Low grade gliomas in eloquent locations - implications for surgical strategy, survival and long term quality of life

Anatomical and subcortical invasiveness in diffuse low-grade astrocytomas differ between IDH status and provide prognostic information

Background

Diffuse astrocytomas preferentially infiltrate eloquent areas affecting the outcome. A preoperative understanding of isocitrate dehydrogenase (IDH) status may offer opportunities for specific targeted therapies impacting treatment management. The aim of this study was to analyze clinical, topographical, radiological in WHO 2 astrocytomas with different IDH status and the long-term patient's outcome.

Methods

A series of confirmed WHO 2 astrocytoma patients (between 2005 and 2015) were retrospectively analyzed. MRI sequences (FLAIR) were used for tumor volume segmentation and to create a frequency map of their locations into the Montreal Neurological Institute (MNI) space. The Brain-Grid (BG) system (standardized radiological tool of intersected lines according to anatomical landmarks) was used as an overlay for infiltration analysis of each tumor. Long-term follow-up was used to perform a survival analysis.

Results

Forty patients with confirmed IDH status (26 IDH-mutant, IDHm/14 IDH-wild type, IDHwt) according to WHO 2021 classification were included with a mean follow-up of 7.8 years. IDHm astrocytomas displayed a lower number of BG-voxels (P < 0.05) and were preferentially located in the anterior insular region. IDHwt group displayed a posterior insular and peritrigonal location. IDHwt group displayed a shorter OS compared with IDHm (P < 0.05), with the infiltration of 7 or more BG-voxels as an independent factor predicting a shorter OS.

Conclusions

IDHm and IDHwt astrocytomas differed in preferential location, number of BG-voxels and OS at long follow-up time. The number of BG-voxels affected the OS in IDHwt was possibly reflecting higher tumor invasiveness. We encourage the systematic use of alternative observational tools, such as gradient maps and the Brain-Grid analysis, to better detect differences of tumor invasiveness in diffuse low-grade gliomas subtypes.

Preoperative assessment of eloquence in neurosurgery: a systematic review

BACKGROUND AND OBJECTIVES

Tumor location and eloquence are two crucial preoperative factors when deciding on the optimal treatment choice in glioma management. Consensus is currently lacking regarding the preoperative assessment and definition of eloquent areas. This systematic review aims to evaluate the existing definitions and assessment methods of eloquent areas that are used in current clinical practice.

METHODS

A computer-aided search of Embase, Medline (OvidSP), and Google Scholar was performed to identify relevant studies. This review includes articles describing preoperative definitions of eloquence in the study's Methods section. These definitions were compared and categorized by anatomical structure. Additionally, various techniques to preoperatively assess tumor eloquence were extracted, along with their benefits, drawbacks and ease of use.

RESULTS

This review covers 98 articles including 12,714 participants. Evaluation of these studies indicated considerable variability in defining eloquence. Categorization of these definitions yielded a list of 32 brain regions that were considered eloquent. The most commonly used methods to preoperatively determine tumor eloquence were anatomical classification systems and structural MRI, followed by DTI-FT, functional MRI and nTMS.

CONCLUSIONS

There were major differences in the definitions and assessment methods of eloquence, and none of them proved to be satisfactory to express eloquence as an objective, quantifiable, preoperative factor to use in glioma decision making. Therefore, we propose the development of a novel, objective, reliable, preoperative classification system to assess eloquence. This should in the future aid neurosurgeons in their preoperative decision making to facilitate personalized treatment paradigms and to improve surgical outcomes.

Health-related quality of life in adults with low-grade gliomas: a systematic review

PURPOSE

Low-grade glioma (LGG) patients may face health-related quality-of-life (HRQoL) impairments, due to the tumour, treatment and associated side-effects and prospects of progression. We systematically identified quantitative studies assessing HRQoL in adult LGG patients, for: aspects of HRQoL impacted; comparisons with non-cancer controls (NCC) and other groups; temporal trends; and factors associated with HRQoL.

METHODS

MEDLINE, CINAHL, Embase, PubMed, and PsycINFO were systematically searched from inception to 14th September 2021. Following independent screening of titles and abstracts and full-texts, population and study characteristics, and HRQoL findings were abstracted from eligible papers, and quality appraised. Narrative synthesis was conducted.

RESULTS

Twenty-nine papers reporting 22 studies (cross-sectional, n = 13; longitudinal, n = 9) were identified. Papers were largely good quality, though many excluded patients with cognitive and communication impairments. Comparators included high-grade gliomas (HGG) (n = 7); NCCs (n = 6) and other patient groups (n = 3). Nineteen factors, primarily treatment (n = 8), were examined for association with HRQoL. There was substantial heterogeneity in HRQoL instruments used, factors and aspects of HRQoL assessed and measurement timepoints. HRQoL, primarily cognitive functioning and fatigue, in adult LGG patients is poor, and worse than in NCCs, though better than in HGG patients. Over time, HRQoL remained low, but stable. Epilepsy/seizure burden was most consistently associated with worse HRQoL.

CONCLUSION

LGG patients experience wide-ranging HRQoL impairments. HRQoL in those with cognitive and communication impairments requires further investigation. These findings may help clinicians recognise current supportive care needs and inform types and timings of support needed, as well as inform future interventions.

Changes in Cognitive Functioning After Surgical Resection of Language-related, Eloquent-area, High-grade Gliomas Under Awake Craniotomy

BACKGROUND

Dominant-hemisphere tumors, especially gliomas, as infiltrative tumors, frequently affect cognitive functioning. Establishing a balance between extensive resection, which is proven to result in longer survival, and less extensive resection, in order to maintain more cognitive abilities, is challenging.

OBJECTIVE

To evaluate changes in cognitive functioning before and after surgical resection of language-related, eloquent-area, high-grade gliomas under awake craniotomy.

METHOD

We provided individuals with newly diagnosed high-grade gliomas of the language-related eloquent areas with the same standard of care, including surgical resection of the glioma using intraoperative sensory-motor and cognitive mapping under awake craniotomy, and the same protocol for chemoradiotherapy. Cognitive functioning was assessed using Addenbrooke's Cognitive Examination-Revised (ACE-R) at four time points (preoperatively, early after surgery, and 3 and 6 months postoperatively).

