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

Awake Craniotomy for Astrocytoma in the Left Frontal Lobe Using Augmented Reality Superimposing Tumor and White Matter Tracts: 2-Dimensional Operative Video

Augmented reality (AR) is expected to serve as an assistive intraoperative technology in neurosurgery.1 Awake craniotomy (AC) for gliomas benefits the extent of resection, survival, and postoperative neurofunctional outcomes.2 In AC, it is critical to understand the cortical and subcortical anatomy.3 We describe the use of AR superimposing tumor and deep white matter tracts in AC. A 29-year-old right-handed woman presented to a local hospital after an episode of generalized convulsions. MRI of the head revealed a widely spreading tumor in the left middle frontal gyrus. After a left frontal craniotomy while the patient was asleep, AR was used to indicate the tumor boundary with subcortical fibers including the corticospinal tract, inferior fronto-occipital fasciculus, and cingulate fasciculus. We performed AR-assisted removal of the tumor on the surface of the middle frontal gyrus. On subcortical stimulation (SCS) of the frontal aslant tract and inferior fronto-occipital fasciculus, the patient stopped naming objects in the picture-naming test, while SCS of the left cingulate gyrus caused the patient to mistake colors in the Stroop test. The subcortical fibers identified by AR coincided with the sites of symptom elicitation by SCS. We eventually removed a large part of the tumor. Postoperative MRI confirmed 96.2% resection. The patient was discharged without any new neurological deficits. AC with AR is useful for resection of gliomas in the dominant hemisphere. The patient consented to the procedure and to the publication of her image. The ethics committee of our hospital does not require approval for case reports.

An update on tests used for intraoperative monitoring of cognition during awake craniotomy

PURPOSE

Mapping higher-order cognitive functions during awake brain surgery is important for cognitive preservation which is related to postoperative quality of life. A systematic review from 2018 about neuropsychological tests used during awake craniotomy made clear that until 2017 language was most often monitored and that the other cognitive domains were underexposed (Ruis, J Clin Exp Neuropsychol 40(10):1081-1104, 218). The field of awake craniotomy and cognitive monitoring is however developing rapidly. The aim of the current review is therefore, to investigate whether there is a change in the field towards incorporation of new tests and more complete mapping of (higher-order) cognitive functions.

METHODS

We replicated the systematic search of the study from 2018 in PubMed and Embase from February 2017 to November 2023, yielding 5130 potentially relevant articles. We used the artificial machine learning tool ASReview for screening and included 272 papers that gave a detailed description of the neuropsychological tests used during awake craniotomy.

RESULTS

Comparable to the previous study of 2018, the majority of studies (90.4%) reported tests for assessing language functions (Ruis, J Clin Exp Neuropsychol 40(10):1081-1104, 218). Nevertheless, an increasing number of studies now also describe tests for monitoring visuospatial functions, social cognition, and executive functions.

CONCLUSIONS

Language remains the most extensively tested cognitive domain. However, a broader range of tests are now implemented during awake craniotomy and there are (new developed) tests which received more attention. The rapid development in the field is reflected in the included studies in this review. Nevertheless, for some cognitive domains (e.g., executive functions and memory), there is still a need for developing tests that can be used during awake surgery.

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.

CompreTAP: Feasibility and reliability of a new language comprehension mapping task via preoperative navigated transcranial magnetic stimulation

OBJECTIVE

Stimulation-based language mapping approaches that are used pre- and intraoperatively employ predominantly overt language tasks requiring sufficient language production abilities. Yet, these production-based setups are often not feasible in brain tumor patients with severe expressive aphasia. This pilot study evaluated the feasibility and reliability of a newly developed language comprehension task with preoperative navigated transcranial magnetic stimulation (nTMS).

METHODS

Fifteen healthy subjects and six brain tumor patients with severe expressive aphasia unable to perform classic overt naming tasks underwent preoperative nTMS language mapping based on an auditory single-word Comprehension TAsk for Perioperative mapping (CompreTAP). Comprehension was probed by button-press responses to auditory stimuli, hence not requiring overt language responses. Positive comprehension areas were identified when stimulation elicited an incorrect or delayed button press. Error categories, case-wise cortical error rate distribution and inter-rater reliability between two experienced specialists were examined.

RESULTS

Overall, the new setup showed to be feasible. Comprehension-disruptions induced by nTMS manifested in no responses, delayed or hesitant responses, searching behavior or selection of wrong target items across all patients and controls and could be performed even in patients with severe expressive aphasia. The analysis agreement between both specialists was substantial for classifying comprehension-positive and -negative sites. Extensive left-hemispheric individual cortical comprehension sites were identified for all patients. Apart from one case presenting with transient worsening of aphasic symptoms, pre-existing language deficits did not aggravate if results were used for subsequent surgical planning.

CONCLUSION

Employing this new comprehension-based nTMS setup allowed to identify language relevant cortical sites in all healthy subjects and severely aphasic patients who were thus far precluded from classic production-based mapping. This pilot study, moreover, provides first indications that the CompreTAP mapping results may support the preservation of residual language function if used for subsequent surgical planning.

Improving specificity of stimulation-based language mapping in stuttering glioma patients: A mixed methods serial case study

Objective

Stimulation-based language mapping relies on identifying stimulation-induced language disruptions, which preexisting speech disorders affecting the laryngeal and orofacial speech system can confound. This study ascertained the effects of preexisting stuttering on pre- and intraoperative language mapping to improve the reliability and specificity of established language mapping protocols in the context of speech fluency disorders.

Method

Differentiation-ability of a speech therapist and two experienced nrTMS examiners between stuttering symptoms and stimulation-induced language errors during preoperative mappings were retrospectively compared (05/2018-01/2021). Subsequently, the impact of stuttering on intraoperative mappings was evaluated in all prospective patients (01/2021-12/2022).

