Safe Resection of Gliomas of the Dominant Angular Gyrus Availing of Preoperative FMRI and Intraoperative DTI: Preliminary Series and Surgical Technique

"False friends" in Language Subcortical Mapping: A Systematic Literature Review

BACKGROUND

Subcortical brain mapping in awake glioma surgery might optimize the extent of resection while minimizing neurological morbidity, but it requires a correct interpretation of responses evoked during surgery. To define, with a systematic review: 1) a comprehensive 'map' of the principal white matter bundles involved in awake surgery on language-related networks, describing the most employed tests and the expected responses; 2) In linguistics, a false friend is a word in a different language that looks or sounds like a word in given language but differs significantly in meaning. Similarly, our aim is to give the surgeons a comprehensive review of potentially misleading responses, namely "false friends", in subcortical language mapping.

METHODS

Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Standardized data extraction was conducted.

RESULTS

Out of a total of 224 initial papers, 67 were included for analysis. Expected responses, common tests, and potential "false friends" were recorded for each of the following white matter bundles: frontal aslant tract, superior and inferior longitudinal fascicles, arcuate fascicle, inferior fronto-occipital fascicle, uncinate fascicle. Practical examples are discussed to underline the risk of intraoperative fallouts ("false friends") that might lead to an early interruption (false positive) or a risky surgical removal (false negative).

CONCLUSIONS

This paper represents a critical review of the present status of subcortical awake mapping and underlines practical "false-friend" in mapping critical crossroads in language-related networks.

Advances in diffuse glial tumors diagnosis

In recent decades, there have been significant advances in the diagnosis of diffuse gliomas, driven by the integration of novel technologies. These advancements have deepened our understanding of tumor oncogenesis, enabling a more refined stratification of the biological behavior of these neoplasms. This progress culminated in the fifth edition of the WHO classification of central nervous system (CNS) tumors in 2021. This comprehensive review article aims to elucidate these advances within a multidisciplinary framework, contextualized within the backdrop of the new classification. This article will explore morphologic pathology and molecular/genetics techniques (immunohistochemistry, genetic sequencing, and methylation profiling), which are pivotal in diagnosis, besides the correlation of structural neuroimaging radiophenotypes to pathology and genetics. It briefly reviews the usefulness of tractography and functional neuroimaging in surgical planning. Additionally, the article addresses the value of other functional imaging techniques such as perfusion MRI, spectroscopy, and nuclear medicine in distinguishing tumor progression from treatment-related changes. Furthermore, it discusses the advantages of evolving diagnostic techniques in classifying these tumors, as well as their limitations in terms of availability and utilization. Moreover, the expanding domains of data processing, artificial intelligence, radiomics, and radiogenomics hold great promise and may soon exert a substantial influence on glioma diagnosis. These innovative technologies have the potential to revolutionize our approach to these tumors. Ultimately, this review underscores the fundamental importance of multidisciplinary collaboration in employing recent diagnostic advancements, thereby hoping to translate them into improved quality of life and extended survival for glioma patients.

Survey Assessment of Utility in Preoperative Magnetic Resonance (MR) Tractography Surgical Planning

BACKGROUND

Although tractography-guided surgery is used by many surgeons, there is controversy in the published literature as it relates to its clinical utility. Here we adopted a survey-based approach with the goal of attaining a broader view of how tractography influence preoperative planning in a sampling of practicing neurosurgeons.

METHODS

Three cases were prepared where the presence of a tumor distorted the optic radiation (case 1), arcuate fasciculus (case 2), and corticospinal tract (case 3). This survey was administered at the Medtronic Cranial Consortium attended by 20 practicing neurosurgeons. To avoid commercial bias, we used both the Brainlab and Medtronic platform to compute tractography. Each participant is asked to vote on a surgical trajectory before and after seeing the tractography images, as well as whether tractography added value in validating their surgical approach.

RESULTS

In the 3 cases surveyed, 16%-44% of the surgeons changed the surgical corridor selected after seeing the tractography images. The most common finding associated with a change in surgical corridor involved intersection of the surgical corridor with visualized tracts. Consistently, >80% of the surgeons surveyed felt that tractography added value in their surgical planning.

CONCLUSIONS

The clinical utility of tractography in preoperative planning varies as a function of surgeon and the tumor anatomy, with >80% of the participating surgeons believing that tractography added value in preoperative surgical planning.

Exploring the arcuate fasciculus from a clinical perspective

In recent years, language function impairment caused by intracranial diseases has gained increasing interest, mainly due to its significant impact on the language and cognitive ability, leading to a serious decline in the quality of life of patients. Consequently, researchers aimed to clarify the quantitative degree of lesions of the arcuate fasciculus and therapeutic targets to promote nerve fiber remodeling. The arcuate fasciculus is extremely prone to damage caused by diseases such as stroke and brain tumor. Hallucinating schizophrenia, autism spectrum disorder, epilepsy, chronic fatigue syndrome, chronic tinnitus, and other diseases can also lead to changes in the fractional anisotropy value of arcuate fasciculus; however, different studies have different conclusions about how this change occurs. To obtain a better understanding, more clinical studies are required. Owing to various advancements in neuroimaging, a better understanding and identification of vital targets for restoration of neurological function are possible. The arcuate fasciculus is stratified into three substructures, each having unique neurological functions. Both diffusion tensor imaging (DTI) sequences and deterministic monitoring techniques render it possible to visually and quantitatively analyze the substructure in three parts. In this review, we examined the progress of the arcuate fasciculus and quantitative DTI technology in recent years.

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.

Resection of high-grade glioma involving language areas assisted by multimodal techniques under general anesthesia: a retrospective study

BACKGROUND

Multimodal techniques-assisted resection of glioma under general anesthesia (GA) has been shown to achieve similar clinical outcomes as awake craniotomy (AC) in some studies. In this study, we aim to validate the use of multimodal techniques can achieve the maximal safe resection of high-grade glioma involving language areas (HGILAs) under GA.

