessible and ready-to-use educational tool, enabling neurosurgeons to improve their knowledge of WMTs and to better learn their oncologic cases, especially in glioma surgery using awake mapping.

CONCLUSIONS

Taking no more than 3-5 min per patient and irrespective of their resource settings, we believe that this method will enable junior surgeons to develop an intuition, and a robust 3-dimensional imagery of WMT by regularly applying it to their cases both before and after surgery to develop an "a la carte" connectome-based perspective to glioma surgery.

Tumor sound, auditory cues, and tissue pathology in glioma surgery: a proof-of-concept study

OBJECTIVE

Visual, tactile, and auditory cues are used during surgery to differentiate tissue type. Auditory cues in glioma surgery have not been studied previously. The objectives of this study were 1) to evaluate the feasibility of recording sound generated by the suction device during glioma surgery in matched tissue samples, and 2) to characterize the acoustic variation that occurs in different tissue samples.

METHODS

This was a prospective observational proof-of-concept study. Recordings were attempted in 20 patients in order meet the accrual target of 10 patients with matched sound and tissue data. For each patient, three 30- to 60-second recordings were made at these sites: normal white matter, infiltrative margin, and tumor. Tissue samples at each site were then reviewed by experienced neuropathologists, and agreement with surgical identification was estimated with the kappa statistic. Acoustic parameters were characterized for each sample.

RESULTS

Data from 20 patients were analyzed. Patient-related or technical issues resulted in missing data for 10 patients, but the final 10 patients had both audio and tissue data for analysis. Among all tissue samples, fair agreement was observed between surgeon identification and actual pathology (κ = 0.24, standard error 0.096, p = 0.006). Acoustic data suggested that 1) the acoustic stimulus is broadband, 2) acoustic features are somewhat consistent within cases, 3) high-entropy values indicate irregularity of sound over time, and 4) bimodal pitch distributions could differentially reflect cues of interest.

CONCLUSIONS

This study supports the feasibility of collecting intraoperative data on acoustic features during glioma surgery, and it provides an example of how an analysis could be performed to compare different types of tissues.

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.

Characterization and Classification of Spatial White Matter Tract Alteration Patterns in Glioma Patients Using Magnetic Resonance Tractography: A Systematic Review and Meta-Analysis

INTRODUCTION

Magnetic resonance (MR) tractography can be used to study the spatial relations between gliomas and white matter (WM) tracts. Various spatial patterns of WM tract alterations have been described in the literature. We reviewed classification systems of these patterns, and investigated whether low-grade gliomas (LGGs) and high-grade gliomas (HGGs) demonstrate distinct spatial WM tract alteration patterns.

METHODS

We conducted a systematic review and meta-analysis to summarize the evidence regarding MR tractography studies that investigated spatial WM tract alteration patterns in glioma patients.

RESULTS

Eleven studies were included. Overall, four spatial WM tract alteration patterns were reported in the current literature: displacement, infiltration, disruption/destruction and edematous. There was a considerable heterogeneity in the operational definitions of these terms. In a subset of studies, sufficient homogeneity in the classification systems was found to analyze pooled results for the displacement and infiltration patterns. Our meta-analyses suggested that LGGs displaced WM tracts significantly more often than HGGs (n = 259 patients, RR: 1.79, 95% CI [1.14, 2.79], I² = 51%). No significant differences between LGGs and HGGs were found for WM tract infiltration (n = 196 patients, RR: 1.19, 95% CI [0.95, 1.50], I² = 4%).

CONCLUSIONS

The low number of included studies and their considerable methodological heterogeneity emphasize the need for a more uniform classification system to study spatial WM tract alteration patterns using MR tractography. This review provides a first step towards such a classification system, by showing that the current literature is inconclusive and that the ability of fractional anisotropy (FA) to define spatial WM tract alteration patterns should be critically evaluated. We found variations in spatial WM tract alteration patterns between LGGs and HGGs, when specifically examining displacement and infiltration in a subset of the included studies.

Advances in molecular and imaging biomarkers in lower-grade gliomas

INTRODUCTION

Lower-grade (grade 2-3) gliomas (LGGs) constitutes a group of primary brain tumors with variable clinical behaviors and treatment responses. Recent advancements in molecular biology have redefined their classification, and novel imaging modalities emerged for the noninvasive diagnosis and follow-up.

AREAS COVERED

This review comprehensively analyses the current knowledge on molecular and imaging biomarkers in LGGs. Key molecular alterations, such as IDH mutations and 1p/19q codeletion, are discussed for their prognostic and predictive implications in guiding treatment decisions. Moreover, the authors explore theranostic biomarkers for the potential of tailored therapies. Additionally, they also describe the utility of advanced imaging modalities, including widely available techniques, as dynamic susceptibility contrast perfusion-weighted imaging and less validated, emerging approaches, for the noninvasive LGGs characterization and follow-up.

EXPERT OPINION

The integration of molecular markers enhanced the stratification of LGGs, leading to the new concept of integrated histomolecular classification. While the IDH mutation is an established key prognostic and predictive marker, recent results from IDH inhibitors trials showed its potential value as a theranostic marker. In this setting, advanced MRI techniques such as 2-D-hydroxyglutarate spectroscopy are very promising for the noninvasive diagnosis and monitoring of LGGs. This progress offers exciting prospects for personalized medicine and improved treatment outcomes in LGGs.

Impact of extent of resection and adjuvant therapy in diffuse gliomas of the spine

BACKGROUND CONTENT

Diffuse gliomas of the spine (DGS)-consisting of intradural intramedullary glioblastoma, astrocytoma, and oligodendroglioma-are exceedingly rare tumors that account for about 2% of primary spinal cord tumors. Much is unknown about their optimal treatment regimen due to a relative lack of clinical outcome data.

PURPOSE

To provide an updated analysis on treatment and outcomes in DGS.

STUDY DESIGN/SETTING

Observational cohort study using The National Cancer Database (NCDB), a multicenter prospectively collected oncology outcomes database. A systematic literature review was also performed to compare the resulting data to previous series.

PATIENT SAMPLE

Patients with histologically confirmed DGS from 2004 to 2018.

OUTCOME MEASURES

Long-term overall survival and short-term 30/90-day postsurgical mortality, 30-day readmission, and prolonged hospital length of stay.

