Neurocognitive changes after awake surgery in glioma patients: a retrospective cohort study

Perioperative Neurocognitive Function in Glioma Surgery

PURPOSE OF REVIEW

This review provides a concise overview of the recent literature regarding preoperative and postoperative neurocognitive functioning (NCF) in patients with glioma. Brief discussion also covers contemporary intraoperative brain mapping work, with a focus on potential influence of mapping upon NCF outcomes following awake surgery.

RECENT FINDINGS

Most patients with glioma exhibit preoperative NCF impairment, with severity varying by germ line and tumoral genetics, tumor grade, and lesion location, among other characteristics. Literature regarding postoperative NCF changes is mixed, though numerous studies indicate a majority of patients exhibit immediate and short-term worsening. This is often followed by recovery over several months; however, a substantial portion of patients harbor persisting declines. Decline appears related to surgically-induced structural and functional brain alterations, both local and distal to the tumor and resection cavity. Importantly, NCF decline may be mitigated to some extent by intraoperative brain mapping, including mapping of both language-mediated and nonverbal functions. Research regarding perioperative NCF in patients with glioma has flourished over recent years. While this has increased our understanding of contributors to NCF and risk of decline associated with surgical intervention, more work is needed to better preserve NCF throughout the disease course.

Differential contribution of language and executive functioning to verbal fluency performance in glioma patients

Glioma patients often suffer from deficits in language and executive functioning. Performance in verbal fluency (generating words within one minute according to a semantic category-category fluency, or given letter-letter fluency) is typically impaired in this patient group. While both language and executive functioning play a role in verbal fluency, the relative contribution of both domains remains unclear. We aim to retrospectively investigate glioma patients' performance on verbal and nonverbal fluency and to explore the influence of language and executive functioning on verbal fluency. Sixty-nine adults with gliomas in eloquent areas underwent a neuropsychological test battery (verbal fluency, nonverbal fluency, language, and executive functioning tests) before surgery (T1) and a subgroup of 31 patients also at three (T2) and twelve months (T3) after surgery. Preoperatively, patients were impaired in all verbal fluency tasks and dissociations were found based on tumour location. In contrast, nonverbal fluency was intact. Different language and executive functioning tests predicted performance on category fluency animals and letter fluency, while no significant predictors for category fluency professions were found. The longitudinal results indicated that category fluency professions deteriorated after surgery (T1-T2, T1-T3) and that nonverbal fluency improved after surgery (T1-T3, T2-T3). Verbal fluency performance can provide information on different possible underlying deficits in language and executive functioning in glioma patients, depending on verbal fluency task selection. Efficient task (order) selection can be based on complexity. Category fluency professions can be selected to detect more permanent long-term deficits.

Verbal fluency predicts work resumption after awake surgery in low-grade glioma patients

BACKGROUND

Resuming professional activity after awake surgery for diffuse low-grade glioma (DLGG) is an important goal, which is not reached in every patient. Cognitive deficits can occur and persist after surgery. In this study, we analyzed the impact of mild cognitive impairments on the work resumption.

METHODS

Fifty-four surgeries (including five redo surgeries) performed between 2012 and 2020 for grade 2 (45) and 3 (nine) DLGG in 49 professionally active patients (mean age 40 [range 23-58.) were included. We retrospectively extracted the results of semantic and phonemic verbal fluency tests from preoperative and 4-month postoperative cognitive assessments. Patients were interviewed about their working life after surgery, between April and June 2021.

RESULTS

Patients (85%) returned to work, most within 3 to 6 months. Patients (76%) reported subjective complaints (primarily fatigue). Self-reported symptoms and individual and clinical variables had no impact on the work resumption. Late-postoperative average Z-scores in verbal fluency tasks were significantly lower than preoperative for the entire cohort (Wilcoxon test, p < 0.001 for semantic and p = 0.008 for phonemic fluency). The decrease in Z-scores was significantly greater (Mann Whitney U-test, semantic, p = 0.018; phonemic, p = 0.004) in the group of patients who did not return to work than in the group of patients who did.

CONCLUSION

The proportion of patients returning to work was comparable to similar studies. A decrease in verbal fluency tasks could predict the inability to return to work.

Cognitive functioning is prognostic in patients with IDH1-wild type and MGMT-unmethylated high-grade gliomas

AIM

To investigate the prognostic factors of survival in patients with high-grade gliomas without isocitrate dehydrogenase-1 (IDH) mutation and O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation.

METHODS

The study enrolled Slovenian patients with high-grade gliomas. Postoperatively, they completed a battery of neuropsychological tests. Demographics and clinical data were collected. The results of cognitive tests were converted to standardized scores and dichotomized based on impairment. A univariate Cox proportional hazard regression model was used to determine clinical predictors, and a multivariate Cox model was used to determine the prognostic value of cognitive test results. Kaplan-Meier curves were constructed, and survival was compared with the log rank test.

