Morbidity profile following aggressive resection of parietal lobe gliomas

Postoperative Neurologic Outcome in Patients Undergoing Resective Surgery for Parietal Lobe Epilepsy: A Systematic Review

BACKGROUND AND OBJECTIVES

Parietal lobe epilepsy (PLE) surgery can be an effective treatment for selected patients with intractable epilepsy but can be associated with the risk of serious neurologic deficits. We performed a systematic review of the literature to obtain a comprehensive summary of the frequency and types of new postoperative neurologic deficits in patients undergoing PLE resective surgery.

METHODS

We searched MEDLINE, Embase, and Cochrane Central Register of Controlled Trials for articles published between January 1, 1990, and April 28, 2022. We included studies that reported postoperative neurologic outcome following PLE resective surgery confined to the parietal lobe. We required that studies included ≥5 patients. The data collected included demographic information and specific details of postoperative neurologic deficits. When available, individual patient data were collected. We used the Risk of Bias in Nonrandomized Studies of Interventions tool to assess the risk of bias and Grading of Recommendations Assessment, Development, and Evaluation to assess the quality of the evidence.

RESULTS

Of the 3,461 articles screened, 33 studies met the inclusion criteria. A total of 370 patients were included. One hundred patients (27.0%) had a new deficit noted postoperatively. Approximately half of the patients with deficits experienced only transient deficits. Motor deficits were the most commonly identified deficit. The rates of motor deficits noted after PLE surgery were 5.7%, 3.2%, and 2.2% for transient, long-term, and duration not specified, respectively. Sensory and visual field deficits were also commonly reported. Gerstmann syndrome was noted postoperatively in 4.9% of patients and was almost always transient. Individual patient data added information on parietal lobe subregion postoperative neurologic outcome.

DISCUSSION

Our systematic review provides a comprehensive summary of the frequency and types of neurologic deficits associated with PLE surgery. A significant percentage of postoperative deficits are transient. In addition to the expected sensory and visual deficits, PLE surgery is associated with a notable risk of motor deficits. The available literature has important deficiencies. Our study highlights gaps in the literature and provides recommendations for future directions.

TRIAL REGISTRATION INFORMATION

This systematic review was registered on PROSPERO (CRD42022313108, May 26, 2022).

Artificial Intelligence Applications in Glioma With 1p/19q Co-Deletion: A Systematic Review

As an important genomic marker for oligodendrogliomas, early determination of 1p/19q co-deletion status is critical for guiding therapy and predicting prognosis in patients with glioma. The purpose of this study is to systematically review the literature concerning the magnetic resonance imaging (MRI) with artificial intelligence (AI) methods for predicting 1p/19q co-deletion status in glioma. PubMed, Scopus, Embase, and IEEE Xplore were searched in accordance with the Preferred Reporting Items for systematic reviews and meta-analyses guidelines. Methodological quality of studies was assessed according to the Quality Assessment of Diagnostic Accuracy Studies-2. Finally, 28 studies were included in the quantitative analysis. Diagnostic test accuracy reached an area under the ROC curve of 0.71-0.98 were reported in 24 studies. The remaining four studies with no available AUC provided an accuracy of 0.75-0. 89. The included studies varied widely in terms of imaging sequences, input features, and modeling methods. The current review highlighted that integrating MRI with AI technology is a potential tool for determination 1p/19q status pre-operatively and noninvasively, which can possibly help clinical decision-making. However, the reliability and feasibility of this approach still need to be further validated and improved in a real clinical setting. EVIDENCE LEVEL: 2. TECHNICAL EFFICACY: 2.

Population-based tract-to-region connectome of the human brain and its hierarchical topology

Connectome maps region-to-region connectivities but does not inform which white matter pathways form the connections. Here we constructed a population-based tract-to-region connectome to fill this information gap. The constructed connectome quantifies the population probability of a white matter tract innervating a cortical region. The results show that ~85% of the tract-to-region connectome entries are consistent across individuals, whereas the remaining (~15%) have substantial individual differences requiring individualized mapping. Further hierarchical clustering on cortical regions revealed dorsal, ventral, and limbic networks based on the tract-to-region connective patterns. The clustering results on white matter bundles revealed the categorization of fiber bundle systems in the association pathways. This tract-to-region connectome provides insights into the connective topology between cortical regions and white matter bundles. The derived hierarchical relation further offers a categorization of gray and white matter structures.

The brain connectome maps region-to-region connections but often ignores the role of the connecting pathways. Here, the authors mapped the tract-to-region relations to reveal the hierarchical relation of fiber bundles and dorsal, ventral, and limbic networks.

Tracing in vivo the dorsal loop of the optic radiation: convergent perspectives from tractography and electrophysiology compared to a neuroanatomical ground truth

The temporo-parietal junction (TPJ) is a cortical area contributing to a multiplicity of visual, language-related, and cognitive functions. In line with this functional richness, also the organization of the underlying white matter is highly complex and includes several bundles. The few studies tackling the outcome and neurological burdens of surgical operations addressing TPJ document the presence of language disturbances and visual field damages, with the latter hardly recovered in time. This observation advocates for identifying and functionally monitoring the optic radiation (OR) bundles that cross the white matter below the TPJ. In the present study, we adopted a multimodal approach to address the anatomo-functional correlates of the OR's dorsal loop. In particular, we combined cadavers' dissection with tractographic and electrophysiological data collected in drug-resistant epileptic patients explored by stereoelectroencephalography (SEEG). Cadaver dissection allowed us to appreciate the course and topography of the dorsal loop. More surprisingly, both tractographic and electrophysiological observations converged on a unitary picture highly coherent with the data obtained by neuroanatomical observation. The combination of diverse and multimodal observations allows overcoming the limitations intrinsic to single methodologies, defining a unitary picture which makes it possible to investigate the dorsal loop both presurgically and at the individual patient level, ultimately contributing to limit the postsurgical damages. Notwithstanding, such a combined approach could serve as a model of investigation for future neuroanatomical inquiries tackling white matter fibers anatomy and function through SEEG-derived neurophysiological data.

Cortical and Subcortical Anatomy of the Parietal Lobe From the Neurosurgical Perspective

Introduction: The anatomical structures of the parietal lobe at the cortical and subcortical levels are related mainly to sensory, visuospatial, visual and language function. The aim of this study was to present an intraoperative perspective of these critical structures in terms of the surgical treatment of intra-axial lesions. The study also discusses the results of the technique and the results of direct brain stimulation under awake conditions.

Materials and Methods: Five adult brains were prepared according to the Klingler technique. Cortical assessments and all measurements were performed with the naked eye, while white matter dissection was performed with microscopic magnification.

Results: Intra-axial lesions within the parietal lobe can be approached through a lateral or superior trajectory. This decision is based on the location of the lesions in relation to the arcuate fascicle/superior longitudinal fascicle (AF/SLF) complex and ventricular system. Regardless of the approach, the functional borders of the resection are defined by the postcentral gyrus anteriorly and Wernicke's speech area inferiorly. On the subcortical level, active identification of the AF/SLF complex and of the optic radiation within the sagittal stratum should be performed. The intraparietal sulcus (IPS) is a reliable landmark for the AF/SLF complex in ~60% of cases.