METHODS

Impact of extent of resection and adjuvant therapy on overall survival was evaluated using Kaplan-Meier estimates and multivariable Cox proportional hazards regression. Univariate and multivariate logistic regression was used to analyze covariables and their prognostic impact on short-term surgical outcomes.

RESULTS

Of the 747 cases that met inclusion criteria, there were 439 astrocytomas, 14 oligodendrogliomas, and 208 glioblastomas. Sixty percent (n=442) of patients received radiation, and 45% (n=324) received chemotherapy. Tumor histology significantly impacted survival; glioblastoma had the poorest survival (median survival time [MS]: 12.3 months), followed by astrocytoma (MS: 70.8 months) and oligodendroglioma (MS: 71.6 months) (p<.001). Gross total resection (GTR) independently conferred a survival benefit in patients with glioblastoma (hazard ratio [HR]: 0.194, p<0.001) and other WHO grade four tumors (HR: 0.223, p=.003). Adjuvant chemotherapy also improved survival in patients with glioblastoma (HR: 0.244, p=.007) and WHO grade four tumors (HR: 0.252, p<.001). Systematic literature review identified 14 prior studies with a combined DGS mortality rate of 1.3%, which is lower than the 4% real-world outcomes calculated from the NCDB. This difference may be explained by selection biases in previously published literature in which only centers with favorable outcomes publish their results.

CONCLUSIONS

There remains a paucity of data regarding treatment paradigms and outcomes for DGS. Our analysis, the largest to date, demonstrates that GTR and adjuvant therapy independently improve survival for certain high-grade subgroups of DGS. This best-available data informs optimal management for such patients.

Quantifying Hand Strength and Isometric Pinch Individuation Using a Flexible Pressure Sensor Grid

Modulating force between the thumb and another digit, or isometric pinch individuation, is critical for daily tasks and can be impaired due to central or peripheral nervous system injury. Because surgical and rehabilitative efforts often focus on regaining this dexterous ability, we need to be able to consistently quantify pinch individuation across time and facilities. Currently, a standardized metric for such an assessment does not exist. Therefore, we tested whether we could use a commercially available flexible pressure sensor grid (Tekscan F-Socket [Tekscan Inc., Norwood, MA, USA]) to repeatedly measure isometric pinch individuation and maximum voluntary contraction (MVC) in twenty right-handed healthy volunteers at two visits. We developed a novel equation informed by the prior literature to calculate isometric individuation scores that quantified percentage of force on the grid generated by the indicated digit. MVC intra-class correlation coefficients (ICCs) for the left and right hands were 0.86 (p < 0.0001) and 0.88 (p < 0.0001), respectively, suggesting MVC measurements were consistent over time. However, individuation score ICCs, were poorer (left index ICC 0.41, p = 0.28; right index ICC -0.02, p = 0.51), indicating that this protocol did not provide a sufficiently repeatable individuation assessment. These data support the need to develop novel platforms specifically for repeatable and objective isometric hand dexterity assessments.

Advances in computational and translational approaches for malignant glioma

Gliomas are the most common primary brain tumors in adults and carry a dismal prognosis for patients. Current standard-of-care for gliomas is comprised of maximal safe surgical resection following by a combination of chemotherapy and radiation therapy depending on the grade and type of tumor. Despite decades of research efforts directed towards identifying effective therapies, curative treatments have been largely elusive in the majority of cases. The development and refinement of novel methodologies over recent years that integrate computational techniques with translational paradigms have begun to shed light on features of glioma, previously difficult to study. These methodologies have enabled a number of point-of-care approaches that can provide real-time, patient-specific and tumor-specific diagnostics that may guide the selection and development of therapies including decision-making surrounding surgical resection. Novel methodologies have also demonstrated utility in characterizing glioma-brain network dynamics and in turn early investigations into glioma plasticity and influence on surgical planning at a systems level. Similarly, application of such techniques in the laboratory setting have enhanced the ability to accurately model glioma disease processes and interrogate mechanisms of resistance to therapy. In this review, we highlight representative trends in the integration of computational methodologies including artificial intelligence and modeling with translational approaches in the study and treatment of malignant gliomas both at the point-of-care and outside the operative theater in silico as well as in the laboratory setting.

CrOssing fiber Modeling in the Peritumoral Area using dMRI (COMPARI)

Visualization of fiber tracts around the tumor is critical for neurosurgical planning and preservation of crucial structural connectivity during tumor resection. Biophysical modeling approaches estimate fiber tract orientations from differential water diffusivity information of diffusion MRI. However, the presence of edema and tumor infiltration presents a challenge to visualize crossing fiber tracts in the peritumoral region. Previous approaches proposed free water modeling to compensate for the effect of water diffusivity in edema, but those methods were limited in estimating complex crossing fiber tracts. We propose a new cascaded multi-compartment model to estimate tissue microstructure in the presence of edema and pathological contaminants in the area surrounding brain tumors. In our model (COMPARI), the isotropic components of diffusion signal, including free water and hindered water, were eliminated, and the fiber orientation distribution (FOD) of the remaining signal was estimated. In simulated data, COMPARI accurately recovered fiber orientations in the presence of extracellular water. In a dataset of 23 patients with highly edematous brain tumors, the amplitudes of FOD and anisotropic index distribution within the peritumoral region were higher with COMPARI than with a recently proposed multi-compartment constrained deconvolution model. In a selected patient with metastatic brain tumor, we demonstrated COMPARI's ability to effectively model and eliminate water from the peritumoral region. The white matter bundles reconstructed with our model were qualitatively improved compared to those of other models, and allowed the identification of crossing fibers. In conclusion, the removal of isotropic components as proposed with COMPARI improved the bio-physical modeling of dMRI in edema, thus providing information on crossing fibers, thereby enabling improved tractography in a highly edematous brain tumor. This model may improve surgical planning tools to help achieve maximal safe resection of brain tumors.

Quantitative assessments of finger individuation with an instrumented glove

BACKGROUND

In clinical and research settings, hand dexterity is often assessed as finger individuation, or the ability to move one finger at a time. Despite its clinical importance, there is currently no standardized, sufficiently sensitive, or fully objective platform for these evaluations.