RESULTS

The study enrolled 49 patients with IDH wild-type, MGMT-unmethylated high-grade gliomas. The median time to progression was 9.92 months (7.25, 12.59) and the overall median survival was 12.19 months (8.95, 15.4). Age and the extent of surgery were significant prognostic factors for survival. After controlling for these factors, cognitive functioning in the domain of verbal fluency remained a significant predictor of survival outcomes.

CONCLUSION

Cognitive functioning in the domain of verbal fluency was associated with overall survival independently of age and the extent of surgery. Cognitive functioning could be an important stratifying tool in this group of patients lacking other predictors.

Neuropsychological impairment in primary malignant brain tumor patients with awake craniotomy: a hospital-based registration study

PURPOSE

Neuroplasticity is an ability to maintain neural circuit function when facing damages. It is one of the reasons that making brain tumors notorious. Therefore, we evaluated the characteristics of patients with primary brain tumors, compared neuropsychological deficits between patients who had awake craniotomy with left- or right-sided tumors, and analyzed the association between white matter tracts and neuropsychological deficits in patients with right-sided tumors.

METHODS

Using the registration dataset of Chang Gung Memory Hospital between 2014 and 2020, this study included a total of 698 adult patients who received craniotomy for primary brain tumors (538 of conventional craniotomy; 160 of awake craniotomy). Neuropsychological assessments were arranged in patients as preoperative evaluation for awake craniotomies.

RESULTS

A lower proportion of right-sided tumors was noted in patient who had awake craniotomy than those who had conventional craniotomy (33.8% and 51.5%, p < 0.001). In awake craniotomy, 88.7% of patients with left-sided tumors and 77.8% of patients with right-sided tumors had neuropsychological impairment. Patients with left-sided tumors had worse preoperative performance compared to those with right-sided tumors in global function (36.2% and 8.0%, p < 0.001), language domain (57.6% and 22.2%, p < 0.001), and attention (36.0% and 18.5%, p = 0.02). Furthermore, in those with right-sided low-grade gliomas, patients involving pathway of superior longitudinal fasciculus (SLF) I had a higher risk of deficits than those without involvement in verbal memory (p = 0.001, Odd ratio = 11.2, 95% CI = 1.8 ~ 71.4) and visual memory (p = 0.048, Odd ratio = 10.5, 95% CI = 1.0 ~ 111).

CONCLUSION

In awake craniotomy, patients with left-sided brain tumors had worse cognitive function than those with right-sided tumors in terms of global function, language, and attention. 77% of patients with right-sided tumors had neuropsychological impairment. Therefore, a comprehensive neuropsychological evaluation and awake craniotomy are necessary for patients with brain tumors.

Baseline neurocognitive dysfunction is ubiquitous in intrinsic brain tumors- results from a large Indian cohort of patients and analysis of factors associated with domain-specific dysfunction

Background

Neurocognitive function (NCF) before surgery is an important marker of baseline performance in patients with brain tumors. Increasingly, neurocognitive deficits (NCD) have been demonstrated in a high proportion of patients. Selection bias (patient, tumor, and surgical procedure related) may influence the prevalence and type of domains involved in patients with gliomas.

Methods

We evaluated baseline NCF in a consecutive cohort of intra-axial tumors in Indian patients (n = 142). A comprehensive battery evaluating five domains - attention & executive function (EF), memory, language, visuospatial function and visuomotor abilities was used. Deficits were categorized as severe and mild-moderate. Factors associated with severe NCD were evaluated.

Results

Severe NCD was present in 90% of the patients, 70% of them having affection of at least 2 domains. Attention-EF, memory and visuomotor speed were most affected. 132 underwent surgery (69 awake, 63 under general anesthesia - GA). The awake cohort had younger patients with lower grade gliomas and more left sided tumors. Multi-domain dysfunction was seen almost equally in awake/GA groups as well as left/right sided tumors. On multivariate analysis, older age, lower educational status and larger tumor volume adversely affected NCF in many of the domains. Only language dysfunction was location specific (temporal lobe tumors) though not laterality (left/right) specific.

Conclusions

NCD were seen in a large majority of cases before surgery, including those undergoing awake surgery. Language may be affected even in tumors in the non-dominant hemisphere. Attention-EF and memory are most affected and need to be factored in while assessing patient performance intraoperatively during awake surgery as well as tailoring rehabilitative measures subsequently.

Neurotoxicity from Old and New Radiation Treatments for Brain Tumors

Research regarding the mechanisms of brain damage following radiation treatments for brain tumors has increased over the years, thus providing a deeper insight into the pathobiological mechanisms and suggesting new approaches to minimize this damage. This review has discussed the different factors that are known to influence the risk of damage to the brain (mainly cognitive disturbances) from radiation. These include patient and tumor characteristics, the use of whole-brain radiotherapy versus particle therapy (protons, carbon ions), and stereotactic radiotherapy in various modalities. Additionally, biological mechanisms behind neuroprotection have been elucidated.