METHODS

HGILAs cases were reviewed and collected between January 2009 and December 2020 in our center. Patients were separated into multimodal group (using neuronavigation, intraoperative MRI combined with direct electrical stimulation [DES] and neuromonitoring [IONM]) and conventional group (neuronavigation alone) and clinical outcomes were compared between groups. Studies of HGILAs were reviewed systematically and the meta-analysis results of previous (GA or AC) studies were compared with our results.

RESULTS

Finally, there were 263 patients in multimodal group and 137 patients in conventional group. Compared to the conventional group, the multimodal group achieved the higher median EOR (100% versus 94.32%, P < 0.001) and rate of gross total resection (GTR) (73.8% versus 36.5%, P < 0.001) and the lower incidence of permanent language deficit (PLD) (9.5% versus 19.7%, P = 0.004). The multimodal group achieved the longer median PFS (16.8 versus 10.3 months, P < 0.001) and OS (23.7 versus 15.7 months, P < 0.001) than the conventional group. The multimodal group achieved a higher rate of GTR than the cohorts in previous multimodal studies under GA and AC (73.8% versus 55.7% [95%CI 32.0-79.3%] versus 53.4% [35.5-71.2%]). The multimodal group had a lower incidence of PLD than the cohorts in previous multimodal studies under GA (9.5% versus 14.0% [5.8-22.1%]) and our incidence of PLD was a little higher than that of previous multimodal studies under AC (9.5% versus 7.5% [3.7-11.2%]). Our multimodal group also achieved a relative longer survival than previous studies.

CONCLUSIONS

Surgery assisted by multimodal techniques can achieve maximal safe resection for HGILAs under GA. Further prospective studies are needed to compare GA with AC for HGILAs.

Diffusion tensor imaging versus intraoperative subcortical mapping for glioma resection: a systematic review and meta-analysis

Maintaining the integrity of crucial fiber tracts allows functional preservation and improved recovery in patients with glioma resection. Diffusion tensor imaging (DTI) and intraoperative subcortical mapping (ISM) are commonly required for pre- and intraoperative assessment of white matter fibers. This study investigated differences of clinical outcomes in glioma resection aided by DTI or ISM. A comprehensive literature retrieval of the PubMed and Embase databases identified several DTI or ISM studies in 2000-2022. Clinical data, including extent of resection (EOR) and postoperative neurological deficits, was collected and statistically analyzed. Heterogeneity was regressed by a random effect model and the Mann-Whitney U test was used to test statistical significance. Publication bias was assessed by Egger test. A total of 14 studies with a pooled cohort of 1837 patients were included. Patients undergoing DTI-navigated glioma surgery showed a higher rate of gross total resection (GTR) than ISM-assisted surgical resection (67.88%, [95% CI 0.55-0.79] vs. 45.73%, [95% CI 0.29-0.63], P = 0.032). The occurrence of early postoperative functional deficit (35.45%, [95% CI 0.13-0.61] vs. 35.60% [95% CI 0.20-0.53], P = 1.000), late postoperative functional deficit (6.00%, [95% CI 0.02-0.11] vs. 4.91% [95% CI 0.03-0.08], P = 1.000) and severe postoperative functional deficit (2.21%, [95% CI 0-0.08] vs. 5.93% [95% CI 0.01-0.16], P = 0.393) were similar between the DTI and ISM group, respectively. While DTI-navigation resulted in a higher rate of GTR, the occurrence of postoperative neurological deficits between DTI and ISM groups was comparable. Together, these data indicate that both techniques could safely facilitate glioma resection.

Supramarginal Gyrus and Angular Gyrus Subcortical Connections: A Microanatomical and Tractographic Study for Neurosurgeons

Background and Objectives: This article aims to investigate the subcortical microanatomy of the supramarginal gyrus (SMG) and angular gyrus (AnG) using a microfiber dissection technique and diffusion tensor imaging (DTI)/fiber tractography (FT). The cortical and subcortical structures of this region are highly functional, and their lesions often present clinically. For this reason, the possibility of post-surgical deficits is high. We focused on the supramarginal gyrus and the angular gyrus and reviewed their anatomy from a topographic, functional and surgical point of view, and aimed to raise awareness especially for neurosurgeons. Methods: Four previously frozen, formalin-fixed human brains were examined under the operating microscope using the fiber dissection technique. Four hemispheres were dissected from medial to lateral under the surgical microscope. Brain magnetic resonance imaging (MRI) of 20 healthy adults was examined. Pre-central and post-central gyrus were preserved to achieve topographic dominance in dissections of brain specimens. Each stage was photographed. Tractographic brain magnetic resonance imaging of 10 healthy adults was examined radiologically. Focusing on the supramarginal and angular gyrus, the white matter fibers passing under this region and their intersection areas were examined. These two methods were compared anatomically from the lateral view and radiologically from the sagittal view. Results: SMG and AnG were determined in brain specimens. The pre-central and post-central gyrus were topographically preserved. The superior and medial temporal gyrus, and inferior and superior parietal areas were decorticated from lateral to medial. U fibers, superior longitudinal fasciculus II (SLF II), superior longitudinal fasciculus III (SLF III), arcuat fasciculus (AF) and middle longitudinal fasciculus (MdLF) fiber groups were shown and subcortical fiber structures belonging to these regions were visualized by the DTI/FT method. The subcortical fiber groups under the SMG and the AnG were observed anatomically and radiologically to have a dense and complex structure. Conclusions: Due to the importance of the subcortical connections of SMG and AnG on speech function, tumoral lesions and surgeries of this region are of particular importance. The anatomical architecture of the complex subcortical structure, which is located on the projection of the SMG and AnG areas, was shown with a DTI/FT examination under a topographic dominance, preserving the pre-central and post-central gyrus. In this study, the importance of the anatomical localization, connections and functions of the supramarginal and angular gyrus was examined. More anatomical and radiological studies are needed to better understand this region and its connections.