METHODS

Here we developed two novel individuation scores and tested them against a previously developed score using a commercially available instrumented glove and data collected from 20 healthy adults. Participants performed individuation for each finger of each hand as well as whole hand open-close at two study visits separated by several weeks. Using the three individuation scores, intra-class correlation coefficients (ICC) and minimal detectable changes (MDC) were calculated. Individuation scores were further correlated with subjective assessments to assess validity.

RESULTS

We found that each score emphasized different aspects of individuation performance while generating scores on the same scale (0 [poor] to 1 [ideal]). These scores were repeatable, but the quality of the metrics varied by both equation and finger of interest. For example, index finger intra-class correlation coefficients (ICC's) were 0.90 (< 0.0001), 0.77 (< 0.001), and 0.83 (p < 0.0001), while pinky finger ICC's were 0.96 (p < 0.0001), 0.88 (p < 0.0001), and 0.81 (p < 0.001) for each score. Similarly, MDCs also varied by both finger and equation. In particular, thumb MDCs were 0.068, 0.14, and 0.045, while index MDCs were 0.041, 0.066, and 0.078. Furthermore, objective measurements correlated with subjective assessments of finger individuation quality for all three equations (ρ = - 0.45, p < 0.0001; ρ = - 0.53, p < 0.0001; ρ = - 0.40, p < 0.0001).

CONCLUSIONS

Here we provide a set of normative values for three separate finger individuation scores in healthy adults with a commercially available instrumented glove. Each score emphasizes a different aspect of finger individuation performance and may be more uniquely applicable to certain clinical scenarios. We hope for this platform to be used within and across centers wishing to share objective data in the physiological study of hand dexterity. In sum, this work represents the first healthy participant data set for this platform and may inform future translational applications into motor physiology and rehabilitation labs, orthopedic hand and neurosurgery clinics, and even operating rooms.

A Diffusion Tensor Imaging-Based Prognostic Classification for Surgery of Intrinsic Lesions Involving the Motor Pathways

BACKGROUND

The critical role of different adjuncts in improving the neurological outcome in intrinsic brain lesions affecting eloquent areas is demonstrated by their more diffuse utilization. Neurosurgeons often rely on preoperative and intraoperative diffusion tensor imaging tractography to improve the operative strategy and prognosis. We aimed to identify and validate a diffusion tensor imaging-based classification considering the relationship between the brain lesion and the corticospinal tract to predict a >50% reduction of motor evoked potentials (MEPs) during surgical excision of lesions involving the motor pathways.

METHODS

We included patients consecutively enrolled at our institution between April 2020 and September 2022 with 3 patterns of increasing complexity according to the relationship between the lesion and the corticospinal tract as identified on preoperative diffusion tensor imaging. Outcome measures were >50% reduction in intraoperative MEPs and neurological outcome defined as unchanged, improved, or worsened.

RESULTS

The study included 83 patients. A statistically significant linear trend between higher rates of reduction of MEPs and higher classification grades was observed (P = 0.001), with sensitivity 0.60, specificity 0.88, accuracy 0.83, and area under the curve 0.75. Higher grades were associated with worse neurological outcomes (P = 0.02).

CONCLUSIONS

The classification proved reliable in anticipating reduction in intraoperative MEPs and in predicting neurological outcome. Using this classification in patients undergoing surgery for lesions involving the motor pathways could help in counseling the patient, surgical planning, enhancing teamwork of operating room personnel, and improving the patient's prognosis.

Reconstruction of the Corticospinal Tract in Patients with Motor-Eloquent High-Grade Gliomas Using Multilevel Fiber Tractography Combined with Functional Motor Cortex Mapping

BACKGROUND AND PURPOSE

Tractography of the corticospinal tract is paramount to presurgical planning and guidance of intraoperative resection in patients with motor-eloquent gliomas. It is well-known that DTI-based tractography as the most frequently used technique has relevant shortcomings, particularly for resolving complex fiber architecture. The purpose of this study was to evaluate multilevel fiber tractography combined with functional motor cortex mapping in comparison with conventional deterministic tractography algorithms.

MATERIALS AND METHODS

Thirty-one patients (mean age, 61.5 [SD, 12.2] years) with motor-eloquent high-grade gliomas underwent MR imaging with DWI (TR/TE = 5000/78 ms, voxel size = 2 × 2 × 2 mm3, 1 volume at b = 0 s/mm2, 32 volumes at b = 1000 s/mm2). DTI, constrained spherical deconvolution, and multilevel fiber tractography-based reconstruction of the corticospinal tract within the tumor-affected hemispheres were performed. The functional motor cortex was enclosed by navigated transcranial magnetic stimulation motor mapping before tumor resection and used for seeding. A range of angular deviation and fractional anisotropy thresholds (for DTI) was tested.

RESULTS

For all investigated thresholds, multilevel fiber tractography achieved the highest mean coverage of the motor maps (eg, angular threshold = 60°; multilevel/constrained spherical deconvolution/DTI, 25% anisotropy threshold = 71.8%, 22.6%, and 11.7%) and the most extensive corticospinal tract reconstructions (eg, angular threshold = 60°; multilevel/constrained spherical deconvolution/DTI, 25% anisotropy threshold = 26,485 mm3, 6308 mm3, and 4270 mm3).

CONCLUSIONS

Multilevel fiber tractography may improve the coverage of the motor cortex by corticospinal tract fibers compared with conventional deterministic algorithms. Thus, it could provide a more detailed and complete visualization of corticospinal tract architecture, particularly by visualizing fiber trajectories with acute angles that might be of high relevance in patients with gliomas and distorted anatomy.

Beyond Avoiding Hemiplegia after Glioma Surgery: The Need to Map Complex Movement in Awake Patient to Preserve Conation

Improving the onco-functional balance has always been a challenge in glioma surgery, especially regarding motor function. Given the importance of conation (i.e., the willingness which leads to action) in patient's quality of life, we propose here to review the evolution of its intraoperative assessment through a reminder of the increasing knowledge of its neural foundations-based upon a meta-networking organization at three levels. Historical preservation of the primary motor cortex and pyramidal pathway (first level), which was mostly dedicated to avoid hemiplegia, has nonetheless shown its limits to prevent the occurrence of long-term deficits regarding complex movement. Then, preservation of the movement control network (second level) has permitted to prevent such more subtle (but possibly disabling) deficits thanks to intraoperative mapping with direct electrostimulations in awake conditions. Finally, integrating movement control in a multitasking evaluation during awake surgery (third level) enabled to preserve movement volition in its highest and finest level according to patients' specific demands (e.g., to play instrument or to perform sports). Understanding these three levels of conation and its underlying cortico-subcortical neural basis is therefore critical to propose an individualized surgical strategy centered on patient's choice: this implies an increasingly use of awake mapping and cognitive monitoring regardless of the involved hemisphere. Moreover, this also pleads for a finer and systematic assessment of conation before, during and after glioma surgery as well as for a stronger integration of fundamental neurosciences into clinical practice.