Results

In the first part, 4.85 % of 103 glioma patients stuttered. While both examiners had a significant agreement for misclassifying pauses in speech flow and prolongations (Κ ≥ 0.50, p ≤ 0.02, respectively), less experience resulted in more misclassified stuttering symptoms. In one awake surgery case within the second part, stuttering decreased the reliability of intraoperative language mapping.Comparison with Existing Method(s): By thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions, the reliability and proportion of stuttering symptoms falsely attributed to stimulation-induced language network disruptions can be improved. This may increase the consistency and specificity of language mapping results in stuttering glioma patients.

Conclusions

Preexisting stuttering negatively impacted language mapping specificity. Thus, surgical planning and the functional outcome may benefit substantially from thoroughly differentiating speech fluency symptoms from stimulation-induced disruptions by trained specialists.

Technical Aspects of Motor and Language Mapping in Glioma Patients

Gliomas are infiltrative primary brain tumors that often invade functional cortical and subcortical regions, and they mandate individualized brain mapping strategies to avoid postoperative neurological deficits. It is well known that maximal safe resection significantly improves survival, while postoperative deficits minimize the benefits associated with aggressive resections and diminish patients’ quality of life. Although non-invasive imaging tools serve as useful adjuncts, intraoperative stimulation mapping (ISM) is the gold standard for identifying functional cortical and subcortical regions and minimizing morbidity during these challenging resections. Current mapping methods rely on the use of low-frequency and high-frequency stimulation, delivered with monopolar or bipolar probes either directly to the cortical surface or to the subcortical white matter structures. Stimulation effects can be monitored through patient responses during awake mapping procedures and/or with motor-evoked and somatosensory-evoked potentials in patients who are asleep. Depending on the patient’s preoperative status and tumor location and size, neurosurgeons may choose to employ these mapping methods during awake or asleep craniotomies, both of which have their own benefits and challenges. Regardless of which method is used, the goal of intraoperative stimulation is to identify areas of non-functional tissue that can be safely removed to facilitate an approach trajectory to the equator, or center, of the tumor. Recent technological advances have improved ISM’s utility in identifying subcortical structures and minimized the seizure risk associated with cortical stimulation. In this review, we summarize the salient technical aspects of which neurosurgeons should be aware in order to implement intraoperative stimulation mapping effectively and safely during glioma surgery.

Cortical and white matter anatomy relevant for the lateral and superior approaches to resect intraaxial lesions within the frontal lobe

Despite being associated with high-order neurocognitive functions, the frontal lobe plays an important role in core neurological functions, such as motor and language functions. The aim of this study was to present a neurosurgical perspective of the cortical and subcortical anatomy of the frontal lobe in terms of surgical treatment of intraaxial frontal lobe lesions. We also discuss the results of direct brain mapping when awake craniotomy is performed. Ten adult cerebral hemispheres were prepared for white matter dissection according to the Klingler technique. Intraaxial frontal lobe lesions are approached with a superior or lateral trajectory during awake conditions. The highly eloquent cortex within the frontal lobe is identified within the inferior frontal gyrus (IFG) and precentral gyrus. The trajectory of the approach is mainly related to the position of the lesion in relation to the arcuate fascicle/superior longitudinal fascicle complex and ventricular system. Knowledge of the cortical and subcortical anatomy and its function within the frontal lobe is essential for preoperative planning and predicting the risk of immediate and long-term postoperative deficits. This allows surgeons to properly set the extent of the resection and type of approach during preoperative planning.

Cortical mapping in glioma surgery: correlation of fMRI and direct electrical stimulation with Human Connectome Project parcellations

OBJECTIVE

Noninvasive brain mapping with functional MRI (fMRI) and mapping with direct electrical stimulation (DES) are important tools in glioma surgery, but the evidence is inconclusive regarding the sensitivity and specificity of fMRI. The Human Connectome Project (HCP) proposed a new cortical parcellation that has not been thoroughly tested in a clinical setting. The main goal of this study was to evaluate the correlation of fMRI and DES mapping with HCP areas in a clinical setting, and to evaluate the performance of fMRI mapping in motor and language tasks in patients with glioma, using DES as the gold standard.

METHODS

Forty patients with supratentorial gliomas were examined using preoperative fMRI and underwent awake craniotomy with DES. Functional activation maps were visualized on a 3D representation of the cortex, classified according to HCP areas, and compared with surgical mapping.

RESULTS

Functional MRI was successful in identifying language and motor HCP areas in most cases, including novel areas such as 55b and the superior longitudinal fasciculus (SLF). Functional MRI had a sensitivity and specificity of 100% and 71%, respectively, for motor function in HCP area 4. Sensitivity and specificity were different according to the area and fMRI protocol; i.e., semantic protocols performed better in Brodmann area (BA) 55b/peri-sylvian language areas with 100% sensitivity and 20% specificity, and word production protocols in BAs 44 and 45 with 70% sensitivity and 80% specificity. Some compensation patterns could be observed, such as motor activation of the postcentral gyrus in precentral gliomas.

CONCLUSIONS

HCP areas can be detected in clinical scenarios of glioma surgery. These areas appear relatively stable across patients, but compensation patterns seem to differ, allowing occasional resection of activating areas. Newly described areas such as 55b and SLF can act as critical areas in language networks. Surgical planning should account for these parcellations.