Prediction of the Topography of the Corticospinal Tract on T1-Weighted MR Images Using Deep-Learning-Based Segmentation

INTRODUCTION

Tractography is an invaluable tool in the planning of tumor surgery in the vicinity of functionally eloquent areas of the brain as well as in the research of normal development or of various diseases. The aim of our study was to compare the performance of a deep-learning-based image segmentation for the prediction of the topography of white matter tracts on T1-weighted MR images to the performance of a manual segmentation.

METHODS

T1-weighted MR images of 190 healthy subjects from 6 different datasets were utilized in this study. Using deterministic diffusion tensor imaging, we first reconstructed the corticospinal tract on both sides. After training a segmentation model on 90 subjects of the PIOP2 dataset using the nnU-Net in a cloud-based environment with graphical processing unit (Google Colab), we evaluated its performance using 100 subjects from 6 different datasets.

RESULTS

Our algorithm created a segmentation model that predicted the topography of the corticospinal pathway on T1-weighted images in healthy subjects. The average dice score was 0.5479 (0.3513-0.7184) on the validation dataset.

CONCLUSIONS

Deep-learning-based segmentation could be applicable in the future to predict the location of white matter pathways in T1-weighted scans.

Magnetic Resonance Imaging of Primary Adult Brain Tumors: State of the Art and Future Perspectives

MRI is undoubtedly the cornerstone of brain tumor imaging, playing a key role in all phases of patient management, starting from diagnosis, through therapy planning, to treatment response and/or recurrence assessment. Currently, neuroimaging can describe morphologic and non-morphologic (functional, hemodynamic, metabolic, cellular, microstructural, and sometimes even genetic) characteristics of brain tumors, greatly contributing to diagnosis and follow-up. Knowing the technical aspects, strength and limits of each MR technique is crucial to correctly interpret MR brain studies and to address clinicians to the best treatment strategy. This article aimed to provide an overview of neuroimaging in the assessment of adult primary brain tumors. We started from the basilar role of conventional/morphological MR sequences, then analyzed, one by one, the non-morphological techniques, and finally highlighted future perspectives, such as radiomics and artificial intelligence.

Advances in the intraoperative delineation of malignant glioma margin

Surgery plays a critical role in the treatment of malignant glioma. However, due to the infiltrative growth and brain shift, it is difficult for neurosurgeons to distinguish malignant glioma margins with the naked eye and with preoperative examinations. Therefore, several technologies were developed to determine precise tumor margins intraoperatively. Here, we introduced four intraoperative technologies to delineate malignant glioma margin, namely, magnetic resonance imaging, fluorescence-guided surgery, Raman histology, and mass spectrometry. By tracing their detecting principles and developments, we reviewed their advantages and disadvantages respectively and imagined future trends.

Predictive model of language deficit after removing glioma involving language areas under general anesthesia

Purpose

To establish a predictive model to predict the occurrence of language deficit for patients after surgery of glioma involving language areas (GILAs) under general anesthesia (GA).

Methods

Patients with GILAs were retrospectively collected in our center between January 2009 and December 2020. Clinical variables (age, sex, aphasia quotient [AQ], seizures and KPS), tumor-related variables (recurrent tumor or not, volume, language cortices invaded or not, shortest distance to language areas [SDLA], supplementary motor area or premotor area [SMA/PMA] involved or not and WHO grade) and intraoperative multimodal techniques (used or not) were analyzed by univariate and multivariate analysis to identify their association with temporary or permanent language deficits (TLD/PLD). The predictive model was established according to the identified significant variables. Receiver operating characteristic (ROC) curve was used to assess the accuracy of the predictive model.

Results

Among 530 patients with GILAs, 498 patients and 441 patients were eligible to assess TLD and PLD respectively. The multimodal group had the higher EOR and rate of GTR than conventional group. The incidence of PLD was 13.4% in multimodal group, which was much lower than that (27.6%, P<0.001) in conventional group. Three factors were associated with TLD, including SDLA (OR=0.85, P<0.001), preoperative AQ (OR=1.04, P<0.001) and multimodal techniques used (OR=0.41, P<0.001). Four factors were associated with PLD, including SDLA (OR=0.83, P=0.001), SMA/PMA involved (OR=3.04, P=0.007), preoperative AQ (OR=1.03, P=0.002) and multimodal techniques used (OR=0.35, P<0.001). The optimal shortest distance thresholds in detecting the occurrence of TLD/PLD were 1.5 and 4mm respectively. The optimal AQ thresholds in detecting the occurrence of TLD/PLD were 52 and 61 respectively. The cutoff values of the predictive probability for TLD/PLD were 23.7% and 16.1%. The area under ROC curve of predictive models for TLD and PLD were 0.70 (95%CI: 0.65-0.75) and 0.72 (95%CI: 0.66-0.79) respectively.

Conclusion

The use of multimodal techniques can reduce the risk of postoperative TLD/PLD after removing GILAs under general anesthesia. The established predictive model based on clinical variables can predict the probability of occurrence of TLD and PLD, and it had a moderate predictive accuracy.

Noninvasive Prediction of Language Lateralization Through Arcuate Fasciculus Tractography in Patients With Low-Grade Gliomas: Correlation With The Wada Test

Language lateralization is unique to humans, so clarifying dominant side is helpful for removing gliomas involving language areas. This study investigated the arcuate fasciculus (AF) reconstructed by diffusion tensor imaging–based tractography (DTT) in predicting language lateralization in patients with low-grade gliomas. Wada test was performed to determine the language Dominant Hemisphere (DH) and the Contralateral Hemisphere. DTI data [1.5-T magnetic resonance imaging (MRI)] was used to reconstruct AF by two independent operators using a DTT method. Fiber number, volume, and fractional anisotropy (FA) of bilateral reconstructed AF were measured. Lateralization indexes (LIs), including Number Index (NI), Volume Index (VI), and FA Index (FI), were accordingly calculated by mean values. A total of 21 patients with WHO Grade II gliomas in the left hemisphere were included. Every patient received a successful Wada test and reconstruction of bilateral AF. DTT metrics of reconstructed AF, such as fiber number, volume, and FA, showed significantly asymmetric between hemispheres. All the LI (NI, VI, and FI) values were statistically higher in the DH determined by the Wada test. No discrepancy was found between the prediction using the cutoff values of DTT metrics and the results of WADA test. The Kappa values were 0.829, 0.696, and 0.611, indicating NI and VI as more reliable predictor than FI although FI itself may also be feasible. Compared with the Wada test, we consider that DTT of AF is a non-invasive, simple, relatively accurate, and feasible method in predicting language lateralization in patients with low-grade gliomas.