Awake craniotomy for brain tumor resection: Patient experience and acceptance in an Asian population

INTRODUCTION

Awake craniotomy is well-established for resection of brain tumor in the eloquent areas. Previous studies from Western countries have reported good level of patient tolerance and acceptance. However, its acceptability in non-Western populations, with different ethnic, social, cultural, religious, and linguistic backgrounds, has not been studied systematically. This study aims to evaluate the experience of patients from an Asian population who underwent awake craniotomy for tumor resection.

METHODS

Data on patient experience were collected by interviewing patients using a structured questionnaire at follow-up appointment. Data on patient demographics and diagnosis were collected from medical records.

RESULTS

Eighteen patients (age 16-68 years) who underwent 20 awake craniotomies were recruited. Preoperatively, all (100%) patients understood the indication for awake craniotomy. Almost all felt fully counseled by the neurosurgeon (90%), anesthetist (100%), and neuropsychologist (95%). Ninety-five percent reported their family to be supportive of awake craniotomy. Seventy-five percent felt adequately prepared on operation day. Intraoperatively, most patients did not experience pain/discomfort (55%) or anxiety (65%). Nearly all found intraoperative motor and language testing to be easy (100% and 90%, respectively). Postoperatively, 100% were satisfied with their care. One hundred percent rated their overall experience as good or excellent. Eighty percent were willing to undergo awake craniotomy again if indicated.

CONCLUSION

Awake craniotomy is well-accepted in an Asian population. All patients had good-to-excellent overall experience, with most willing to undergo awake craniotomy again. Our findings underscore the generalizability of awake craniotomy across different socio-cultural backgrounds and support its utilization in countries with a significant Asian population.

Cortical mapping in multilinguals undergoing awake brain surgery for brain tumors: Illustrative cases and systematic review

BACKGROUND

Awake brain mapping in multilingual patients with brain tumors presents unique challenges to the neurosurgeon. Knowledge of potential eloquent sites is vital to preserve language function.

METHODS

We present two cases of pars opercularis glioma and perform a systematic review in accordance with PRISMA guidelines.

RESULTS

Our review yielded 7 studies, with a total of 25 multilingual brain tumor patients who underwent awake brain mapping. The age ranged from 25 to 62 years. Majority were female (56.5%). Most (52%) were trilingual, while 20% were quadrilingual and 28% were pentalingual. All tumors were left-sided, mostly in the frontal lobe. These were predominantly gliomas. Extent of resection was gross total in 61%. The brain mapping findings were heterogeneous. Some authors reported a greater number of cortical sites for the first language compared to others. Others found that the first and second languages shared cortical sites whereas the third and subsequent languages were located in distant sites. The peri-Sylvian area was also found to be involved in language that was learned at an earlier age. Subsequent languages thus involved more distant sites. A larger number of cortical areas were also activated for languages that were learned later in life. In terms of language disturbance and recovery, there were mixed results.

CONCLUSION

Cortical mapping in multilingual brain tumor patients showed heterogeneity in terms of the location and number of language areas in the face of pathology. These findings may influence neurosurgical and oncological management of tumors in the speech area but emphasize the need to tailor surgical approaches and intraoperative testing to the patient.

Maximal Safe Resection in Glioblastoma Surgery: A Systematic Review of Advanced Intraoperative Image-Guided Techniques

Glioblastoma multiforme (GBM) represents the most common and aggressive central nervous system tumor associated with a poor prognosis. The aim of this study was to depict the role of intraoperative imaging techniques in GBM surgery and how they can ensure the maximal extent of resection (EOR) while preserving the functional outcome. The authors conducted a systematic review following PRISMA guidelines on the PubMed/Medline and Scopus databases. A total of 1747 articles were identified for screening. Studies focusing on GBM-affected patients, and evaluations of EOR and functional outcomes with the aid of advanced image-guided techniques were included. The resulting studies were assessed for methodological quality using the Risk of Bias in Systematic Review tool. Open Science Framework registration DOI 10.17605/OSF.IO/3FDP9. Eighteen studies were eligible for this systematic review. Among the selected studies, eight analyzed Sodium Fluorescein, three analyzed 5-aminolevulinic acid, two evaluated IoMRI imaging, two evaluated IoUS, and three evaluated multiple intraoperative imaging techniques. A total of 1312 patients were assessed. Gross Total Resection was achieved in the 78.6% of the cases. Follow-up time ranged from 1 to 52 months. All studies assessed the functional outcome based on the Karnofsky Performance Status scale, while one used the Neurologic Assessment in Neuro-Oncology score. In 77.7% of the cases, the functional outcome improved or was stable over the pre-operative assessment. Combining multiple intraoperative imaging techniques could provide better results in GBM surgery than a single technique. However, despite good surgical outcomes, patients often present a neurocognitive decline leading to a marked deterioration of the quality of life. Advanced intraoperative image-guided techniques can allow a better understanding of the anatomo-functional relationships between the tumor and the surrounding brain, thus maximizing the EOR while preserving functional outcomes.

Localization patterns of speech and language errors during awake brain surgery: a systematic review

Awake craniotomy with direct electrical stimulation (DES) is the standard treatment for patients with eloquent area gliomas. DES detects speech and language errors, which indicate functional boundaries that must be maintained to preserve quality of life. During DES, traditional object naming or other linguistic tasks such as tasks from the Dutch Linguistic Intraoperative Protocol (DuLIP) can be used. It is not fully clear which speech and language errors occur in which brain locations. To provide an overview and to update DuLIP, a systematic review was conducted in which 102 studies were included, reporting on speech and language errors and the corresponding brain locations during awake craniotomy with DES in adult glioma patients up until 6 July 2020. The current findings provide a crude overview on language localization. Even though subcortical areas are in general less often investigated intraoperatively, still 40% out of all errors was reported at the subcortical level and almost 60% at the cortical level. Rudimentary localization patterns for different error types were observed and compared to the dual-stream model of language processing and the DuLIP model. While most patterns were similar compared to the models, additional locations were identified for articulation/motor speech, phonology, reading, and writing. Based on these patterns, we propose an updated DuLIP model. This model can be applied for a more adequate "location-to-function" language task selection to assess different linguistic functions during awake craniotomy, to possibly improve intraoperative language monitoring. This could result in a better postoperative language outcome in the future.