Conclusion: Knowledge of the cortical and subcortical anatomical and functional borders of the resection is crucial in preoperative planning, prediction of the risk of postoperative deficits, and intraoperative decision making.

Correlation between Stage and Histopathological Features and Clinical Outcomes in Patients with Glioma Tumors

BACKGROUND: Brain tumor incidence continues to increase during the last decade in several countries. Determining the response of intracranial tumors to treatment remains a major challenge in the field of neuro-oncology. Karnofsky Performance Status Scale (KPS) is a widely used method for assessing the functional status of a patient. AIM: This study aims to determine the relationship between stadium and histopathological features with clinical outcomes in patients with glioma tumors. METHODS: This was an observational analytic study with a retrospective approach at the H. Adam Malik General Hospital in Medan from September 2019 to September 2020. The study population was glioma patients. The research sample was 36 subjects taken consecutively. The independent variables of the study were stage and histopathological features, while the dependent variable of the study was KPS. Statistical analysis with Gamma test. RESULTS: Mean age was 38.11 ± 13.86 years. Most subjects were male, amounting to 20 subjects (55.6%). The most common type of glioma tumor was anaplastic astrocytoma, amounting to 8 subjects (22.2%). The highest tumor stage was a high-grade glioma, amounting to 19 subjects (52.8%), and the most histopathological features based on WHO criteria were WHO grade 3, totaling 13 subjects (36.1%). Most KPS is 80–100 with 19 subjects (52.8%). There is a significant correlation between the stage and histopathological features with KPS with a moderate correlation strength (p = 0.036; r = 0.598) (p = 0.024; r = 0.508) CONCLUSION: There is a significant correlation between stage and histopathological features with KPS with moderate correlation strength

What effects does awake craniotomy have on functional and survival outcomes for glioblastoma patients?

PURPOSE

Neurosurgeons adopt several different surgical approaches to deal with glioblastomas (GB) located in or near eloquent areas. Some attempt maximal safe resection by awake craniotomy (AC), but doubts persist concerning the real benefits of this type of surgery in this situation. We performed a retrospective study to evaluate the extent of resection (EOR), functional and survival outcomes after AC of patients with GB in critical locations.

METHODS

Forty-six patients with primary GB treated with the Stupp regimen between 2004 and 2019, for whom brain mapping was feasible, were included. We assessed EOR, postoperative language and/or motor deficits three months after AC, progression-free survival (PFS) and overall survival (OS).

RESULTS

Complete resection was achieved in 61% of the 46 GB patients. The median PFS was 6.8 months (CI 6.1; 9.7) and the median OS was 17.6 months (CI 14.8; 34.1). Three months after AC, more than half the patients asymptomatic before surgery remained asymptomatic, and one third of patients with symptoms before surgery experienced improvements in language, but not motor functions. The risk of postoperative deficits was higher in patients with preoperative deficits or incomplete resection. Furthermore, the presence of postoperative deficits was an independent predictive factor for shorter PFS.

CONCLUSION

AC is an option for the resection of GB in critical locations. The observed survival outcomes are typical for GB patients in the Stupp era. However, the success of AC in terms of the recovery or preservation of language and/or motor functions cannot be guaranteed, given the aggressiveness of the tumor.

Predicting Isocitrate Dehydrogenase (IDH) Mutation Status in Gliomas Using Multiparameter MRI Radiomics Features

BACKGROUND

Accurate and noninvasive detection of isocitrate dehydrogenase (IDH, including IDH1 and IDH2) status is clinically meaningful for molecular stratification of glioma, but remains challenging.

PURPOSE

To establish a model for classifying IDH status in gliomas based on multiparametric MRI.

STUDY TYPE

Retrospective, radiomics.

POPULATION

In all, 105 consecutive cases of grade II-IV glioma with 50 IDH1 or IDH2 mutant (IDHm) and 55 IDH wildtype (IDHw) were separated into a training cohort (n = 73) and a test cohort (n = 32).

FIELD STRENGTH/SEQUENCE

Contrast-enhanced T₁ -weighted (CE-T₁ W), T₂ -weighted (T₂ W), and arterial spin labeling (ASL) images were acquired at 3.0T.

ASSESSMENT

Two doctors manually labeled the volume of interest (VOI) on CE-T₁ W, then T₂ W and ASL were coregistered to CE-T₁ W. A total of 851 radiomics features were extracted on each VOI of three sequences. From the training cohort, all radiomics features with age and gender were processed by the Mann-Whitney U-test, Pearson test, and least absolute shrinkage and selection operator to obtain optimal feature groups to train support vector machine models. The accuracy and area under curve (AUC) of all models for classifying the IDH status were calculated on the test cohort. Two subtasks were performed to verify the efficiency of texture features and the Pearson test in IDH status classification, respectively.

STATISTICAL TESTS

The permutation test with Bonferroni correction; chi-square test.

RESULTS

The accuracy and AUC of the classifier, which combines the features of all three sequences, achieved 0.823 and 0.770 (P < 0.05), respectively. The best model established by texture features only had an AUC of 0.819 and an accuracy of 0.761. The best model established without the Pearson test got an AUC of 0.747 and an accuracy of 0.719.

DATA CONCLUSION

IDH genotypes of glioma can be identified by radiomics features from multiparameter MRI. The Pearson test improved the performance of the IDH classification models.

LEVEL OF EVIDENCE

4 TECHNICAL EFFICACY STAGE: 1.

Network Neuroscience and the Adapted Mind: Rethinking the Role of Network Theories in Evolutionary Psychology

Evolutionary psychology is the comprehensive study of cognition and behavior in the light of evolutionary theory, a unifying paradigm integrating a huge diversity of findings across different levels of analysis. Since natural selection shaped the brain into a functionally organized system of interconnected neural structures rather than an aggregate of separate neural organs, the network-based account of anatomo-functional architecture is bound to yield the best mechanistic explanation for how the brain mediates the onset of evolved cognition and adaptive behaviors. While this view of a flexible and highly distributed organization of the brain is more than a century old, it was largely ignored up until recently. Technological advances are only now allowing this approach to find its rightful place in the scientific landscape. Historically, early network theories mostly relied on lesion studies and investigations on white matter circuitry, subject areas that still provide great empirical findings to this day. Thanks to new neuroimaging techniques, the traditional localizationist framework, in which any given cognitive process is thought to be carried out by its dedicated brain structure, is slowly being abandoned in favor of a network-based approach. We argue that there is a special place for network neuroscience in the upcoming quest for the biological basis of information-processing systems identified by evolutionary psychologists. By reviewing history of network theories, and by addressing several theoretical and methodological implications of this view for evolutionary psychologists, we describe the current state of knowledge about human neuroanatomy for those who wish to be mindful of both evolutionary and network neuroscience paradigms.

