Challenging the Myth of Right Nondominant Hemisphere: Lessons from Corticosubcortical Stimulation Mapping in Awake Surgery and Surgical Implications

Awake craniotomy in epilepsy surgery includes previously inoperable patients with preserved efficiency and safety

Introduction: Whilst awake craniotomy has been widely used historically in epilepsy surgery, the safety and efficacy of this approach in epilepsy surgery has been sparsely investigated in controlled studies. The objective of this study is to investigate the safety and efficacy of awake resection in epilepsy surgery and focuses on the possibility to widen surgical indications with awake surgery. Methods: Fifteen patients operated with awake epilepsy surgery were compared to 30 matched controls undergoing conventional/asleep epilepsy surgery. The groups were compared with regard to neurological complications, seizure control and location of resection. Results: Regarding seizure control, 86% of patients in the awake group reached Engel grade 1-2 compared to 73% in the control group, operated with conventional/asleep surgery, not a statistically significant difference. Neither was there a statistical significant difference regarding postoperative neurological complications. However, there was a significant difference in location of the resection when comparing the two groups. Of the 15 patients operated with awake intraoperative mapping, four had previously been considered as non-operable by epilepsy surgery centres, due to vicinity to eloquent brain regions and predicted risk of post-operative neurological deficits. Discussion: The results show that awake epilepsy surgery yields similar level of seizure control when compared to conventional asleep surgery, with maintained safety in regard to neurological complications. Furthermore, the results indicate that awake craniotomy in epilepsy surgery is feasible and possible in patients otherwise regarded as inoperable with epileptigenic zone in proximity to eloquent brain structures.

Long-term neuroplasticity in language networks after anterior temporal lobe resection

OBJECTIVE

Anterior temporal lobe resection (ATLR) is an effective treatment for drug-resistant temporal lobe epilepsy (TLE), although language deficits may occur after both left and right ATLR. Functional reorganization of the language network has been observed in the ipsilateral and contralateral hemispheres within 12 months after ATLR, but little is known of longer-term plasticity effects. Our aim was to examine the plasticity of language functions up to a decade after ATLR, in relation to cognitive profiles.

METHODS

We examined 24 TLE patients (12 left [LTLE]) and 10 controls across four time points: pre-surgery, 4 months, 12 months, and ~9 years post-ATLR. Participants underwent standard neuropsychological assessments (naming, phonemic, and categorical fluency tests) and a verbal fluency functional magnetic resonance imaging (fMRI) task. Using a flexible factorial design, we analyzed longitudinal fMRI activations from 12 months to ~9 years post-ATLR, relative to controls, with separate analyses for people with hippocampal sclerosis (HS). Change in cognitive profiles was correlated with the long-term change in fMRI activations to determine the "efficiency" of reorganized networks.

RESULTS

LTLE patients had increased long-term engagement of the left extra-temporal and contralateral temporal regions, with better language performance linked to bilateral activation. Those with HS exhibited more widespread bilateral activations. RTLE patients showed plasticity in the left extra-temporal regions, with better language outcomes associated with these areas. Both groups of patients achieved cognitive stability over 9 years, with more than 50% of LTLE patients improving. Older age, longer epilepsy duration, and lower pre-operative cognitive reserve negatively affected long-term language performance.

SIGNIFICANCE

Neuroplasticity continues for up to ~9 years post-epilepsy surgery in LTLE and RTLE, with effective language recovery linked to bilateral engagement of temporal and extra-temporal regions. This adaptive reorganization is associated with improved cognitive outcomes, challenging the traditional view of localized surgery effects. These findings emphasize the need for early intervention, tailored pre-operative counseling, and the potential for continued cognitive gains with extended post-ATLR rehabilitation.

Intraoperative mapping of the right hemisphere: a systematic review of protocols that evaluate cognitive and social cognitive functions

The right hemisphere of the brain is often referred to as the non-dominant hemisphere. Though this is meant to highlight the specialized role of the left hemisphere in language, the use of this term runs the risk of oversimplifying or minimizing the essential functions of the right hemisphere. There is accumulating evidence from functional MRI, clinical lesion studies, and intraoperative mapping data that implicate the right hemisphere in a diverse array of cognitive functions, including visuospatial functions, attentional processes, and social cognitive functions. Neuropsychological deficits following right hemisphere resections are well-documented, but there is a general paucity of literature focusing on how to best map these functions during awake brain surgery to minimize such deficits. To address this gap in the literature, a systematic review was conducted to examine the cognitive and emotional processes associated with the right hemisphere and the neuropsychological tasks frequently used for mapping the right hemisphere during awake brain tumor surgery. It was found that the most employed tests to assess language and speech functions in patients with lesions in the right cerebral hemisphere were the naming task and the Pyramids and Palm Trees Test (PPTT). Spatial cognition was typically evaluated using the line bisection task, while social cognition was assessed through the Reading the Mind in the Eyes (RME) test. Dual-tasking and the movement of the upper and lower limbs were the most frequently used methods to evaluate motor/sensory functions. Executive functions were typically assessed using the N-back test and Stroop test. To the best of our knowledge, this is the first comprehensive review to help provide guidance on the cognitive functions most at risk and methods to map such functions during right awake brain surgery.

Systematic Review Registration

PROSPERO database [CRD42023483324].

Human intraparietal sulcal morphology relates to individual differences in language and memory performance

The sulco-gyral pattern is a qualitative feature of the cortical anatomy that is determined in utero, stable throughout lifespan and linked to brain function. The intraparietal sulcus (IPS) is a nodal associative brain area, but the relation between its morphology and cognition is largely unknown. By labelling the left and right IPS of 390 healthy participants into two patterns, according to the presence or absence of a sulcus interruption, here we demonstrate a strong association between the morphology of the right IPS and performance on memory and language tasks. We interpret the results as a morphological advantage of a sulcus interruption, probably due to the underlying white matter organization. The right-hemisphere specificity of this effect emphasizes the neurodevelopmental and plastic role of sulcus morphology in cognition prior to lateralisation processes. The results highlight a promising area of investigation on the relationship between cognitive performance, sulco-gyral pattern and white matter bundles.

Functional and oncological outcomes after right hemisphere glioma resection in awake versus asleep patients: a systematic review and meta-analysis

The right hemisphere has been underestimated by being considered as the non-dominant hemisphere. However, it is involved in many functions, including movement, language, cognition, and emotion. Therefore, because lesions on this side are usually not resected under awake mapping, there is a risk of unfavorable neurological outcomes. The goal of this study is to compare the functional and oncological outcomes of awake surgery (AwS) versus surgery under general anesthesia (GA) in supratentorial right-sided gliomas. A systematic review of the literature according to PRISMA guidelines was performed up to March 2023. Four databases were screened. Primary outcome to assess was return to work (RTW). Secondary outcomes included the rate of postoperative neurological deficit, postoperative Karnofsky Performance Status (KPS) score and the extent of resection (EOR). A total of 32 articles were included with 543 patients who underwent right hemisphere tumor resection under awake surgery and 294 under general anesthesia. There were no significant differences between groups regarding age, gender, handedness, perioperative KPS, tumor location or preoperative seizures. Preoperative and long-term postoperative neurological deficits were statistically lower after AwS (p = 0.03 and p < 0.01, respectively), even though no difference was found regarding early postoperative course (p = 0.32). A subsequent analysis regarding type of postoperative impairment was performed. Severe postoperative language deficits were not different (p = 0.74), but there were fewer long-term mild motor and high-order cognitive deficits (p < 0.05) in AwS group. A higher rate of RTW (p < 0.05) was documented after AwS. The EOR was similar in both groups. Glioma resection of the right hemisphere under awake mapping is a safer procedure with a better preservation of high-order cognitive functions and a higher rate of RTW than resection under general anesthesia, despite similar EOR.