Association of extent of resection and functional outcomes in diffuse low-grade glioma: systematic review & meta-analysis

BACKGROUND

Surgical resection offers survival benefits in patients with diffuse low-grade glioma (DLGG) but its association with functional outcomes is uncertain. This systematic review assessed functional outcomes associated with extent of resection (EoR) in adults with DLGG.

METHODS

We searched Medline, Embase and CENTRAL on the 19th of February 2021 for observational studies reporting functional outcomes after surgical resection for patients aged ≥ 18 years with a new diagnosis of supratentorial DLGG according to any World Health Organization classification of primary brain tumors. The Newcastle-Ottawa Scale (NOS) informed our risk of bias assessments. The proportion of patients returning to work within 12 months entered a random-effects meta-analysis. PROSPERO registration number CRD42021238387.

RESULTS

There were seven eligible moderate to high-quality (NOS > 6) observational studies identified from 1,183 records involving 234 patients with DLGG. Functional outcomes reported included neurocognition (n = 2 studies), performance status (n = 3), quality of life (QoL) (n = 1) and return to work (n = 6). The proportion of patients who returned to work within 12 months of surgery was 84% (95% confidence interval [CI] 50-96%, I-squared = 38%, 5 studies) for gross total resection, 66% (95% CI 14-96%, I2 = 57%, 5 studies) for subtotal resection, and 31% (95% CI 4-82%, I2 = 0%, 4 studies) for partial resection. There was insufficient data on other functional outcomes for quantitative synthesis.

CONCLUSION

A higher proportion of DLGG patients returned to work following gross total resection compared with those who had a subtotal or partial resection. Further studies with standardized assessments can clarify the association between EoR and different functional outcomes.

Frontal aslant tract in the non-dominant hemisphere: A systematic review of anatomy, functions, and surgical applications

Knowledge of both the spatial organization and functions of white-matter fiber tracts is steadily increasing. We report here the anatomy and functions of the frontal aslant tract (FAT) in the non-dominant hemisphere (usually the right hemisphere). Despite the structural symmetry between the right and left FAT, these two tracts seem to display functional asymmetry, with several brain functions in common, but others, such as visuospatial and social cognition, music processing, shifting attention or working memory, more exclusively associated with the right FAT. Further studies are required to determine whether damage to the right FAT causes permanent cognitive impairment. Such studies will constitute the best means of testing whether this tract is a critical pathway that must be taken into account during neurosurgical procedures and the essential tasks to be incorporated into intraoperative monitoring during awake craniotomy.

The need to consider return to work as a main outcome in patients undergoing surgery for diffuse low-grade glioma: a systematic review

OBJECTIVE

For a long time, return to work (RTW) has been neglected in patients harboring a diffuse low-grade glioma (LGG). However, a majority of LGG patients worked at time of diagnosis. Moreover, these patients now live longer given current treatment paradigms, especially thanks to early maximal surgery.

METHODS

We systematically searched available medical databases for studies that reported data on RTW in patients who underwent resection for LGG.

RESULTS

A total of 30 studies were selected: 19 considered RTW (especially rate and timing) as an outcome and 11 used scales of health-related quality of life (HRQoL) which included work-related aspects. Series that considered RTW as a main endpoint were composed of 1014 patients, with postoperative RTW rates ranging from 31 to 97.1% (mean 73.1%). Timing to RTW ranged from 15 days to 22 months (mean 6.3 months). Factors related to an increased proportion of RTW were: younger age, better neurologic status, having a white-collar occupation, working pre-operatively, being the sole breadwinner, the use of awake surgery, and greater extent of resection. Female sex, older age, poor neurologic status, pre-operative history of work absences, slow lexical access speed, and postoperative seizures were negatively related to RTW. No studies that used HRQoL scales directly investigated RTW rate or timing.

CONCLUSIONS

RTW was scarcely analyzed in LGG patients who underwent resection. However, because they are usually young, with no or only mild functional deficits and have a longer life expectancy, postoperative RTW should be assessed more systematically and accurately as a main outcome. As majority (61.5-100%) of LGG patients were working at time of surgery, the responsibility of neurosurgeons is to bring these patients back to their previous activities according to his/her wishes. RTW might also be included as a critical endpoint for future prospective studies and randomized control trials on LGGs.

Synergetic reorganization of the contralateral structure and function in patients with unilateral frontal glioma

Objective

This study aimed to investigate the contralateral structural and functional plasticity induced by frontal gliomas.

Methods

Patients with left (n = 49) or right (n = 52) frontal diffuse glioma were enrolled along with 35 age- matched healthy controls (HCs). The gray-matter volumes (GMVs) of the contralesional region were measured using the voxel-based morphometry (VBM) analysis. Additionally, the amplitude of low-frequency fluctuation (ALFF) of the contralesional region was calculated via resting state functional magnetic resonance imaging (MRI) to assess functional alterations.

Result

The GMV of the contralateral orbitofrontal cortex of the right or left frontal gliomas was significantly larger than the corresponding GMV in the controls. In the patients with right frontal glioma, the GMV and ALFF in the left inferior frontal gyrus were significantly increased compared with those in the controls.

Conclusion

Glioma invasion of the frontal lobe can induce contralateral structural compensation and functional compensation, which show synergy in the left inferior frontal gyrus. Our findings explain why patients with unilateral frontal glioma can have functional balance, and offer the possibility of preserving the brain function while maximizing tumor removal.

Early volumetric, perfusion, and diffusion MRI changes after mutant isocitrate dehydrogenase (IDH) inhibitor treatment in IDH1-mutant gliomas

Background

Inhibition of the isocitrate dehydrogenase (IDH)-mutant enzyme is a novel therapeutic target in IDH-mutant gliomas. Imaging biomarkers of IDH inhibitor treatment efficacy in human IDH-mutant gliomas are largely unknown. This study investigated early volumetric, perfusion, and diffusion MRI changes in IDH1-mutant gliomas during IDH inhibitor treatment.