Comparative Quantification of Diffusion Tensor Tractography Using Automated Whole Brain MRI Tractography for Intracranial Tumor Surgery: Technical Note

With the improvement of diffusion tensor imaging (DTI) and algorithms, diffusion tensor tractography (DTT) may provide quantitative information on white matter tracts (WMT) that may help quantitatively assess WMT integrity and distortion, which may help with correlations of neurologic function or prognosis. This manuscript is the first to describe a technical method for quantitative analysis of clinically relevant white matter tracts during intracranial tumor surgery. The authors quantitatively analyzed relevant proximal WMT, pre and postoperatively, in a patient undergoing cranial surgery using DTT software to evaluate fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), axial diffusivity (AD), geodesic anisotropy (GA), tract count, and tract volume. A method was then established to formulate quantitative comparisons between pre and postoperative WMT. Quantitative assessment of the corticospinal and optic radiation tracts revealed significant increases in the FA, GA, and tract count in the corticospinal and optic radiations postoperatively (p<.0001). MD, RD, and AD were found to be significantly diminished postoperatively (p<.0001). The postoperative optic radiations showed diminished volume as a result of damage to the tract pathway. To conclude, the utilization of white matter tractography provides a technical advancement that allows for quantitative comparative assessments of white matter tracts, which could assess the degree of brain changes following tumor surgery.

Quantitative mapping of the brain's structural connectivity using diffusion MRI tractography: A review

Diffusion magnetic resonance imaging (dMRI) tractography is an advanced imaging technique that enables in vivo reconstruction of the brain's white matter connections at macro scale. It provides an important tool for quantitative mapping of the brain's structural connectivity using measures of connectivity or tissue microstructure. Over the last two decades, the study of brain connectivity using dMRI tractography has played a prominent role in the neuroimaging research landscape. In this paper, we provide a high-level overview of how tractography is used to enable quantitative analysis of the brain's structural connectivity in health and disease. We focus on two types of quantitative analyses of tractography, including: 1) tract-specific analysis that refers to research that is typically hypothesis-driven and studies particular anatomical fiber tracts, and 2) connectome-based analysis that refers to research that is more data-driven and generally studies the structural connectivity of the entire brain. We first provide a review of methodology involved in three main processing steps that are common across most approaches for quantitative analysis of tractography, including methods for tractography correction, segmentation and quantification. For each step, we aim to describe methodological choices, their popularity, and potential pros and cons. We then review studies that have used quantitative tractography approaches to study the brain's white matter, focusing on applications in neurodevelopment, aging, neurological disorders, mental disorders, and neurosurgery. We conclude that, while there have been considerable advancements in methodological technologies and breadth of applications, there nevertheless remains no consensus about the "best" methodology in quantitative analysis of tractography, and researchers should remain cautious when interpreting results in research and clinical applications.

The importance of axonal directions in the brainstem injury during neurosurgical interventions

Brainstem, which connects the distal part of the brain and the spinal cord, contains main motor and sensory nerves and facilitates communication between the cerebrum, cerebellum, and spinal cord. Due to the complicated anatomy and neurostructure of brainstem, surgical interventions to resect brainstem tumors are particularly challenging, and new approaches to reduce the risk of surgical brain injury are of utmost importance. Although previous studies have investigated the structural anisotropy of brain white matter, the effect of axonal fibers on the mechanical properties of white matter has not yet been fully understood. The current study aims to compare the effect of axonal orientation on changes in material properties of brainstem under large deformations and failure through a novel approach. Using diffusion tensor imaging (DTI) on ex-vivo bovine brains, we determined the orientation of axons in brainstem. We extracted brainstem samples in two orthogonal directions, parallel and perpendicular to the axons, and subjected to uniaxial tension to reach the failure at loading rates of 50 mm/min and 150 mm/min. The results showed that the tearing energy and failure strain of samples with axons parallel to the force direction were approximately 1.5 times higher than the samples with axons perpendicular to the force direction. The results also revealed that as the sample's initial length increases, its failure strain decreases. These results emphasize the importance of the axon orientation in the mechanical properties of brainstem, and suggest that considering the directional-dependent behavior for this tissue could help to propose new surgical interventions for reducing the risk of injury during tumor resection.

Functional Outcomes and Health-Related Quality of Life Following Glioma Surgery

Functional outcome following glioma surgery is defined as how the patient functions or feels. Functional outcome is a coprimary end point of surgery in patients with diffuse glioma, together with oncological outcome. In this review, we structure the functional outcome measurements following glioma surgery as reported in the last 5 yr. We review various perspectives on functional outcome of glioma surgery with available measures, and offer suggestions for their use. From the recent neurosurgical literature, 160 publications were retrieved fulfilling the selection criteria. In these publications, neurological outcomes were reported most often, followed by activities of daily living, seizure outcomes, neurocognitive outcomes, and health-related quality of life or well-being. In more than a quarter of these publications functional outcome was not reported. A minimum essential consensus set of functional outcome measurements would benefit comparison across neurosurgical reports. The consensus set should be based on a combination of clinician- and patient-reported outcomes, assessed at a predefined time before and after surgery. The selected measurements should have psychometric properties supporting the intended use including validity-related evidence, reliability, and sensitivity to detect meaningful change with minimal burden to ensure compliance. We circulate a short survey as a start towards reporting guidelines. Many questions remain to better understand, report, and improve functional outcome following glioma surgery.