Cognitive functioning in a cohort of high-grade glioma patients

BACKGROUND

High grade gliomas are associated with cognitive problems. The aim of the study was to investigate cognitive functioning in a cohort of patients with high grade glioma, according to isocitrate dehydrogenase (IDH) and methyl guanine methyl transferase (MGMT) status and other clinical characteristics.

PATIENTS AND METHODS

The patients with the high-grade glioma treated in Slovenia in given period of time were included in study. Postoperatively they completed neuropsychological assessment consisting of Slovenian Verbal Learning Test, Slovenian Controlled Oral Word Association Test, Trail Making Test Part A and B and self-evaluation questionnaire. We analysed results (z-scores and dichotomized results) also according to IDH mutation and MGMT methylation. We examined differences between groups using T-test, Mann-Whitney U, χ² and Kendall's Tau tests.

RESULTS

Out of 275 patients in the cohort, we included 90. Forty-six percent of patients were unable to participate due to poor performance status and other conditions related to tumour. Patients with the IDH mutation were younger, with better performance status, larger proportions of grade III tumours and MGMT methylation. In this group cognitive functioning is significantly better in the domains of immediate recall, short delayed recall and delayed recall, and in the fields of executive functioning and recognition. There were no differences in cognitive functioning in regard to MGMT status. Grade III tumours were associated with more frequent MGMT methylation. Self-assessment proved week tool, associated only with immediate recall.

CONCLUSIONS

We found no differences in cognitive functioning according to MGMT status, but cognition was better when IDH mutation was present. In a cohort study of patients with high-grade glioma, almost half were unable to participate in a study, which points to an overrepresentation of patients with better cognitive functioning in the research.

A timeline of cognitive functioning in glioma patients who undergo awake brain tumor surgery

BACKGROUND

The purpose of awake brain tumor surgery is to maximize the resection of the tumor and to minimize the risk of neurological and cognitive impairments. The aim of this study is to gain understanding of the development of possible postoperative cognitive deficits after awake brain tumor surgery in patients with suspected gliomas, by comparing preoperative, early postoperative, and late postoperative functioning. A more detailed timeline will be helpful in informing candidates for surgery about what to expect regarding their cognitive functioning.

METHODS

Thirty-seven patients were included in this study. Cognitive functioning was measured by means of a broad cognitive screener preoperatively, days after surgery and months after surgery in patients who underwent awake brain tumor surgery with cognitive monitoring. The cognitive screener included tests for object naming, reading, attention span, working memory, inhibition, inhibition/switching, and visuoperception. We performed a Friedman ANOVA to analyze on group level.

RESULTS

Overall, no significant differences were found between preoperative cognitive functioning, early postoperative cognitive functioning, and late postoperative cognitive functioning, except for performances on the inhibition task. Directly after surgery, patients were significantly slower on this task. However, in the following months after surgery, they returned to their preoperative level.

CONCLUSION

The timeline of cognitive functioning after awake tumor surgery appeared overall stable in the early and late postoperative phase, except for inhibition, which is more difficult in the first days after awake brain tumor surgery. This more detailed timeline of cognitive functioning, in combination with future research, can possibly be contributing in informing patients and caregivers what to expect after awake brain tumor surgery.

Predictive models and survival analysis of postoperative mental health disturbances in adult glioma patients

Background and Objectives

Patients with primary malignant brain tumors may experience mental health disturbances that can significantly affect their daily life. This study aims to identify risk factors and generate predictive models for postoperative mental health disturbances (PMHDs) in adult glioma patients in accordance with different clinical periods; additionally, survival analyses will be performed.

Methods

This longitudinal cohort study included 2,243 adult patients (age at diagnosis ≥ 18 years) with nonrecurrent glioma who were pathologically diagnosed and had undergone initial surgical resection. Six indicators of distress, sadness, fear, irritability, mood and enjoyment of life, ranging from 0-10, were selected to assess PMHDs in glioma patients in the third month after surgery, mainly referring to the M.D. Anderson Symptom Inventory Brain Tumor Module (MDASI-BT). Factor analysis (FA) was applied on these indicators to divide participants into PMHD and control groups based on composite factor scores. Survival analyses were performed, and separate logistic regression models were formulated for preoperative and postoperative factors predicting PMHDs.