"I do not feel my hand where I see it": causal mapping of visuo-proprioceptive integration network in a surgical glioma patient

A recent tasked-based fMRI study unveiled a network of areas implicated in the process of visuo-proprioceptive integration of the right hand. In this study, we report a case of a patient operated on in awake conditions for a glioblastoma of the left superior parietal lobule. When stimulating a white matter site in the anterior wall of the cavity, the patient spontaneously reported a discrepancy between the visual and proprioceptive perceptions of her right hand. Using several multimodal approaches (axono-cortical evoked potentials, tractography, resting-state functional connectivity), we demonstrated converging support for the hypothesis that tumor-induced plasticity redistributed the left-lateralized network of right-hand visuo-proprioceptive integration towards its right-lateralized homolog.

Outpatient neurosurgery in neuro-oncology

Technological breakthroughs along with modern application of awake craniotomy and new neuroanesthesia protocols have led to a progressive development in outpatient brain tumor surgery and improved surgical outcomes. As a result, outpatient neurosurgery has become a standard of care at the authors' center due to its clinical benefits and impact on patient recovery and overall satisfaction. On the other hand, the financial savings derived from its application is also another favorable factor exerting influence on patients, health care systems, and society. Although validated several years ago and with recent data supporting its application, outpatient brain tumor surgery has not gained the traction that it deserves, based on scientific skepticism and perceived potential for medicolegal issues. The goal of this review, based on the available literature and the senior author's experience in outpatient brain tumor surgery, was to evaluate the most important aspects regarding indications, clinical outcomes, economic burden, and patient perceptions.

The Role of Extent of Resection in IDH1 Wild-Type or Mutant Low-Grade Gliomas

BACKGROUND

Maximizing extent of resection (EOR) improves outcomes in adults with World Health Organization (WHO) grade II low-grade gliomas (LGG). However, recent studies demonstrate that LGGs bearing a mutation in the isocitrate dehydrogenase 1 (IDH1) gene are a distinct molecular and clinical entity. It remains unclear whether maximizing EOR confers an equivalent clinical benefit in IDH mutated (mtIDH) and IDH wild-type (wtIDH) LGGs.

OBJECTIVE

To assess the impact of EOR on malignant progression-free survival (MPFS) and overall survival (OS) in mtIDH and wtIDH LGGs.

METHODS

We performed a retrospective review of 74 patients with WHO grade II gliomas and known IDH mutational status undergoing resection at a single institution. EOR was assessed with quantitative 3-dimensional volumetric analysis. The effect of predictor variables on MPFS and OS was analyzed with Cox regression models and the Kaplan-Meier method.

RESULTS

Fifty-two (70%) mtIDH patients and 22 (30%) wtIDH patients were included. Median preoperative tumor volume was 37.4 cm3; median EOR of 57.6% was achieved. Univariate Cox regression analysis confirmed EOR as a prognostic factor for the entire cohort. However, stratifying by IDH status demonstrates that greater EOR independently prolonged MPFS and OS for wtIDH patients (hazard ratio [HR] = 0.002 [95% confidence interval {CI} 0.000-0.074] and HR = 0.001 [95% CI 0.00-0.108], respectively), but not for mtIDH patients (HR = 0.84 [95% CI 0.17-4.13] and HR = 2.99 [95% CI 0.15-61.66], respectively).

CONCLUSION

Increasing EOR confers oncologic and survival benefits in IDH1 wtLGGs, but the impact on IDH1 mtLGGs requires further study.

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.

Non-invasive genotype prediction of chromosome 1p/19q co-deletion by development and validation of an MRI-based radiomics signature in lower-grade gliomas

PURPOSE

To perform radiomics analysis for non-invasively predicting chromosome 1p/19q co-deletion in World Health Organization grade II and III (lower-grade) gliomas.

METHODS

This retrospective study included 277 patients histopathologically diagnosed with lower-grade glioma. Clinical parameters were recorded for each patient. We performed a radiomics analysis by extracting 647 MRI-based features and applied the random forest algorithm to generate a radiomics signature for predicting 1p/19q co-deletion in the training cohort (n = 184). The clinical model consisted of pertinent clinical factors, and was built using a logistic regression algorithm. A combined model, incorporating both the radiomics signature and related clinical factors, was also constructed. The receiver operating characteristics curve was used to evaluate the predictive performance. We further validated the predictability of the three developed models using a time-independent validation cohort (n = 93).

RESULTS

The radiomics signature was constructed as an independent predictor for differentiating 1p/19q co-deletion genotypes, which demonstrated superior performance on both the training and validation cohorts with areas under curve (AUCs) of 0.887 and 0.760, respectively. These results outperformed the clinical model (AUCs of 0.580 and 0.627 on training and validation cohorts). The AUCs of the combined model were 0.885 and 0.753 on training and validation cohorts, respectively, which indicated that clinical factors did not present additional improvement for the prediction.

CONCLUSION

Our study highlighted that an MRI-based radiomics signature can effectively identify the 1p/19q co-deletion in histopathologically diagnosed lower-grade gliomas, thereby offering the potential to facilitate non-invasive molecular subtype prediction of gliomas.

A multi-sequence and habitat-based MRI radiomics signature for preoperative prediction of MGMT promoter methylation in astrocytomas with prognostic implication

Objectives

Oxygen 6-methylguanine-DNA methyltransferase (MGMT) promoter methylation is a significant prognostic biomarker in astrocytomas, especially for temozolomide (TMZ) chemotherapy. This study aimed to preoperatively predict MGMT methylation status based on magnetic resonance imaging (MRI) radiomics and validate its value for evaluation of TMZ chemotherapy effect.

Methods

We retrospectively reviewed a cohort of 105 patients with grade II-IV astrocytomas. Radiomic features were extracted from the tumour and peritumoral oedema habitats on contrast-enhanced T1-weighted images, T2-weighted fluid-attenuated inversion recovery images and apparent diffusion coefficient (ADC) maps. The following radiomics analysis was structured in three phases: feature reduction, signature construction and discrimination statistics. A fusion radiomics signature was finally developed using logistic regression modelling. Predictive performance was compared between the radiomics signature, previously reported clinical factors and ADC parameters. Validation was additionally performed on a time-independent cohort (n = 31). The prognostic value of the signature on overall survival for TMZ chemotherapy was explored using Kaplan Meier estimation.

Results

The fusion radiomics signature exhibited supreme power for predicting MGMT promoter methylation, with area under the curve values of 0.925 in the training cohort and 0.902 in the validation cohort. Performance of the radiomics signature surpassed that of clinical factors and ADC parameters. Moreover, the radiomics approach successfully divided patients into high-risk and low-risk groups for overall survival after TMZ chemotherapy (p = 0.03).

Conclusions

The proposed radiomics signature accurately predicted MGMT promoter methylation in patients with astrocytomas, and achieved survival stratification for TMZ chemotherapy, thus providing a preoperative basis for individualised treatment planning.

Key Points

• Radiomics using magnetic resonance imaging can preoperatively perform satisfactory prediction of MGMT methylation in grade II-IV astrocytomas.

• Habitat-based radiomics can improve efficacy in predicting MGMT methylation status.

• Multi-sequence radiomics signature has the power to evaluate TMZ chemotherapy effect.

Electronic supplementary material

The online version of this article (10.1007/s00330-018-5575-z) contains supplementary material, which is available to authorized users.