Recovery of major cognitive deficits following awake surgery for insular glioma: a case report

Background: Resection of insular tumours utilising modern neurosurgical techniques has become commonplace since its safety and reduced morbidity was first established. Interest has grown in the cognitive consequences of insula neurosurgery and studies have largely shown postoperative stability or minor decline. Major or widespread improvements in cognitive functioning following resection of insular tumours have not previously been reported.Case description: A 34-year-old, left-handed man with a right insular low-grade glioma (LGG) presented with seizures, nausea, altered sensation, poor balance and extensive cognitive decline. Comprehensive neuropsychological assessment highlighted a striking left hemispatial neglect and impairments in attention, working memory, verbal learning and fluency. During an awake craniotomy with functional cortical mapping, he reported intraoperative improvements in hand function and processing speed. Resolution of the neglect and significant improvements in cognition, mood and functioning were observed at follow-up and sustained over several years.Conclusions: This case highlights that right insular LGGs can cause significant cognitive and functional deficits and that neurosurgery has the potential to alleviate these difficulties to an extent beyond those documented in the extant literature.

Performance of intraoperative neurocognitive tests during awake surgery for patients with diffuse low-grade glioma

Despite great advancements and the diffusion of awake surgery for brain tumors, the literature shows that the tests applied during the procedure are heterogeneous and non-standardized. This prospective, observational, descriptive study collected data on intraoperative brain mapping and the performance of multiple neurocognitive tests in 51 awake surgeries for diffuse low-grade glioma. Frequency of use and rate of intraoperative findings of different neurocognitive tests were analyzed. Patients mean age at the time of surgery was 35.1 (20-57) years. We performed 26 (51.0%) surgeries on the left hemisphere (LH) and 25 (49.0%) on the right hemisphere (RH). Significant differences were observed between the total number of functional findings (cortical and subcortical) identified in the LH and RH (p = 0.004). In subcortical findings alone, the differences remained significant (p = 0.0004). The RH subcortical region showed the lowest number of intraoperative findings, and this was correlated with functional outcome: Karnofsky performance scale at five days (p = 0.022), three months (p = 0.002) and one year (p = 0.002) post-surgery. On average, more tests were used to map the RH, with a lower frequency of both cortical and subcortical functional findings. Even though subcortical findings were less frequent than cortical findings, they were crucial to defining the resection margins. Based on the intraoperative findings, frequency of use, and rate of findings per use of the tests analyzed, the most relevant tests for each hemisphere for awake brain mapping were identified.

Spontaneous unilateral spatial neglect recovery after brain tumour resection: A multimodal diffusion and rs-fMRI case report

Patients with unilateral spatial neglect (USN) are unable to explore or to report stimuli presented in the left personal and extra-personal space. USN is usually caused by lesion of the right parietal lobe: nowadays, it is also clear the key role of structural connections (the second and the third branch of the right Superior Longitudinal Fasciculus, respectively, SLF II and III) and functional networks (Dorsal and Ventral Attention Network, respectively, DAN and VAN) in USN. In this multimodal case report, we have merged those structural and functional information derived from a patient with a right parietal lobe tumour and USN before surgery. Functional, structural and neuropsychological data were also collected 6 months after surgery, when the USN was spontaneously recovered. Diffusion metrics and Functional Connectivity (FC) of the right SLF and DAN, before and after surgery, were compared with the same data of a patient with a tumour in a similar location, but without USN, and with a control sample. Results indicate an impairment in the right SLF III and a reduction of FC of the right DAN in patients with USN before surgery compared to controls; after surgery, when USN was recovered, patient's diffusion metrics and FC showed no differences compared to the controls. This single case and its multimodal approach reinforce the crucial role of the right SLF III and DAN in the development and recovery of egocentric and allocentric extra-personal USN, highlighting the need to preserve these structural and functional areas during brain surgery.

Right hemisphere and metaphor comprehension: A connectionist perspective

Metaphor comprehension is a cognitively complex task, with evidence pointing to the engagement of multiple cerebral areas. In addition, the involvement of the right hemisphere appears to vary with cognitive effort. Therefore, the interconnecting pathways of such distributed cortical centers should be taken into account when studying this topic. Despite this, the potential contribution of white matter fasciculi has received very little attention in the literature to date and is not mentioned in most metaphor comprehension studies. To highlight the probable implications of the right inferior fronto-occipital fasciculus, right superior longitudinal system, and callosal radiations, we bring together findings from different research fields. The aim is to describe important insights enabled by the cross-fertilization of functional neuroimaging, clinical findings, and structural connectivity.

Grey Matter Reshaping of Language-Related Regions Depends on Tumor Lateralization

A brain tumor in the left hemisphere can decrease language laterality as assessed through fMRI. However, it remains unclear whether or not this decreased language laterality is associated with a structural reshaping of the grey matter, particularly within the language network. Here, we examine if the disruption of the language hubs exclusively affects the macrostructural properties of the contralateral homologues or whether it affects both hemispheres. This study uses voxel-based morphometry applied to high-resolution MR T1-weighted MPRAGE images from 31 adult patients' left hemisphere, which is dominant for language. Eighteen patients had brain tumors in the left hemisphere, and thirteen had tumors in the right hemisphere. A cohort of 71 healthy individuals matched with respect to age and sex was used as a baseline. We defined 10 ROIs per hemisphere involved in language function. Two separate repeated-measure ANOVAs were conducted with the volume per region as the dependent variable. For the patients, tumor lateralization (right versus left) served as a between-subject factor. The current study demonstrated that the presence of a brain tumor generates global volumetric changes affecting the left language regions and their contralateral homologues. These changes are mediated by the lateralization of the lesion. Our findings suggest that functional mechanisms are supported by the rearrangement of the grey matter.

Low grade gliomas guide-lines elaborated by the tumor section of Spanish Society of Neurosurgery

Adult low-grade gliomas (Low Grade Gliomas, LGG) are tumors that originate from the glial cells of the brain and whose management involves great controversy, starting from the diagnosis, to the treatment and subsequent follow-up. For this reason, the Tumor Group of the Spanish Society of Neurosurgery (GT-SENEC) has held a consensus meeting, in which the most relevant neurosurgical issues have been discussed, reaching recommendations based on the best scientific evidence. In order to obtain the maximum benefit from these treatments, an individualised assessment of each patient should be made by a multidisciplinary team. Experts in each LGG treatment field have briefly described it based in their experience and the reviewed of the literature. Each area has been summarized and focused on the best published evidence. LGG have been surrounded by treatment controversy, although during the last years more accurate data has been published in order to reach treatment consensus. Neurosurgeons must know treatment options, indications and risks to participate actively in the decision making and to offer the best surgical treatment in every case.

Continuous Real-Time Neuropsychological Testing during Resection Phase in Left and Right Prefrontal Brain Tumors

BACKGROUND

Executive functions are multi-component and are based on large-scale brain networks. For patients undergoing brain surgery in the prefrontal cortex, resection in the anterior prefrontal sites is assisted by continuous monitoring of their performance on several tasks measuring components of executive functions. In this study, we did not test patients during direct cortical stimulation, but during resection itself. We chose tests routinely used to assess executive functions and included them in a protocol for left (LH) and right (RH) hemisphere prefrontal resections. This protocol is meant to be used during real-time neuropsychological testing (RTNT)-an already established monitoring technique.

METHODS

We retrospectively reviewed a consecutive series of 29 adult patients with glioma in the superior and middle frontal areas who performed the RTNT sequence throughout the resection phase. The testing protocol comprised 10 tests for LH frontal resections and 9 tests for RH frontal resections.

RESULTS

RH patients showed a median performance on RTNT with significantly lower scores for visuo-spatial attention and emotion processing (95% Confidence Interval Lower bound of 66.55 and 82.57, respectively, χ2 (7) = 32.8, p < 0.001). LH patients showed a median performance on RTNT, with significantly lower scores for selective attention and working memory (95% Confidence Interval Lower bound of 51.12, χ2 (5) = 20.31 p < 0.001) and minimum scores for the same task and for the Stroop test (χ2 (5) = 17.86, p < 0.005). The delta for accuracy between the first and the last RTNT run was not statistically significant (RH patients: χ2 (7) = 10.49, p > 0.05, n.s.; LH patients: χ2 (5) = 3.35, p > 0.05, n.s.). Mean extent of resection was 95.33% ± 9.72 for the RH group and 94.64% ± 6.74 for the LH group. Patients showed good performance post- vs. pre-surgery. The greater difference in the number of LH patients scoring within the normal range was found for the symbol-digit modality test (83.3% to 62%), Stroop test (100% to 77%) and short-term memory (84.61% to 72.72%) and working memory (92.3% to 63.63%). For RH patients, the main changes were observed on the clock drawing test (100% to 77.7%) and cognitive estimation (100% to 72.7%).