Results

A total of 2,243 adult glioma patients were included in this study. Based on factor analysis results, 300 glioma patients had PMHDs in the third postoperative month, and the remaining 1,943 were controls. Candidate predictors for PMHDs in the preoperative model were associated with age, clinical symptoms (intracranial space-occupying lesion, muscle weakness and memory deterioration), and tumor location (corpus callosum, basal ganglia and brainstem), whereas age, clinical symptoms (nausea and memory deterioration), tumor location (basal ganglia and brainstem), hospitalization days, WHO grade 4, postoperative chemotherapy or radiotherapy and postoperative Karnofsky Performance Scale (KPS) served as important factors in the postoperative model. In addition, the median overall survival (OS) time for glioma patients with PMHDs was 19 months, compared to 13 months for glioblastoma, IDH-wild type (GBM) patients with PMHDs.

Conclusion

The risk factors for PMHDs were identified. These findings may provide new insights into predicting the probability of PMHD occurrence in glioma patients in addition to aiding effective early intervention and improving prognosis based on different clinical stages.

The impact of etiology in lesion-symptom mapping - A direct comparison between tumor and stroke

INTRODUCTION

Lesion-symptom mapping is a key tool in understanding the relationship between brain structures and behavior. However, the behavioral consequences of lesions from different etiologies may vary because of how they affect brain tissue and how they are distributed. The inclusion of different etiologies would increase the statistical power but has been critically debated. Meanwhile, findings from lesion studies are a valuable resource for clinicians and used across different etiologies. Therefore, the main objective of the present study was to directly compare lesion-symptom maps for memory and language functions from two populations, a tumor versus a stroke population.

METHODS

Data from two different studies were combined. Both the brain tumor (N = 196) and stroke (N = 147) patient populations underwent neuropsychological testing and an MRI, pre-operatively for the tumor population and within three months after stroke. For this study, we selected two internationally widely used standardized cognitive tasks, the Rey Auditory Verbal Learning Test and the Verbal Fluency Test. We used a state-of-the-art machine learning-based, multivariate voxel-wise approach to produce lesion-symptom maps for these cognitive tasks for both populations separately and combined.

RESULTS

Our lesion-symptom mapping results for the separate patient populations largely followed the expected neuroanatomical pattern based on previous literature. Substantial differences in lesion distribution hindered direct comparison. Still, in brain areas with adequate coverage in both groups, considerable LSM differences between the two populations were present for both memory and fluency tasks. Post-hoc analyses of these locations confirmed that the cognitive consequences of focal brain damage varied between etiologies.

CONCLUSION

The differences in the lesion-symptom maps between the stroke and tumor population could partly be explained by differences in lesion volume and topography. Despite these methodological limitations, both the lesion-symptom mapping results and the post-hoc analyses confirmed that etiology matters when investigating the cognitive consequences of lesions with lesion-symptom mapping. Therefore, caution is advised with generalizing lesion-symptom results across etiologies.

Presurgical predictors of early cognitive outcome after brain tumor resection in glioma patients

Gliomas are commonly characterized by neurocognitive deficits that strongly impact patients' and caregivers' quality of life. Surgical resection is the mainstay of therapy, and it can also cause cognitive impairment. An important clinical problem is whether patients who undergo surgery will show post-surgical cognitive impairment above and beyond that present before surgery. The relevant rognostic factors are largely unknown. This study aims to quantify the cognitive impairment in glioma patients 1-week after surgery and to compare different pre-surgical information (i.e., cognitive performance, tumor volume, grading, and lesion topography) towards predicting early post-surgical cognitive outcome. We retrospectively recruited a sample of N = 47 patients affected by high-grade and low-grade glioma undergoing brain surgery for tumor resection. Cognitive performance was assessed before and immediately after (∼1 week) surgery with an extensive neurocognitive battery. Multivariate linear regression models highlighted the combination of predictors that best explained post-surgical cognitive impairment. The impact of surgery on cognitive functioning was relatively small (i.e., 85% of test scores across the whole sample indicated no decline), and pre-operative cognitive performance was the main predictor of early post-surgical cognitive outcome above and beyond information from tumor topography and volume. In fact, structural lesion information did not significantly improve the accuracy of prediction made from cognitive data before surgery. Our findings suggest that post-surgery neurocognitive deficits are only partially explained by preoperative brain damage. The present results suggest the possibility to make reliable, individualized, and clinically relevant predictions from relatively easy-to-obtain information.

Neurocognitive Outcome and Seizure Freedom After Awake Surgery of Gliomas

Objectives

Gliomas are often diagnosed due to epileptic seizures as well as neurocognitive deficits. First treatment choice for patients with gliomas in speech-related areas is awake surgery, which aims at maximizing tumor resection while preserving or improving patient’s neurological status. The present study aimed at evaluating neurocognitive functioning and occurrence of epileptic seizures in patients suffering from gliomas located in language-related areas before and after awake surgery as well as during their follow up course of disease.

Materials and Methods

In this prospective study we included patients who underwent awake surgery for glioma in the inferior frontal gyrus, superior temporal gyrus, or anterior temporal lobe. Preoperatively, as well as in the short-term (median 4.1 months, IQR 2.1-6.0) and long-term (median 18.3 months, IQR 12.3-36.6) postoperative course, neurocognitive functioning, neurologic status, the occurrence of epileptic seizures and number of antiepileptic drugs were recorded.