Dutch Diagnostic Instrument for Mild Aphasia (DIMA): standardisation and a first clinical application in two brain tumour patients

Brain tumour patients with mild language disturbances are typically underdiagnosed due to lack of sensitive tests leading to negative effects in daily communicative and social life. We aim to develop a Dutch standardised test-battery, the Diagnostic Instrument for Mild Aphasia (DIMA) to detect characteristics of mild aphasia at the main linguistic levels phonology, semantics and (morpho-)syntax in production and comprehension. We designed 4 DIMA subtests: 1) repetition (words, non-words, compounds and sentences), 2) semantic odd-picture-out (objects and actions), 3) sentence completion and 4) sentence judgment (accuracy and reaction time). A normative study was carried out in a healthy Dutch-speaking population (N = 211) divided into groups of gender, age and education. Clinical application of DIMA was demonstrated in two brain tumour patients (glioma and meningioma). Standard language tests were also administered: object naming, verbal fluency (category and letter), and Token Test. Performance was at ceiling on all sub-tests, except semantic odd-picture-out actions, with an effect of age and education on most subtests. Clinical application DIMA: repetition was impaired in both cases. Reaction time in the sentence judgment test (phonology and syntax) was impaired (not accuracy) in one patient. Standard language tests: category fluency was impaired in both cases and object naming in one patient. The Token Test was not able to detect language disturbances in both cases. DIMA seems to be sensitive to capture mild aphasic deficits. DIMA is expected to be of great potential for standard assessment of language functions in patients with also other neurological diseases than brain tumours.

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.

Functional network and structural connections involved in picture naming

We mapped the left hemisphere cortical regions and fiber bundles involved in picture naming in adults by integrating task-based fMRI with dMRI tractography. We showed that a ventral pathway that "maps image and sound to meaning" involves the middle occipital, inferior temporal, superior temporal, inferior frontal gyri, and the temporal pole where a signal exchange is made possible by the inferior fronto-occipital, inferior longitudinal, middle longitudinal, uncinate fasciculi, and the extreme capsule. A dorsal pathway that "maps sound to speech" implicates the inferior temporal, superior temporal, inferior frontal, precentral gyri, and the supplementary motor area where the arcuate fasciculus and the frontal aslant ensure intercommunication. This study provides a neurocognitive model of picture naming and supports the hypothesis that the ventral indirect route passes through the temporal pole. This further supports the idea that the inferior and superior temporal gyri may play pivotal roles within the dual-stream framework of language.

Repeated Awake Surgical Resection(s) for Recurrent Diffuse Low-Grade Gliomas: Why, When, and How to Reoperate?

Early maximal surgical resection is the first treatment in diffuse low-grade glioma (DLGG), because the reduction of tumor volume delays malignant transformation and extends survival. Awake surgery with intraoperative mapping and behavioral monitoring enables to preserve quality of life (QoL). However, because of the infiltrative nature of DLGG, relapse is unavoidable, even after (supra)total resection. Therefore, besides chemotherapy and radiotherapy, the question of reoperation(s) is increasingly raised, especially because patients with DLGG usually enjoy a normal life with long-lasting projects. Here, the purpose is to review the literature in the emerging field of iterative surgeries in DLGG. First, long-term follow-up results showed that patients with DLGG who underwent multiple surgeries had an increased survival (above 17 years) with preservation of QoL. Second, the criteria guiding the decision to reoperate and defining the optimal timing are discussed, mainly based on the dynamic intercommunication between the glioma relapse (including its kinetics and pattern of regrowth) and the reactional cerebral reorganization—i.e., mechanisms underpinning reconfiguration within and across neural networks to enable functional compensation. Third, how to adapt medico-surgical strategy to this individual spatiotemporal brain tumor interplay is detailed, by considering the perpetual changes in connectome. These data support early reoperation in recurrent DLGG, before the onset of symptoms and before malignant transformation. Repeat awake resection(s) should be integrated in a global management including (neo)adjuvant medical treatments, to enhance long-lasting functional and oncological outcomes. The prediction of potential and limitation of neuroplasticity at each step of the disease must be improved to anticipate personalized multistage therapeutic attitudes.

Constant Multi-Tasking With Time Constraint to Preserve Across-Network Dynamics Throughout Awake Surgery for Low-Grade Glioma: A Necessary Step to Enable Patients Resuming an Active Life

Awake surgery for brain gliomas improves resection while minimizing morbidity. Although intraoperative mapping was originally used to preserve motor and language functions, the considerable increase of life expectancy, especially in low-grade glioma, resulted in the need to enhance patients’ long-term quality of life. If the main goal of awake surgery is to resume normal familial and socio-professional activities, preventing hemiparesis and aphasia is not sufficient: cognitive and emotional functions must be considered. To monitor higher-order functions, e.g., executive control, semantics or mentalizing, further tasks were implemented into the operating theater. Beyond this more accurate investigation of function-specific neural networks, a better exploration of the inter-system communication is required. Advances in brain connectomics led to a meta-network perspective of neural processing, which emphasizes the pivotal role of the dynamic interplay between functional circuits to allow complex and flexible, goal-directed behaviors. Constant multi-tasking with time constraint in awake patients may be proposed during intraoperative mapping, since it provides a mirror of the (dys)synchronization within and across neural networks and it improves the sensitivity of behavioral monitoring by increasing cognitive demand throughout the resection. Electrical mapping may hamper the patient to perform several tasks simultaneously whereas he/she is still capable to achieve each task in isolation. Unveiling the meta-network organization during awake mapping by using a more ecological multi-demand testing, more representative of the real-life conditions, constitutes a reliable way to tailor the surgical onco-functional balance based upon the expectations of each patient, enabling him/her to resume an active life with long-lasting projects.