CONCLUSIONS

Frontal RTNT offers continuous and reliable feedback on the patients' cognitive status during resection in frontal areas.

Grey matter reshaping of language-related regions depends on tumor lateralization

A brain tumor in the left hemisphere can decrease language laterality as assessed with fMRI. However, it remains unclear whether or not this decreased language laterality is associated with a structural reshaping of the grey matter, particularly within the language network. Here, we examine if the disruption of language hubs exclusively affects macrostructural properties of contralateral homologues (as suggested by previous research), or whether it affects both hemispheres. This study uses voxel-based morphometry applied to high-resolution MR T1-weighted MPRAGE images from 31 adult patients left-dominant for language. Eighteen patients had brain tumors in the left hemisphere, and 13 had tumors in the right hemisphere. A cohort of 71 healthy individuals matched on age and sex was used as a baseline. We defined 10 ROIs per hemisphere known to subserve language function. Two separate repeated-measures ANOVAs were conducted with the volume per region as the dependent variables. For the patients, tumor lateralization (right versus left) served as a between-subject factor. The current study demonstrated that the presence of a brain tumor generates a global volumetric change affecting left language regions and their contralateral homologues. These changes are mediated by the lateralization of the lesion. Our findings suggest that compensatory functional mechanisms are supported by the rearrangement of the grey matter, although future longitudinal research should determine the temporal course of such changes.

The impact of brain lesions on health-related quality of life in patients with WHO CNS grade 3 or 4 glioma: a lesion-function and resting-state fMRI analysis

PURPOSE

In glioma patients, tumor development and multimodality therapy are associated with changes in health-related quality of life (HRQoL). It is largely unknown how different types and locations of tumor- and treatment-related brain lesions, as well as their relationship to white matter tracts and functional brain networks, affect HRQoL.

METHODS

In 121 patients with pretreated gliomas of WHO CNS grades 3 or 4, structural MRI, O-(2-[¹⁸F]fluoroethyl)-L-tyrosine (FET) PET, resting-state functional MRI (rs-fMRI) and self-reported HRQoL questionnaires (EORTC QLQ-C30/BN20) were obtained. Resection cavities, T1-enhancing lesions, T2/FLAIR hyperintensities, and lesions with pathologically increased FET uptake were delineated. Effects of tumor lateralization, involvement of white matter tracts or resting-state network nodes by different types of lesions and within-network rs-fMRI connectivity were analyzed in terms of their interaction with HRQoL scores.

RESULTS

Right hemisphere gliomas were associated with significantly less favorable outcomes in physical, role, emotional and social functioning, compared with left-sided tumors. Most functional HRQoL scores correlated significantly with right-sided white-matter tracts involvement by T2/FLAIR hyperintensities and with loss of within-network functional connectivity of right-sided nodes. Tumors of the left hemisphere caused significantly more communication deficits.

CONCLUSION

In pretreated high-grade gliomas, right hemisphere lesions are associated with reduced HRQoL scores in most functional domains except communication ability, compared to tumors of the left hemisphere. These relationships are mainly observed for T2/FLAIR lesions involving structural and functional networks in the right hemisphere. The data suggest that sparing the right hemisphere from treatment-related tissue damage may improve HRQoL in glioma patients.

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

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

Segregated circuits for phonemic and semantic fluency: A novel patient-tailored disconnection study

Phonemic and semantic fluency are neuropsychological tests widely used to assess patients' language and executive abilities and are highly sensitive tests in detecting language deficits in glioma patients. However, the networks that are involved in these tasks could be distinct and suggesting either a frontal (phonemic) or temporal (semantic) involvement. 42 right-handed patients (26 male, mean age = 52.5 years, SD=±13.3) were included in this retrospective study. Patients underwent awake (54.8%) or asleep (45.2%) surgery for low-grade (16.7%) or high-grade-glioma (83.3%) in the frontal (64.3%) or temporal lobe (35.7%) of the left (50%) or right (50%) hemisphere. Pre-operative tractography was reconstructed for each patient, with segmentation of the inferior fronto-occipital fasciculus (IFOF), arcuate fasciculus (AF), uncinate fasciculus (UF), inferior longitudinal fasciculus (ILF), third branch of the superior longitudinal fasciculus (SLF-III), frontal aslant tract (FAT), and cortico-spinal tract (CST). Post-operative percentage of damage and disconnection of each tract, based on the patients' surgical cavities, were correlated with verbal fluencies scores at one week and one month after surgery. Analyses of differences between fluency scores at these timepoints (before surgery, one week and one month after surgery) were performed; lesion-symptom mapping was used to identify the correlation between cortical areas and post-operative scores. Immediately after surgery, a transient impairment of verbal fluency was observed, that improved within a month. Left hemisphere lesions were related to a worse verbal fluency performance, being a damage to the left superior frontal or temporal gyri associated with phonemic or semantic fluency deficit, respectively. At a subcortical level, disconnection analyses revealed that fluency scores were associated to the involvement of the left FAT and the left frontal part of the IFOF for phonemic fluency, and the association was still present one month after surgery. For semantic fluency, the correlation between post-surgery performance emerged for the left AF, UF, ILF and the temporal part of the IFOF, but disappeared at the follow-up. This approach based on the patients' pre-operative tractography, allowed to trace for the first time a dissociation between white matter pathways integrity and verbal fluency after surgery for glioma resection. Our results confirm the involvement of a frontal anterior pathway for phonemic fluency and a ventral temporal pathway for semantic fluency. Finally, our longitudinal results suggest that the frontal executive pathway requires a longer interval to recover compared to the semantic one.

Personal space regulation is affected by unilateral temporal lesions beyond the amygdala

We constantly face situations involving interactions with others that require us to automatically adjust our physical distances to avoid discomfort or anxiety. A previous case study has demonstrated that the integrity of both amygdalae is essential to regulate interpersonal distances. Despite unilateral lesion to the amygdala, as to other sectors of the medial temporal cortex, are known to also affect social behavior, their role in the regulation of interpersonal distances has never been investigated. Here, we sought to fill this gap by testing three patients with unilateral temporal lesions following surgical resections, including one patient with a lesion mainly centered on the amygdala and two with lesions to adjacent medial temporal cortex, on two versions of the stop distance paradigm (i.e. in a virtual reality environment and in a real setting). Our results showed that all three patients set shorter interpersonal distances compared to neurotypical controls. In addition, compared to controls, none of the patients adjusted such physical distances depending on facial emotional expressions, despite they preserved ability to categorize them. Finally, patients' heart rate responses differed from controls when viewing approaching faces. Our findings bring compelling evidence that unilateral lesions within the medial temporal cortex, not necessarily restricted to the amygdala, are sufficient to alter interpersonal distance, thus shedding new light on the neural circuitry regulating distance in social interactions.

Awake Mapping With Transopercular Approach in Right Insular-Centered Low-Grade Gliomas Improves Neurological Outcomes and Return to Work

BACKGROUND

Asleep vs awake surgery for right insula-centered low-grade glioma (LGG) is still debated.

OBJECTIVE

To compare neurological outcomes and return to work after resection for right insular/paralimbic LGG performed without vs with awake mapping.

METHODS

A personal surgical experience of right insula-centered LGG was analyzed, by comparing 2 consecutive periods. In the first period (group 1), patients underwent asleep surgery with motor mapping. In the second period (group 2), patients underwent intraoperative awake mapping of movement and cognitive functions.

RESULTS

This consecutive series included 143 LGGs: 41 in group 1 (1999-2009) and 102 in group 2 (2009-2020). There were no significant difference concerning preoperative clinicoradiological characteristics and histopathology results between both groups. Intraoperative motor mapping was positive in all cases in group 1. In group 2, beyond motor mapping, somatosensory, visuospatial, language, and/or cognitive functions were identified during cortical-subcortical stimulation. Postoperatively, 3 patients experienced a long-lasting deterioration with 2 hemiparesis due to deep stroke (1.3%) and 1 severe depressive syndrome, all of them in group 1 vs none in group 2 (P = .022). The rate of RTW was 81.5% in group 1 vs 95.5% in group 2 (P = .016). The tumor volume and extent of resection did not significantly differ across both groups.