Methods

Twenty-nine IDH1-mutant glioma patients who received IDH inhibitor and obtained anatomical, perfusion, and diffusion MRI pretreatment at 3-6 weeks (n = 23) and/or 2-4 months (n = 14) of treatment were retrospectively studied. Normalized relative cerebral blood volume (nrCBV), apparent diffusion coefficient (ADC), and fluid-attenuated inversion recovery (FLAIR) hyperintensity volume were analyzed.

Results

After 3-6 weeks of treatment, nrCBV was significantly increased (P = .004; mean %change = 24.15%) but not FLAIR volume (P = .23; mean %change = 11.05%) or ADC (P = .52; mean %change = -1.77%). Associations between shorter progression-free survival (PFS) with posttreatment nrCBV > 1.55 (P = .05; median PFS, 240 vs 55 days) and increased FLAIR volume > 4 cm³ (P = .06; 227 vs 29 days) trended toward significance. After 2-4 months, nrCBV, FLAIR volume, and ADC were not significantly different from baseline, but an nrCBV increase > 0% (P = .002; 1121 vs 257 days), posttreatment nrCBV > 1.8 (P = .01; 1121 vs. 270 days), posttreatment ADC < 1.15 μm²/ms (P = .02; 421 vs 215 days), median nrCBV/ADC ratio increase > 0% (P = .02; 1121 vs 270 days), and FLAIR volume change > 4 cm³ (P = .03; 421 vs 226.5 days) were associated with shorter PFS.

Conclusions

Increased nrCBV at 3-6 weeks of treatment may reflect transient therapeutic and/or tumor growth changes, whereas nrCBV, ADC, and FLAIR volume changes occurring at 2-4 months of treatment may more accurately reflect antitumor response to IDH inhibition.

A phase II pilot randomized controlled trial to assess the feasibility of the "supra-marginal" surgical resection of malignant glioma (G-SUMIT: Glioma supra marginal incision trial) study protocol

Background

High-grade gliomas are the most common primary malignant brain tumor in adults having a median survival of only 13–16 months. This is despite the current standard of maximal safe surgical resection followed by fractionated radiotherapy and chemotherapy. Extending the tumor resection limit beyond the gadolinium (GAD)-enhancing margin (i.e., supra-marginal resection) could in principle provide an added survival benefit as it has been shown that > 80% of post-operative tumor recurrence is within a 2-cm region surrounding the original GAD-enhancing margin. However, this must be weighed against the risk of potential damage to functional brain tissue.

Methods

In this phase II pilot randomized control trial (RCT), we aim to assess the feasibility of “supra-marginal” resection extending 1 cm beyond the enhancing tumor in adults with radiographic evidence of GAD-enhancing intra-axial tumor consistent with high-grade glioma in a safe anatomical location and a Karnofsky Performance Score > 60. With six academic institutions with established neurosurgical oncology practices in participation, we aim to enroll 72 patients over 2 years. Primary outcomes include evaluating the feasibility of performing a large-scale trial with regard to recruitment, allocation, and outcome documentation as well as safety data. Secondary outcomes include determining if there is an increased survival benefit with supra-marginal resection and impact on quality of life (Modified Rankin Scale (mRS), EuroQol-5D (ED-5D), 30-day all-cause mortality).

Discussion

Recent studies have revealed survival advantages comparing supra-marginal resection to standard attempt at gross total resection (GTR) with no additional perioperative surgical risk; however, the current quality of evidence is low and under-powered. Therefore, there are no current practice guidelines, and the philosophy of surgical resection is guided by individual surgeon preferences on an individual patient basis. This creates additional uncertainty and is potentially detrimental to our patients. This clinical equipoise supports the need for an adequately powered RCT to determine whether a supra-marginal resection can have a positive impact on survival for patients with HGGs. Our pilot RCT will test the feasibility of comparing the standard gross total resection of GAD-enhancing tumors and supra-marginal resection to prepare for a larger definitive multicenter RCT.

Trial registration

ClinicalTrials.gov, NCT04737577. Registered on February 4, 2021

Supplementary Information

The online version contains supplementary material available at 10.1186/s40814-022-01104-1.

Experiences of language and communication after brain-tumour treatment: A long-term follow-up after glioma surgery

The purpose of this study was to explore how persons having received various treatments for glioma, a type of brain tumour, experience their language, speech, and communication in everyday life. Twelve persons with low-grade glioma and one with high-grade glioma who had undergone tumour resection in 2014-2016 in different tumour locations were interviewed using a semi-structured protocol. The video-recorded interviews were transcribed and analysed using qualitative content analysis, which revealed three manifest categories, nine sub-categories and one latent theme. Participants experienced changed communication that affected word finding, motor speech and comprehension. They also expressed how communication required a greater effort; time and context were important factors and participants felt frustrated with their communication. Further, they were dealing with changes and used multiple strategies to manage communication. For most participants it did not affect their everyday life, but it was not like before. In addition, participants adapted their way of living to manage illness-related problems. Uncertainty was a latent theme which emanated from the participants' illness experience, reflecting how living with a slow-growing brain tumour affects life-decisions and views of perceived symptoms. Discussion of how results can be interpreted in relation to previous research and health care are included.

Role of Asleep Surgery for Supplementary Motor Area Tumors

Background The supplementary motor area (SMA) is involved in planning of voluntary motor activities. Tumors in SMA usually present with seizures and, rarely, motor deficits. Postoperatively, these patients may develop SMA syndrome. Patients with SMA tumors usually undergo awake craniotomy along with neuromonitoring for maximal safe resection, and some of these patients tend to have residual tumor.

Objective To completely excise the SMA region tumors under general anesthesia without causing any permanent neurological deficits.

Methods We operated upon four patients with SMA region tumor under general anesthesia (GA) with direct electrocortical stimulation (DES). Motor-evoked potential was used to monitor corticospinal tracts through corkscrew or strip electrodes. Intraoperative MRI was done to assess the tumor excision.

Results All four patients had complete resection of tumor and, postoperatively, all four developed SMA syndrome. All of them recovered completely over a period of time.