Language assessment in awake brain surgery: the Portuguese adaptation of the Dutch linguistic intraoperative protocol (DuLIP)

Awake brain surgery, combined with neurophysiological evaluation and intraoperative mapping, is one of the preferential lines of treatment when approaching low-grade gliomas. Speech and language assessment is used while applying Direct Electrical Stimulation (DES) and during the resection of a lesion/tumour, as it allows to establish related eloquent areas and optimise the extent of the resection and avoid impairments. Patients need to be assessed pre, intra and post-surgery, but in under resourced countries such as Portugal, there are still no standardised and validated tools to conduct this type of evaluation. To address this need, the tasks of the Dutch Linguistic Intraoperative Protocol (DuLIP) were adapted to European Portuguese, and the resulting materials were standardised for a group of 144 Portuguese participants. For each task, the impact of age, gender and schooling were measured. The resulting Portuguese version of the DuLIP (DuLIP-EP) consists of 17 tasks, including phonological, syntactic, semantic, naming and articulatory tests. No significant differences were found between male and female participants. However, schooling influenced phonological and syntactic fluency, object naming and verb generation. Schooling and age had a significant impact on semantic fluency and reading with semantic odd word out tasks. This is the first contribution to the standardisation of a tool that can be used during an awake brain surgery in Portugal, which includes a new phonological odd word out task that is not currently available in the Dutch version.

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

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

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

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

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

Prosopagnosia following nonlanguage dominant inferior temporal lobe low-grade glioma resection in which the inferior longitudinal fasciculus was disrupted preoperatively: illustrative case

BACKGROUND

Prosopagnosia is a rare neurological condition characterized by the impairment of face perception with preserved visual processing and cognitive functioning and is associated with injury to the fusiform gyrus and inferior longitudinal fasciculus (ILF). Reports of this clinical impairment following resection of right temporal lobe diffuse gliomas in the absence of contralateral injury are exceedingly scarce and not expected as a complication of surgery.

OBSERVATIONS

The authors describe the case of a young female patient found to have an incidental diffuse glioma in the right inferior temporal lobe despite evidence of preoperative ILF disruption by the tumor. Following resection of the lesion, despite the preoperative disruption to the ILF by the tumor, the patient developed prosopagnosia. There was no evidence of contralateral, left-sided ILF injury.

LESSONS

Given the significant functional impairment associated with prosopagnosia, neurosurgeons should be aware of the exceedingly rare possibility of a visual-processing deficit following unilateral and, in this case, right-sided inferior temporal lobe glioma resections. More investigation is needed to determine whether preoperative testing can determine dominance of facial-processing networks for patients with lesions in the right inferior posterior temporooccipital lobe and whether intraoperative mapping could help prevent this complication.

Anatomical aspects of the insula, opercula and peri-insular white matter for a transcortical approach to insular glioma resection

The insula is a lobe located deep in each hemisphere of the brain and is surrounded by eloquent cortical, white matter, and basal ganglia structures. The aim of this study was to provide an anatomical description of the insula and white matter tracts related to surgical treatment of gliomas through a transcortical approach. The study also discusses surgical implications in terms of intraoperative brain mapping. Five adult brains were prepared according to the Klingler technique. Cortical anatomy was evaluated with the naked eye, whereas white matter dissection was performed with the use of a microscope. The widest exposure of the insular surface was noted through the temporal operculum, mainly in zones III and IV according to the Berger-Sanai classification. By going through the pars triangularis in all cases, the anterior insular point and most of zone I were exposed. The narrowest and deepest operating field was observed by going through the parietal operculum. This method provided a suitable approach to zone II, where the corticospinal tract is not covered by the basal ganglia and is exposed just under the superior limiting sulcus. At the subcortical level, the identification of the inferior frontoocipital fasciculus at the level of the limen insulae is critical in terms of preserving the lenticulostriate arteries. Detailed knowledge of the anatomy of the insula and subcortical white matter that is exposed through each operculum is essential in preoperative planning as well as in the intraoperative decision-making process in terms of intraoperative brain mapping.

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.

Balancing task sensitivity with reliability for multimodal language assessments

OBJECTIVE

Intraoperative tasks for awake language mapping are typically selected based on the language tracts that will likely be encountered during tumor resection. However, diminished attention and arousal secondary to perioperative sedatives may reduce a task's usefulness for identifying eloquent cortex. For instance, accuracy in performing select language tasks may be high preoperatively but decline in the operating room. In the present study, the authors sought to identify language tasks that can be performed with high accuracy in both situational contexts so the neurosurgical team can be confident that speech errors committed during awake language mapping result from direct cortical stimulation to eloquent cortex, rather than from poor performance in general.

METHODS

We administered five language tasks to 44 patients: picture naming (PN), text reading (TR), auditory object naming (AN), repetition of 4-syllable words (4SYL), and production of syntactically intact sentences (SYNTAX). Performance was assessed using the 4-point scale of the quick aphasia battery 24 hours preoperatively and intraoperatively. We next determined whether or not accuracy on each task was higher preoperatively than intraoperatively. We also determined whether 1) intraoperative accuracy on a given task predicted intraoperative performance on the other tasks and 2) low preoperative accuracy on a task predicted a decrease in accuracy intraoperatively.

RESULTS

Relative to preoperative accuracy, intraoperative accuracy declined on PN (3.90 vs 3.82, p = 0.0001), 4SYL (3.96 vs 3.91, p = 0.0006), and SYNTAX (3.85 vs 3.67, p = 0.0001) but not on TR (3.96 vs 3.94, p = 0.13) or AN (3.70 vs 3.58, p = 0.058). Intraoperative accuracy on PN and AN independently predicted intraoperative accuracy on the remaining language tasks (p < 0.001 and p < 0.01, respectively). Finally, low preoperative accuracy on SYNTAX predicted a decrease in accuracy on this task intraoperatively (R2 = 0.36, p = 0.00002).

CONCLUSIONS

While TR lacks sensitivity in identifying language deficits at baseline, accuracy on TR is stable across testing settings. Baseline accuracy on the other four of our five language tasks was not predictive of intraoperative performance, signifying the need to repeat language tests prior to stimulation mapping to confirm reliability.