Mapping visuospatial attention: the greyscales task in combination with repetitive navigated transcranial magnetic stimulation

BACKGROUND

Visuospatial attention is executed by the frontoparietal cortical areas of the brain. Damage to these areas can result in visual neglect. We therefore aimed to assess a combination of the greyscales task and repetitive navigated transcranial magnetic stimulation (rTMS) to identify cortical regions involved in visuospatial attention processes. This pilot study was designed to evaluate an approach in a cohort of healthy volunteers, with the future aim of using this technique to map brain tumor patients before surgery. Ten healthy, right-handed subjects underwent rTMS mapping of 52 cortical spots in both hemispheres. The greyscales task was presented tachistoscopically and was time-locked to rTMS pulses. The task pictures showed pairs of horizontal rectangles shaded continuously from black at one end to white at the other, mirror-reversed. On each picture the subject was asked to report which of the two greyscales appeared darker overall. The responses were categorized into "leftward" and "rightward," depending on whether the subject had chosen the rectangle with the darker end on the left or the right. rTMS applied to cortical areas involved in visuospatial attention is supposed to affect lateral shifts in spatial bias. These shifts result in an altered performance on the greyscales task compared to the baseline performance without rTMS stimulation.

RESULTS

In baseline conditions, 9/10 subjects showed classic pseudoneglect to the left. Leftward effects also occurred more often in mapping conditions. Yet, calculated rightward deviations were strikingly greater in magnitude (p < 0.0001). Overall, the right hemisphere was found to be more suggestible than the left hemisphere. Both rightward and leftward deviation scores were higher for the rTMS of this brain side (p < 0.0001). Right hemispheric distributions accord well with current models of visuospatial attention (Corbetta et al. Nat Neurosci 8(11):1603-1610, 2005). We observed leftward deviations triggered by rTMS within superior frontal and posterior parietal areas and rightward deviations within inferior frontal areas and the temporoparietal junction (TPJ).

CONCLUSION

The greyscales task, in combination with rTMS, yields encouraging results in the examination of the visuospatial attention function. Future clinical implications should be evaluated.

Microsurgical Anatomy of the Vertical Rami of the Superior Longitudinal Fasciculus: An Intraparietal Sulcus Dissection Study

BACKGROUND

A number of vertical prolongations of the superior longitudinal fasciculus, which we refer to as the vertical rami (Vr), arise at the level of the supramarginal gyrus, directed vertically toward the parietal lobe.

OBJECTIVE

To provide the first published complete description of the white matter tracts (WMT) of the Vr, their relationship to the intraparietal and parieto-occipital sulci (IPS-POS complex), and their importance in neurosurgical approaches to the parietal lobe.

METHODS

Subcortical dissections of the Vr and WMT of the IPS were performed. Findings were correlated with a virtual dissection using high-resolution diffusion tensor imaging (DTI) tractography data derived from the Human Connectome Project. Example planning of a transparietal, transsulcal operative corridor is demonstrated using an integrated neuronavigation and optical platform.

RESULTS

The Vr were shown to contain component fibers of the superior longitudinal fasciculus (SLF)-II and SLF-III, with contributions from the middle longitudinal fasciculus merging into the medial bank of the IPS. The anatomic findings correlated well with DTI tractography. The line extending from the lateral extent of the POS to the IPS marks an ideal sulcal entry point that we have termed the IPS-POS Kassam-Monroy (KM) Point, which can be used to permit a safe parafascicular surgical trajectory to the trigone.

CONCLUSION

The Vr are a newly conceptualized group of tracts merging along the banks of the IPS, mediating connectivity between the parietal lobe and dorsal stream/SLF. We suggest a refined surgical trajectory to the ventricular atrium utilizing the posterior third of the IPS, at or posterior to the IPS-POS Point, in order to mitigate risk to the Vr and its considerable potential for postsurgical morbidity.

Parietal association deficits in patients harboring parietal lobe gliomas: a prospective study

OBJECTIVE

Although the parietal lobe is a common site for glioma formation, current literature is scarce, consists of retrospective studies, and lacks consistency with regard to the incidence, nature, and severity of parietal association deficits (PADs). The aim of this study was to assess the characteristics and incidence of PADs in patients suffering from parietal lobe gliomas through a prospective study and a battery of comprehensive neuropsychological tests.

METHODS

Between 2012 and 2016 the authors recruited 38 patients with glioma confined in the parietal lobe. Patients were examined for primary and secondary association deficits with a dedicated battery of neuropsychological tests. The PADs were grouped into 5 categories: visuospatial attention, gnosis, praxis, upper-limb coordination, and language. For descriptive analysis tumors were divided into high- and low-grade gliomas and also according to patient age and tumor size.

RESULTS

Parietal association deficits were elicited in 80% of patients, thus being more common than primary deficits (50%). Apraxia was the most common PAD (47.4%), followed by anomic aphasia and subcomponents of Gerstmann's syndrome (34.2% each). Other deficits such as hemineglect, stereoagnosia, extinction, and visuomotor ataxia were also detected, albeit at lower rates. There was a statistically nonsignificant difference between PADs and sex (72.2% males, 85% females) and age (77.8% at ≤ 60 years, 80% at age > 60 years), but a statistically significant difference between the > 4 cm and the ≤ 4 cm diameter group (p = 0.02, 94.7% vs 63.2%, respectively). There was a tendency (p = 0.094) for low-grade gliomas to present with fewer PADs (50%) than high-grade gliomas (85.7%). Tumor laterality showed a strong correlation with hemineglect (p = 0.004, predilection for right hemisphere), anomia (p = 0.001), and Gerstmann's symptoms (p = 0.01); the last 2 deficits showed a left (dominant) hemispheric preponderance.

CONCLUSIONS

This is the first study to prospectively evaluate the incidence and nature of PADs in patients with parietal gliomas. It could be that the current literature may have underestimated the true incidence of deficits. Dedicated neuropsychological examination detects a high frequency of PADs, the most common being apraxia, followed by anomia and subcomponents of Gerstmann's syndrome. Nevertheless, a direct correlation between the clinical deficit and its anatomical substrate is only possible to a limited extent, highlighting the need for intraoperative cortical and subcortical functional mapping.

In Vivo Microscopy in Neurosurgical Oncology

Intraoperative neurosurgical histopathologic diagnoses rely on evaluation of rapid tissue preparations such as frozen sections and smears with conventional light microscopy. Although useful, these techniques are time consuming and therefore cannot provide real-time intraoperative feedback. In vivo molecular imaging techniques are emerging as novel methods for generating real-time diagnostic histopathologic images of tumors and their surrounding tissues. These imaging techniques rely on contrast generated by exogenous fluorescent dyes, autofluorescence of endogenous molecules, fluorescence decay of excited molecules, or light scattering. Large molecular imaging instruments are being miniaturized for clinical in vivo use. This review discusses pertinent imaging systems that have been developed for neurosurgical use and imaging techniques currently under development for neurosurgical molecular imaging.

