Right Hemisphere Cognitive Functions: From Clinical and Anatomic Bases to Brain Mapping During Awake Craniotomy Part I: Clinical and Functional Anatomy

Endoscopic Cystoventricular Stenting in Awake Patients with Electrical Stimulation Mapping for Convexity Cysts: Three Case Reports and a Systematic Review

Surgical interventions for arachnoid cysts and glioependymal cysts primarily focus on cyst decompression and establishing communication with cerebrospinal fluid spaces. However, a standardized surgical strategy for symptomatic convexity cysts lacking surrounding cerebrospinal fluid space is still lacking due to the limited number of cases. This systematic review aims to evaluate surgical interventions for symptomatic convexity cysts and proposes a safe and effective treatment approach we have developed. A systematic review of the literature was conducted following Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Surgical techniques were categorized into cystoperitoneal shunt, cyst excision, cyst fenestration, cyst ventriculostomy, and several uniquely modified methods. Using a method different from these previous reports, we performed endoscopic cystoventricular stenting via burr hole in 3 cases of convexity cysts. While traditional methods have proven effective, cystoperitoneal shunt may lead to malfunction, infection, and subdural hematoma; wall excision is invasive and increases morbidity risks. Fenestration and cystoventriculostomy have also reported cases of recurrence. Other methods also pose issues, including off-label use of instruments and inadequate consideration for removal. The method we performed for placing the stent catheter with multiple side holes demonstrated long-term effectiveness. Furthermore, the surgery was conducted with the patient fully awake, and the use of electrical stimulation mapping enabled preservation of higher neurocognitive functions, including language, working memory, and spatial cognition, at the puncture site. This novel approach offers advantages such as minimally invasive procedure, preservation of safe brain function, and long-term patency. Further studies are warranted to validate these findings and improve surgical strategies for convexity cysts.

Multilayer network analysis in patients with end-stage kidney disease

This study aimed to investigate alterations in a multilayer network combining structural and functional layers in patients with end-stage kidney disease (ESKD) compared with healthy controls. In all, 38 ESKD patients and 43 healthy participants were prospectively enrolled. They exhibited normal brain magnetic resonance imaging (MRI) without any structural lesions. All participants, both ESRD patients and healthy controls, underwent T1-weighted imaging, diffusion tensor imaging (DTI), and resting-state functional MRI (rs-fMRI) using the same three-tesla MRI scanner. A structural connectivity matrix was generated using the DTI and DSI programs, and a functional connectivity matrix was created using the rs-fMRI and SPM programs in the CONN toolbox. Multilayer network analysis was conducted based on structural and functional connectivity matrices using BRAPH. Significant differences were observed at the global level in the multilayer network between patients with ESKD and healthy controls. The weighted multiplex participation was lower in patients with ESKD than in healthy controls (0.6454 vs. 0.7212, adjusted p = 0.049). However, other multilayer network measures did not differ. The weighted multiplex participation in the right subcentral gyrus, right opercular part of the inferior frontal gyrus, right occipitotemporal medial lingual gyrus, and right postcentral gyrus in patients with ESKD was lower than that in the corresponding regions in healthy controls (0.6704 vs. 0.8562, 0.8593 vs. 0.9388, 0.7778 vs. 0.8849, and 0.6825 vs. 0.8112; adjusted p < 0.05, respectively).This study demonstrated that the multilayer network combining structural and functional layers in patients with ESKD was different from that in healthy controls. The specific differences in weighted multiplex participation suggest potential disruptions in the integrated communication between different brain regions in these patients.