CONCLUSION

This is the first study comparing asleep vs awake surgery for right insula-centered LGG. Despite similar extent of resection, functional outcomes were significantly better in awake patients by avoiding permanent neurological impairment and by increasing RTW. These results support the mapping of higher-order functions during awake procedure.

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

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

The Effect of Right Temporal Lobe Gliomas on Left and Right Hemisphere Neural Processing During Speech Perception and Production Tasks

Using fMRI, we investigated how right temporal lobe gliomas affecting the posterior superior temporal sulcus alter neural processing observed during speech perception and production tasks. Behavioural language testing showed that three pre-operative neurosurgical patients with grade 2, grade 3 or grade 4 tumours had the same pattern of mild language impairment in the domains of object naming and written word comprehension. When matching heard words for semantic relatedness (a speech perception task), these patients showed under-activation in the tumour infiltrated right superior temporal lobe compared to 61 neurotypical participants and 16 patients with tumours that preserved the right postero-superior temporal lobe, with enhanced activation within the (tumour-free) contralateral left superior temporal lobe. In contrast, when correctly naming objects (a speech production task), the patients with right postero-superior temporal lobe tumours showed higher activation than both control groups in the same right postero-superior temporal lobe region that was under-activated during auditory semantic matching. The task dependent pattern of under-activation during the auditory speech task and over-activation during object naming was also observed in eight stroke patients with right hemisphere infarcts that affected the right postero-superior temporal lobe compared to eight stroke patients with right hemisphere infarcts that spared it. These task-specific and site-specific cross-pathology effects highlight the importance of the right temporal lobe for language processing and motivate further study of how right temporal lobe tumours affect language performance and neural reorganisation. These findings may have important implications for surgical management of these patients, as knowledge of the regions showing functional reorganisation may help to avoid their inadvertent damage during neurosurgery.

Benefit of Action Naming Over Object Naming for Visualization of Subcortical Language Pathways in Navigated Transcranial Magnetic Stimulation-Based Diffusion Tensor Imaging-Fiber Tracking

Visualization of functionally significant subcortical white matter fibers is needed in neurosurgical procedures in order to avoid damage to the language network during resection. In an effort to achieve this, positive cortical points revealed during preoperative language mapping with navigated transcranial magnetic stimulation (nTMS) can be employed as regions of interest (ROIs) for diffusion tensor imaging (DTI) fiber tracking. However, the effect that the use of different language tasks has on nTMS mapping and subsequent DTI-fiber tracking remains unexplored. The visualization of ventral stream tracts with an assumed lexico-semantic role may especially benefit from ROIs delivered by the lexico-semantically demanding verb task, Action Naming. In a first step, bihemispheric nTMS language mapping was administered in 18 healthy participants using the standard task Object Naming and the novel task Action Naming to trigger verbs in a small sentence context. Cortical areas in which nTMS induced language errors were identified as language-positive cortical sites. In a second step, nTMS-based DTI-fiber tracking was conducted using solely these language-positive points as ROIs. The ability of the two tasks’ ROIs to visualize the dorsal tracts Arcuate Fascicle and Superior Longitudinal Fascicle, the ventral tracts Inferior Longitudinal Fascicle, Uncinate Fascicle, and Inferior Fronto-Occipital Fascicle, the speech-articulatory Cortico-Nuclear Tract, and interhemispheric commissural fibers was compared in both hemispheres. In the left hemisphere, ROIs of Action Naming led to a significantly higher fraction of overall visualized tracts, specifically in the ventral stream’s Inferior Fronto-Occipital and Inferior Longitudinal Fascicle. No difference was found between tracking with Action Naming vs. Object Naming seeds for dorsal stream tracts, neither for the speech-articulatory tract nor the inter-hemispheric connections. While the two tasks appeared equally demanding for phonological-articulatory processes, ROI seeding through the task Action Naming seemed to better visualize lexico-semantic tracts in the ventral stream. This distinction was not evident in the right hemisphere. However, the distribution of tracts exposed was, overall, mirrored relative to those in the left hemisphere network. In presurgical practice, mapping and tracking of language pathways may profit from these findings and should consider inclusion of the Action Naming task, particularly for lesions in ventral subcortical regions.

Bihemispheric Navigated Transcranial Magnetic Stimulation Mapping for Action Naming Compared to Object Naming in Sentence Context

Preoperative language mapping with navigated transcranial magnetic stimulation (nTMS) is currently based on the disruption of performance during object naming. The resulting cortical language maps, however, lack accuracy when compared to intraoperative mapping. The question arises whether nTMS results can be improved, when another language task is considered, involving verb retrieval in sentence context. Twenty healthy German speakers were tested with object naming and a novel action naming task during nTMS language mapping. Error rates and categories in both hemispheres were compared. Action naming showed a significantly higher error rate than object naming in both hemispheres. Error category comparison revealed that this discrepancy stems from more lexico-semantic errors during action naming, indicating lexico-semantic retrieval of the verb being more affected than noun retrieval. In an area-wise comparison, higher error rates surfaced in multiple right-hemisphere areas, but only trends in the left ventral postcentral gyrus and middle superior temporal gyrus. Hesitation errors contributed significantly to the error count, but did not dull the mapping results. Inclusion of action naming coupled with a detailed error analysis may be favorable for nTMS mapping and ultimately improve accuracy in preoperative planning. Moreover, the results stress the recruitment of both left- and right-hemispheric areas during naming.

Deciphering the frontostriatal circuitry through the fiber dissection technique: direct structural evidence on the morphology and axonal connectivity of the fronto-caudate tract

OBJECTIVE

The authors sought to investigate the very existence and map the topography, morphology, and axonal connectivity of a thus far ill-defined subcortical pathway known as the fronto-caudate tract (FCT) since there is a paucity of direct structural evidence regarding this pathway in the relevant literature.

METHODS

Twenty normal adult cadaveric formalin-fixed cerebral hemispheres (10 left and 10 right) were explored through the fiber microdissection technique. Lateral to medial and medial to lateral dissections were carried out in a tandem manner in all hemispheres. Attention was focused on the prefrontal area and central core since previous diffusion tensor imaging studies have recorded the tract to reside in this territory.

RESULTS

In all cases, the authors readily identified the FCT as a fan-shaped pathway lying in the most medial layer of the corona radiata and traveling across the subependymal plane before terminating on the superolateral margin of the head and anterior part of the body of the caudate nucleus. The FCT could be adequately differentiated from adjacent fiber tracts and was consistently recorded to terminate in Brodmann areas 8, 9, 10, and 11 (anterior pre-supplementary motor area and the dorsolateral, frontopolar, and fronto-orbital prefrontal cortices). The authors were also able to divide the tract into a ventral and a dorsal segment according to the respective topography and connectivity observed. Hemispheric asymmetries were not observed, but instead the authors disclosed asymmetry within the FCT, with the ventral segment always being thicker and bulkier than the dorsal one.

CONCLUSIONS

By using the fiber microdissection technique, the authors provide sound structural evidence on the topography, morphology, and connectional anatomy of the FCT as a distinct part of a wider frontostriatal circuitry. The findings are in line with the tract's putative functional implications in high-order motor and behavioral processes and can potentially inform current surgical practice in the fields of neuro-oncology and functional neurosurgery.

The Associations Between White Matter Disruptions and Cognitive Decline at the Early Stage of Subcortical Vascular Cognitive Impairment: A Case-Control Study

Objective

Emerging evidence suggests that white matter (WM) disruption is associated with the incidence of subcortical vascular cognitive impairment (SVCI). However, our knowledge regarding this relationship in the early stage of SVCI is limited. We aimed to investigate the associations between WM disruptions and cognitive declines at the early stage of SVCI.

Method

We performed a case–control study, involving 22 cases and 19 controls. The cases were patients at the early stage of SVCI, which was defined as subcortical ischemic vascular disease with normal global cognitive measures (pre-SVCI). The controls were healthy people matched by age, sex, and education years. We assessed the differences in a battery of neuropsychological tests between the two groups, investigated the diffusion changes in 40 WM tracts among the participants via an atlas-based segmentation strategy, and compared the differences between the cases and controls by multiple linear regression analysis. We then evaluated the relationships between diffusion indices and cognitive assessment scores by Pearson’s correlation.