Mapping of Arithmetic Processing by Navigated Repetitive Transcranial Magnetic Stimulation in Patients with Parietal Brain Tumors and Correlation with Postoperative Outcome

BACKGROUND

Preserving functionality is important during neurosurgical resection of brain tumors. Specialized centers also map further brain functions apart from motor and language functions, such as arithmetic processing (AP). The mapping of AP by navigated repetitive transcranial magnetic stimulation (nrTMS) in healthy volunteers has been reported.

OBJECTIVE

The present study aimed to correlate the results of mapping AP with functional patient outcomes.

METHODS

We included 26 patients with parietal brain tumors. Because of preoperative impairment of AP, mapping was not possible in 8 patients (31%). We stimulated 52 cortical sites by nrTMS while patients performed a calculation task. Preoperatively and postoperatively, patients underwent a standardized number-processing and calculation test (NPCT). Tumor resection was blinded to nrTMS results, and the change in NPCT performance was correlated to resected AP-positive spots as identified by nrTMS.

RESULTS

The resection of AP-positive sites correlated with a worsening of the postoperative NPCT result in 12 cases. In 3 cases, no AP-positive sites were resected and the postoperative NPCT result was similar to or better than preoperatively. Also, in 3 cases, the postoperative NPCT result was better than preoperatively, although AP-positive sites were resected.

CONCLUSIONS

Despite presenting only a few cases, nrTMS might be a useful tool for preoperative mapping of AP. However, the reliability of the present results has to be evaluated in a larger series and by intraoperative mapping data.

Evoking visual neglect-like deficits in healthy volunteers - an investigation by repetitive navigated transcranial magnetic stimulation

In clinical practice, repetitive navigated transcranial magnetic stimulation (rTMS) is of particular interest for non-invasive mapping of cortical language areas. Yet, rTMS studies try to detect further cortical functions. Damage to the underlying network of visuospatial attention function can result in visual neglect-a severe neurological deficit and influencing factor for a significantly reduced functional outcome. This investigation aims to evaluate the use of rTMS for evoking visual neglect in healthy volunteers and the potential of specifically locating cortical areas that can be assigned for the function of visuospatial attention. Ten healthy, right-handed subjects underwent rTMS visual neglect mapping. Repetitive trains of 5 Hz and 10 pulses were applied to 52 pre-defined cortical spots on each hemisphere; each cortical spot was stimulated 10 times. Visuospatial attention was tested time-locked to rTMS pulses by a landmark task. Task pictures were displayed tachistoscopically for 50 ms. The subjects' performance was analyzed by video, and errors were referenced to cortical spots. We observed visual neglect-like deficits during the stimulation of both hemispheres. Errors were categorized into leftward, rightward, and no response errors. Rightward errors occurred significantly more often during stimulation of the right hemisphere than during stimulation of the left hemisphere (mean rightward error rate (ER) 1.6 ± 1.3 % vs. 1.0 ± 1.0 %, p = 0.0141). Within the left hemisphere, we observed predominantly leftward errors rather than rightward errors (mean leftward ER 2.0 ± 1.3 % vs. rightward ER 1.0 ± 1.0 %; p = 0.0005). Visual neglect can be elicited non-invasively by rTMS, and cortical areas eloquent for visuospatial attention can be detected. Yet, the correlation of this approach with clinical findings has to be shown in upcoming steps.

Non-invasive Mapping of Face Processing by Navigated Transcranial Magnetic Stimulation

Background: Besides motor and language function, tumor resections within the frontal and parietal lobe have also been reported to cause neuropsychological impairment like prosopagnosia.

Objective: Since non-navigated transcranial magnetic stimulation (TMS) has previously been used to map neuropsychological cortical function, this study aims to evaluate the feasibility and spatial discrimination of repetitive navigated TMS (rTMS) mapping for detection of face processing impairment in healthy volunteers. The study was also designed to establish this examination for preoperative mapping in brain tumor patients.

Methods: Twenty healthy and purely right-handed volunteers (11 female, 9 male) underwent rTMS mapping for cortical face processing function using 5 Hz/10 pulses. Both hemispheres were investigated randomly with an interval of 2 weeks between mapping sessions. Fifty-two predetermined cortical spots of the whole hemispheres were mapped after baseline measurement. The task consisted of 80 portraits of popular persons, which had to be named while rTMS was applied.

Results: In 80% of all subjects rTMS elicited naming errors in the right middle middle frontal gyrus (mMFG). Concerning anomia errors, the highest error rate (35%) was achieved in the bilateral triangular inferior frontal gyrus (trIFG). With regard to similarly or wrongly named persons, we observed 10% error rates mainly in the bilateral frontal lobes.

Conclusion: It seems feasible to map the cortical face processing function and to generate face processing impairment via rTMS. The observed localizations are well in accordance with the contemporary literature, and the mapping did not interfere with rTMS-induced language impairment. The clinical usefulness of preoperative mapping has to be evaluated subsequently.

Language outcomes after resection of dominant inferior parietal lobule gliomas

OBJECTIVE The dominant inferior parietal lobule (IPL) contains cortical and subcortical regions essential for language. Although resection of IPL tumors could result in language deficits, little is known about the likelihood of postoperative language morbidity or the risk factors predisposing to this outcome. METHODS The authors retrospectively examined a series of patients who underwent resections of gliomas from the dominant IPL. Postoperative language outcomes were characterized across the patient population. To identify factors associated with postoperative language morbidity, the authors then compared features between those patients who experienced postoperative deficits and those who experienced no postoperative language dysfunction. RESULTS Twenty-four patients were identified for analysis. Long-term language deficits occurred in 29.2% of patients (7 of 24): 3 of these patients had experienced preoperative language deficits, whereas new long-term language deficits occurred in 4 patients (16.7%; 4 of 24). Of those patients who exhibited preoperative language deficits, 62.5% (5 of 8) experienced long-term resolution of their language deficits with surgical treatment. All patients underwent intraoperative brain mapping by direct electrical stimulation. Awake, intraoperative cortical language mapping was performed on 17 patients (70.8%). Positive cortical language sites were identified in 23.5% of these patients (4 of 17). Awake, intraoperative subcortical language mapping was performed in 8 patients (33.3%). Positive subcortical language sites were identified in 62.5% of these patients (5 of 8). Patients with positive cortical language sites exhibited a higher rate of long-term language deficits (3 of 4, 75%), compared with those who did not (1 of 13, 7.7%; p = 0.02). Although patients with positive subcortical language sites exhibited a higher rate of long-term language deficits than those who exhibited only negative sites (40.0% vs 0.0%, respectively), this difference was not statistically significant (p = 0.46). Additionally, patients with long-term language deficits were older than those without deficits (p < 0.05). CONCLUSIONS In a small number of patients with preoperative language deficits, IPL glioma resection resulted in improved language function. However, in patients with intact preoperative language function, resection of IPL gliomas may result in new language deficits, especially if the tumors are diffuse, high-grade lesions. Thus, language-dominant IPL glioma resection is not risk-free, yet it is safe and its morbidity can be reduced by the use of cortical and subcortical stimulation mapping.