Endoscopic technology and repair techniques

In this chapter, we describe advances in endoscopic endonasal surgery that have impacted skull base meningioma surgery. After reviewing the technical innovations in endoscopy, we describe the advances as they relate to each surgical step. We discuss preoperative planning and approach and the utility of neuronavigation and neuromonitoring. We then discuss endoscopic instrumentation, technology for tumor debulking (ultrasonic aspirators, radiofrequency ablators, suction debriders), and hemostatic agents as they relate to tumor resection and hemostasis. In the end, we discuss techniques of skull base reconstruction and closure (nasoseptal flap, gasket seal and bilayer button).

Tractography and the connectome in neurosurgical treatment of gliomas: the premise, the progress, and the potential

The ability of diffusion tensor MRI to detect the preferential diffusion of water in cerebral white matter tracts enables neurosurgeons to noninvasively visualize the relationship of lesions to functional neural pathways. Although viewed as a research tool in its infancy, diffusion tractography has evolved into a neurosurgical tool with applications in glioma surgery that are enhanced by evolutions in crossing fiber visualization, edema correction, and automated tract identification. In this paper the current literature supporting the use of tractography in brain tumor surgery is summarized, highlighting important clinical studies on the application of diffusion tensor imaging (DTI) for preoperative planning of glioma resection, and risk assessment to analyze postoperative outcomes. The key methods of tractography in current practice and crucial white matter fiber bundles are summarized. After a review of the physical basis of DTI and post-DTI tractography, the authors discuss the methodologies with which to adapt DT image processing for surgical planning, as well as the potential of connectomic imaging to facilitate a network approach to oncofunctional optimization in glioma surgery.

Identification of risk factors for poor language outcome in surgical resection of glioma involving the arcuate fasciculus: an observational study

The arcuate fasciculus is a critical component of the neural substrate of human language function. Surgical resection of glioma adjacent to the arcuate fasciculus likely damages this region. In this study, we evaluated the outcome of surgical resection of glioma adjacent to the arcuate fasciculus under the guidance of magnetic resonance imaging and diffusion tensor imaging, and we aimed to identify the risk factors for postoperative linguistic deficit. In total, 54 patients with primary glioma adjacent to the arcuate fasciculus were included in this observational study. These patients comprised 38 men and 16 women (aged 43 ± 11 years). All patients underwent surgical resenction of glioma under the guidance of magnetic resonance imaging and diffusion tensor imaging. Intraoperative images were updated when necessary for further resection. The gross total resection rate of the 54 patients increased from 38.9% to 70.4% by intraoperative magnetic resonance imaging. Preoperative language function and glioma-to-arcuate fasciculus distance were associated with poor language outcome. Multivariable logistic regression analyses showed that glioma-to-arcuate fasciculus distance was the major independent risk factor for poor outcome. The cutoff point of glioma-to-arcuate fasciculus distance for poor outcome was 3.2 mm. These findings suggest that intraoperative magnetic resonance imaging combined with diffusion tensor imaging of the arcuate fasciculus can help optimize tumor resection and result in the least damage to the arcuate fasciculus. Notably, glioma-to-arcuate fasciculus distance is a key independent risk factor for poor postoperative language outcome. This study was approved by the Ethics Committee of the Chinese PLA General Hospital, China (approval No. S2014-096-01) on October 11, 2014.

State-of-the-art imaging for glioma surgery

Diffuse gliomas are infiltrative primary brain tumors with a poor prognosis despite multimodal treatment. Maximum safe resection is recommended whenever feasible. The extent of resection (EOR) is positively correlated with survival. Identification of glioma tissue during surgery is difficult due to its diffuse nature. Therefore, glioma resection is imaging-guided, making the choice for imaging technique an important aspect of glioma surgery. The current standard for resection guidance in non-enhancing gliomas is T2 weighted or T2w-fluid attenuation inversion recovery magnetic resonance imaging (MRI), and in enhancing gliomas T1-weighted MRI with a gadolinium-based contrast agent. Other MRI sequences, like magnetic resonance spectroscopy, imaging modalities, such as positron emission tomography, as well as intraoperative imaging techniques, including the use of fluorescence, are also available for the guidance of glioma resection. The neurosurgeon’s goal is to find the balance between maximizing the EOR and preserving brain functions since surgery-induced neurological deficits result in lower quality of life and shortened survival. This requires localization of important brain functions and white matter tracts to aid the pre-operative planning and surgical decision-making. Visualization of brain functions and white matter tracts is possible with functional MRI, diffusion tensor imaging, magnetoencephalography, and navigated transcranial magnetic stimulation. In this review, we discuss the current available imaging techniques for the guidance of glioma resection and the localization of brain functions and white matter tracts.

Tractography in Neurosurgery: A Systematic Review of Current Applications

The ability to visualize the brain's fiber connections noninvasively in vivo is relatively young compared with other possibilities of functional magnetic resonance imaging. Although many studies showed tractography to be of promising value for neurosurgical care, the implications remain inconclusive. An overview of current applications is presented in this systematic review. A search was conducted for (("tractography" or "fiber tracking" or "fibre tracking") and "neurosurgery") that produced 751 results. We identified 260 relevant articles and added 20 more from other sources. Most publications concerned surgical planning for resection of tumors (n = 193) and vascular lesions (n = 15). Preoperative use of transcranial magnetic stimulation was discussed in 22 of these articles. Tractography in skull base surgery presents a special challenge (n = 29). Fewer publications evaluated traumatic brain injury (TBI) (n = 25) and spontaneous intracranial bleeding (n = 22). Twenty-three articles focused on tractography in pediatric neurosurgery. Most authors found tractography to be a valuable addition in neurosurgical care. The accuracy of the technique has increased over time. There are articles suggesting that tractography improves patient outcome after tumor resection. However, no reliable biomarkers have yet been described. The better rehabilitation potential after TBI and spontaneous intracranial bleeding compared with brain tumors offers an insight into the process of neurorehabilitation. Tractography and diffusion measurements in some studies showed a correlation with patient outcome that might help uncover the neuroanatomical principles of rehabilitation itself. Alternative corticofugal and cortico-cortical networks have been implicated in motor recovery after ischemic stroke, suggesting more complex mechanisms in neurorehabilitation that go beyond current models. Hence tractography may potentially be able to predict clinical deficits and rehabilitation potential, as well as finding possible explanations for neurologic disorders in retrospect. However, large variations of the results indicate a lack of data to establish robust diagnostical concepts at this point. Therefore, in vivo tractography should still be interpreted with caution and by experienced surgeons.