Results

The pre-SVCI group exhibited significant differences in the Montreal cognitive assessment (MoCA), Rey–Osterrieth Complex Figure (R-O)-copy, and Trail Making Test (TMT)-B test compared with the controls. Compared with the controls, some long associative and projective bundles, such as the right anterior corona radiata (ACR), the right inferior fronto-occipital fasciculus (IFOF), and the left external capsule (EC), were extensively damaged in cases after Bonferroni correction (p < 0.05/40). Damages to specific fibers, such as the right ACR, IFOF, and posterior thalamic radiation (PTR), exhibited significant correlations with declines in MoCA, R-O delay, and the Mini-Mental State Examination (MMSE), respectively, after Bonferroni correction (p < 0.05/14).

Conclusion

Long WM tracts, especially those in the right hemisphere, were extensively damaged in the pre-SVCI patients and correlated with declines in executive functions and spatial processing. Patients of pre-SVCI are likely at an ultra-early stage of SVCI, and there is a very high risk of this condition becoming SVCI.

New Philosophy, Clinical Pearls, and Methods for Intraoperative Cognition Mapping and Monitoring "à la carte" in Brain Tumor Patients

The purpose of surgery for brain tumors involving eloquent neural circuits is to maximize the extent of resection while preserving an optimal quality of life. To this end, especially in diffuse glioma, the goal is to remove the cerebral parenchyma invaded by the neoplasm up to the individual cortico-subcortical networks critical for brain functions. Intraoperative mapping combined with real-time cognitive monitoring throughout the resection in awake patient is thus highly recommended to resume a normal life. Indeed, beyond avoiding hemiplegia or aphasia, enjoying a familial, social, and professional life implies that motor and language mapping is not sufficient. Identifying and sparing neural networks that subserve cognition (movement control, visuospatial cognition, executive functions, multimodal semantics, metacognition) and mentalizing (theory of mind, which plays a key role for social cognition) is essential to preserve an adapted behavior. Here, the aim is to review when and how to map these critical functions, which have nonetheless been neglected for many decades by neurosurgeons. In fact, the disorders generated by surgical injuries of circuits underpinning nonmotor and nonspeech functions are usually not immediately visible on postoperative standard clinical examination, leading the physician to believe that the patient has no deficit. Yet, cognitive or emotional disturbances may subsequently prevent to resume an active life, as to work full time. Therefore, a systematic neuropsychological assessment should be performed before, during, and after mapping-guided surgery, regardless of the tumor location, to preserve the functional connectome intraoperatively and to plan a postoperative tailored cognitive rehabilitation according to the patient's needs.

Role of Clinical Neuropsychologists in Awake-Craniotomy

Background

Awake craniotomy encompasses surgical resection of focal zone of neurological impairment, using intraoperative functional zone mapping. The strength of the procedure is maximum retention of functionally significant zones to ensure better function and quality of life outcomes in patients. A clinical neuropsychologist plays a vital role in profiling the patient’s cognitive and psychosocial functioning as well as increasing the efficacy of functional zone mapping procedures.

Objective

Aim of this article is to summarize the literature on the role of clinical neuropsychologists in awake craniotomy and underscoring the need for establishing standardized operating procedures for neuropsychologists in awake craniotomy highlighting experiential anecdotes from a tertiary care facility.

Materials and Methods

A review of articles that elucidate the role of clinical neuropsychologists was done and summarized to highlight the role of clinical neuropsychologists. An attempt was made to explain the implementation of this role in regular clinical practice at a tertiary care facility.

Results

The role of a clinical neuropsychologist is highly crucial at pre-/during and postawake craniotomy, and has a significant bearing on the overall psychological outcome of the individual. The need for a standardized protocol to unify practice and increase the efficacy of the awake-craniotomy procedure is put forth. Recommendations for future directions in research to increase the scope of neuropsychologists in awake craniotomy have also been made.

Language network reorganization before and after temporal lobe epilepsy surgery

OBJECTIVE

Epilepsy surgery is the recommended treatment option for patients with drug-resistant temporal lobe epilepsy (TLE). This method offers a good chance of seizure freedom but carries a considerable risk of postoperative language impairment. The extremely variable neurocognitive profiles in surgical epilepsy patients cannot be fully explained by extent of resection, fiber integrity, or current task-based functional MRI (fMRI). In this study, the authors aimed to investigate pathology- and surgery-triggered language organization in TLE by using fMRI activation and network analysis as well as considering structural and neuropsychological measures.

METHODS

Twenty-eight patients with unilateral TLE (16 right, 12 left) underwent T1-weighted imaging, diffusion tensor imaging, and task-based language fMRI pre- and postoperatively (n = 15 anterior temporal lobectomy, n = 11 selective amygdalohippocampectomy, n = 2 focal resection). Twenty-two healthy subjects served as the control cohort. Functional connectivity, activation maps, and laterality indices for language dominance were analyzed from fMRI data. Postoperative fractional anisotropy values of 7 major tracts were calculated. Naming, semantic, and phonematic verbal fluency scores before and after surgery were correlated with imaging parameters.

RESULTS

fMRI network analysis revealed widespread, bihemispheric alterations in language architecture that were not captured by activation analysis. These network changes were found preoperatively and proceeded after surgery with characteristic patterns in the left and right TLEs. Ipsilesional fronto-temporal connectivity decreased in both left and right TLE. In left TLE specifically, preoperative atypical language dominance predicted better postoperative verbal fluency and naming function. In right TLE, left frontal language dominance correlated with good semantic verbal fluency before and after surgery, and left fronto-temporal language laterality predicted good naming outcome. Ongoing seizures after surgery (Engel classes ID-IV) were associated with naming deterioration irrespective of seizure side. Functional findings were not explained by the extent of resection or integrity of major white matter tracts.

CONCLUSIONS

Functional connectivity analysis contributes unique insight into bihemispheric remodeling processes of language networks after epilepsy surgery, with characteristic findings in left and right TLE. Presurgical contralateral language recruitment is associated with better postsurgical language outcome in left and right TLE.

Disconnection of posterior part of the frontal aslant tract causes acute phase motor functional deficit

The frontal aslant tract (FAT) mainly connects the supplementary motor area (SMA) and inferior frontal gyrus. The left FAT is involved in language-related functions, while the functional role of the right FAT is not fully understood. The aim of this study was to investigate the function of the right FAT by dividing it into three segments according to the anatomical structure. A total of 34 right frontal gliomas who had undergone surgery were studied. Participants were assessed for the acute and chronic phases of several neuropsychological and motor functions. FAT was reconstructed into the anterior, middle, and posterior segments according to the cortical connections as the medial prefrontal cortex, pre-SMA, and SMA proper, respectively. The relationships between the damaged severity of each FAT segment and behavioral scores were analyzed. A significant relationship was observed only in the acute phase motor function and posterior segment of the FAT. The middle segment was involved in motor function, but it did not have a sufficient significance level compared to the posterior segment. Our study revealed that the right FAT can be divided into three segments and that its posterior segment is related to acute phase motor function.

The inferior fronto-occipital fascicle: a century of controversies from anatomy theaters to operative neurosurgery

INTRODUCTION

Since its first description in the early 19th century, the inferior frontooccipital fascicle (IFOF) and its anatomo-functional features were neglected in the neuroscientific literature for the last century. In the last decade, the rapid development of in vivo imaging for the reconstruction of white matter (WM) connectivity (i.e., tractography) and the consequent interest in more traditional ex vivo methods (postmortem dissection) have allowed a renewed debate about course, termination territories, anatomical relationships, and functional roles of this fascicle.

EVIDENCE ACQUISITION

We reviewed the main current knowledge concerning the structural and functional anatomy of the IFOF and possible implications in neurosurgical practice.

EVIDENCE SYNTHESIS

The IFOF connects the occipital cortex, the temporo-basal areas, the superior parietal lobule, and the pre-cuneus to the frontal lobe, passing through the ventral third of subinsular WM of the external capsule. This wide distribution of cortical terminations provides multimodal integration between several functional networks, including language, non-verbal semantic processing, object identification, visuo-spatial processing and planning, reading, facial expression recognition, memory and conceptualization, emotional and neuropsychological behavior. This anatomo-functional organization has important implication also in neurosurgical practice, especially when approaching the frontal, insular, temporo-parieto-occipital regions and the ventricular system.