Real time optical Biopsy: Time-resolved Fluorescence Spectroscopy instrumentation and validation

The Time-resolved fluorescence spectroscopy (TR-FS) has the potential to differentiate tumor and normal tissue in real time during surgical excision. In this manuscript, we describe the design of a novel TR-FS device, along with preliminary data on detection accuracy for fluorophores in a mixture. The instrument is capable of near real-time fluorescence lifetime acquisition in multiple spectral bands and analysis. It is also able to recover fluorescence lifetime with sub-20ps accuracy as validated with individual organic fluorescence dyes and dye mixtures yielding lifetime values for standard fluorescence dyes that closely match with published data. We also show that TR-FS is able to quantify the relative concentration of fluorescence dyes in a mixture by the unmixing of lifetime decays. We show that the TR-FS prototype is able to identify in near-real time the concentrations of dyes in a complex mixture based on previously trained data. As a result, we demonstrate that in complex mixtures of fluorophores, the relative concentration information is encoded in the fluorescence lifetime across multiple spectral bands. We show for the first time the temporal and spectral measurements of a mixture of fluorochromes and the ability to differentiate relative concentrations of each fluorochrome mixture in real time.

Identifying preoperative language tracts and predicting postoperative functional recovery using HARDI q-ball fiber tractography in patients with gliomas

OBJECT

Diffusion MRI has uniquely enabled in vivo delineation of white matter tracts, which has been applied to the segmentation of eloquent pathways for intraoperative mapping. The last decade has also seen the development from earlier diffusion tensor models to higher-order models, which take advantage of high angular resolution diffusion-weighted imaging (HARDI) techniques. However, these advanced methods have not been widely implemented for routine preoperative and intraoperative mapping.

The authors report on the application of residual bootstrap q-ball fiber tracking for routine mapping of potentially functional language pathways, the development of a system for rating tract injury to evaluate the impact on clinically assessed language function, and initial results predicting long-term language deficits following glioma resection.

METHODS

The authors have developed methods for the segmentation of 8 putative language pathways including dorsal phonological pathways and ventral semantic streams using residual bootstrap q-ball fiber tracking. Furthermore, they have implemented clinically feasible preoperative acquisition and processing of HARDI data to delineate these pathways for neurosurgical application. They have also developed a rating scale based on the altered fiber tract density to estimate the degree of pathway injury, applying these ratings to a subset of 35 patients with pre- and postoperative fiber tracking. The relationships between specific pathways and clinical language deficits were assessed to determine which pathways are predictive of long-term language deficits following surgery.

RESULTS

This tracking methodology has been routinely implemented for preoperative mapping in patients with brain gliomas who have undergone awake brain tumor resection at the University of California, San Francisco (more than 300 patients to date). In this particular study the authors investigated the white matter structure status and language correlation in a subcohort of 35 subjects both pre- and postsurgery. The rating scales developed for fiber pathway damage were found to be highly reproducible and provided significant correlations with language performance. Preservation of the left arcuate fasciculus (AF) and the temporoparietal component of the superior longitudinal fasciculus (SLF-tp) was consistent in all patients without language deficits (p < 0.001) at the long-term follow-up. Furthermore, in patients with short-term language deficits, the AF and/or SLF-tp were affected, and damage to these 2 pathways was predictive of a long-term language deficit (p = 0.005).

CONCLUSIONS

The authors demonstrated the successful application of q-ball tracking in presurgical planning for language pathways in brain tumor patients and in assessing white matter tract integrity postoperatively to predict long-term language dysfunction. These initial results predicting long-term language deficits following tumor resection indicate that postoperative injury to dorsal language pathways may be prognostic for long-term clinical language deficits.

Study results suggest the importance of dorsal stream tract preservation to reduce language deficits in patients undergoing glioma resection, as well as the potential prognostic value of assessing postoperative injury to dorsal language pathways to predict long-term clinical language deficits.

Continuous physical examination during subcortical resection in awake craniotomy patients: Its usefulness and surgical outcome

OBJECTIVES

To evaluate the value of physical examination as a monitoring tool during subcortical resection in awake craniotomy patients and surgical outcomes.

PATIENTS AND METHODS

Authors reviewed medical records of patients underwent awake craniotomy with continuous physical examination for pathology adjacent to the eloquent area.

RESULTS

Between January 2006 and August 2015, there were 37 patients underwent awake craniotomy with continuous physical examination. Pathology was located in the left cerebral hemisphere in 28 patients (75.7%). Thirty patients (81.1%) had neuroepithelial tumors. Degree of resections were defined as total, subtotal, and partial in 16 (43.2%), 11 (29.7%) and 10 (27.0%) patients, respectively. Median follow up duration was 14 months. The reasons for termination of subcortical resection were divided into 3 groups as follows: 1) by anatomical landmark with the aid of neuronavigation in 20 patients (54%), 2) by reaching subcortical stimulation threshold in 8 patients (21.6%), and 3) by abnormal physical examination in 9 patients (24.3%). Among these 3 groups, there were statistically significant differences in the intraoperative (p=0.002) and early postoperative neurological deficit (p=0.005) with the lowest deficit in neuronavigation group. However, there were no differences in neurological outcome at later follow up (3-months p=0.103; 6-months p=0.285). There were no differences in the degree of resection among the groups.

CONCLUSION

Continuous physical examination has shown to be of value as an additional layer of monitoring of subcortical white matter during resection and combining several methods may help increase the efficacy of mapping and monitoring of subcortical functions.

Effects of intracranial meningioma location, size, and surgery on neurocognitive functions: a 3-year prospective study

OBJECT Current recommendations stress the need for cognitive parameters to be integrated in the evaluation of outcomes for intracranial meningioma surgery. The aim of this prospective study was to examine neurocognitive function in meningioma patients pre- and postoperatively. METHODS Patients with skull base (anterior and middle fossa) and convexity (anterior and posterior) meningiomas (n = 54) underwent neuropsychological examination prior to and 1 year after surgery. A control group (n = 52) of healthy volunteers matched for age, sex, and education underwent the same examination. Assessments included executive, memory, and motor functions with standardized testing. Patients with convexity meningiomas were clinically assessed for parietal association cortex functions. RESULTS All patients performed significantly worse (p < 0.05) in most neurocognitive domains than controls. The skull base group showed more disturbances in memory than the convexity group (p < 0.05). The anterior convexity group showed more deficits in executive function than the posterior convexity group, which presented with parietal association cortex deficits. Verbal deficits were more pronounced in the left hemisphere than in the right hemisphere. Patients with a large tumor (> 4 cm) had more severe neurocognitive deficits than those with a small tumor (< 4 cm). Postoperatively, patients showed no deterioration in neurocognitive function. Instead, significant improvement (p < 0.05) was observed in some executive, motor, and parietal association cortex functions. CONCLUSIONS According to the authors' findings, intracranial meningiomas may cause neurocognitive deficits in patients. Surgery does not cause a deterioration in cognitive function; instead, it may lead to improvements in some functions. Permanent neuropsychological postoperative deficits should be interpreted as tumor-induced rather than due to surgery.