SlicerDMRI: Diffusion MRI and Tractography Research Software for Brain Cancer Surgery Planning and Visualization

PURPOSE

We present SlicerDMRI, an open-source software suite that enables research using diffusion magnetic resonance imaging (dMRI), the only modality that can map the white matter connections of the living human brain. SlicerDMRI enables analysis and visualization of dMRI data and is aimed at the needs of clinical research users. SlicerDMRI is built upon and deeply integrated with 3D Slicer, a National Institutes of Health-supported open-source platform for medical image informatics, image processing, and three-dimensional visualization. Integration with 3D Slicer provides many features of interest to cancer researchers, such as real-time integration with neuronavigation equipment, intraoperative imaging modalities, and multimodal data fusion. One key application of SlicerDMRI is in neurosurgery research, where brain mapping using dMRI can provide patient-specific maps of critical brain connections as well as insight into the tissue microstructure that surrounds brain tumors.

PATIENTS AND METHODS

In this article, we focus on a demonstration of SlicerDMRI as an informatics tool to enable end-to-end dMRI analyses in two retrospective imaging data sets from patients with high-grade glioma. Analyses demonstrated here include conventional diffusion tensor analysis, advanced multifiber tractography, automated identification of critical fiber tracts, and integration of multimodal imagery with dMRI.

RESULTS

We illustrate the ability of SlicerDMRI to perform both conventional and advanced dMRI analyses as well as to enable multimodal image analysis and visualization. We provide an overview of the clinical rationale for each analysis along with pointers to the SlicerDMRI tools used in each.

CONCLUSION

SlicerDMRI provides open-source and clinician-accessible research software tools for dMRI analysis. SlicerDMRI is available for easy automated installation through the 3D Slicer Extension Manager.

Application of diffusion tensor tractography in the surgical treatment of brain tumors located in functional areas

The present study aimed to explore the application of diffusion tensor tractography (DTT) in the preoperative planning and prognostic evaluation of tumors located in the functional areas of the brain. A total of 42 patients diagnosed with intracranial tumors were randomly assigned to either the trial or the control group. DT imaging (DTI) was performed on the basis of preoperative conventional magnetic resonance imaging (MRI) and analyzed for patients in the trial group. Patients in the control group underwent only routine MRI scans. The effect of DTT on the prognosis of patients was evaluated by tumor resection rate and quality of life evaluation using Karnofsky performance score (KPS) comparison between the trial and control groups. There were no significant differences for total tumor removal rate in the trial group (85.71%) compared with that in the control group (71.43%) (P>0.05). The rate of postoperative symptom improvement in the trial group (85.71%) was significantly higher compared with that in the control group (47.62%) (P<0.05). The KPS value of the trial group was significantly higher postoperatively (78.57±17.40) compared with that preoperatively (66.67±16.23) (P<0.05). The KPS value of the control group postoperatively (72.38±19.21) was significantly higher compared with that preoperatively (66.67±16.00) (P<0.05). The postoperative KPS improvement rate [postoperative value-preoperative value)/preoperative value] of the trial group was significantly higher compared with that in the control group. In conclusion, the use of DTT is an effective supplement to traditional MRI, with particular relevance in preoperative planning, particularly for tumors in the functional area of the brain, and can significantly improve the prognostic function of patients.

Fiber-tract localized diffusion coefficients highlight patterns of white matter disruption induced by proximity to glioma

Gliomas account for 26.5% of all primary central nervous system tumors. Recent studies have used diffusion tensor imaging (DTI) to extract white matter fibers and the diffusion coefficients derived from MR processing to provide useful, non-invasive insights into the extent of tumor invasion, axonal integrity, and gross differentiation of glioma from metastasis. Here, we extend this work by examining whether a tract-based analysis can improve non-invasive localization of tumor impact on white matter integrity. This study retrospectively analyzed preoperative magnetic resonance sequences highlighting contrast enhancement and DTI scans of 13 subjects that were biopsy-confirmed to have either high or low-grade glioma. We reconstructed the corticospinal tract and superior longitudinal fasciculus by applying atlas-based regions of interest to fibers derived from whole-brain deterministic streamline tractography. Within-subject comparison of hemispheric diffusion coefficients (e.g., fractional anisotropy and mean diffusivity) indicated higher levels of white matter degradation in the ipsilesional hemisphere. Novel application of along-tract analyses revealed that tracts traversing the tumor region showed significant white matter degradation compared to the contralesional hemisphere and ipsilesional tracts displaced by the tumor.

The Value of White Matter Tractography by Diffusion Tensor Imaging in Altering a Neurosurgeon's Operative Plan

OBJECTIVE

To investigate if the implementation of white matter (WM) fiber tractography by diffusion tensor imaging in presurgical planning for supratentorial tumors proximal to eloquent WM tracts can alter a neurosurgeon's operative strategy.

METHODS

A retrospective review was conducted of patients with supratentorial brain tumors within eloquent WM tracts who underwent diffusion tensor imaging (DTI) tractography as part of their preoperative assessment. These patients were classified into 3 different DTI groups per the radiology reports: group 1, intact WM tracts; group 2, deviated and/or displaced WM bundles; and group 3, patients with an established WM injury (interrupted and/or destroyed tracts). A blinded prospective behavioral study followed, in which 4 neurosurgeons reviewed the preoperative images at 2 different times (magnetic resonance imaging without DTI, followed by a review of the DTI). They provided estimations about the DTI group of each individual eloquent WM category in every patient, and their planned surgical approach.