Results

Between 09/2012 and 09/2019, a total of 27 glioma patients, aged 36.1 ± 11.8 years, were included. Tumor resection was complete in 15, subtotal in 6 and partial in 6 patients, respectively. While preoperatively impairment in at least one neurocognitive domain was found in 37.0% of patients, postoperatively, in the short-term, 36.4% of patients presented a significant deterioration in word fluency (p=0.009) and 34.8% of patients in executive functions (p=0.049). Over the long-term, scores improved to preoperative baseline levels. The number of patients with mood disturbances significantly declined from 66.7% to 34.8% after surgery (p=0.03). Regarding seizures, these were present in 18 (66.7%) patients prior to surgery. Postoperatively, 22 (81.5%) patients were treated with antiepileptic drugs with all patients presenting seizure-freedom.

Conclusions

In patients suffering from gliomas in eloquent areas, the combination of awake surgery, regular neurocognitive assessment - considering individual patients´ functional outcome and rehabilitation needs – and the individual adjustment of antiepileptic therapy results in excellent patient outcome in the long-term course.

Recurrent Low-Grade Gliomas: Does Reoperation Affect Neurocognitive Functioning?

BACKGROUND

Reoperations in patients with recurrent low-grade gliomas (RLGG) were proposed to control tumor residual and delay the risk of malignant transformation over time.

OBJECTIVE

To investigate neurocognitive outcomes in patients with RLGG who underwent a second surgery with awake monitoring.

METHODS

In this retrospective study, patients who underwent a second awake surgery for RLGG were included. Patients had presurgical and 3-mo postsurgical neuropsychological assessments. Data were converted into Z-scores and combined by the cognitive domain. Number of patients with cognitive deficits (Z-score <-1.65), variations of Z-scores, and extent of resection (EOR) were analyzed.

RESULTS

Sixty-two patients were included (mean age: 41.2 ± 10.0 yr). None had permanent neurological deficits postoperatively. Eight patients (12.9%) had a cognitive deficit preoperatively. Four additional patients (6.5%) had a cognitive deficit 3 mo after reoperation. Among other patients, 13 (21.0%) had a mild decline without cognitive deficits while 29 (46.8%) had no change of their performances and 8 (12.9%) improved. Overall, 94.2% of the patients returned to work. There were no correlations between EOR and Z-scores. Total/subtotal resections were achieved in 91.9% of the patients (mean residual: 3.1 cm3). Fifty-eight patients (93.5%) were still alive after an overall follow-up of 8.3 yr.

CONCLUSION

Reoperation with awake monitoring in patients with RLGG was compatible with an early recovery of neuropsychological abilities. Four patients (6.5%) presented a new cognitive deficit at 3 mo postoperatively. Total/subtotal resections were achieved in most patients. Based on these favorable outcomes, reoperation should be considered in a more systematic way.

Resting-State Electroencephalography Functional Connectivity Networks Relate to Pre- and Postoperative Language Functioning in Low-Grade Glioma and Meningioma Patients

Introduction: Preservation of language functioning in patients undergoing brain tumor surgery is essential because language impairments negatively impact the quality of life. Brain tumor patients have alterations in functional connectivity (FC), the extent to which brain areas functionally interact. We studied FC networks in relation to language functioning in glioma and meningioma patients. Method: Patients with a low-grade glioma (N = 15) or meningioma (N = 10) infiltrating into/pressing on the language-dominant hemisphere underwent extensive language testing before and 1 year after surgery. Resting-state EEG was registered preoperatively, postoperatively (glioma patients only), and once in healthy individuals. After analyzing FC in theta and alpha frequency bands, weighted networks and Minimum Spanning Trees were quantified by various network measures. Results: Pre-operative FC network characteristics did not differ between glioma patients and healthy individuals. However, hub presence and higher local and global FC are associated with poorer language functioning before surgery in glioma patients and predict worse language performance at 1 year after surgery. For meningioma patients, a greater small worldness was related to worse language performance and hub presence; better average clustering and global integration were predictive of worse outcome on language function 1 year after surgery. The average eccentricity, diameter and tree hierarchy seem to be the network metrics with the more pronounced relation to language performance. Discussion: In this exploratory study, we demonstrated that preoperative FC networks are informative for pre- and postoperative language functioning in glioma patients and to a lesser extent in meningioma patients.

Neurocognition and Health-Related Quality of Life Among Patients with Brain Tumors

Patients with brain tumors experience great symptom burden across various domains of functioning, with associated decreases in health-related quality of life and general well-being. Impaired neurocognitive functioning is among the primary concerns of these patients. Unfortunately, most patients will experience such impairment at some point in the disease. However, impaired neurocognitive functioning, symptom burden, and well-being vary according numerous patient-, tumor-, and treatment-related factors. Recent work has furthered our understanding of these contributors to patient functioning and health-related quality of life and also points to various potential targets for prevention and intervention strategies, though more efficacious treatments remain needed.