RESULTS

The preoperative evaluation revealed a range of cognitive impairments in 70.7% of the individuals, affecting all of the cognitive subdomains (mostly attention and visuospatial abilities). Overall cognitive functioning (ie, ACE-R score) dropped by 13.5% (P= 0.169) early postoperatively. At the 3-month evaluation, an average of 15.3% (P= 0.182) recovery in cognitive functioning was observed (mostly in verbal fluency: 39.1%). This recovery improved further, reaching 29% (P< 0.001) at the 6-month evaluation. The greatest improvement occurred in verbal fluency: 68.8%,P= 0.001.

CONCLUSION

Extensive resection of eloquent-area gliomas with the aid of modern neuroimaging and neuromonitoring techniques under awake craniotomy is possible without significant long-term cognitive sequela.

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.

Lower-Grade Gliomas: An Epidemiological Voxel-Based Analysis of Location and Proximity to Eloquent Regions

Background

Glioma is the most common intra-axial tumor, and its location relative to critical areas of the brain is important for treatment decision-making. Studies often report tumor location based on anatomical taxonomy alone since the estimation of eloquent regions requires considerable knowledge of functional neuroanatomy and is, to some degree, a subjective measure. An unbiased and reproducible method to determine tumor location and eloquence is desirable, both for clinical use and for research purposes.

Objective

To report on a voxel-based method for assessing anatomical distribution and proximity to eloquent regions in diffuse lower-grade gliomas (World Health Organization grades 2 and 3).

Methods

A multi-institutional population-based dataset of adult patients (≥18 years) histologically diagnosed with lower-grade glioma was analyzed. Tumor segmentations were registered to a standardized space where two anatomical atlases were used to perform a voxel-based comparison of the proximity of segmentations to brain regions of traditional clinical interest.

Results

Exploring the differences between patients with oligodendrogliomas, isocitrate dehydrogenase (IDH) mutated astrocytomas, and patients with IDH wild-type astrocytomas, we found that the latter were older, more often had lower Karnofsky performance status, and that these tumors were more often found in the proximity of eloquent regions. Eloquent regions are found slightly more frequently in the proximity of IDH-mutated astrocytomas compared to oligodendrogliomas. The regions included in our voxel-based definition of eloquence showed a high degree of association with performing biopsy compared to resection.

Conclusion

We present a simple, robust, unbiased, and clinically relevant method for assessing tumor location and eloquence in lower-grade gliomas.

Alternative language paradigms for functional magnetic resonance imaging as presurgical tools for inducing crossed cerebro-cerebellar language activations in brain tumor patients

OBJECTIVES

Crossed cerebro-cerebellar BOLD activations have recently come to light as additional diagnostic features for patients with brain tumors. The covert verb generation (VG) task is a widely used language paradigm to determine these language-related crossed activations. Here we demonstrate these crossed activations in two additional language paradigms, the semantic and phonological association tasks. We propose the merit of these tasks to language lateralization determination in the clinic as they are easy to monitor and suitable for patients with aphasia.

METHODS

Patients with brain tumors localized at different cortical sites (n = 71) performed three language paradigms, namely the VG task as well as the semantic (SA) and phonological (PA) association tasks with button-press responses. Respective language activations in disparate cortical regions and the cerebellum were assigned laterality. Agreements in laterality between the two new tasks and the verb generation task were tested using Cohen's kappa.

RESULTS

Both tasks significantly agreed in cortical and cerebellar lateralization with the verb generation task in patients. Additionally, a McNemar test confirmed the presence of crossed activations in the cortex and the cerebellum in the entire subject population.

CONCLUSION

We demonstrated that the semantic and phonological association tasks resulted in crossed cerebro-cerebellar language lateralization activations as those observed due to the covert verb generation task. This may suggest the possibility of these tasks being used conjointly with the traditional verb generation task, especially for subjects that may be unable to perform the latter.

KEY POINTS

• The semantic and phonological association tasks can be useful as additional presurgical fMRI language lateralization paradigms for brain tumor patients along with the standard verb generation task. • All three tasks also confirm the presence of crossed cerebro-cerebellar language activations in the current subject population.

Risk of early failure of VP shunts implanted for hydrocephalus after craniotomies for brain tumors in adults

Risks and survival times of ventriculoperitoneal (VP) shunts implanted due to hydrocephalus after craniotomies for brain tumors are largely unknown. The purpose of this study was to determine the overall timing of VP shunting and its failure after craniotomy for brain tumors in adults. The authors also wished to explore risk factors for early VP shunt failure (within 90 days). A population-based consecutive patient cohort of all craniotomies for intracranial tumors leading to VP shunt dependency in adults (> 18 years) from 2004 to 2013 was studied. Patients with pre-existing VP shunts prior to craniotomy were excluded. The survival time of VP shunts, i.e., the shunt longevity, was calculated from the day of shunt insertion post-craniotomy for a brain tumor until the day of shunt revision requiring replacement or removal of the shunt system. Out of 4774 craniotomies, 85 patients became VP shunt-dependent (1.8% of craniotomies). Median time from craniotomy to VP shunting was 1.9 months. Patients with hydrocephalus prior to tumor resection (N = 39) had significantly shorter time to shunt insertion than those without (N = 46) (p < 0.001), but there was no significant difference with respect to early shunt failure. Median time from shunt insertion to shunt failure was 20 days (range 1–35). At 90 days, 17 patients (20%) had confirmed shunt failure. Patient age, sex, tumor location, primary/secondary craniotomy, extra-axial/intra-axial tumor, ventricular entry, post-craniotomy bleeding, and infection did not show statistical significance. The risk of early shunt failure (within 90 days) of shunts after craniotomies for brain tumors was 20%. This study can serve as benchmark for future studies.