RESULTS

Fifteen patients (mean age, 58.3 years) were included in the study. The neurosurgeons provided a correct DTI group estimation in 53%, 60%, and 57% of the cases that involved motor/sensory pathway tracts, optic tracts, and language tracts, respectively. The neurosurgeons underestimated DTI group 3 in the motor category and in the optic category 75% of the time. DTI did not alter the planned surgical approach.

CONCLUSIONS

DTI WM tractography helped neurosurgeons to correctly identify patients with interrupted motor and optic pathway tracts so they could be more aggressive with the extent of tumor resection, despite its inability to alter the operative approach.

High-field intraoperative MRI and glioma surgery: results after the first 100 consecutive patients

BACKGROUND

High-field intraoperative MRI (IoMRI) is part of the neurosurgical armamentarium to improve the extent of glioma resection (EOR).

OBJECTIVE

To report our oncological and functional outcomes using IoMRI for neuronavigated glioma surgery.

METHODS

In this prospective monocentric study, we reported 100 consecutive adult patients operated on for glioma using IoMRI with neuronavigation, under general anesthesia without intraoperative stimulation, from July 2014 to April 2017. The volumetric evaluation was based on the FLAIR hypersignal for non-enhancing tumors after Gadolinium infusion and on the T1 hypersignal after Gadolinium infusion for enhancing tumors. We evaluated the surgical workflow, the EOR and the clinical outcomes (using Karnofsky performance score (KPS)).

RESULTS

Sixty-nine patients underwent one IoMRI, and 31 from two IoMRI controls. At first IoMRI, the median tumor residue was higher in the FLAIR group than in the T1G+ group whereas no more difference was reported after the second IoMRI between the 2 groups (p = 0.56). Additional resection was performed 6 times more frequently in the FLAIR group (OR = 5.7, CI (1.9-17)). The median EOR was 100% (IQR, 93.6-100) whatever the tumor type (first surgery or recurrence) and location. Higher residues were reported only in the insula area (p = 0.004). The median KPS was 90 (IQR, 80-100) at discharge, 3, 6 and 12 months after surgery, with no statistical difference between low- and high-grade gliomas (p = 0.34).

CONCLUSION

IoMRI neuronavigated surgery provided maximal EOR whatever the type of glioma and location. IoMRI was all the more useful for non- or minimally enhancing tumors. The step by step surgical resection, introducing the concept of "staged volume" surgery, ensured a high security for the surgeon and low permanent morbidity for the patients.

Current Applications of Diffusion Tensor Imaging and Tractography in Intracranial Tumor Resection

In the treatment of brain tumors, surgical intervention remains a common and effective therapeutic option. Recent advances in neuroimaging have provided neurosurgeons with new tools to overcome the challenge of differentiating healthy tissue from tumor-infiltrated tissue, with the aim of increasing the likelihood of maximizing the extent of resection volume while minimizing injury to functionally important regions. Novel applications of diffusion tensor imaging (DTI), and DTI-derived tractography (DDT) have demonstrated that preoperative, non-invasive mapping of eloquent cortical regions and functionally relevant white matter tracts (WMT) is critical during surgical planning to reduce postoperative deficits, which can decrease quality of life and overall survival. In this review, we summarize the latest developments of applying DTI and tractography in the context of resective surgery and highlight its utility within each stage of the neurosurgical workflow: preoperative planning and intraoperative management to improve postoperative outcomes.

The Role and Real Effect of an Iterative Surgical Approach for the Management of Recurrent High-Grade Glioma: An Observational Analytic Cohort Study

BACKGROUND

The benefits of multiple interventions on the recurrence of high-grade gliomas are renowned. However, the real effect of repeated operations on the survival parameters does not seem to have been assessed. The aim of the present study was to determine whether reoperation for selected patients is safe and feasible.

METHODS

A total of 78 patients with high-grade glioma had undergone surgery from 2004 to 2014. All the patients had met the following inclusion criteria: American Society of Anesthesiologists score 1-3, Karnofsky performance scale score >60, and reintervention ≥4 months after the first surgery. The following parameters were evaluated: overall survival (OS) after diagnosis and reintervention, progression-free survival (PFS) after reintervention, number of surgical procedures, and OS of patients who had undergone surgery >2 times. The results were compared with those of 78 patients with high-grade glioma who had undergone adjuvant chemotherapy.

RESULTS

OS at 1 year was 100%. At 2 years, OS was 39.4% for those with glioblastoma and 58.3% for those with anaplastic astrocytoma. PFS after 6 months was 53.03% for glioblastoma and 75.0% for anaplastic astrocytoma. Of the 78 patients, 55 had undergone reoperation, with 15 requiring a third intervention and 8 requiring 4. Major complications developed in only 2 patients. Statistical analysis revealed no significant differences in complications or worsening neurological status.

CONCLUSIONS

These data showed excellent outcomes in terms of OS and PFS and clinical conditions after multiple surgical procedures. Therefore, reintervention appears to be a feasible and safe solution for selected patients.

A purely functional Imaging based approach for transcortical resection of lesion involving the dominant atrium: Towards safer, imaging-guided, tailored cortico-leucotomies

BACKGROUND AND STUDY OBJECT

The Dominant Atrium (DA) is a crossroad of eloquent white matter bundles difficult to preserve with a standard "anatomical" approach. The aim of this work is to evaluate the results of a cohort of patients who underwent surgery with the aid of a purely functional MRI and DTI-based approach.

MATERIALS AND METHODS

43 patients suffering from lesions involving the DA have been included in the final cohort and studied in regards to quality of life (KPS); a special attention was lent on the incidence of new or worsening of preexisting neurological deficits, with a focus on motor, visual and speech disturbances after the surgical treatment. Patient, surgery and lesion-related data were recorded to identify the relationships with outcome. Eloquent areas fMRI and the course of Arcuate Fasciculus (AF), Inferior frontooccipital fasciculus (IFOF), Optic radiation (OR) and corticospinal tract (CST) have been investigated with preoperative MRI sequences and DTI reconstruction.