Intraoperative mapping of executive function using electrocorticography for patients with low-grade gliomas

Background

Intraoperative functional mapping with direct electrical stimulation during awake surgery for patients with diffuse low-grade glioma has been used in recent years to optimize the balance between surgical resection and quality of life following surgery. Mapping of executive functions is particularly challenging because of their complex nature, with only a handful of reports published so far. Here, we propose the recording of neural activity directly from the surface of the brain using electrocorticography to map executive functions and demonstrate its feasibility and potential utility.

Methods

To track a neural signature of executive function, we recorded neural activity using electrocorticography during awake surgery from the frontal cortex of three patients judged to have an appearance of diffuse low-grade glioma. Based on existing functional magnetic resonance imaging (fMRI) evidence from healthy participants for the recruitment of areas associated with executive function with increased task demands, we employed a task difficulty manipulation in two counting tasks performed intraoperatively. Following surgery, the data were extracted and analyzed offline to identify increases in broadband high-gamma power with increased task difficulty, equivalent to fMRI findings, as a signature of activity related to executive function.

Results

All three patients performed the tasks well. Data were recorded from five electrode strips, resulting in data from 15 channels overall. Eleven out of the 15 channels (73.3%) showed significant increases in high-gamma power with increased task difficulty, 26.6% of the channels (4/15) showed no change in power, and none of the channels showed power decrease. High-gamma power increases with increased task difficulty were more likely in areas that are within the canonical frontoparietal network template.

Conclusions

These results are the first step toward developing electrocorticography as a tool for mapping of executive function complementarily to direct electrical stimulation to guide resection. Further studies are required to establish this approach for clinical use.

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.

Intraoperative Cognitive Mapping Tasks for Direct Electrical Stimulation in Clinical and Neuroscientific Contexts

Direct electrical stimulation (DES) has been widely applied in both guidance of lesion resection and scientific research; however, the design and selection of intraoperative cognitive mapping tasks have not been updated in a very long time. We introduce updated mapping tasks for language and non-language functions and provide recommendations for optimal design and selection of intraoperative mapping tasks. In addition, with DES becoming more critical in current neuroscientific research, a task design that has not been widely used in DES yet (subtraction and conjunction paradigms) was introduced for more delicate mapping of brain functions especially for research purposes. We also illustrate the importance of designing a common task series for DES and other non-invasive mapping techniques. This review gives practical updated guidelines for advanced application of DES in clinical and neuroscientific research.

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

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

Return to Work Following Surgery for Incidental Diffuse Low-Grade Glioma: A Prospective Series With 74 Patients

BACKGROUND

Therapeutic strategy concerning incidental low-grade glioma (ILGG) is still debated. Early "prophylactic" surgery has been proposed in asymptomatic patients with favorable neurological and oncological outcomes.

OBJECTIVE

To assess postoperative ability to resume employment following awake surgery in asymptomatic ILGG patients. To assess extent of resection (EOR), timeline for adjuvant oncological treatment, and survival.

METHODS

A total of 74 patients with ILGG who underwent awake surgery with intraoperative mapping were prospectively included, with a minimum follow-up of 12 mo. All clinicoradiological data were collected, and statistical correlations with return to work (RTW) were performed.

RESULTS

A total of 66 patients (97.1%) among 68 patients with preoperative professional activities resumed their employment including 62 (91.2%) within 12 mo. Mean time before RTW was 6.8 mo (median: 6 mo, range: 1-36). Two patients experienced seizure-related legal issues impacting their RTW. Clinicoradiological features did not correlate with RTW apart from postoperative seizures (P = .02). Mean EOR was 95.7%. A total of 43 patients (58.1%) underwent supratotal/total resections. All patients recovered from transient deficits at 3 mo. No patients received consecutive adjuvant treatment. A total of 24 patients (32.4%) were reoperated, 24 patients received chemotherapy, and 7 patients (9.5%) received radiotherapy, on average 73.1 mo after surgery. Mean follow-up was 67 mo (range 12-240). Four patients (5.4%) died during the follow-up.

CONCLUSION

We observed a high rate of RTW (97.1%, including 91.2% within 12 mo) after awake surgery in ILGG patients. Delayed resumption of work was due to employer not clearing them for RTW, personal choice, and, in rare occasions, related to seizures.

Preoperative Applications of Navigated Transcranial Magnetic Stimulation

Preoperative mapping of cortical structures prior to neurosurgical intervention can provide a roadmap of the brain with which neurosurgeons can navigate critical cortical structures. In patients undergoing surgery for brain tumors, preoperative mapping allows for improved operative planning, patient risk stratification, and personalized preoperative patient counseling. Navigated transcranial magnetic stimulation (nTMS) is one modality that allows for highly accurate, image-guided, non-invasive stimulation of the brain, thus allowing for differentiation between eloquent and non-eloquent cortical regions. Motor mapping is the best validated application of nTMS, yielding reliable maps with an accuracy similar to intraoperative cortical mapping. Language mapping is also commonly performed, although nTMS language maps are not as highly concordant with direct intraoperative cortical stimulation maps as nTMS motor maps. Additionally, nTMS has been used to localize cortical regions involved in other functions such as facial recognition, calculation, higher-order motor processing, and visuospatial orientation. In this review, we evaluate the growing literature on the applications of nTMS in the preoperative setting. First, we analyze the evidence in support of the most common clinical applications. Then we identify usages that show promise but require further validation. We also discuss developing nTMS techniques that are still in the experimental stage, such as the use of nTMS to enhance postoperative recovery. Finally, we highlight practical considerations when utilizing nTMS and, importantly, its safety profile in neurosurgical patients. In so doing, we aim to provide a comprehensive review of the role of nTMS in the neurosurgical management of a patient with a brain tumor.