Life after surgical resection of a low-grade glioma: A prospective cross-sectional study evaluating health-related quality of life

Health related quality of life (HRQoL) has become an important consideration in LGG patients. We report the largest prospective, longitudinal, cross-sectional cohort study of HRQoL in LGG patients, aiming to identify actionable determinants of HRQoL. Post-operative LGG adults at a large tertiary center underwent HRQoL assessment using the EORTC QLQ-C30 questionnaire administered at follow-up visits and by mail. Scores at 12 month intervals were compared with those from a normative reference population. Spearman's Rho was used to evaluate correlation of subdomain and symptom scores with global HRQoL and change over time. There were 167 participants and 366 questionnaires analysed. Patients reported reduced global HRQoL at nearly every 12 month interval with significant impairments at 12, 72, 108, and 120+ months postoperative. They also reported a significant impairment in each functional subdomain at 12 months, which persisted to varying degrees over 120 months, as did significant fatigue and insomnia. Role, emotional, and social subdomains, as well as fatigue, were significantly associated with global HRQoL at the first 12 month interval. Overall, there was no significant correlation between time from surgery and global HRQoL or the subdomain functional or symptom sections of the QLQ-C30. LGG patients report considerable, sustained impairments in HRQoL after surgery, particularly in cognitive, emotional, and social function, as well as suffering significant fatigue and insomnia. These are strongly associated with global HRQoL and thus can be considered determinants of global HRQoL that with intervention, may improve HRQoL for our LGG patients. This is the largest prospective longitudinal study of HRQoL in postoperative LGG patients yet reported and is ongoing. It identifies several determinants of impaired HRQoL with available management options and interventions that have the potential to significantly improve HRQoL in these patients.

Functional Mapping for Glioma Surgery, Part 1: Preoperative Mapping Tools

Although intraoperative mapping of brain areas was shown to promote greater extent of resection and reduce functional deficits, this was shown only recently for some noninvasive techniques. Yet, proper surgical planning, indication, and patient consultation require reliable noninvasive techniques. Because functional magnetic resonance imaging, tractography, and neurophysiologic methods like navigated transcranial magnetic stimulation and magnetoencephalography allow identifying eloquent areas prior to resective surgery and tailor the surgical approach, this article provides an overview on the individual strengths and limitations of each modality.

Advancements in predicting outcomes in patients with glioma: a surgical perspective

Introduction: Diffuse glioma is a challenging neurosurgical entity. Although surgery does not provide a cure, it may greatly influence survival, brain function, and quality of life. Surgical treatment is by nature highly personalized and outcome prediction is very complex. To engage and succeed in this balancing act it is important to make best use of the information available to the neurosurgeon.Areas covered: This narrative review provides an update on advancements in predicting outcomes in patients with glioma that are relevant to neurosurgeons.Expert opinion: The classical 'gut feeling' is notoriously unreliable and better prediction strategies for patients with glioma are warranted. There are numerous tools readily available for the neurosurgeon in predicting tumor biology and survival. Predicting extent of resection, functional outcome, and quality of life remains difficult. Although machine-learning approaches are currently not readily available in daily clinical practice, there are several ongoing efforts with the use of big data sets that are likely to create new prediction models and refine the existing models.

Intraoperative 3D ultrasound-guided resection of diffuse low-grade gliomas: radiological and clinical results

OBJECTIVE

Extent of resection (EOR) and residual tumor volume are linked to prognosis in low-grade glioma (LGG) and there are various methods for facilitating safe maximal resection in such patients. In this prospective study the authors assess radiological and clinical results in consecutive patients with LGG treated with 3D ultrasound (US)-guided resection under general anesthesia.

METHODS

Consecutive LGGs undergoing primary surgery guided with 3D US between 2008 and 2015 were included. All LGGs were classified according to the WHO 2016 classification system. Pre- and postoperative volumetric assessments were performed, and volumetric results were linked to overall and malignant-free survival. Pre- and postoperative health-related quality of life (HRQoL) was evaluated.

RESULTS

Forty-seven consecutive patients were included. Twenty LGGs (43%) were isocitrate dehydrogenase (IDH)-mutated, 7 (14%) were IDH wild-type, 19 (40%) had both IDH mutation and 1p/19q codeletion, and 1 had IDH mutation and inconclusive 1p/19q status. Median resection grade was 93.4%, with gross-total resection achieved in 14 patients (30%). An additional 24 patients (51%) had small tumor remnants < 10 ml. A more conspicuous tumor border (p = 0.02) and lower University of California San Francisco prognostic score (p = 0.01) were associated with less remnant tumor tissue, and overall survival was significantly better with remnants < 10 ml (p = 0.03). HRQoL was maintained or improved in 86% of patients at 1 month. In both cases with severe permanent deficits, relevant ischemia was present on diffusion-weighted postoperative MRI.

CONCLUSIONS

Three-dimensional US-guided LGG resections under general anesthesia are safe and HRQoL is preserved in most patients. Effectiveness in terms of EOR appears to be consistent with published studies using other advanced neurosurgical tools. Avoiding intraoperative vascular injury is a key factor for achieving good functional outcome.

Quality-adjusted life years in glioma patients: a systematic review on currently available data and the lack of evidence-based utilities

BACKGROUND

Cost-effectiveness studies gain importance in the context of rising health care expenses and treatment options. Especially in the neuro-oncological context, surgical therapy may increase overall survival, but restrain the patient by postoperative disability. Quality-adjusted life years, express treatment effects and are based on health utilities. In our study, we analyze the current evidence on health economic evaluations in glioma patients.

MATERIAL AND METHODS

We performed a systematic database search including Medline and Cochrane Library. Studies were critically appraised for statistical analyzes including glioma patients, health economic modeling and detailed health outcome. Study evidence was classified according to levels of evidence for therapeutic studies from the Centre for Evidence-Based Medicine (Oxford).

RESULTS

37 studies (1995-2018) were identified, 29 matched our inclusion criteria. Studies addressed surgical cost-efficiency and/or the standard treatment, postoperative chemotherapy (n = 6) and 5-ALA (n = 3). Only 16 studies used QALY as the outcome measure, most used overall survival or life years gained (LYG). Utilities were either based on one single study (Garside et al. in Health Technol Assess 11:iii-iv, ix-221) or derived from visual analogue scale (VAS). None assessed quality of life values for specific health statuses or utilities. Incremental cost-effectiveness ratios varied from 8325€ per QALY (5-ALA) to 518,342€ per LYG (tumor treating fields).

CONCLUSIONS

Only one study generated utility values to conduct cost-effectiveness analysis (CEA); most studies used indirect outcomes such as LYG or based their model on previously published data. Health economic evaluations lack specific utilities, further investigations are necessary to conduct reliable CEA in the neurosurgical context.