Multiclass classification of Autism Spectrum Disorder, attention deficit hyperactivity disorder, and typically developed individuals using fMRI functional connectivity analysis

Neurodevelopmental conditions, such as Autism Spectrum Disorder (ASD) and Attention Deficit Hyperactivity Disorder (ADHD), present unique challenges due to overlapping symptoms, making an accurate diagnosis and targeted intervention difficult. Our study employs advanced machine learning techniques to analyze functional magnetic resonance imaging (fMRI) data from individuals with ASD, ADHD, and typically developed (TD) controls, totaling 120 subjects in the study. Leveraging multiclass classification (ML) algorithms, we achieve superior accuracy in distinguishing between ASD, ADHD, and TD groups, surpassing existing benchmarks with an area under the ROC curve near 98%. Our analysis reveals distinct neural signatures associated with ASD and ADHD: individuals with ADHD exhibit altered connectivity patterns of regions involved in attention and impulse control, whereas those with ASD show disruptions in brain regions critical for social and cognitive functions. The observed connectivity patterns, on which the ML classification rests, agree with established diagnostic approaches based on clinical symptoms. Furthermore, complex network analyses highlight differences in brain network integration and segregation among the three groups. Our findings pave the way for refined, ML-enhanced diagnostics in accordance with established practices, offering a promising avenue for developing trustworthy clinical decision-support systems.

Updating functional brain units: Insights far beyond Luria

This paper reviews Luria's model of the three functional units of the brain. To meet this objective, several issues were reviewed: the theory of functional systems and the contributions of phylogenesis and embryogenesis to the brain's functional organization. This review revealed several facts. In the first place, the relationship/integration of basic homeostatic needs with complex forms of behavior. Secondly, the multi-scale hierarchical and distributed organization of the brain and interactions between cells and systems. Thirdly, the phylogenetic role of exaptation, especially in basal ganglia and cerebellum expansion. Finally, the tripartite embryogenetic organization of the brain: rhinic, limbic/paralimbic, and supralimbic zones. Obviously, these principles of brain organization are in contradiction with attempts to establish separate functional brain units. The proposed new model is made up of two large integrated complexes: a primordial-limbic complex (Luria's Unit I) and a telencephalic-cortical complex (Luria's Units II and III). As a result, five functional units were delineated: Unit I. Primordial or preferential (brainstem), for life-support, behavioral modulation, and waking regulation; Unit II. Limbic and paralimbic systems, for emotions and hedonic evaluation (danger and relevance detection and contribution to reward/motivational processing) and the creation of cognitive maps (contextual memory, navigation, and generativity [imagination]); Unit III. Telencephalic-cortical, for sensorimotor and cognitive processing (gnosis, praxis, language, calculation, etc.), semantic and episodic (contextual) memory processing, and multimodal conscious agency; Unit IV. Basal ganglia systems, for behavior selection and reinforcement (reward-oriented behavior); Unit V. Cerebellar systems, for the prediction/anticipation (orthometric supervision) of the outcome of an action. The proposed brain units are nothing more than abstractions within the brain's simultaneous and distributed physiological processes. As function transcends anatomy, the model necessarily involves transition and overlap between structures. Beyond the classic approaches, this review includes information on recent systemic perspectives on functional brain organization. The limitations of this review are discussed.

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.

Awake Craniotomy for Gliomas in the Non-Dominant Right Hemisphere: A Comprehensive Review

Awake surgery has become a standard practice for managing diffuse low-grade gliomas (LGGs), particularly in eloquent brain areas, and is established as a gold standard technique for left-dominant-hemisphere tumors. However, the intraoperative monitoring of functions in the right non-dominant hemisphere (RndH) is often neglected, highlighting the need for a better understanding of neurocognitive testing for complex functions in the right hemisphere. This article aims to comprehensively review the current literature on the benefits of awake craniotomy in gliomas of the non-dominant right hemisphere. A systematic review was conducted using the PubMed and ScienceDirect databases with keywords such as "right hemisphere", "awake surgery", "direct electrical brain stimulation and mapping", and "glioma". The search focused on anatomical and surgical aspects, including indications, tools, and techniques of awake surgery in right cerebral hemisphere gliomas. The literature search identified 74 sources, including original articles, books, monographs, and review articles. Two papers reported large series of language assessment cases in 246 patients undergoing awake surgery with detailed neurological semiology and mapping techniques, while the remaining studies were predominantly neuroradiological and neuroimaging in nature. Awake craniotomy for non-dominant-hemisphere gliomas is an essential tool. The term "non-dominant" should be revised, as this hemisphere contributes significantly to essential cognitive functions in the human brain.