Reducing the Cognitive Footprint of Brain Tumor Surgery

The surgical management of brain tumors is based on the principle that the extent of resection improves patient outcomes. Traditionally, neurosurgeons have considered that lesions in “non-eloquent” cerebrum can be more aggressively surgically managed compared to lesions in “eloquent” regions with more known functional relevance. Furthermore, advancements in multimodal imaging technologies have improved our ability to extend the rate of resection while minimizing the risk of inducing new neurologic deficits, together referred to as the “onco-functional balance.” However, despite the common utilization of invasive techniques such as cortical mapping to identify eloquent tissue responsible for language and motor functions, glioma patients continue to present post-operatively with poor cognitive morbidity in higher-order functions. Such observations are likely related to the difficulty in interpreting the highly-dimensional information these technologies present to us regarding cognition in addition to our classically poor understanding of the functional and structural neuroanatomy underlying complex higher-order cognitive functions. Furthermore, reduction of the brain into isolated cortical regions without consideration of the complex, interacting brain networks which these regions function within to subserve higher-order cognition inherently prevents our successful navigation of true eloquent and non-eloquent cerebrum. Fortunately, recent large-scale movements in the neuroscience community, such as the Human Connectome Project (HCP), have provided updated neural data detailing the many intricate macroscopic connections between cortical regions which integrate and process the information underlying complex human behavior within a brain “connectome.” Connectomic data can provide us better maps on how to understand convoluted cortical and subcortical relationships between tumor and human cerebrum such that neurosurgeons can begin to make more informed decisions during surgery to maximize the onco-functional balance. However, connectome-based neurosurgery and related applications for neurorehabilitation are relatively nascent and require further work moving forward to optimize our ability to add highly valuable connectomic data to our surgical armamentarium. In this manuscript, we review four concepts with detailed examples which will help us better understand post-operative cognitive outcomes and provide a guide for how to utilize connectomics to reduce cognitive morbidity following cerebral surgery.

Lesion-Function Analysis from Multimodal Imaging and Normative Brain Atlases for Prediction of Cognitive Deficits in Glioma Patients

Simple Summary

This prospective cross-sectional study utilized standard structural MR imaging and amino acid PET in conjunction with brain atlases of gray matter functional regions and white matter tracts, and elastic registration techniques to estimate the influence of the type and location of treatment-related brain damage or recurrent tumors on cognitive functioning in a group of well-doing WHO Grade III/IV glioma patients at follow-up after treatment. The negative impact of T2/FLAIR hyperintensities, supposed to be mainly caused by radiotherapy, on cognitive performance far exceeded that of surgical brain defects or recurrent tumors. The affection of functional nodes and fiber tracts of the left hemisphere and especially of the left temporal lobe by T2/FLAIR hyperintensities was highly correlated with verbal episodic memory dysfunction. These observations imply that radiotherapy for gliomas of the left hemisphere should be individually tailored by means of publicly available brain atlases and registration techniques.

Abstract

Cognitive deficits are common in glioma patients following multimodality therapy, but the relative impact of different types and locations of treatment-related brain damage and recurrent tumors on cognition is not well understood. In 121 WHO Grade III/IV glioma patients, structural MRI, O-(2-[18F]fluoroethyl)-L-tyrosine FET-PET, and neuropsychological testing were performed at a median interval of 14 months (range, 1–214 months) after therapy initiation. Resection cavities, T1-enhancing lesions, T2/FLAIR hyperintensities, and FET-PET positive tumor sites were semi-automatically segmented and elastically registered to a normative, resting state (RS) fMRI-based functional cortical network atlas and to the JHU atlas of white matter (WM) tracts, and their influence on cognitive test scores relative to a cohort of matched healthy subjects was assessed. T2/FLAIR hyperintensities presumably caused by radiation therapy covered more extensive brain areas than the other lesion types and significantly impaired cognitive performance in many domains when affecting left-hemispheric RS-nodes and WM-tracts as opposed to brain tissue damage caused by resection or recurrent tumors. Verbal episodic memory proved to be especially vulnerable to T2/FLAIR abnormalities affecting the nodes and tracts of the left temporal lobe. In order to improve radiotherapy planning, publicly available brain atlases, in conjunction with elastic registration techniques, should be used, similar to neuronavigation in neurosurgery.