CONCLUSIONS

The IFOF is the most extensive associative bundle of the human connectome. Its multi-layer organization reflects important implications in many aspects of brain functional processing. Accurate awareness of IFOF functional anatomy and integration between multimodal datasets coming from different sources has crucial implications for both neuroscientific knowledge and quality of neurosurgical treatments.

Brain connectomics applied to oncological neuroscience: from a traditional surgical strategy focusing on glioma topography to a meta-network approach

The classical way for surgical selection and planning in cerebral glioma mainly focused on tumor topography. The emerging science of connectomics, which aims of mapping brain connectivity, resulted in a paradigmatic shift from a modular account of cerebral organization to a meta-network perspective. Adaptive behavior is actually mediated by constant changes in interactions within and across large-scale delocalized neural systems underlying conation, cognition, and emotion. Here, to optimize the onco-functional balance of glioma surgery, the purpose is to switch toward a connectome-based resection taking account of both relationships between the tumor and critical distributed circuits (especially subcortical pathways) as well as the perpetual instability of the meta-network. Such dynamic in the neural spatiotemporal integration permits functional reallocation leading to neurological recovery after massive resection in structures traditionally thought as "inoperable." This better understanding of connectome increases benefit/risk ratio of surgery (i) by selecting resection in areas deemed "eloquent" according to a localizationist dogma; (ii), conversely, by refining intraoperative awake cognitive mapping and monitoring in so-called non-eloquent areas; (iii) by improving preoperative information, enabling an optimal selection of intrasurgical tasks tailored to the patient's wishes; (iv) by developing an "oncological disconnection surgery"; (v) by defining a personalized multistep surgical strategy adapted to individual brain reshaping potential; and (vi) ultimately by preserving environmentally and socially appropriate behavior, including return to work, while increasing the extent of (possibly repeated) resection(s). Such a holistic vision of neural processing can enhance reliability of connectomal surgery in oncological neuroscience and may also be applied to restorative neurosurgery.

The Use of Standardized Intraoperative Language Tests in Awake Craniotomies: A Scoping Review

Assessment of speech and language functions is an essential part of awake craniotomies. Although standardized and validated tests have several advantages compared to homemade (or mixed) batteries, in the literature it is unclear how such tests are used or whether they are used at all. In this study, we performed a scoping review in order to locate standardized and validated intraoperative language tests. Our inquiry included two databases (PubMED and MEDLINE), gray literature, and snowball referencing. We discovered 87 studies reporting use of mixed batteries, which consist of homemade tasks and tests borrowed from other settings. The tests we found to meet the validation and standardization criteria we set were ultimately three (n = 3) and each one has its own advantages and disadvantages. We argue that tests with high sensitivity and specificity not only can lead to better outcomes postoperatively, but they can also help us to gain a better understanding of the neuroanatomy of language.

Microsurgical resection of fronto-temporo-insular gliomas in the non-dominant hemisphere, under general anesthesia using adjunct intraoperative MRI and no cortical and subcortical mapping: a series of 20 consecutive patients

Fronto-temporo-insular (FTI) gliomas continue to represent a surgical challenge despite numerous technical advances. Some authors advocate for surgery in awake condition even for non-dominant hemisphere FTI, due to risk of sociocognitive impairment. Here, we report outcomes in a series of patients operated using intraoperative magnetic resonance imaging (IoMRI) guided surgery under general anesthesia, using no cortical or subcortical mapping. We evaluated the extent of resection, functional and neuropsychological outcomes after IoMRI guided surgery under general anesthesia of FTI gliomas located in the non-dominant hemisphere. Twenty patients underwent FTI glioma resection using IoMRI in asleep condition. Seventeen tumors were de novo, three were recurrences. Tumor WHO grades were II:12, III:4, IV:4. Patients were evaluated before and after microsurgical resection, clinically, neuropsychologically (i.e., social cognition) and by volumetric MR measures (T1G+ for enhancing tumors, FLAIR for non-enhancing). Fourteen (70%) patients benefited from a second IoMRI. The median age was 33.5 years (range 24–56). Seizure was the inaugural symptom in 71% of patients. The median preoperative volume was 64.5 cm³ (min 9.9, max 211). Fourteen (70%) patients underwent two IoMRI. The final median EOR was 92% (range 69–100). The median postoperative residual tumor volume (RTV) was 4.3 cm³ (range 0–38.2). A vast majority of residual tumors were located in the posterior part of the insula. Early postoperative clinical events (during hospital stay) were three transient left hemiparesis (which lasted less than 48 h) and one prolonged left brachio-facial hemiparesis. Sixty percent of patients were free of any symptom at discharge. The median Karnofsky Performance Score was of 90 both at discharge and at 3 months. No significant neuropsychological impairment was reported, excepting empathy distinction in less than 40% of patients. After surgery, 45% of patients could go back to work. In our experience and using IoMRI as an adjunct, microsurgical resection of non-dominant FTI gliomas under general anesthesia is safe. Final median EOR was 92%, with a vast majority of residual tumors located in the posterior insular part. Patients experienced minor neurological and neuropsychological morbidity. Moreover, neuropsychological evaluation reported a high preservation of sociocognitive abilities. Solely empathy seemed to be impaired in some patients.

Updated perspectives on awake neurosurgery with cognitive and emotional assessment for patients with low-grade gliomas

Introduction: Thanks to early extensive surgical resection combined with medical oncological therapies, life expectancy dramatically increased in low-grade glioma (LGG), with an overall survival currently over 15 years. Therefore, patients should be able to maintain valuable family and socio-professional activities.Areas covered: For many decades, cognitive and emotional aspects were neglected by surgical and medical neurooncologists. The goal of surgery was to avoid hemiplegia and/or aphasia, with no considerations regarding behavior. However, because LGG patients live longer, they must be cognitively and affectively able to make long-term projects. Preservation of higher-order functions should be considered systematically in LGG surgery by means of awake cognitive/emotional mapping and monitoring.Expert opinion: The aim is to incorporate recent advances in neurosciences, which proposed revisited models of cerebral processing relying on a meta-network perspective, into the pre-, intra- and postoperative procedure. In this connectomal approach, brain functions result from complex interactions within and between neural networks. This improved understanding of a constant instability of the neural system allows a better cognitive/emotional assessment before and after each treatment over years, in order to preserve personality and adaptive behavior for each LGG patient, based on his/her own definition of quality of life. It is time to create oncological neurosciences.

Role of Preoperative Assessment in Predicting Tumor-Induced Plasticity in Patients with Diffuse Gliomas

When diffuse gliomas (DG) affect the brain’s potential to reorganize functional networks, patients can exhibit seizures and/or language/cognitive impairment. The tumor–brain interaction and the individual connectomic organization cannot be predicted preoperatively. We aimed to, first, investigate the relationship between preoperative assessment and intraoperative findings of eloquent tumors in 36 DG operated with awake surgery. Second, we also studied possible mechanisms of tumor-induced brain reorganization in these patients. FLAIR-MRI sequences were used for tumor volume segmentation and the Brain-Grid system (BG) was used as an overlay for infiltration analysis. Neuropsychological (NPS) and/or language assessments were performed in all patients. The distance between eloquent spots and tumor margins was measured. All variables were used for correlation and logistic regression analyses. Eloquent tumors were detected in 75% of the patients with no single variable able to predict this finding. Impaired NPS functions correlated with invasive tumors, crucial location (A4C2S2/A3C2S2-voxels, left opercular-insular/sub-insular region) and higher risk of eloquent tumors. Epilepsy was correlated with larger tumor volumes and infiltrated A4C2S2/A3C2S2 voxels. Language impairment was correlated with infiltrated A3C2S2 voxel. Peritumoral cortical eloquent spots reflected an early compensative mechanism with age as possible influencing factor. Preoperative NPS impairment is linked with high risk of eloquent tumors. A systematic integration of extensive cognitive assessment and advanced neuroimaging can improve our comprehension of the connectomic brain organization at the individual scale and lead to a better oncological/functional balance.