Newer Paradigms in Language Neurobiology

The field of language research has seen tremendous progress in the last two decades. Advances in neuro-imaging and stimulation mapping have changed the way we conceive the neural basis of speech and language processing. In the past, the Wernicke-Lichtheim model was the most influential model explaining the neuro-anatomical basis of language. More recently, the concept of dual stream language processing has emerged, wherein separate dorsal and ventral networks are synergistically involved in phonological (sound to articulation) and semantic (sound to meaning) processing respectively. In this review article, we highlight new insights and approaches to the neurobiology of language, across different aspects of language processing like perception, comprehension, production, hemisphere lateralization, role of subcortical structures and effect of damage to language networks.

Functional Mapping for Glioma Surgery, Part 2: Intraoperative Mapping Tools

Intraoperative functional mapping of tumor and peri-tumor tissue is a well-established technique for avoiding permanent neurologic deficits and maximizing extent of resection. Motor, language, and other cognitive domains may be assessed with intraoperative tasks. This article describes techniques used for motor and language mapping including awake mapping considerations in addition to less traditional intraoperative testing paradigms for cognition. It also discusses complications associated with mapping and insights into complication avoidance.

Management of Diffuse Low-Grade Glioma: The Renaissance of Robust Evidence

The surgical management of diffuse low-grade gliomas (DLGGs) has undergone a paradigm shift toward striving for maximal safe resection when feasible. While extensive observational data supports this transition, unbiased evidence in the form of high quality randomized-controlled trials (RCTs) is lacking. Furthermore, despite a high volume of molecular, genetic, and imaging data, the field of neuro-oncology lacks personalized care algorithms for individuals with DLGGs based on a robust foundation of evidence. In this manuscript, we (1) discuss the logistical and philosophical challenges hindering the development of surgical RCTs for DLGGs, (2) highlight the potential impact of well-designed international prospective observational registries, (3) discuss ways in which cutting-edge computational techniques can be harnessed to generate maximal insight from high volumes of multi-faceted data, and (4) outline a comprehensive plan of action that will enable a multi-disciplinary approach to future DLGG management, integrating advances in clinical medicine, basic molecular research and large-scale data mining.

Subjective experience, cognitive functioning and trauma level of patients undergoing awake craniotomy due to brain tumor - Preliminary study

BACKUP AND OBJECTIVE

Awake craniotomy (AC) for brain tumors, when the patient is conscious during the operation, allows to reduce the risk of motor disability and aphasia, however, it may be a source of extreme stress. The aim of our study was to examine the patients' subjective experience of the surgery including the level of psychological trauma and cognitive functioning.

METHOD

Eighteen patients operated due to brain tumor were enrolled in this study. The Essener Trauma-Inventory Questionnaire and the Addenbrooke's Cognitive Examination (ACE III) were administrated. The patients' experience with awake craniotomy was evaluated with a qualitative descriptive survey.

RESULTS

All patients remembered the intraoperative neuropsychological examination and several sensations like: drilling, cold, head clamp fixation or having eyes covered. In most of the patients the postoperative psychological trauma experience did not reach the clinical level. The ACE III postoperative scores revealed partial cognitive deficits with the lowest scores in memory and word fluency domains. Slight amnestic aphasia was observed postoperatively only in two patients.

CONCLUSIONS

Awake craniotomy for resection of brain tumors is well-tolerated by patients and does not cause significant psychological trauma. Nonetheless, anxiety about the procedure warrants further study and individualized neuropsychological care is needed for the emotional preparation of the patient.

Functional Mapping before and after Low-Grade Glioma Surgery: A New Way to Decipher Various Spatiotemporal Patterns of Individual Neuroplastic Potential in Brain Tumor Patients

Intraoperative direct electrostimulation mapping (DEM) is currently the gold-standard for glioma surgery, since functional-based resection allows an optimization of the onco-functional balance (increased resection with preserved quality of life). Besides intrasurgical awake mapping of conation, cognition, and behavior, preoperative mapping by means of functional neuroimaging (FNI) and transcranial magnetic stimulation (TMS) has increasingly been utilized for surgical selection and planning. However, because these techniques suffer from several limitations, particularly for direct functional mapping of subcortical white matter pathways, DEM remains crucial to map neural connectivity. On the other hand, non-invasive FNI and TMS can be repeated before and after surgical resection(s), enabling longitudinal investigation of brain reorganization, especially in slow-growing tumors like low-grade gliomas. Indeed, these neoplasms generate neuroplastic phenomena in patients with usually no or only slight neurological deficits at diagnosis, despite gliomas involving the so-called "eloquent" structures. Here, data gained from perioperative FNI/TMS mapping methods are reviewed, in order to decipher mechanisms underpinning functional cerebral reshaping induced by the tumor and its possible relapse, (re)operation(s), and postoperative rehabilitation. Heterogeneous spatiotemporal patterns of rearrangement across patients and in a single patient over time have been evidenced, with structural changes as well as modifications of intra-hemispheric (in the ipsi-lesional and/or contra-lesional hemisphere) and inter-hemispheric functional connectivity. Such various fingerprints of neural reconfiguration were correlated to different levels of cognitive compensation. Serial multimodal studies exploring neuroplasticity might lead to new management strategies based upon multistage therapeutic approaches adapted to the individual profile of functional reallocation.

Language mapping: A systematic review of protocols that evaluate linguistic functions in awake surgery

Nowadays, numerous neuropsychological tests are available for multidisciplinary teams to perform awake brain surgery but none-or very few-of them constitutes a mandatory prerequisite. No consensus has been reached about the choice of intraoperative tests, which can be relatively simple for certain primary functions, but can be much more difficult for high-level cognitive functions. This review aims to give an overview about the assessment of language during awake brain surgery in adults and focus on the analysis of the different language protocols that have been published, to compile the most used standardized tests that evaluate different linguistic cognitive processes. We performed a systematic review about awake brain surgery studies that mentioned a specific test or protocol for assessing language in adults from the last 15 years. The search yielded 3,504 articles. 120 studies reported a linguistic protocol or test. This review allowed to obtain a defined neuropsychological picture of the essential tasks that a linguistic protocol in awake surgery should compile. This review will help clinicians in selecting tasks for monitoring cognition during awake brain surgery as well as contributes to enlighten the efficacy of linguistics protocols in order to minimize language deficits in awake surgery.