A Novel Language Paradigm for Intraoperative Language Mapping: Feasibility and Evaluation

(1) Background-Mapping language using direct cortical stimulation (DCS) during an awake craniotomy is difficult without using more than one language paradigm that particularly follows the demand of DCS by not exceeding the assessment time of 4 s to prevent intraoperative complications. We designed an intraoperative language paradigm by combining classical picture naming and verb generation, which safely engaged highly relevant language functions. (2) Methods-An evaluation study investigated whether a single trial of the language task could be performed in less than 4 s in 30 healthy subjects and whether the suggested language paradigm sufficiently pictured the cortical language network using functional magnetic resonance imaging (fMRI) in 12 healthy subjects. In a feasibility study, 24 brain tumor patients conducted the language task during an awake craniotomy. The patients' neuropsychological outcomes were monitored before and after surgery. (3) Results-The fMRI results in healthy subjects showed activations in a language-associated network around the (left) sylvian fissure. Single language trials could be performed within 4 s. Intraoperatively, all tumor patients showed DCS-induced language errors while conducting the novel language task. Postoperatively, mild neuropsychological impairments appeared compared to the presurgical assessment. (4) Conclusions-These data support the use of a novel language paradigm that safely monitors highly relevant language functions intraoperatively, which can consequently minimize negative postoperative neuropsychological outcomes.

Neuropsychological assessments before and after awake surgery for incidental low-grade gliomas

OBJECTIVE

Early surgery in presumed asymptomatic patients with incidental low-grade glioma (ILGG) has been suggested to improve maximal resection rates and overall survival. However, no study has reported on the impact of such preventive treatment on cognitive functioning. The aim of this study was to investigate neuropsychological outcomes in patients with ILGG who underwent preventive surgery.

METHODS

This was a retrospective analysis of a consecutive series of patients with ILGG who underwent awake surgery and who had presurgical and 3-month postsurgical neuropsychological assessments. Data were normalized into z-scores and regrouped by cognitive domains. Clinicoradiological data, histomolecular profile, and differences in z-scores (Δz-scores) were analyzed.

RESULTS

Forty-seven patients were included (mean age 39.2 ± 11.3 years). Twenty-eight patients (59.6%) underwent supratotal or total resections. All patients were still alive after a mean follow-up of 33.0 ± 30.8 months. Forty-one patients (87.2%) had stable (n = 34, 72.3%) or improved (Δz-score > 1; n = 7, 14.9%) neurocognitive outcomes after surgery. Six patients (12.8%) presented a slight impairment (Δz-score < -1) in at least one cognitive domain. The mean presurgical and postsurgical z-scores were comparable except in the psychomotor speed and attention domain. A significant correlation between presurgical executive functioning and tumor volume was reported, whereas the extent of resection and histomolecular profile did not impact neuropsychological outcomes.

CONCLUSIONS

Early surgical treatment in presumed asymptomatic patients with ILGG was associated with stable or improved neuropsychological outcomes in 87.2% of patients at 3 months, with only mild cognitive decline observed in 6 patients. In return, supratotal or total resections were achieved in most patients, and all patients were still alive at the end of the follow-up.

Awake surgery for right frontal lobe glioma can preserve visuospatial cognition and spatial working memory

PURPOSE

Awake surgery is the standard treatment to preserve motor and language functions. This longitudinal study aimed to evaluate the resection rate and preservation of neurocognitive functions in patients with right frontal lobe glioma who underwent awake surgery.

METHODS

Thirty-three patients (mean age, 48.0 years) with right frontal lobe glioma who underwent awake surgery at our hospital between 2013 and 2019 were included. Fourteen, thirteen, and six cases had WHO classification grades of II, III, and IV, respectively. We evaluated visuospatial cognition (VSC) and spatial working memory (SWM) before and three months after surgery. Relevant brain areas for VSC and SWM were intraoperatively mapped, whenever the task was successfully accomplished. Therefore, patients were divided into an intraoperative evaluation group and a non-evaluation group for each function, and the resection rate and functional outcomes were compared.

RESULTS

The removal rate in the evaluation group for VSC and SWM were similar to that in the non-evaluation group. Chronic impairment rate of VSC was significantly lower in the evaluation than in the non-evaluation group (5.6% vs. 33.3%, p = 0.034). No patient showed postoperative SWM impairment in the evaluation group as opposed to the non-evaluation group (16.7%, p = 0.049). The probability of resection of the deeper posterior part of the middle frontal gyrus, the relevant area of VSC, was higher in the non-evaluation group than in the evaluation group.

CONCLUSIONS

We statistically verified that awake surgery for right frontal lobe glioma results in successful preservation of VSC and SWM with satisfying resection rates.

Impaired neurocognitive function in glioma patients: from pathophysiology to novel intervention strategies

PURPOSE OF REVIEW

This review succinctly summarizes the recent literature regarding etiological contributors to impaired neurocognitive function (NCF) in adult patients with glioma. A brief overview of intervention and prevention strategies is also provided.