The Cologne Picture Naming Test for Language Mapping and Monitoring (CoNaT): An Open Set of 100 Black and White Object Drawings

Language assessment using a picture naming task crucially relies on the interpretation of the given verbal response by the rater. To avoid misinterpretations, a language-specific and linguistically controlled set of unambiguous, clearly identifiable and common object-word pairs is mandatory. We, here, set out to provide an open-source set of black and white object drawings, particularly suited for language mapping and monitoring, e.g., during awake brain tumour surgery or transcranial magnetic stimulation, in German language. A refined set of 100 black and white drawings was tested in two consecutive runs of randomised picture order and was analysed in respect of correct, prompt, and reliable object recognition and naming in a series of 132 healthy subjects between 18 and 84 years (median 25 years, 64% females) and a clinical pilot cohort of 10 brain tumour patients (median age 47 years, 80% males). The influence of important word- and subject-related factors on task performance and reliability was investigated. Overall, across both healthy subjects and patients, excellent correct object naming rates (97 vs. 96%) as well as high reliability coefficients (Goodman-Kruskal's gamma = 0.95 vs. 0.86) were found. However, the analysis of variance revealed a significant, overall negative effect of low word frequency (p < 0.05) and high age (p < 0.0001) on task performance whereas the effect of a low educational level was only evident for the subgroup of 72 or more years of age (p < 0.05). Moreover, a small learning effect was observed across the two runs of the test (p < 0.001). In summary, this study provides an overall robust and reliable picture naming tool, optimised for the clinical use to map and monitor language functions in patients. However, individual familiarisation before the clinical use remains advisable, especially for subjects that are comparatively prone to spontaneous picture naming errors such as older subjects of low educational level and patients with clinically apparent word finding difficulties.

Converging Evidence for Differential Specialization and Plasticity of Language Systems

Functional specialization and plasticity are fundamental organizing principles of the brain. Since the mid-1800s, certain cognitive functions have been known to be lateralized, but the provenance and flexibility of hemispheric specialization remain open questions. Language is a uniquely human phenomenon that requires a delicate balance between neural specialization and plasticity, and language learning offers the perfect window to study these principles in the human brain. In the current study, we conducted two separate functional MRI experiments with language learners (male and female), one cross-sectional and one longitudinal, involving distinct populations and languages, and examined hemispheric lateralization and learning-dependent plasticity of the following three language systems: reading, speech comprehension, and verbal production. A multipronged analytic approach revealed a highly consistent pattern of results across the two experiments, showing (1) that in both native and non-native languages, while language production was left lateralized, lateralization for language comprehension was highly variable across individuals; and (2) that with increasing non-native language proficiency, reading and speech comprehension displayed substantial changes in hemispheric dominance, with languages tending to lateralize to opposite hemispheres, while production showed negligible change and remained left lateralized. These convergent results shed light on the long-standing debate of neural organization of language by establishing robust principles of lateralization and plasticity of the main language systems. Findings further suggest involvement of the sensorimotor systems in language lateralization and its plasticity.SIGNIFICANCE STATEMENT The human brain exhibits a remarkable ability to support a vast variety of languages that may be acquired at different points in the life span. Language is a complex construct involving linguistic as well as visual, auditory, and motor processes. Using functional MRI, we examined hemispheric specialization and learning-dependent plasticity of three language systems-reading, speech comprehension, and verbal production-in cross-sectional and longitudinal experiments in language learners. A multipronged analytic approach revealed converging evidence for striking differences in hemispheric specialization and plasticity among the language systems. The results have major theoretical and practical implications for our understanding of fundamental principles of neural organization of language, language testing and recovery in patients, and language learning in healthy populations.

Cognitive functioning in patients with low-grade glioma: effects of hemispheric tumor location and surgical procedure

OBJECTIVE

The authors evaluated the cognitive performance of patients with low-grade glioma (LGG) before and after surgery, and specifically investigated 1) the effects of hemispheric tumor location and 2) the type of surgery (either with or without intraoperative stimulation mapping [ISM]).

METHODS

Patients underwent neuropsychological assessment 1 day before (T0) and 3 months after (T3) surgery. ISM targeted motor and/or language functions, but no other cognitive functions. Using 2-way mixed ANOVAs, differences between groups (i.e., for patients with right- vs left-sided lesions and normative controls [NCs], and also for patients operated on with vs without ISM and NCs), effects over time (T0-T3), and interaction effects in cognitive functioning were explored. Individual changes over time were assessed with reliable change indices for each neuropsychological test.

RESULTS

In total, 77 patients with LGG were included (38 and 39 patients with right- and left-sided lesions, respectively; and 42 patients with and 35 patients without ISM). The majority of patients who were operated on with ISM had left-sided lesions. Patients with right- and left-sided lesions scored significantly lower on 6 and 3 out of 8 tests, respectively, compared to NCs. No significant differences between hemispheric groups were found at T0 or at T3. Patients with left-sided lesions showed significant deterioration of performance on verbal memory and sustained attention over time. Patients who underwent operation with versus without ISM scored significantly lower on 6 and 3 out of 8 tests, respectively, compared to NCs. Patients in the ISM group scored significantly lower on the Stroop test, shifting attention test, and verbal fluency test than patients without ISM. Also, the ISM group showed a significant decline in mean cognitive flexibility and sustained attention performance over time.

CONCLUSIONS

Cognitive impairments were found in patients irrespective of hemispheric tumor location, whereby patients who were operated on with ISM performed slightly worse after surgery than patients without ISM. The authors conclude that there is room for improvement of cognitive functioning in surgically treated patients with LGG. The use of specific tests for higher cognitive functions during surgery may potentially improve functional outcome, but that is to be determined in future studies and balanced against oncological outcome. Implementation of neuropsychological assessments into the clinical management of patients with LGG should be encouraged, to inform and alert patients and clinicians on the status of cognitive functioning.

Intraoperative brain mapping of language, cognitive functions, and social cognition in awake surgery of low-grade gliomas located in the right non-dominant hemisphere

OBJECTIVE

The aim of our study was to evaluate the usefulness of cortical-subcortical intraoperative brain mapping (ioBM) in resective awake surgery of low-grade gliomas (LGG) of the right non-dominant hemisphere (RndH). It was estimated how ioBM may affect both the extent of resection and postoperative outcome of language, spatial cognition, social cognition, and executive functions including attention and working memory.

PATIENTS AND METHODS

Fifteen patients that underwent ioBM in resective awake surgery of LGG located on the RndH, were included. A cohort of 15 patients with the same tumour location operated under general anaesthesia without brain mapping was used as control. Specific intraoperative tasks for each location were carried out and results registered. Neuropsychological assessment was performed preoperatively and at 6 months after surgery.

RESULTS

In the group of patients operated by using ioBM in awake surgery, an 86.66 % mean of resection was obtained compared to 60.33 % in the control group. Speech arrest and incorrect naming responses were elicited in higher proportion in frontal and insular locations. Parietal stimulation associated higher number of incorrect responses in social cognition task. Parietal and temporal stimulation were more frequently associated with incorrect performance of spatial cognition task. Parietal stimulation associated with higher frequency incorrect execution of attention and working memory tasks. After comparing clinical and neuropsychological results in both cohorts, worst outcome at 6 months was observed in the group of patients operated under general anaesthesia without brain mapping, especially in parietal and insular locations.

CONCLUSIONS

Intraoperative identification of language, cognitive functions, and social cognition of RndH by means of ioBM, can be of paramount importance in improving the extent of resection of low-grade gliomas and positively affects clinical and neuropsychological outcome at six months.

Converging Evidence for Differential Specialization and Plasticity of Language Systems

Functional specialization and plasticity are fundamental organizing principles of the brain. Since the mid-1800s, certain cognitive functions have been known to be lateralized, but the provenance and flexibility of hemispheric specialization remain open questions. Language is a uniquely human phenomenon that requires a delicate balance between neural specialization and plasticity, and language learning offers the perfect window to study these principles in the human brain. In the current study, we conducted two separate functional MRI experiments with language learners (male and female), one cross-sectional and one longitudinal, involving distinct populations and languages, and examined hemispheric lateralization and learning-dependent plasticity of the following three language systems: reading, speech comprehension, and verbal production. A multipronged analytic approach revealed a highly consistent pattern of results across the two experiments, showing (1) that in both native and non-native languages, while language production was left lateralized, lateralization for language comprehension was highly variable across individuals; and (2) that with increasing non-native language proficiency, reading and speech comprehension displayed substantial changes in hemispheric dominance, with languages tending to lateralize to opposite hemispheres, while production showed negligible change and remained left lateralized. These convergent results shed light on the long-standing debate of neural organization of language by establishing robust principles of lateralization and plasticity of the main language systems. Findings further suggest involvement of the sensorimotor systems in language lateralization and its plasticity.