Non-invasive mapping of calculation function by repetitive navigated transcranial magnetic stimulation

Concerning calculation function, studies have already reported on localizing computational function in patients and volunteers by functional magnetic resonance imaging and transcranial magnetic stimulation. However, the development of accurate repetitive navigated TMS (rTMS) with a considerably higher spatial resolution opens a new field in cognitive neuroscience. This study was therefore designed to evaluate the feasibility of rTMS for locating cortical calculation function in healthy volunteers, and to establish this technique for future scientific applications as well as preoperative mapping in brain tumor patients. Twenty healthy subjects underwent rTMS calculation mapping using 5 Hz/10 pulses. Fifty-two previously determined cortical spots of the whole hemispheres were stimulated on both sides. The subjects were instructed to perform the calculation task composed of 80 simple arithmetic operations while rTMS pulses were applied. The highest error rate (80 %) for all errors of all subjects was observed in the right ventral precentral gyrus. Concerning division task, a 45 % error rate was achieved in the left middle frontal gyrus. The subtraction task showed its highest error rate (40 %) in the right angular gyrus (anG). In the addition task a 35 % error rate was observed in the left anterior superior temporal gyrus. Lastly, the multiplication task induced a maximum error rate of 30 % in the left anG. rTMS seems feasible as a way to locate cortical calculation function. Besides language function, the cortical localizations are well in accordance with the current literature for other modalities or lesion studies.

Morbidity after intracranial tumor surgery: sensitivity and specificity of retrospective review of medical records compared with patient-reported outcomes at 30 days

OBJECT

Published outcome reports in neurosurgical literature frequently rely on data from retrospective review of hospital records at discharge, but the sensitivity and specificity of retrospective assessments of surgical morbidity is not known. The aim of this study was to elucidate the sensitivity and specificity of retrospective assessment of morbidity after intracranial tumor surgery by comparing it to patient-reported outcomes at 30 days.

METHODS

In 191 patients who underwent surgery for the treatment of intracranial tumors, we evaluated newly acquired neurological deficits within the motor, language, and cognitive domains. Traditional retrospective discharge data were collected by review of hospital records. Patient-reported data were obtained by structured phone interviews at 30 days after surgery. Data on perioperative medical and surgical complications were obtained from both hospital records and patient interviews conducted 30 days postoperatively.

RESULTS

Sensitivity values for retrospective review of hospital records as compared with patient-reported outcomes were 0.52 for motor deficits, 0.4 for language deficits, and 0.07 for cognitive deficits. According to medical records, 158 patients were discharged with no new or worsened deficits, but only 117 (74%) of these patients confirmed this at 30 days after surgery. Specificity values were high (0.97-0.99), indicating that new deficits were unlikely to be found by retrospective review of hospital records at discharge when the patients did not report any at 30 days. Major perioperative complications were all identified through retrospective review of hospital records.

CONCLUSIONS

Retrospective assessment of medical records at discharge from hospital may greatly underestimate the incidence of new neurological deficits after brain tumor surgery when compared with patient-reported outcomes after 30 days.

Awake craniotomy to maximize glioma resection: methods and technical nuances over a 27-year period

OBJECT

Awake craniotomy is currently a useful surgical approach to help identify and preserve functional areas during cortical and subcortical tumor resections. Methodologies have evolved over time to maximize patient safety and minimize morbidity using this technique. The goal of this study is to analyze a single surgeon's experience and the evolving methodology of awake language and sensorimotor mapping for glioma surgery.

METHODS

The authors retrospectively studied patients undergoing awake brain tumor surgery between 1986 and 2014. Operations for the initial 248 patients (1986–1997) were completed at the University of Washington, and the subsequent surgeries in 611 patients (1997–2014) were completed at the University of California, San Francisco. Perioperative risk factors and complications were assessed using the latter 611 cases.

RESULTS

The median patient age was 42 years (range 13–84 years). Sixty percent of patients had Karnofsky Performance Status (KPS) scores of 90–100, and 40% had KPS scores less than 80. Fifty-five percent of patients underwent surgery for high-grade gliomas, 42% for low-grade gliomas, 1% for metastatic lesions, and 2% for other lesions (cortical dysplasia, encephalitis, necrosis, abscess, and hemangioma). The majority of patients were in American Society of Anesthesiologists (ASA) Class 1 or 2 (mild systemic disease); however, patients with severe systemic disease were not excluded from awake brain tumor surgery and represented 15% of study participants. Laryngeal mask airway was used in 8 patients (1%) and was most commonly used for large vascular tumors with more than 2 cm of mass effect. The most common sedation regimen was propofol plus remifentanil (54%); however, 42% of patients required an adjustment to the initial sedation regimen before skin incision due to patient intolerance. Mannitol was used in 54% of cases. Twelve percent of patients were active smokers at the time of surgery, which did not impact completion of the intraoperative mapping procedure. Stimulation-induced seizures occurred in 3% of patients and were rapidly terminated with ice-cold Ringer's solution. Preoperative seizure history and tumor location were associated with an increased incidence of stimulation-induced seizures. Mapping was aborted in 3 cases (0.5%) due to intraoperative seizures (2 cases) and patient emotional intolerance (1 case). The overall perioperative complication rate was 10%.

CONCLUSIONS

Based on the current best practice described here and developed from multiple regimens used over a 27-year period, it is concluded that awake brain tumor surgery can be safely performed with extremely low complication and failure rates regardless of ASA classification; body mass index; smoking status; psychiatric or emotional history; seizure frequency and duration; and tumor site, size, and pathology.

The Art of Intraoperative Glioma Identification

A major dilemma in brain-tumor surgery is the identification of tumor boundaries to maximize tumor excision and minimize postoperative neurological damage. Gliomas, especially low-grade tumors, and normal brain have a similar color and texture, which poses a challenge to the neurosurgeon. Advances in glioma resection techniques combine the experience of the neurosurgeon and various advanced technologies. Intraoperative methods to delineate gliomas from normal tissue consist of (1) image-based navigation, (2) intraoperative sampling, (3) electrophysiological monitoring, and (4) enhanced visual tumor demarcation. The advantages and disadvantages of each technique are discussed. A combination of these methods is becoming widely accepted in routine glioma surgery. Gross total resection in conjunction with radiation, chemotherapy, or immune/gene therapy may increase the rates of cure in this devastating disease.

Awake craniotomy for supratentorial gliomas: why, when and how?

Awake craniotomy has become an increasingly utilized procedure in the treatment of supratentorial intra-axial tumors. The popularity of this procedure is partially attributable to improvements in intraoperative technology and anesthetic techniques. The application of awake craniotomy to the field of neuro-oncology has decreased iatrogenic postoperative neurological deficits, allowed for safe maximal tumor resection and improved healthcare resource stewardship by permitting early patient discharge. In this article, we review recent evidence for the utility of awake craniotomy in the resection of gliomas and describe the senior author's experience in performing this procedure. Furthermore, we explore innovative applications of awake craniotomy to outpatient tumor resections and the conduct of neurosurgery in resource-poor settings. We conclude that awake craniotomy is an effective and versatile neurosurgical procedure with expanding applications in neuro-oncology.