Differences in spatial distribution between WHO 2016 low-grade glioma molecular subgroups

Background

Several studies reported a correlation between anatomic location and genetic background of low-grade gliomas (LGGs). As such, tumor location may contribute to presurgical clinical decision-making. Our purpose was to visualize and compare the spatial distribution of different WHO 2016 gliomas, frequently aberrated single genes and DNA copy number alterations within subgroups, and groups of postoperative tumor volume.

Methods

Adult grade II glioma patients (WHO 2016 classified) diagnosed between 2003 and 2016 were included. Tumor volume and location were assessed with semi-automatic software. All volumes of interest were mapped to a standard reference brain. Location heatmaps were created for each WHO 2016 glioma subgroup, frequently aberrated single genes and copy numbers (CNVs), as well as heatmaps according to groups of postoperative tumor volume. Differences between subgroups were determined using voxelwise permutation testing.

Results

A total of 110 IDH mutated astrocytoma patients, 92 IDH mutated and 1p19q co-deleted oligodendroglioma patients, and 22 IDH wild-type astrocytoma patients were included. We identified small regions in which specific molecular subtypes occurred more frequently. IDH-mutated LGGs were more frequently located in the frontal lobes and IDH wild-type tumors more frequently in the basal ganglia of the right hemisphere. We found no localizations of significant difference for single genes/CNVs in subgroups, except for loss of 9p in oligodendrogliomas with a predilection for the left parietal lobes. More extensive resections in LGG were associated with frontal locations.

Conclusions

WHO low-grade glioma subgroups show differences in spatial distribution. Our data may contribute to presurgical clinical decision-making in LGG patients.

A novel radiological classification system for cerebral gliomas: The Brain-Grid

Purpose

Standard radiological/topographical classifications of gliomas often do not reflect the real extension of the tumor within the lobar-cortical anatomy. Furthermore, these systems do not provide information on the relationship between tumor growth and the subcortical white matter architecture. We propose the use of an anatomically standardized grid system (the Brain-Grid) to merge serial morphological magnetic resonance imaging (MRI) scans with a representative tractographic atlas. Two illustrative cases are presented to show the potential advantages of this classification system.

Methods

MRI scans of 39 patients (WHO grade II and III gliomas) were analyzed with a standardized grid created by intersecting longitudinal lines on the axial, sagittal, and coronal planes. The anatomical landmarks were chosen from an average brain, spatially normalized to the Montreal Neurological Institute (MNI) space and the Talairach space. Major white matter pathways were reconstructed with a deterministic tracking algorithm on a reference atlas and analyzed using the Brain-Grid system.

Results

In all, 48 brain grid voxels (areas defined by 3 coordinates, axial (A), coronal (C), sagittal (S) and numbers from 1 to 4) were delineated in each MRI sequence and on the tractographic atlas. The number of grid voxels infiltrated was consistent, also in the MNI space. The sub-cortical insula/basal ganglia (A3-C2-S2) and the fronto-insular region (A3-C2-S1) were most frequently involved. The inferior fronto-occipital fasciculus, anterior thalamic radiation, uncinate fasciculus, and external capsule were the most frequently associated pathways in both hemispheres.

Conclusions

The Brain-Grid based classification system provides an accurate observational tool in all patients with suspected gliomas, based on the comparison of grid voxels on a morphological MRI and segmented white matter atlas. Important biological information on tumor kinetics including extension, speed, and preferential direction of progression can be observed and even predicted with this system. This novel classification can easily be applied to both prospective and retrospective cohorts of patients and increase our comprehension of glioma behavior.

Prevalence of symptoms in glioma patients throughout the disease trajectory: a systematic review

BACKGROUND

Glioma patients suffer from a wide range of symptoms which influence quality of life negatively. The aim of this review is to give an overview of symptoms most prevalent in glioma patients throughout the total disease trajectory, to be used as a basis for the development of a specific glioma Patient Reported Outcome Measure (PROM) for early assessment and monitoring of symptoms in glioma patients.

METHODS

A systematic review focused on symptom prevalence in glioma patients in different phases of disease and treatment was performed in MEDLINE, CINAHL and EMBASE according to PRISMA recommendations. We calculated weighted means for prevalence rates per symptom.

RESULTS

The search identified 2.074 unique papers, of which 32 were included in this review. In total 25 symptoms were identified. The ten most prevalent symptoms were: seizures (37%), cognitive deficits (36%), drowsiness (35%), dysphagia (30%), headache (27%), confusion (27%), aphasia (24%), motor deficits (21%), fatigue (20%) and dyspnea (20%).

CONCLUSIONS

Eight out of ten of the most prevalent symptoms in glioma patients are related to the central nervous system and therefore specific for glioma. Our findings emphasize the importance of tailored symptom care for glioma patients and may aid in the development of specific PROMs for glioma patients in different phases of the disease.

Imaging practice in low-grade gliomas among European specialized centers and proposal for a minimum core of imaging

OBJECTIVE

Imaging studies in diffuse low-grade gliomas (DLGG) vary across centers. In order to establish a minimal core of imaging necessary for further investigations and clinical trials in the field of DLGG, we aimed to establish the status quo within specialized European centers.

METHODS

An online survey composed of 46 items was sent out to members of the European Low-Grade Glioma Network, the European Association of Neurosurgical Societies, the German Society of Neurosurgery and the Austrian Society of Neurosurgery.

RESULTS

A total of 128 fully completed surveys were received and analyzed. Most centers (n = 96, 75%) were academic and half of the centers (n = 64, 50%) adhered to a dedicated treatment program for DLGG. There were national differences regarding the sequences enclosed in MRI imaging and use of PET, however most included T1 (without and with contrast, 100%), T2 (100%) and TIRM or FLAIR (20, 98%). DWI is performed by 80% of centers and 61% of centers regularly performed PWI.

CONCLUSION

A minimal core of imaging composed of T1 (w/wo contrast), T2, TIRM/FLAIR, PWI and DWI could be identified. All morphologic images should be obtained in a slice thickness of ≤ 3 mm. No common standard could be obtained regarding advanced MRI protocols and PET.