RESULTS

The final cohort consisted of 43 patients, 19 males and 24 females; average age was 56.8 years. We recorded 9 transient and 3 permanent postoperative deficits, only one of those was caused by an edema interference with DTI reconstruction. Preoperative functional status, histology and volume of the lesion proved to be independent factors affecting results.

CONCLUSIONS

A purely functional surgical approach to the DA provided promising preliminary results. A direct DTI-fMRI visualization of the eloquent structures proximal to DA allows surgeon to conceive an ultra-precise and "tailored" cortico-leucotomy for an optimal exposure of the lesion.

Identifying clinical risk in low grade gliomas and appropriate treatment strategies, with special emphasis on the role of surgery

INTRODUCTION

Diffuse low-grade glioma (DLGG) is a chronic tumoral disease that ineluctably grows, migrates along white matter pathways, and progresses to a higher grade of malignancy. Areas covered: To determine the best individualized treatment attitude for each DLGG patient, and to redefine it over the years, i.e. to optimize the 'onco-functional balance' of serial and multimodal therapies, the understanding of the natural history of this chronic disease is crucial but not sufficient. A paradigmatic shift is to tailor the individual management according to the dynamic relationships between DLGG course and neural remodeling. In this spirit, a better knowledge of brain plasticity in a connectomal account of cerebral processing has enabled a dramatic improvement of both oncological and functional outcomes in DLGG patients, by increasing overall survival while preserving (or even improving) the quality of life. Expert commentary: Here, we propose an individualized and recursive therapeutic strategy in DLGG, leading to the concept of a 'personalized functional neuro-oncology', by emphasizing the role of early and maximal safe surgical resection(s) reliably achieved using intraoperative mapping of cortico-subcortical networks in awake patients.

White matter tractography for neurosurgical planning: A topography-based review of the current state of the art

We perform a review of the literature in the field of white matter tractography for neurosurgical planning, focusing on those works where tractography was correlated with clinical information such as patient outcome, clinical functional testing, or electro-cortical stimulation. We organize the review by anatomical location in the brain and by surgical procedure, including both supratentorial and infratentorial pathologies, and excluding spinal cord applications. Where possible, we discuss implications of tractography for clinical care, as well as clinically relevant technical considerations regarding the tractography methods. We find that tractography is a valuable tool in variable situations in modern neurosurgery. Our survey of recent reports demonstrates multiple potentially successful applications of white matter tractography in neurosurgery, with progress towards overcoming clinical challenges of standardization and interpretation.

Intraoperative MRI for the management of brain lesions adjacent to eloquent areas

BACKGROUND

The aim of our study was to report the usefulness of intraoperative MRI guidance in the resection of brain lesions adjacent to eloquent areas.

PATIENTS AND METHODS

A single center prospective series of gliomas amenable to optimized resection with intraoperative MRI between September 2014 and December 2015.

RESULTS

The study included 56 patients. The median duration of the first intraoperative MRI was 38min, interquartile range (IQR 30-46). Fourteen patients (40%) underwent a second intraoperative MRI, which had a median duration of 26min (IQR, 18-30). The median total operative time was 265min (IQR, 242-337). After the first intraoperative MRI, the median residual glioma volume of the 35 gliomas adjacent to eloquent areas was 7.04cm³ (IQR, 2.22-13.8), which did not significantly differ from the other gliomas (P=0.07). After the second intraoperative MRI, the median residual glioma volume was 3.86cm³ (IQR, 0.82-6.99), which did not significantly differ from the other patients (P=0.700). On the postoperative MRI, the median extent of the glioma resections adjacent to eloquent areas was 99.78% (IQR, 88.9-100), which was not significantly different from the rest of the population (P=0.290). At 6 months after surgery, the median Karnofsky Performance Score was 90, and 2.8% of the patients presented a permanent new neurological deficit.

CONCLUSION

Our results suggest that intraoperative MRI is an effective and safe technique to improve the extent of brain lesion resections close to eloquent areas.

Brain Metastases: Surgical Treatment and Overall Survival

BACKGROUND

Brain metastases occur in 10%-40% of patients with cancer and are more common than primary brain tumors (30%-40%); their incidence is growing because of improvements in control of systemic disease, better radiologic detection, and prolonged survival. Modern treatment of brain metastases has dramatically changed the expected prognosis. Traditionally, the prognosis has been considered very poor, and patients were referred to palliative treatment because of their terminal stage; however, new prognostic indexes have been proposed to evaluate these patients. The aim of our study was to determine the long-term effect of surgery on overall survival (OS) in patients with brain metastases from dissimilar primary tumors and to identify prognostic variables associated with prolonged survival.

METHODS

We retrospectively reviewed a consecutive series of patients who underwent surgery between January 2010 and October 2014 for cerebral metastases from lung, kidney, breast, and gastrointestinal cancers and melanoma. Variables included age; sex; histology; location of lesions; and specific treatments patients had undergone including chemotherapy, radiotherapy, and surgery, individually or combined.

RESULTS

No patients deteriorated after surgery. At discharge, 19 patients (26.76%) had an unchanged postoperative neurologic examination, whereas 52 patients (73.23%) showed improvement (χ² = 34.84, P < 0.0001). Expected OS, considering all tumor subtypes, was 372.24 months; the patients in our series had an OS of 787 months, more than twice the expected OS; specifically, average expected survival of each patient was 5.24 months, whereas actual survival was 11.08 months (P = 0.000008).

CONCLUSIONS

Surgery is a safe and effective procedure for cerebral metastases and should not be considered an aggressive treatment in such disease. In our series, 55% of patients had a survival >6 months and a significant improvement in terms of actual versus expected survival. Surgical resection should be considered the primary option for patients with brain metastases.