Virtual Reality-Assisted Awake Craniotomy: A Retrospective Study

BACKGROUND

Awake craniotomy (AC) with brain mapping for language and motor functions is often performed for tumors within or adjacent to eloquent brain regions. However, other important functions, such as vision and visuospatial and social cognition, are less frequently mapped, at least partly due to the difficulty of defining tasks suitable for the constrained AC environment.

OBJECTIVE

The aim of this retrospective study was to demonstrate, through illustrative cases, how a virtual reality headset (VRH) equipped with eye tracking can open up new possibilities for the mapping of language, the visual field and complex cognitive functions in the operating room.

METHODS

Virtual reality (VR) tasks performed during 69 ACs were evaluated retrospectively. Three types of VR tasks were used: VR-DO80 for language evaluation, VR-Esterman for visual field assessment and VR-TANGO for the evaluation of visuospatial and social functions.

RESULTS

Surgery was performed on the right hemisphere for 29 of the 69 ACs performed (42.0%). One AC (1.5%) was performed with all three VR tasks, 14 ACs (20.3%) were performed with two VR tasks and 54 ACs (78.3%) were performed with one VR task. The median duration of VRH use per patient was 15.5 min. None of the patients had "VR sickness". Only transitory focal seizures of no consequence and unrelated to VRH use were observed during AC. Patients were able to perform all VR tasks. Eye tracking was functional, enabling the medical team to analyze the patients' attention and exploration of the visual field of the VRH directly.

CONCLUSIONS

This preliminary experiment shows that VR approaches can provide neurosurgeons with a way of investigating various functions, including social cognition during AC. Given the rapid advances in VR technology and the unbelievable sense of immersion provided by the most recent devices, there is a need for ongoing reflection and discussions of the ethical and methodological considerations associated with the use of these advanced technologies in AC and brain mapping procedures.

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.

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.

A systematic review of the use of subcortical intraoperative electrical stimulation mapping for monitoring of executive deficits and neglect: what is the evidence so far?

BACKGROUND

Over the past decade, the functional importance of white matter pathways has been increasingly acknowledged in neurosurgical planning. A method to directly study anatomo-functional correlations is direct electrical stimulation (DES). DES has been widely accepted by neurosurgeons as a reliable tool to minimize the occurrence of permanent postoperative motor, vision, and language deficits. In recent years, DES has also been used for stimulation mapping of other cognitive functions, such as executive functions and visuospatial awareness.

METHODS

The aim of this review is to summarize the evidence so far from DES studies on subcortical pathways that are involved in visuospatial awareness and in the following three executive functions: (1) inhibitory control, (2) working memory, and (3) cognitive flexibility.

RESULTS

Eleven articles reported on intraoperative electrical stimulation of white matter pathways to map the cognitive functions and explicitly clarified which subcortical tract was stimulated. The results indicate that the right SLF-II is involved in visuospatial awareness, the left SLF-III and possibly the right SLF-I are involved in working memory, and the cingulum is involved in cognitive flexibility.

CONCLUSIONS

We were unable to draw any more specific conclusions, nor unequivocally establish the critical involvement of pathways in executive functions or visuospatial awareness due to the heterogeneity of the study types and methods, and the limited number of studies that assessed these relationships. Possible approaches for future research to obtain converging and more definite evidence for the involvement of pathways in specific cognitive functions are discussed.

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.

Augmented reality-assisted roadmaps during periventricular brain surgery

Visualizing major periventricular anatomical landmarks intraoperatively during brain tumor removal is a decisive measure toward preserving such structures and thus the patient's postoperative quality of life. The aim of this study was to describe potential standardized preoperative planning using standard landmarks and procedures and to demonstrate the feasibility of using augmented reality (AR) to assist in performing surgery according to these "roadmaps." The authors have depicted stepwise AR surgical roadmaps applied to periventricular brain surgery with the aim of preserving major cognitive function. In addition to the technological aspects, this study highlights the importance of using emerging technologies as potential tools to integrate information and to identify and visualize landmarks to be used during tumor removal.