IMPORTANCE OF THE STUDY

We believe that our study makes a significant contribution to the literature because we were able to determine similarities in numerous aspects of LGG imaging. Using the proposed "minimal core of imaging" in clinical routine will facilitate future cooperative studies.

Resection of gliomas deemed inoperable by neurosurgeons based on preoperative imaging studies

OBJECTIVE

Maximal safe resection is a primary objective in the management of gliomas. Despite this objective, surgeons and referring physicians may, on the basis of radiological studies alone, assume a glioma to be unresectable. Because imaging studies, including functional MRI, may not localize brain functions (such as language) with high fidelity, this simplistic approach may exclude some patients from what could be a safe resection. Intraoperative direct electrical stimulation (DES) allows for the accurate localization of functional areas, thereby enabling maximal resection of tumors, including those that may appear inoperable based solely on radiological studies. In this paper the authors describe the extent of resection (EOR) and functional outcomes following resections of tumors deemed inoperable by referring physicians and neurosurgeons.

METHODS

The authors retrospectively examined the cases of 58 adult patients who underwent glioma resection within 6 months of undergoing a brain biopsy of the same lesion at an outside hospital. All patients exhibited unifocal supratentorial disease and preoperative Karnofsky Performance Scale scores ≥ 70. The EOR and 6-month functional outcomes for this population were characterized.

RESULTS

Intraoperative DES mapping was performed on 96.6% (56 of 58) of patients. Nearly half of the patients (46.6%, 27 of 58) underwent an awake surgical procedure with DES. Overall, the mean EOR was 87.6% ± 13.6% (range 39.0%–100%). Gross-total resection (resection of more than 99% of the preoperative tumor volume) was achieved in 29.3% (17 of 58) of patients. Subtotal resection (95%–99% resection) and partial resection (PR; < 95% resection) were achieved in 12.1% (7 of 58) and 58.6% (34 of 58) of patients, respectively. Of the cases that involved PR, the mean EOR was 79.4% ± 12.2%. Six months after surgery, no patient was found to have a new postoperative neurological deficit. The majority of patients (89.7%, 52 of 58) were free of neurological deficits both pre- and postoperatively. The remainder of patients exhibited either residual but stable deficits (5.2%, 3 of 58) or complete correction of preoperative deficits (5.2%, 3 of 58).

CONCLUSIONS

The use of DES enabled maximal safe resections of gliomas deemed inoperable by referring neurosurgeons. With rare exceptions, tumor resectability cannot be determined solely by radiological studies.

Fluorescence-guidance in non-Gadolinium enhancing, but FET-PET positive gliomas

OBJECTIVES

We report on five patients with gadolinium-negative (non-enhancing magnetic resonance imaging-MRI) but ¹⁸F-fluoroethyl tyrosine positron-emission tomography (FET-PET) positive glioma (NEG) undergoing surgery under fluorescence-guidance with fluorescein sodium 10% (FL, Alkon, Germany) in combination with a dedicated light filter (YELLOW 560 nm, Carl Zeiss Meditec, Germany).

PATIENTS AND METHOD

Since 2017, five patients (3 female, 2 male; mean age 45.4 years) underwent fluorescence-guided surgery for supratentorial, intracerebral lesions which showed no contrast-enhancement in the preoperative MRI but were, however, strongly suspicious for gliomas. Accordingly, all patients received a preoperative FET-PET scan and detailed histopathological workup was performed. After giving written informed consent, all patients received 5 mg/kg of FL at the induction of anesthesia. Surgery was conducted under white light and under the YELLOW 560 nm filter. We reviewed the surgical protocols, navigational storage and the image databases of our surgical microscopes for evidence of intraoperative fluorescence that corresponded to the FET-PET positive area.

RESULTS

In all patients we found distinct accordances between the FET-PET positive areas and the fluorescing regions within the targeted lesions. Histopathological workup of the fluorescent tissue revealed anaplastic oligodendroglioma, IDH-mutant and 1p/19-codeleted (WHO grade III) (n = 2), anaplastic astrocytoma, IDH-mutant (WHO grade III) (n = 1), oligodendroglioma, IDH-mutant and 1p/19q-codeleted (WHO grade II) (n = 1) and pilocytic astrocytoma (WHO grade I) (n = 1). No adverse events were noted.

DISCUSSION AND CONCLUSION

Despite the lack of gadolinium-enhancement in the preoperative MRI, all patients intravenously received FL to guide resection. Irrespective of the final grading, FL was extremely helpful in detecting the lesions and in identifying their border zones. In selected patients with NEG, but strong metabolic activity according to the FET-PET, FL may significantly increase the accuracy of surgery.

Glioma surgery with intraoperative mapping-balancing the onco-functional choice

BACKGROUND

Balancing survival versus risk of inducing functional deficits is a challenge when resecting gliomas in or near eloquent areas. Our objectives were to assess deficits prior to and at 6 and 12 months after awake craniotomies with cortical and subcortical mapping in patients with suspected grade 2 gliomas in eloquent areas. We analyzed whether pre- and intraoperative factors were linked to an increased risk of postoperative deficits.

METHOD

Retrospective study of 92 consecutive patients operated between January 2010 and June 2014. All deficits reported by any healthcare professional and KPS-score preoperatively, immediately postoperatively (day 1-10), at 6 months and 12 months, were analyzed.

RESULTS

A decrease in neurological and or cognitive function was common in the first days after surgery, with a significant improvement at 6 months after surgery and further improvement at 12 months. Immediately after surgery, 33% of the patients had severe deficits compared to 2% prior to surgery; this improved to 9% at 6 months and 3% at 12 months. However, at 12 months, 18% of the patients had new or worsened minor or moderate deficits and only 10% had no deficits compared to 39% prior to surgery. There were only minor changes in KPS. None of the recorded pre/intraoperative factors were found significantly to influence the risk of moderate/severe late postoperative deficits.

CONCLUSION

A significant amount of the patients in this study experienced new or worsened neurological and or cognitive deficits during follow-up. We found a higher frequency of deficits than normally reported. This is due to the inclusion of mild deficits, the use of patient-reported data, and our focus on cognitive deficits. Our study indicates that the impact of awake craniotomy with mapping on patient outcome is larger than expected. This in no way negates the use of the technique.