SIGNIFICANCE STATEMENT The human brain exhibits a remarkable ability to support a vast variety of languages that may be acquired at different points in the life span. Language is a complex construct involving linguistic as well as visual, auditory, and motor processes. Using functional MRI, we examined hemispheric specialization and learning-dependent plasticity of three language systems—reading, speech comprehension, and verbal production—in cross-sectional and longitudinal experiments in language learners. A multipronged analytic approach revealed converging evidence for striking differences in hemispheric specialization and plasticity among the language systems. The results have major theoretical and practical implications for our understanding of fundamental principles of neural organization of language, language testing and recovery in patients, and language learning in healthy populations.

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.

Experiences of awake surgery in non-tumoural epilepsy in eloquent localizations

BACKGROUND

Whilst modern awake intraoperative mapping has been widely accepted and implemented in the last decades in neuro-oncology, sparse reports have been published on the safety and efficiency of this approach in epilepsy surgery.

METHOD

This article reports four cases with different locations of epileptogenic zones as examples of possible safe and efficient resections.

RESULT

The results of the resections on seizure control were Engel 1 (no disabling seizures) in all cases and no patient experienced significant neurological deficits.

DISCUSSION

The discussion focuses on aspects of the future of epilepsy surgery in a hodotopical paradigm.

Network-level causal analysis of set-shifting during trail making test part B: A multimodal analysis of a glioma surgery case

The trail making test part B (TMT-B) is one of the most widely used task for the assessment of set-shifting ability in patients. However, the set of brain regions impacting TMT-B performance when lesioned is still poorly known. In this case report, we provide a multimodal analysis of a patient operated on while awake for a diffuse low-grade glioma located in the right supramarginal gyrus. TMT-B performance was probed intraoperatively. Direct electrical stimulation of the white matter in the depth of the resection generated shifting errors. Using the recent methodology of axono-cortical-evoked potentials (ACEP), we demonstrated that the eloquent fibers were connected to the posterior end of the middle temporal gyrus (MTG). This was further confirmed by a tractography analysis of the postoperative diffusion MRI. Finally, the functional connectivity maps of this MTG seed were assessed in both pre- and post-operative resting state MRI. These maps matched with the Control network B (13th) and Default B (17th) from the 17-networks parcellation of (Yeo et al., 2011). Last but not least, we showed that the dorsal attention B (6th), the control A & B networks (12th and 13th) and the default A (16th) have been preserved here but disconnected after a more extensive resection in a previous glioma case within the same area, and in whom TMT-B was definitively impaired. Taken together, these data support the need of a network-level approach to identify the neural basis of the TMT-B and point to the Control network B as playing an important role in set-shifting.

Anesthesia management for low-grade glioma awake surgery: a European Low-Grade Glioma Network survey

BACKGROUND

Awake surgery has become a key treatment of diffuse low-grade gliomas (DLGG) and is divided in three main phases: opening, tumor resection - during which the patient needs to be fully awake - and closure. The anesthetic management of awake neurosurgery is a challenge, and there are currently no guidelines.

OBJECTIVE

The objective of the survey was to explore differences and commonalities regarding the anesthetic management of awake DLGG surgery within the European Low-Grade Glioma Network (ELGGN) centers.

METHODS

A form that contained 14 questions about the anesthetic management was sent to 28 centers in May 2015.

RESULTS

Twenty centers responded. During the opening and closing non-awake periods, 56% of teams chose general anesthesia with mechanical ventilation for at least one period (asleep-awake-asleep, SAS protocol), and 44% monitored anesthesia care including sedation without mechanical ventilation (MAC protocol). In case of SAS, all the teams chose intravenous anesthesia, 82% used laryngeal mask instead of endotracheal intubation during the opening sequence, and 71% during closure. Local and regional anesthesia was practiced by all the teams. The most frequently reported cause of pain was dural and cerebral vessels manipulation (77%). Pain management was mostly based on paracetamol (70%) and remifentanil (55%).

CONCLUSION

Our survey showed that there was an equivalent proportion of centers using SAS or MAC protocols in the anesthetic management of awake surgery in ELGGN centers. The advantages and disadvantages of each anesthesia protocol were reviewed.

Comparing Glioblastoma Surgery Decisions Between Teams Using Brain Maps of Tumor Locations, Biopsies, and Resections

Purpose

The aim of glioblastoma surgery is to maximize the extent of resection while preserving functional integrity, which depends on the location within the brain. A standard to compare these decisions is lacking. We present a volumetric voxel-wise method for direct comparison between two multidisciplinary teams of glioblastoma surgery decisions throughout the brain.

Methods

Adults undergoing first-time glioblastoma surgery from 2012 to 2013 performed by two neuro-oncologic teams were included. Patients had had a diagnostic biopsy or resection. Preoperative tumors and postoperative residues were segmented on magnetic resonance imaging in three dimensions and registered to standard brain space. Voxel-wise probability maps of tumor location, biopsy, and resection were constructed for each team to compare patient referral bias, indication variation, and treatment variation. To evaluate the quality of care, subgroups of differentially resected brain regions were analyzed for survival and functional outcome.

Results

One team included 101 patients, and the other included 174; 91 tumors were biopsied, and 181 were resected. Patient characteristics were largely comparable between teams. Distributions of tumor locations were dissimilar, suggesting referral bias. Distributions of biopsies were similar, suggesting absence of indication variation. Differentially resected regions were identified in the anterior limb of the right internal capsule and the right caudate nucleus, indicating treatment variation. Patients with (n = 12) and without (n = 6) surgical removal in these regions had similar overall survival and similar permanent neurologic deficits.

Conclusion

Probability maps of tumor location, biopsy, and resection provide additional information that can inform surgical decision making across multidisciplinary teams for patients with glioblastoma.

Neurocognitive and functional outcomes in patients with diffuse frontal lower-grade gliomas undergoing intraoperative awake brain mapping

OBJECTIVE

Lower-grade gliomas (LGGs) are often observed within eloquent regions, which indicates that tumor resection in these areas carries a potential risk for neurological disturbances, such as motor deficit, language disorder, and/or neurocognitive impairments. Some patients with frontal tumors exhibit severe impairments of neurocognitive function, including working memory and spatial awareness, after tumor removal. The aim of this study was to investigate neurocognitive and functional outcomes of frontal LGGs in both the dominant and nondominant hemispheres after awake brain mapping.

METHODS

Data from 50 consecutive patients with diffuse frontal LGGs in the dominant and nondominant hemispheres who underwent awake brain surgery between December 2012 and September 2018 were retrospectively analyzed. The goal was to map neurocognitive functions such as working memory by using working memory tasks, including digit span testing and N-back tasks.

RESULTS

Due to awake language mapping, the frontal aslant tract was frequently identified as a functional boundary in patients with left superior frontal gyrus tumors (76.5%). Furthermore, functional boundaries were identified while evaluating verbal and spatial working memory function by stimulating the dorsolateral prefrontal cortex using the digit span and visual N-back tasks in patients with right superior frontal gyrus tumors (7.1%). Comparing the preoperative and postoperative neuropsychological assessments from the Wechsler Adult Intelligence Scale-Third Edition (WAIS-III) and Wechsler Memory Scale-Revised (WMS-R), significant improvement following awake surgery was observed in mean Perceptual Organization (Z = -2.09, p = 0.04) in WAIS-III scores. Postoperative mean WMS-R scores for Visual Memory (Z = -2.12, p = 0.03) and Delayed Recall (Z = -1.98, p = 0.04) were significantly improved compared with preoperative values for every test after awake surgery. No significant deterioration was noted with regard to neurocognitive functions in a comprehensive neuropsychological test battery. In the postoperative course, early transient speech and motor disturbances were observed in 30.0% and 28.0% of patients, respectively. In contrast, late permanent speech and motor disturbances were observed in 0% and 4.0%, respectively.

CONCLUSIONS

It is noteworthy that no significant postoperative deterioration was identified compared with preoperative status in a comprehensive neuropsychological assessment. The results demonstrated that awake functional mapping enabled favorable neurocognitive and functional outcomes after surgery in patients with diffuse frontal LGGs.