Conclusion SMA tumors can be excised completely under GA with DES, thereby increasing progression-free survival.

Group-level stability but individual variability of neurocognitive status after awake resections of right frontal IDH-mutated glioma

Awake surgery for low-grade gliomas is currently considered the best procedure to improve the extent of resection and guarantee a "worth living life" for patients, meaning avoiding not only motor but also cognitive deficits. However, tumors located in the right hemisphere, especially in the right frontal lobe, are still rarely operated on in awake condition; one of the reasons possibly being that there is little information in the literature describing the rates and nature of long-lasting neuropsychological deficits following resection of right frontal glioma. To investigate long-term cognitive deficits after awake surgery in right frontal IDH-mutated glioma. We retrospectively analyzed a consecutive series of awake surgical resections between 2012 and 2020 for right frontal IDH-mutated glioma. We studied the patients' subjective complaints and objective neuropsychological evaluations, both before and after surgery. Our results were then put in perspective with the literature. Twenty surgical cases (including 5 cases of redo surgery) in eighteen patients (medium age: 42.5 [range 26-58]) were included in the study. The median preoperative volume was 37 cc; WHO grading was II, III and IV in 70%, 20%, and 10% of cases, respectively. Preoperatively, few patients had related subjective cognitive or behavioral impairment, while evaluations revealed mild deficits in 45% of cases, most often concerning executive functions, attention, working memory and speed processing. Immediate postoperative evaluations showed severe deficits of executive functions in 75% of cases but also attentional deficits (65%), spatial neglect (60%) and behavioral disturbances (apathy, aprosodia/amimia, emotional sensitivity, anosognosia). Four months after surgery, although psychometric z-scores were unchanged at the group level, individual evaluations showed a slight decrease of performance in 9/20 cases for at least one of the following domains: executive functions, speed processing, attention, semantic cognition, social cognition. Our results are generally consistent with those of the literature, confirming that the right frontal lobe is a highly eloquent area and suggesting the importance of operating these patients in awake conditions.

Eloquent Lower Grade Gliomas, a Highly Vulnerable Cohort: Assessment of Patients' Functional Outcome After Surgery Based on the LoG-Glio Registry

Majority of lower grade glioma (LGG) are located eloquently rendering surgical resection challenging. Aim of our study was to assess rate of permanent deficits and its predisposing risk factors. We retrieved 83 patients harboring an eloquently located LGGs from the prospective LoG-Glio Database. Patients without surgery or incomplete postoperative data were excluded. Sign rank test, explorative correlations by Spearman ρ and multivariable regression for new postoperative deficits were calculated. Eloquent region involved predominantly motor (45%) and language (40%). At first follow up after 3 months permanent neuro-logical deficits (NDs) were noted in 39%. Mild deficits remained in 29% and severe deficits in 10%. Complete tumor removal (CTR) was successfully in 62% of intended cases. Postoperative and 3-month follow up National Institute of Health Stroke Score (NIHSS) showed significantly lower values than preoperatively (p<0.001). 38% cases showed a decreased NIHSS at 3-month, while occurrence was only 14% at 9-12-month follow up. 6/7 patients with mild aphasia recovered after 9-12 months, while motor deficits present at 3-month follow up were persistent in majority of patients. Eastern oncology group functional status (ECOG) significantly decreased by surgery (p < 0.001) in 31% of cases. Between 3-month and 9-12-months follow up no significant improvement was seen. In the multivariable model CTR (p=0.019, OR 31.9), and ECOG>0 (p=0.021, OR 8.5) were independent predictors for permanent postoperative deficit according to NIHSS at 3-month according to multivariable regression model. Patients harboring eloquently located LGG are highly vulnerable for permanent deficits. Almost one third of patients have a permanent reduction of their functional status based on ECOG. Risk of an extended resection has to be balanced with the respective oncological benefit. Especially, patients with impaired pre-operative status are at risk for new permanent deficits. There is a relevant improvement of neurological symptoms in the first year after surgery, especially for patients with slight aphasia.

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.

Functional Approaches to the Surgery of Brain Gliomas

In the surgery of gliomas, recent years have witnessed unprecedented theoretical and technical development, which extensively increased indication to surgery. On one hand, it has been solidly demonstrated the impact of gross total resection on life expectancy. On the other hand, the paradigm shift from classical cortical localization of brain function towards connectomics caused by the resurgence of awake surgery and the advent of tractography has permitted safer surgeries focused on subcortical white matter tracts preservation and allowed for surgical resections within regions, such as Broca's area or the primary motor cortex, which were previously deemed inoperable. Furthermore, new asleep electrophysiological techniques have been developed whenever awake surgery is not an option, such as operating in situations of poor compliance (including paediatric patients) or pre-existing neurological deficits. One such strategy is the use of intraoperative neurophysiological monitoring (IONM), enabling the identification and preservation of functionally defined, but anatomically ambiguous, cortico-subcortical structures through mapping and monitoring techniques. These advances tie in with novel challenges, specifically risk prediction and the impact of neuroplasticity, the indication for tumour resection beyond visible borders, or supratotal resection, and most of all, a reappraisal of the importance of the right hemisphere from early psychosurgery to mapping and preservation of social behaviour, executive control, and decision making.Here we review current advances and future perspectives in a functional approach to glioma surgery.

Tracking the Corticospinal Tract in Patients With High-Grade Glioma: Clinical Evaluation of Multi-Level Fiber Tracking and Comparison to Conventional Deterministic Approaches