Anatomo-functional study of the temporo-parieto-occipital region: dissection, tractographic and brain mapping evidence from a neurosurgical perspective

The temporo-parieto-occipital (TPO) junction is a complex brain territory heavily involved in several high-level neurological functions, such as language, visuo-spatial recognition, writing, reading, symbol processing, calculation, self-processing, working memory, musical memory, and face and object recognition. Recent studies indicate that this area is covered by a thick network of white matter (WM) connections, which provide efficient and multimodal integration of information between both local and distant cortical nodes. It is important for neurosurgeons to have good knowledge of the three-dimensional subcortical organisation of this highly connected region to minimise post-operative permanent deficits. The aim of this dissection study was to highlight the subcortical functional anatomy from a topographical surgical perspective. Eight human hemispheres (four left, four right) obtained from four human cadavers were dissected according to Klingler's technique. Proceeding latero-medially, the authors describe the anatomical courses of and the relationships between the main pathways crossing the TPO. The results obtained from dissection were first integrated with diffusion tensor imaging reconstructions and subsequently with functional data obtained from three surgical cases, all resection of infiltrating glial tumours using direct electrical mapping in awake patients. The subcortical limits for performing safe lesionectomies within the TPO region are as follows: within the parietal region, the anterior horizontal part of the superior longitudinal fasciculus and, more deeply, the arcuate fasciculus; dorsally, the vertical projective thalamo-cortical fibres. For lesions located within the temporal and occipital lobes, the resection should be tailored according to the orientation of the horizontal associative pathways (the inferior fronto-occipital fascicle, inferior longitudinal fascicle and optic radiation). The relationships between the WM tracts and the ventricle system were also examined. These results indicate that a detailed anatomo-functional awareness of the WM architecture within the TPO area is mandatory when approaching intrinsic brain lesions to optimise surgical results and to minimise post-operative morbidity.

Intraoperative mass spectrometry mapping of an onco-metabolite to guide brain tumor surgery

For many intraoperative decisions surgeons depend on frozen section pathology, a technique developed over 150 y ago. Technical innovations that permit rapid molecular characterization of tissue samples at the time of surgery are needed. Here, using desorption electrospray ionization (DESI) MS, we rapidly detect the tumor metabolite 2-hydroxyglutarate (2-HG) from tissue sections of surgically resected gliomas, under ambient conditions and without complex or time-consuming preparation. With DESI MS, we identify isocitrate dehydrogenase 1-mutant tumors with both high sensitivity and specificity within minutes, immediately providing critical diagnostic, prognostic, and predictive information. Imaging tissue sections with DESI MS shows that the 2-HG signal overlaps with areas of tumor and that 2-HG levels correlate with tumor content, thereby indicating tumor margins. Mapping the 2-HG signal onto 3D MRI reconstructions of tumors allows the integration of molecular and radiologic information for enhanced clinical decision making. We also validate the methodology and its deployment in the operating room: We have installed a mass spectrometer in our Advanced Multimodality Image Guided Operating (AMIGO) suite and demonstrate the molecular analysis of surgical tissue during brain surgery. This work indicates that metabolite-imaging MS could transform many aspects of surgical care.

Selection of intraoperative tasks for awake mapping based on relationships between tumor location and functional networks

Intraoperative electrical brain mapping is currently the most reliable method to identify eloquent cortical and subcortical structures at the individual level and to optimize the extent of resection of intrinsic brain tumors. The technique allows the preservation of quality of life, not only allowing avoidance of severe neurological deficits but also facilitating preservation of high neurocognitive functions. To accomplish this goal, however, it is crucial to optimize the selection of appropriate intraoperative tasks, given the limited intrasurgical awake time frame. In this review, the authors' aim was to propose specific parameters that could be used to build a personalized protocol for each patient. They have focused on lesion location and relationships with functional networks to guide selection of intrasurgical tasks in an effort to increase reproducibility among neurooncological centers.

Fiber dissection and diffusion tensor imaging tractography study of the temporoparietal fiber intersection area

BACKGROUND

Lesion studies and recent surgical series report important sequelae when the inferior parietal lobe and posterior temporal lobe are damaged. Millions of axons cross through the white matter underlying these cortical areas; however, little is known about the complex organization of these connections.

OBJECTIVE

To analyze the subcortical anatomy of a specific region within the parietal and temporal lobes where 7 long-distances tracts intersect, ie, the temporoparietal fiber intersection area (TPFIA).

METHODS

Four postmortem human hemispheres were dissected, and 4 healthy hemispheres were analyzed through the use of diffusion tensor imaging--based tractography software. The different tracts that intersect at the posterior temporal and parietal lobes were isolated, and the relations with the surrounding structures were analyzed.

RESULTS

Seven tracts pass through the TPFIA: horizontal portion of the superior longitudinal fasciculus, arcuate fasciculus, middle longitudinal fasciculus, inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, optic radiations, and tapetum. The TPFIA was located deep to the angular gyrus, posterior portion of the supramarginal gyrus, and posterior portion of the superior, middle, and inferior temporal gyri.

CONCLUSION

The TPFIA is a critical neural crossroad; it is traversed by 7 white matter tracts that connect multiple areas of the ipsilateral and contralateral hemisphere. It is also a vulnerable part of the network in that a lesion within this area will produce multiple disconnections. This is valuable information when a surgical approach through the parieto-temporo-occipital junction is planned. To decrease surgical risks, a detailed diffusion tensor imaging tractography reconstruction of the TPFIA should be performed, and intraoperative electric stimulation should be strongly considered.

Cost-utility of maximal safe resection of WHO grade II gliomas within eloquent areas

BACKGROUND

Despite the growing use of intraoperative electrical stimulation (IES) mapping for resection of WHO grade II gliomas (GIIG) located within eloquent areas, some authors claim that this is a complex, time-consuming and expensive approach, and not well tolerated by patients, so they rely on other mapping techniques. Here we analyze the health related quality of life, direct and indirect costs of surgeries with and without intraoperative electrical stimulation (IES) mapping for resection of GIIG within eloquent areas.

METHODS

A cohort of 11 subjects with GIIG within eloquent areas who had IES while awake (group A) was matched by tumor side and location to a cohort of 11 subjects who had general anesthesia without IES (group B). Direct and indirect costs (measured as loss of labor productivity) and utility (measured in quality adjusted life years, QALYs), were compared between groups.

RESULTS

Total mean direct costs per patient were $38,662.70 (range $19,950.70 to $61,626.40) in group A, and $32,116.10 (range $22,764.50 to $46,222.50) in group B (p = 0.279). Total mean indirect costs per patient were $10,640.10 (range $3,010.10 to $86,940.70) in group A, and $48,804.70 (range $3,340.10 to $98,400.60) in group B (p = 0.035). Mean costs per QALY were $12,222.30 (range $3,801.10 to $47,422.90) in group A, and $31,927.10 (range $6,642.90 to $64,196.50) in group B (p = 0.023).

CONCLUSIONS

Asleep-awake-asleep craniotomies with IES are associated with an increase in direct costs. However, these initial expenses are ultimately offset by medium and long-term costs averted from a decrease in morbidity and preservation of the patient's professional life. The present study emphasizes the importance to switch to an aggressive and safer surgical strategy in GIIG within eloquent areas.