RECENT FINDINGS

A majority of patients with glioma exhibit NCF deficits, most frequently in memory and executive functioning. Impairments are often disabling and associated with reduced quality of life and survival. Cause is multifactorial and includes the tumour itself, treatments received and associated comorbidities. Although modern techniques such as brain mapping, dosing modifications and prophylactic medication aim to improve the NCF outcomes following neurosurgical resection and radiation therapy, a sizeable proportion of patients continue to evidence treatment-related NCF declines related to adverse effects to both local and distributed cerebral networks. Numerous patient and tumour characteristics, including genetic markers and sociodemographic factors, influence the pattern and severity of NCF impairment. Some rehabilitative and pharmacologic approaches show promise in mitigating NCF impairment in this population, though benefits are somewhat modest and larger scale intervention studies are needed.

SUMMARY

Research regarding NCF in patients with glioma has dramatically proliferated, providing insights into the mechanisms underlying impaired NCF and pointing to potential interventions, though further work is needed.

Isocitrate Dehydrogenase, Patient-Reported Outcomes, and Cognitive Functioning of Glioma Patients: a Systematic Review

PURPOSE OF REVIEW

Isocitrate dehydrogenase (IDH) mutation status has important prognostic implications in glioma patients, with IDH wild-type (IDH-WT) gliomas being associated with worse prognosis and shorter survival when compared with IDH mutant (IDH-mut) gliomas. Optimization of quality of life is a priority in the management of glioma patients. The goal of this systematic review was to identify studies that explored the association of IDH mutation status with patient-reported outcomes (PROs) and cognitive functioning of glioma patients.

RECENT FINDINGS

Studies that evaluated the association of IDH mutation status with PROs and/or cognitive functioning of glioma patients were identified from the Pubmed/MEDLINE, Clarivate analytics, and Google Scholar databases. Eight studies (7 journal articles and 2 conference abstracts) with a total of 658 low-grade glioma and high-grade glioma patients investigated the association of cognitive functioning and/or QoL with IDH status. IDH-WT status was associated with greater cognitive impairment relative to IDH-Mut status in three studies, while one study did not find the association between IDH status and perioperative cognitive functioning. One study reported worse postoperative cognitive functioning patients with IDH-WT vs. IDH-mut gliomas. In one study, IDH-WT status was linked to greater impairment on physical and communication functioning after surgery. IDH-WT gliomas are associated with greater cognitive burden than IDH-Mut tumors. The association of IDH status with QoL remains less clear. Assessment of IDH status should be considered when evaluating QoL and cognitive complaints of glioma patients. Further studies linking glioma molecular phenotypes with PROs and cognitive functioning are encouraged.

Role of the default mode resting-state network for cognitive functioning in malignant glioma patients following multimodal treatment

BACKGROUND

Progressive cognitive decline following multimodal neurooncological treatment is a common observation in patients suffering from malignant glioma. Alterations of the default-mode network (DMN) represent a possible source of impaired neurocognitive functioning and were analyzed in these patients.

METHODS

Eighty patients (median age, 51 years) with glioma (WHO grade IV glioblastoma, n = 57; WHO grade III anaplastic astrocytoma, n = 13; WHO grade III anaplastic oligodendroglioma, n = 10) and ECOG performance score 0-1 underwent resting-state functional MRI (rs-fMRI) and neuropsychological testing at a median interval of 13 months (range, 1-114 months) after initiation of therapy. For evaluation of structural and metabolic changes after treatment, anatomical MRI and amino acid PET using O-(2-[18F]fluoroethyl)-L-tyrosine (FET) were simultaneously acquired to rs-fMRI on a hybrid MR/PET scanner. A cohort of 80 healthy subjects matched for gender, age, and educational status served as controls.

RESULTS

The connectivity pattern within the DMN (12 nodes) of the glioma patients differed significantly from that of the healthy subjects but did not depend on age, tumor grade, time since treatment initiation, presence of residual/recurrent tumor, number of chemotherapy cycles received, or anticonvulsive medication. Small changes in the connectivity pattern were observed in patients who had more than one series of radiotherapy. In contrast, structural tissue changes located at or near the tumor site (including resection cavities, white matter lesions, edema, and tumor tissue) had a strong negative impact on the functional connectivity of the adjacent DMN nodes, resulting in a marked dependence of the connectivity pattern on tumor location. In the majority of neurocognitive domains, glioma patients performed significantly worse than healthy subjects. Correlation analysis revealed that reduced connectivity in the left temporal and parietal DMN nodes was associated with low performance in language processing and verbal working memory. Furthermore, connectivity of the left parietal DMN node also correlated with processing speed, executive function, and verbal as well as visual working memory. Overall DMN connectivity loss and cognitive decline were less pronounced in patients with higher education.

CONCLUSION

Personalized treatment strategies for malignant glioma patients should consider the left parietal and temporal DMN nodes as vulnerable regions concerning neurocognitive outcome.