Survey on current cognitive practices within the European Low-Grade Glioma Network: towards a European assessment protocol

BACKGROUND

The European Low-Grade Glioma network indicated a need to better understand common practices regarding the managing of diffuse low-grade gliomas. This area has experienced great advances in recent years.

METHOD

A general survey on the managing of diffuse low-grade gliomas was answered by 21 centres in 11 European countries. Here we focused on specific questions regarding perioperative and intraoperative cognitive assessments.

RESULTS

More centres referred to the same speech and language therapist and/or neuropsychologist across all assessments; a core of assessment tools was routinely used across centres; fluency tasks were commonly used in the perioperative stages, and object naming during surgery; tasks that tapped on attention, executive functions, visuospatial awareness, calculation and emotions were sparsely administered; preoperative assessments were performed 1 month or 1 week before surgery; timing for postoperative assessments varied; finally, more centres recommended early rehabilitation, whenever needed.

CONCLUSIONS

There is an emerging trend towards following similar practices for the management of low-grade gliomas in Europe. Our results are descriptive and formalise current discussions in our group. Also, they contribute towards the development of a European assessment protocol.

Fatigue in patients with low grade glioma: systematic evaluation of assessment and prevalence

Fatigue is the most prevalent and disabling symptom in cancer patients. Yet, scientific literature on this topic is scarce and reports disparate results. This study systematically reviews how fatigue is assessed in patients with low-grade glioma and evaluates its prevalence in LGG patients. A systematic literature search was performed in PubMed, Embase and PsychINFO for articles reporting on fatigue in patients with LGG. Two reviewers independently extracted data from selected articles. Inclusion criteria were: (1) patients with suspected or confirmed LGG; (2) fatigue was assessed as primary or secondary outcome measure; (3) age≥ 18 years; (4) full-length article written in English or Dutch. In total, 19 articles were selected, including 971 patients. Seven self-assessment instruments were identified. Prevalence rates ranged from 39 to 77%. Fatigue was found to be a common side effect of treatment. The prevalence rates ranged from 20 to 76% when fatigue was reported as a mild or moderate side effect and fatigue was prevalent in 4% when reported as a severe side effect. Fatigue is a common problem in LGG patients that warrants more therapeutic and scientific attention. Gaining deeper insight in the underlying mechanisms of fatigue is essential in targeting therapy to individual patients.

Resection of Navigated Transcranial Magnetic Stimulation-Positive Prerolandic Motor Areas Causes Permanent Impairment of Motor Function

BACKGROUND: Navigated transcranial magnetic stimulation (nTMS) helps to determine the distribution of motor eloquent areas prior to brain surgery. Yet, the eloquence of primary motor areas frontal to the precentral gyrus identified via nTMS is unclear.

OBJECTIVE: To investigate the resection of nTMS-positive prerolandic motor areas and its correlation with postsurgical impairment of motor function.

METHODS: Forty-three patients with rolandic or prerolandic gliomas (WHO grade I-IV) underwent nTMS prior to surgery. Only patients without ischemia within the motor system in postoperative MRI diffusion sequences were enrolled. Based on the 3-dimensional fusion of preoperative nTMS motor mapping data with postsurgical MRI scans, we identified nTMS points that were resected in the infiltration zone of the tumor. We then classified the resected points according to the localization and latency of their motor evoked potentials. Surgery-related paresis was graded as transient (≤6 weeks) or permanent (&gt;6 weeks).

RESULTS: Out of 43, 31 patients (72%) showed nTMS-positive motor points in the prerolandic gyri. In general, 13 out of 43 patients (30%) underwent resection of nTMS points. Ten out of these patients showed postoperative paresis. There were 2 (15%) patients with a transient and 8 (62%) with a permanent surgery-related paresis. In 3 cases (23%), motor function remained unimpaired.

CONCLUSION: After resection of nTMS-positive motor points, 62% of patients suffered from a new permanent paresis. Thus, even though they are located in the superior or middle frontal gyrus, these cortical areas must undergo intraoperative mapping.

Gamma Knife Radiosurgery for Low-Grade Gliomas: Clinical Results at Long-Term Follow-Up of Tumor Control and Patients' Quality of Life

OBJECTIVE

First-line therapy for low-grade gliomas (LGGs) is surgery, in some cases followed by radiotherapy and chemotherapy. Gamma Knife radiosurgery (GKRS) has gained more relevance in the management of these tumors. The aim of this study was to assess efficacy and safety of GKRS for treatment of LGGs.

METHODS

Between 2001 and 2014, 42 treatments were performed on 39 patients harboring LGGs; 48% of patients underwent previous surgery, and 20.5% underwent previous radiotherapy. Mean tumor volume was 2.7 cm³, and median margin dose was 15 Gy.

RESULTS

Mean follow-up was 60.5 months (range, 6-164 months). Actuarial progression-free survival was 74.9%, 52.8%, and 39.1% at 1 year, 5 years, and 10 years; actuarial overall survival was 97.4%, 94.6%, and 91.8% at 9 months, 1 year, and 5 years. Solid tumor control was achieved in 69.2% of patients, whereas cystic enlargement was recorded in 12.9% of cases. At last follow-up, volume reduction was recorded in 57.7% of cases, and median volume decreased by 33.3%. Clinical improvement was observed in 52.4% of patients. Karnofsky performance scale score was improved in 15 patients (45.5%), unchanged in 17 patients (51.5%), and worsened in 1 patient (3%). Mean posttreatment scores of 36-item short form health survey domains did not significantly differ from scores in a healthy Italian population.

CONCLUSIONS

This study confirms safety and effectiveness of GKRS for LGGs in controlling tumor growth, relevantly improving patients' overall and progression-free survival. GKRS improved patients' functional performance and quality of life, optimizing social functioning and minimizing disease-related psychological impact.