Standard awake surgery versus hypnosis aided awake surgery for the management of high grade gliomas: A non-randomized cohort comparison controlled trial

Hypnosis could extend the time of Intraoperative Neuropsychological Testing and Brain Mapping in Awake Surgery. A clinical validation for the Hypnosis aided AS (HAs) is still ongoing and further evidences are required. The objective of the present study is to compare two homogeneous cohorts of patients undergoing AS, the first with the aid of the hypnosis and the second according to a standard AS (SAs) protocols. The clinical, radiological and surgical data of two comparable procedures cohorts were retrospectively examined for the present study. All surgeries in Group A were performed with a HAs protocol. Procedures belonging to Group B were performed with a SAs protocol. Endpoints: to compare 1. Incidence of complications in the immediate postoperative period, 2. Clinical and neurological status in the immediate postoperative period and 30 days after surgery, 3. Duration of surgical interventions, 4. Extent of Resection (EOR). The final cohort is composed of 15 procedures; 6 belonging to Group A and 9 to Group B. The different methods outline statistically comparable results from the clinical (Neurological outcomes) both in the postoperative period and one month after surgery and from the surgical point of view (comparable EOR). The incidence of complications is comparable either. The duration of the procedures was significantly longer in HAs group. Hypnosis is a promising approach to increasing the duration of intraoperative "testability" of patients at the price of a longer operative time. A specific professional is needed to induce hypnosis in the difficult intraoperative setting.

Italian consensus and recommendations on diagnosis and treatment of low-grade gliomas. An intersociety (SINch/AINO/SIN) document

In 2018, the SINch (Italian Society of Neurosurgery) Neuro-Oncology Section, AINO (Italian Association of Neuro-Oncology) and SIN (Italian Association of Neurology) Neuro-Oncology Section formed a collaborative Task Force to look at the diagnosis and treatment of low-grade gliomas (LGGs). The Task Force included neurologists, neurosurgeons, neuro-oncologists, pathologists, radiologists, radiation oncologists, medical oncologists, a neuropsychologist and a methodologist. For operational purposes, the Task Force was divided into five Working Groups: diagnosis, surgical treatment, adjuvant treatments, supportive therapies, and follow-up. The resulting guidance document is based on the available evidence and provides recommendations on diagnosis and treatment of LGG patients, considering all aspects of patient care along their disease trajectory.

Neuropsychological management of the awake patient surgery: A protocol based on 3-year experience with glial tumors

INTRODUCTION

Glial brain tumours usually require neurosurgical treatment and they are associated with cognitive, emotional and behavioural impairments. Awake intraoperative brain mapping is the gold standard technique used to optimize the onco-functional balance. Neuropsychological assessment and intervention have relevance in this type of procedures. Currently, there is a lack of protocolled structure for the neuropsychological intervention being able to satisfy patient needs.

METHOD

A retrospective descriptive study of 52 patients was performed, all of them with a diagnosis of glial tumour. The structure of the protocol developed in our centre is reported, also data of neuropsychological evaluation, comparing baseline performance with both immediate posterior performance, and long term performance.

RESULTS

We describe our experience in each step of the intervention, highlighting the development of eight neurocognitive protocols for intraoperative brain mapping. The results of the neuropsychological examination objectify deficits in the immediate after surgery assessment which are reduced in the long-term assessment.

CONCLUSIONS

We emphasize the need of providing and structuring the cognitive and emotional aspects of patients suffering from any pathology that entails acquired brain damage in hospital environment. This type of approach is aimed at increasing the quality of life of cancer patients by structuring and optimizing tasks during their surgical intervention and attending to the neuropsychological difficulties they suffer.

Effects of supra-total resection in neurocognitive and oncological outcome of high-grade gliomas comparing asleep and awake surgery

PURPOSE

Awake surgery is an established technique for resection of low-grade gliomas, while its possible benefit for resection of high-grade gliomas (HGGs) needs further confirmations. This retrospective study aims to compare overall survival, extent of resection (EOR) and cognitive outcome in two groups of HGGs patients submitted to asleep or awake surgery.

METHODS

Thirty-three patients submitted to Gross Total Resection of contrast-enhancing area of HGGs were divided in two homogeneous groups: awake (AWg; N = 16) and asleep surgery (ASg; N = 17). All patients underwent to an extensive neuropsychological assessment before surgery (time_1), 1-week (time_2) and 4-months (time_3) after surgery. We performed analyses to assess differences in cognitive performances between groups, cognitive outcomes in each group and EOR. A comparison of overall survival (OS) between the two groups was conducted.

RESULTS

Statistical analyses showed no differences between groups at time_2 and time_3 in each cognitive domain, excluding selective attention that resulted higher in the AWg before surgery. Regarding cognitive outcomes, we found a reversible worsening of memory and constructional praxis, and a significant recovery at time_3, similar for both groups. Assessment of time_3 in respect to time_1 never showed differences (all ps > .074). Moreover we found a significant lower level of tumor infiltration after surgery for AWg (p < .05), with an influence on OS (p < .05). Indeed, patients of AWg showed a significant longer OS in comparison to those in the ASg (p < .01). This result was confirmed even considering only wildtype Glioblastoma (p < .05).

CONCLUSION

These results indicate that awake surgery, and in general a supra-total resection of enhancing area, can improve OS in HGGs patients, preserving neuro-cognitive profile and quality of life.

The challenge of overcoming the language barrier for brain tumor awake surgery in migrants: a feasibility study in five patient cases

OBJECTIVE

To assess the feasibility of awake surgery for a brain tumor in a population of non-French-speaking migrants in Paris, France.