Immersive Virtual Reality and Ocular Tracking for Brain Mapping During Awake Surgery: Prospective Evaluation Study

Background

Language mapping during awake brain surgery is currently a standard procedure. However, mapping is rarely performed for other cognitive functions that are important for social interaction, such as visuospatial cognition and nonverbal language, including facial expressions and eye gaze. The main reason for this omission is the lack of tasks that are fully compatible with the restrictive environment of an operating room and awake brain surgery procedures.

Objective

This study aims to evaluate the feasibility and safety of a virtual reality headset equipped with an eye-tracking device that is able to promote an immersive visuospatial and social virtual reality (VR) experience for patients undergoing awake craniotomy.

Methods

We recruited 15 patients with brain tumors near language and/or motor areas. Language mapping was performed with a naming task, DO 80, presented on a computer tablet and then in 2D and 3D via the VRH. Patients were also immersed in a visuospatial and social VR experience.

Results

None of the patients experienced VR sickness, whereas 2 patients had an intraoperative focal seizure without consequence; there was no reason to attribute these seizures to virtual reality headset use. The patients were able to perform the VR tasks. Eye tracking was functional, enabling the medical team to analyze the patients’ attention and exploration of the visual field of the virtual reality headset directly.

Conclusions

We found that it is possible and safe to immerse the patient in an interactive virtual environment during awake brain surgery, paving the way for new VR-based brain mapping procedures.

Trial Registration

ClinicalTrials.gov NCT03010943; https://clinicaltrials.gov/ct2/show/NCT03010943.

Preclinical evidences of aluminum-induced neurotoxicity in hippocampus and pre-frontal cortex of rats exposed to low doses

Aluminum (Al) is a neurotoxicant agent implicated in several behavioral, neuropathological and neurochemical changes associated with cognitive impairments. Nevertheless, mechanisms of damage and safety concentrations are still very discussed. Thus, the main purpose of this study was to investigate whether two aluminum low doses were able to produce deleterious effects on cognition of adult rats, including oxidative stress in hippocampus and prefrontal cortex, two important areas for cognition. For this, thirty adult Wistar rats were divided into three groups: Al1 (8.3 mg/kg/day), Al2 (32 mg/kg/day) and Control (Ultrapure Water), in which all three groups received their solutions containing or not AlCl₃ by intragastric gavage for 60 days. After the experimental period, the short- and long-term memories were assessed by the object recognition test and step-down inhibitory avoidance. After euthanizing, prefrontal cortex and hippocampus samples were dissected for Al levels measurement and evaluation of oxidative biochemistry. Only Al2 increased Al levels in hippocampal parenchyma significantly; both concentrations did not impair short-term memory, while long-term memory was affected in Al1 and Al2. In addition, oxidative stress was observed in prefrontal and hippocampus in Al1 and Al2. Our results indicate that, in a translational perspective, humans are subjected to deleterious effects of Al over cognition even when exposed to low concentrations, by triggering oxidative stress and poor long-term memory performance.

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.

The ventral attention network: the mirror of the language network in the right brain hemisphere

Resting-state functional MRI (RfMRI) analyses have identified two anatomically separable fronto-parietal attention networks in the human brain: a bilateral dorsal attention network and a right-lateralised ventral attention network (VAN). The VAN has been implicated in visuospatial cognition and, thus, potentially in the unilateral spatial neglect associated with right hemisphere lesions. Its parietal, frontal and temporal endpoints are thought to be structurally supported by undefined white matter tracts. We investigated the white matter tract connecting the VAN. We used three approaches to study the structural anatomy of the VAN: (a) independent component analysis on RfMRI (50 subjects), defining the endpoints of the VAN, (b) tractography in the same 50 healthy volunteers, with regions of interest defined by the MNI coordinates of cortical areas involved in the VAN used in a seed-based approach and (c) dissection, by Klingler's method, of 20 right hemispheres, for ex vivo studies of the fibre tracts connecting VAN endpoints. The VAN includes the temporoparietal junction and the ventral frontal cortex. The endpoints of the superior longitudinal fasciculus in its third portion (SLF III) and the arcuate fasciculus (AF) overlap with the VAN endpoints. The SLF III connects the supramarginal gyrus to the ventral portion of the precentral gyrus and the pars opercularis. The AF connects the middle and inferior temporal gyrus and the middle and inferior frontal gyrus. We reconstructed the structural connectivity of the VAN and considered it in the context if the pathophysiology of unilateral neglect and right hemisphere awake brain surgery.