Network Plasticity and Intraoperative Mapping for Personalized Multimodal Management of Diffuse Low-Grade Gliomas

Gliomas are the most frequent primary brain tumors and include a variety of different histological tumor types and malignancy grades. Recent achievements in terms of molecular and imaging fields have created an unprecedented opportunity to perform a comprehensive interdisciplinary assessment of the glioma pathophysiology, with direct implications in terms of the medical and surgical treatment strategies available for patients. The current paradigm shift considers glioma management in a comprehensive perspective that takes into account the intricate connectivity of the cerebral networks. This allowed significant improvement in the outcome of patients with lesions previously considered inoperable. The current review summarizes the current theoretical framework integrating the adult human brain plasticity and functional reorganization within a dynamic individualized treatment strategy for patients affected by diffuse low-grade gliomas. The concept of neuro-oncology as a brain network surgery has major implications in terms of the clinical management and ensuing outcomes, as indexed by the increased survival and quality of life of patients managed using such an approach.

Functional preoperative and intraoperative mapping and monitoring: increasing safety and efficacy in glioma surgery

Greater extent of resection (EOR) of low-grade gliomas is associated with improved survival. Proximity to eloquent cortical regions often limits resectability and elevates the risk of surgery-related deficits. Therefore, functional localization of eloquent cortex or subcortical fiber tracts can enhance the EOR and functional outcome. Imaging techniques such as functional MRI and diffusion tensor imaging fiber tracking, and neurophysiological methods like navigated transcranial magnetic stimulation and magnetoencephalography, make it possible to identify eloquent areas prior to resective surgery and to tailor indication and surgical approach but also to assess the surgical risk. Intraoperative monitoring with direct cortical stimulation and subcortical stimulation enables surgeons to preserve essential functional tissue during surgery. Through tailored pre- and intraoperative mapping and monitoring the EOR can be maximized, with reduced rates of surgery-related deficits.

CXCL12 and CXCR4 as predictive biomarkers of glioma recurrence pattern after total resection

PURPOSE OF THE STUDY

Previous studies have shown that the pattern of recurrence for glioma is related to the direction of glioma cell invasion. Recent studies demonstrated that the CXCL12/CXCR4 signaling pathway mediates cellular invasion in glioma. Therefore, in this study, we investigated the possible relationship between CXCL12/CXCR4 expression and recurrence pattern in glioma.

PATIENTS AND METHODS

Immunohistochemical techniques were used to assess CXCL12/CXCR4 expression in 42 glioma tissues following total resection. According to magnetic resonance imaging (MRI) of gliomas, the recurrence pattern was classified as close or distant pattern. The relationship between recurrence pattern and CXCL12/CXCR4 expression were initially examined by Chi-squared analysis. The prognostic significance of CXCL12 and CXCR4 was determined by log-rank tests and COX proportional hazards model.

RESULTS

CXCL12 was expressed mainly in vascular endothelial cells and CXCR4 was expressed mainly in tumor cells. The recurrence pattern was significantly related to the expression level of CXCL12 in vascular endothelial cells (P=0.002) and CXCR4 in tumor cells (P=0.004). However, CXCL12 and CXCR4 were not independent prognostic factors for progression-free survival or overall survival in glioma patients.

CONCLUSION

The glioma recurrence pattern is related to CXCL12 expression levels in vascular endothelial cells and CXCR4 expression levels in tumor cells; thus, implicating the CXCL12/CXCR4 signaling pathway as a potential target for glioma therapy.

The Value of Pre- and Intraoperative Adjuncts on the Extent of Resection of Hemispheric Low-Grade Gliomas: A Retrospective Analysis

BACKGROUND

To achieve maximal resection with minimal risk of postoperative neurologic morbidity, different neurosurgical adjuncts are being used during low-grade glioma (LGG) surgery.

OBJECTIVES

To investigate the effect of pre- and intraoperative adjuncts on the extent of resection (EOR) of hemispheric LGGs.

METHODS

Medical records were reviewed to identify patients of any sex, ≥ 18 years of age, who underwent LGG surgery at X Hospital between January 2005 and July 2013. Patients were divided into eight subgroups based on the use of various combinations of a neuronavigation system alone (NN), functional MRI-diffusion tensor imaging (fMRI-DTI) guided neuronavigation (FD), intraoperative MRI (MR), and direct electrical stimulation (DES). Initial and residual tumors were measured, and mean EOR was compared between groups.

RESULTS

Of all 128 patients, gross total resection was achieved in 23.4%. Overall mean EOR was 81.3% ± 20.5%. Using DES in combination with fMRI-DTI (mean EOR: 86.7% ± 12.4%) on eloquent tumors improved mean EOR significantly after adjustment for potential confounders when compared with NN alone (mean EOR: 76.4% ± 25.5%; p = 0.001).

CONCLUSIONS

Using DES in combination with fMRI and DTI significantly improves EOR when LGGs are located in eloquent areas compared with craniotomies in which only NN was used.

Primo non nocere or maximum survival in grade 2 gliomas? A medical ethical question

BACKGROUND

Maximum safe resection is the "gold standard" in surgical treatment of grade 2 gliomas (G2Gs), aiming to achieve maximal survival benefit with minimal risk of functional deficit.

OBJECTIVE

To investigate the attitude of patients and experts towards more extensive surgery with a trade-off between neurological function and survival time.

METHODS

Eight patients and seven experts participated in semi-structured focus group interviews.

RESULTS

Both patients and experts accepted the premise of balancing neurological function versus longevity. Some patients would accept an increased risk of permanent neurological deficits in order to obtain a chance of increased survival. There was a significant variance in what constituted "quality of life" both between patients and for the individual patient over time.

CONCLUSIONS

In important life-changing decisions there is no "one size fits all". We find that it is ethically acceptable to offer more extensive surgery than is possible within the concept of maximal safe surgery as a treatment option, when balancing the principles of beneficence, non-maleficience, autonomy and justice supports the decision. At the same time it must be remembered that even when the patients have made a well-informed decision, some will regret it. In that situation it will be our job as healthcare professionals to support them and help carry some of this burden.

Linear array ultrasound in low-grade glioma surgery: histology-based assessment of accuracy in comparison to conventional intraoperative ultrasound and intraoperative MRI

INTRODUCTION

In low-grade glioma (LGG) surgery, intraoperative differentiation between tumor and most likely tumor-free brain tissue can be challenging. Intraoperative ultrasound can facilitate tumor resection. The aim of this study is to evaluate the accuracy of linear array ultrasound in comparison to conventional intraoperative ultrasound (cioUS) and intraoperative high-field MRI (iMRI).