While the diagnosis of high-grade glioma (HGG) is still associated with a considerably poor prognosis, neurosurgical tumor resection provides an opportunity for prolonged survival and improved quality of life for affected patients. However, successful tumor resection is dependent on a proper surgical planning to avoid surgery-induced functional deficits whilst achieving a maximum extent of resection (EOR). With diffusion magnetic resonance imaging (MRI) providing insight into individual white matter neuroanatomy, the challenge remains to disentangle that information as correctly and as completely as possible. In particular, due to the lack of sensitivity and accuracy, the clinical value of widely used diffusion tensor imaging (DTI)-based tractography is increasingly questioned. We evaluated whether the recently developed multi-level fiber tracking (MLFT) technique can improve tractography of the corticospinal tract (CST) in patients with motor-eloquent HGGs. Forty patients with therapy-naïve HGGs (mean age: 62.6 ± 13.4 years, 57.5% males) and preoperative diffusion MRI [repetition time (TR)/echo time (TE): 5000/78 ms, voxel size: 2x2x2 mm3, one volume at b=0 s/mm2, 32 volumes at b=1000 s/mm2] underwent reconstruction of the CST of the tumor-affected and unaffected hemispheres using MLFT in addition to deterministic DTI-based and deterministic constrained spherical deconvolution (CSD)-based fiber tractography. The brain stem was used as a seeding region, with a motor cortex mask serving as a target region for MLFT and a region of interest (ROI) for the other two algorithms. Application of the MLFT method substantially improved bundle reconstruction, leading to CST bundles with higher radial extent compared to the two other algorithms (delineation of CST fanning with a wider range; median radial extent for tumor-affected vs. unaffected hemisphere - DTI: 19.46° vs. 18.99°, p=0.8931; CSD: 30.54° vs. 27.63°, p=0.0546; MLFT: 81.17° vs. 74.59°, p=0.0134). In addition, reconstructions by MLFT and CSD-based tractography nearly completely included respective bundles derived from DTI-based tractography, which was however favorable for MLFT compared to CSD-based tractography (median coverage of the DTI-based CST for affected vs. unaffected hemispheres - CSD: 68.16% vs. 77.59%, p=0.0075; MLFT: 93.09% vs. 95.49%; p=0.0046). Thus, a more complete picture of the CST in patients with motor-eloquent HGGs might be achieved based on routinely acquired diffusion MRI data using MLFT.

Cognitive preservation following awake mapping-based neurosurgery for low-grade gliomas: a longitudinal, within-patient design study

BACKGROUND

Awake surgery with intraoperative electrical mapping emerged as a gold-standard approach in newly diagnosed diffuse low-grade glioma (DLGG) to optimize the extent of resection (EOR) while sparing critical brain structures. However, no study has assessed to what extent cognitive recovery occurs following awake mapping-guided neurosurgery in a large, longitudinal and homogeneous series of DLGG.

METHODS

A longitudinal study on the cognitive status of 157 DLGG patients was performed. Neuropsychological assessments were done before and three months after awake mapping-based surgery. Z-scores and variations of Z-scores were computed to determine the number of patients with cognitive deficit(s) or decline. Clinical, surgical, and histopathological variables were studied to investigate factors contributing to neurocognitive outcomes.

RESULTS

87 patients (55.4%) had preoperative cognitive impairments. Statistical analysis between the preoperative (baseline) and postoperative assessments demonstrated a significant difference in three domains (Executive, Psychomotor Speed and Attention, Verbal Episodic Memory). 86% of patients exhibited no postoperative cognitive decline and among them 10% exhibited cognitive improvement. The mean EOR was 92.3%±7.8%. The EOR, postoperative volume, and tumor lateralization had a significant association with cognitive decline. No patients demonstrated permanent post-operative neurologic deficits, but 5.8% did not resume their preoperative professional activities. The 5-year survival rate was 82.2%.

CONCLUSIONS

This is the largest series ever reported with systematic longitudinal neuropsychological assessment. 86% of patients demonstrated no cognitive decline despite large resections and only 5.8% did not return to work. This work supports the practice of awake surgery with cognitive mapping as safe and effective in DLGG patients.

Quality of life following awake surgery depends on ability of executive function, verbal fluency, and movement

INTRODUCTION

The outcome of awake surgery has been evaluated based on functional factors, return to work, and oncological aspects, and there have been no reports directly examining QOL. This study aimed to investigate the outcome of QOL following awake surgery and to determine the functional factors influencing QOL.

METHODS

Seventy patients with WHO grade II/III gliomas were included. For the assessment of QOL, we used the SF-36 and calculated summary and sub-component scores. Three summary component scores, including physical (PCS), mental (MCS), and role/social summary (RCS) component scores, were computed based on sub-component scores. Additionally, various assessments of neurological/neuropsychological function were performed. We performed univariate and multiple regression analyses to investigate the functional factors influencing the SF-36.

RESULTS

PCS and MCS were maintained, but only RCS was low to 42.0 ± 16.1. We then focused on the RCS and its sub-components: general health (GH), role physical (RP), social functioning (SF), and role emotional (RE). Multiple regression analysis showed following significant correlations between the sub-component scores and brain functions: GH to executive function and movement (p = 0.0033 and 0.032), RP to verbal fluency and movement (p = 0.0057 and 0.0010), and RE to verbal fluency (p = 0.020). Furthermore, when the sub-component scores were compared between groups with and without functional deficits related to GH, RP, and RE, each score was significantly lower in the groups with functional deficits (p = 0.012, 0.014, and 0.0049, respectively).

CONCLUSIONS

In patients who underwent awake surgery, a subset of patients had low QOL because of poor RCS. Functional factors influencing QOL included executive function, verbal fluency, and movement.

The frontal aslant tract and its role in executive functions: a quantitative tractography study in glioma patients

Focal white matter lesions can cause cognitive impairments due to disconnections within or between networks. There is some preliminary evidence that there are specific hubs and fiber pathways that should be spared during surgery to retain cognitive performance. A tract potentially involved in important higher-level cognitive processes is the frontal aslant tract. It roughly connects the posterior parts of the inferior frontal gyrus and the superior frontal gyrus. Functionally, the left frontal aslant tract has been associated with speech and the right tract with executive functions. However, there currently is insufficient knowledge about the right frontal aslant tract’s exact functional importance. The aim of this study was to investigate the role of the right frontal aslant tract in executive functions via a lesion-symptom approach. We retrospectively examined 72 patients with frontal glial tumors and correlated measures from tractography (distance between tract and tumor, and structural integrity of the tract) with cognitive test performances. The results indicated involvement of the right frontal aslant tract in shifting attention and letter fluency. This involvement was not found for the left tract. Although this study was exploratory, these converging findings contribute to a better understanding of the functional frontal subcortical anatomy. Shifting attention and letter fluency are important for healthy cognitive functioning, and when impaired they may greatly influence a patient’s wellbeing. Further research is needed to assess whether or not damage to the right frontal aslant tract causes permanent cognitive impairments, and consequently identifies this tract as a critical pathway that should be taken into account during neurosurgical procedures.