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.

White matter dissection and structural connectivity of the human vertical occipital fasciculus to link vision-associated brain cortex

The vertical occipital fasciculus (VOF) is an association fiber tract coursing vertically at the posterolateral corner of the brain. It is re-evaluated as a major fiber tract to link the dorsal and ventral visual stream. Although previous tractography studies showed the VOF’s cortical projections fall in the dorsal and ventral visual areas, the post-mortem dissection study for the validation remains limited. First, to validate the previous tractography data, we here performed the white matter dissection in post-mortem brains and demonstrated the VOF’s fiber bundles coursing between the V3A/B areas and the posterior fusiform gyrus. Secondly, we analyzed the VOF’s structural connectivity with diffusion tractography to link vision-associated cortical areas of the HCP MMP1.0 atlas, an updated map of the human cerebral cortex. Based on the criteria the VOF courses laterally to the inferior longitudinal fasciculus (ILF) and craniocaudally at the posterolateral corner of the brain, we reconstructed the VOF’s fiber tracts and found the widespread projections to the visual cortex. These findings could suggest a crucial role of VOF in integrating visual information to link the broad visual cortex as well as in connecting the dual visual stream.

Immersing Patients in a Virtual Reality Environment for Brain Mapping During Awake Surgery: Safety Study

BACKGROUND

Brain mapping by direct electrical stimulation during awake craniotomy is now a standard procedure that reduces the risk of permanent neurologic deficits. Virtual reality technology immerses the patient in a virtually controlled, interactive world, offering a unique opportunity to develop innovative tasks for perioperative mapping of complex cognitive functions. The objective of this prospective single-center study was to evaluate the tolerance and safety of a virtual reality headset (VRH) and immersive virtual experiences in patients undergoing awake craniotomy and brain mapping by direct electrical stimulation.

METHODS

The study included 30 patients with a brain tumor near the language area. Language mapping was performed with a naming task, DO 80, presented on a digital tablet and then in two-dimensional and three-dimensional formats through a VRH. During wound closure, different virtual reality experiences were proposed to the patient, offering different types of virtual motion or interaction with an avatar piloted by a neuropsychologist.

RESULTS

Two patients could not use the VRH owing to technical issues. No procedure was aborted, no patient experienced virtual reality sickness and all patients reported they would repeat the procedure. Despite a high rate of intraoperative focal seizures, there was no argument to attribute the seizures to VRH use.

CONCLUSIONS

This study shows that it is possible during awake brain surgery to immerse the patient in a virtual environment and to interact with the patient, opening the field of new brain mapping procedures for complex cognitive functions.

Using a Virtual Reality Social Network During Awake Craniotomy to Map Social Cognition: Prospective Trial

Background

In awake craniotomy, it is possible to temporarily inactivate regions of the brain using direct electrical stimulation, while the patient performs neuropsychological tasks. If the patient shows decreased performance in a given task, the neurosurgeon will not remove these regions, so as to maintain all brain functions.

Objective

The objective of our study was to describe our experience of using a virtual reality (VR) social network during awake craniotomy and discuss its future applications for perioperative mapping of nonverbal language, empathy, and theory of mind.

Methods

This was a single-center, prospective, unblinded trial. During wound closure, different VR experiences with a VR headset were proposed to the patient. This project sought to explore interactions with the neuropsychologist’s avatar in virtual locations using a VR social network as an available experience.

Results

Three patients experienced VR. Despite some limitations due to patient positioning during the operation and the limitation of nonverbal cues inherent to the app, the neuropsychologist, as an avatar, could communicate with the patient and explore gesture communication while wearing a VR headset.

Conclusions

With some improvements, VR social networks can be used in the near future to map social cognition during awake craniotomy.

Trial Registration

ClinicalTrials.gov NCT03010943; https://clinicaltrials.gov/ct2/show/NCT03010943 (Archived at WebCite at http://www.webcitation.org/70CYDil0P)