METHODS

We prospectively enrolled 13 patients harboring a LGG of WHO Grade II. After assumed near total removal, a resection control was performed using navigated cioUS, navigated lioUS, and iMRI. We harvested 30 navigated biopsies from the resection cavity and compared the histopathological findings with the respective imaging results. Spearman's rho was calculated to test for significant correlations. Sensitivity and specificity as well as receiver operating characteristics (ROC) were calculated to assess test performance of each imaging modality.

RESULTS

Imaging results of lioUS correlated significantly (p < 0.009) with iMRI. Both iMRI and lioUS correlated significantly with final histopathological diagnosis (p < 0.006, p < 0.014). cioUS did not correlate with other imaging findings or with final diagnosis. The highest sensitivity for residual tumor detection was found in iMRI (83 %), followed by lioUS (79 %). The sensitivity of cioUS was only 21 %. Specificity was highest in cioUS (100 %), whereas iMRI and lioUS both achieved 67 %. ROC curves showed fair results for iMRI and lioUS and a poor result for cioUS.

CONCLUSIONS

Intraoperative resection control in LGGs using lioUS reaches a degree of accuracy close to iMRI. Test results of lioUS are superior to cioUS. cioUS often fails to discriminate solid tumors from "normal" brain tissue during resection control. Only in lesions <10 cc cioUS does show good accuracy.

Navigated transcranial magnetic stimulation improves the treatment outcome in patients with brain tumors in motor eloquent locations

BACKGROUND

Neurological and oncological outcomes of motor eloquent brain-tumor patients depend upon the ability to localize functional areas and the respective proposed therapy. We set out to determine whether the use of navigated transcranial magnetic stimulation (nTMS) had an impact on treatment and outcome in patients with brain tumors in motor eloquent locations.

METHODS

We enrolled 250 consecutive patients and compared their functional and oncological outcomes to a matched pre-nTMS control group (n = 115).

RESULTS

nTMS mapping results disproved suspected involvement of primary motor cortex in 25.1% of cases, expanded surgical indication in 14.8%, and led to planning of more extensive resection in 35.2% of cases and more restrictive resection in 3.5%. In comparison with the control group, the rate of gross total resections increased significantly from 42% to 59% (P < .05). Progression-free-survival for low grade glioma was significantly better in the nTMS group at 22.4 months than in control group at 15.4 months (P < .05). Integration of nTMS led to a nonsignificant change of postoperative deficits from 8.5% in the control group to 6.1% in the nTMS group.

CONCLUSIONS

nTMS provides crucial data for preoperative planning and surgical resection of tumors involving essential motor areas. Expanding surgical indications and extent of resection based on nTMS enables more patients to undergo surgery and might lead to better neurological outcomes and higher survival rates in brain tumor patients. The impact of this study should go far beyond the neurosurgical community because it could fundamentally improve treatment and outcome, and its results will likely change clinical practice.

Supratentorial gliomas in eloquent areas: which parameters can predict functional outcome and extent of resection?

BACKGROUND

To date, few parameters have been found that can aid in patient selection and surgical strategy for eloquent area gliomas.

AIMS

The aim of the study was to analyze preoperative and intraoperative factors that can predict functional outcome and extent of resection in eloquent area tumors.

PATIENTS AND METHODS

A retrospective analysis was conducted on 60 patients harboring supratentorial gliomas in eloquent areas undergoing awake surgery. The analysis considered clinical, neuroradiologic (morphologic), intraoperative, and postoperative factors. End-points were extent of resection (EOR) as well as functional short- and long-term outcome. Postoperatively, MRI objectively established the EOR. χ(2) analyses were used to evaluate parameters that could be predictive. Multivariate logistic regression analyses were used to evaluate the best combination to predict binary positive outcomes.

RESULTS

In 90% of the cases, subcortical stimulation was positive in the margins of the surgical cavity. Postoperatively, 51% of the patients deteriorated but 90% of the patients regained their preoperative neurological score. Factors negatively affecting EOR were volume, degree of subcortical infiltration, and presence of paresis (P<0.01). Sharp margins and cystic components were more amenable to gross total resection (P<0.01). Contrast enhancement (P<0.02), higher grade (P<0.01), paresis (P<0.01), and residual tumor in the cortex (P<0.02) negatively affected long-term functional outcomes, whereas postoperative deterioration could not be predicted for any factor other than paresis. Subcortical stimulation did not correlate with deterioration, both postoperatively (P<0.08) and at follow-up (P<0.042).

CONCLUSIONS

Biological and morphological factors such as type of margins, volume, preoperative neurological status, cystic components, histology and the type of infiltration into the white matter must be considered when planning intraoperative mapping.

The preoperative use of navigated transcranial magnetic stimulation facilitates early resection of suspected low-grade gliomas in the motor cortex

BACKGROUND

Resection is recommended for low-grade gliomas, but often it is not performed if the tumor is suspected of invading the primary motor cortex. The study aim is to assess what influence preoperative navigated transcranial magnetic stimulation (nTMS) has on the treatment strategy and clinical outcome for suspected low-grade gliomas in presumed motor eloquent location.

METHODS

This paper reports on all our patients with gliomas in the primary motor cortex that were non-enhancing on MRI, since we began using nTMS (n = 11). For the comparison group, we identified the 11 most recent such patients just before we started using nTMS.

RESULTS

Exact delineation of motor functional versus non-functional cortical tissue was provided by nTMS in all cases, also within the area of altered FLAIR signal. In 6 out of 11 cases, the nTMS mapping result changed the treatment plan towards early and more extensive resection. Only one nTMS patient had another seizure within the follow-up period, whereas four patients in the comparison group had further seizures. In the nTMS group, 1 of 4 patients with pre-op neurological deficits improved by one year; whereas the comparison group had increased neurological deficits in 3 of the 8 patients not having surgery. The median (range) change of tumor volume from baseline to 1 year was -83 % (-67 % to -100 %) in the nTMS group, but +12 % (+40 % to -56 %) in the comparison group (p < 0.001).

CONCLUSIONS

nTMS provides accurate motor mapping results also in infiltrative gliomas and enables more frequent and more extensive surgical resection of non-enhancing gliomas in or near the primary motor cortex. The substantial differences observed here in neurological and oncological outcomes suggest that further comparative research is warranted.