METHODS

The Lariboisière database of awake surgeries was retrospectively reviewed, from the first case in 2011 up to July 2018. Inclusion criteria were patients being migrated in France during their adulthood, patients being unable to speak neither French nor English. Clinical and radiological data were collected from the electronic medical charts.

RESULTS

Five patients fulfilled inclusion criteria. Pathological diagnosis included three glioma, one meningioma, and one melanoma metastasis. The standard awake protocol of our center was followed as usual, with the additional involvement of an interpreter at each step. In the five cases, the awake procedure allowed the surgeon to tailor the resection according to functional boundaries. Resections were complete in three cases and subtotal in two cases. No neurological deficits were observed. All patients returned to their preoperative socio-professional status.

CONCLUSIONS

Awake surgery for a brain tumor can be offered to migrants, in spite of the poor verbal communication between the patient and the caring staff. A team dedicated to awake surgery and including an interpreter is the key to successfully overcome the language barrier, before, during, and after the surgery.

A Connectomic Atlas of the Human Cerebrum-Chapter 12: Tractographic Description of the Middle Longitudinal Fasciculus

The middle longitudinal fasciculus (MdLF) is a small and somewhat controversial white matter tract of the human cerebrum, confined to the posterior superior temporal region from which it courses posteriorly to connect at the occipital-parietal interface. The tract appears to be involved in language processing as well as auditory organization and localization, while sub-serving other higher level cognitive functions that have yet to be fully elucidated. Little is known about the specific, interparcellation connections that integrate to form the MdLF. Utilizing diffusion spectrum magnetic resonance imaging tractography coupled with the human cortex parcellation data presented earlier in this supplement, we aim to describe the macro-connectome of the MdLF in relation to the linked parcellations present within the human cortex. The purpose of this study is to present this information in an indexed, illustrated, and tractographically aided series of figures and tables for anatomic and clinical reference.

Mapping critical cortical hubs and white matter pathways by direct electrical stimulation: an original functional atlas of the human brain

OBJECTIVE

The structural and functional organization of brain networks subserving basic daily activities (i.e. language, visuo-spatial cognition, movement, semantics, etc.) are not completely understood to date. Here, we report the first probabilistic cortical and subcortical atlas of critical structures mediating human brain functions based on direct electrical stimulation (DES), a well-validated tool for the exploration of cerebral processing and for performing safe surgical interventions in eloquent areas.

METHODS

We collected 1162 cortical and 659 subcortical DES responses during testing of 16 functional domains in 256 patients undergoing awake surgery. Spatial coordinates for each functional response were calculated, and probability distributions for the entire patient cohort were mapped onto a standardized three-dimensional brain template using a multinomial statistical analysis. In addition, matching analyses were performed against prior established anatomy-based cortical and white matter (WM) atlases.

RESULTS

The probabilistic maps for each functional domain were provided. The topographical analysis demonstrated a wide spatial distribution of cortical functional responses, while subcortical responses were more restricted, localizing to known WM pathways. These DES-derived data showed reliable matching with existing cortical and WM atlases as well as recent neuroimaging and neurophysiological data.

CONCLUSIONS

We present the first integrated and comprehensive cortical-subcortical atlas of structures essential for humans' neural functions based on highly-specific DES mapping during real-time neuropsychological testing. This novel atlas can serve as a complementary tool for neuroscientists, along with data obtained from other modalities, to improve and refine our understanding of the functional anatomy of critical brain networks.

Direct electrical stimulation mapping of cognitive functions in the human brain

Direct electrical stimulation (DES) is a well-established clinical tool for mapping cognitive functions while patients are undergoing awake neurosurgery or invasive long-term monitoring to identify epileptogenic tissue. Despite the proliferation of a range of invasive and noninvasive methods for mapping sensory, motor and cognitive processes in the human brain, DES remains the clinical gold standard for establishing the margins of brain tissue that can be safely removed while avoiding long-term neurological deficits. In parallel, and principally over the last two decades, DES has emerged as a powerful scientific tool for testing hypotheses of brain organization and mechanistic hypotheses of cognitive function. DES can cause transient "lesions" and thus can support causal inferences about the necessity of stimulated brain regions for specific functions, as well as the separability of sensory, motor and cognitive processes. This Special Issue of Cognitive Neuropsychology emphasizes the use of DES as a research tool to advance understanding of normal brain organization and function.

Integrated datasets of normalized brain with functional localization using intra-operative electrical stimulation

PURPOSE

The purpose of this study was to transform brain mapping data into a digitized intra-operative MRI and integrated brain function dataset for predictive glioma surgery considering tumor resection volume, as well as the intra-operative and postoperative complication rates.

METHODS

Brain function data were transformed into digitized localizations on a normalized brain using a modified electric stimulus probe after brain mapping. This normalized brain image with functional information was then projected onto individual patient's brain images including predictive brain function data.

RESULTS

Log data were successfully acquired using a medical device integrated into intra-operative MR images, and digitized brain function was converted to a normalized brain data format in 13 cases. For the electrical stimulation positions in which patients showed speech arrest (SA), speech impairment (SI), motor and sensory responses during cortical mapping processes in awake craniotomy, the data were tagged, and the testing task and electric current for the stimulus were recorded. There were 13 SA, 7 SI, 8 motor and 4 sensory responses (32 responses) in total. After evaluation of transformation accuracy in 3 subjects, the first transformation from intra- to pre-operative MRI using non-rigid registration was calculated as 2.6 ± 1.5 and 2.1 ± 0.9 mm, examining neighboring sulci on the electro-stimulator position and the cortex surface near each tumor, respectively; the second transformation from pre-operative to normalized brain was 1.7 ± 0.8 and 1.4 ± 0.5 mm, respectively, representing acceptable accuracy.

CONCLUSION

This image integration and transformation method for brain normalization should facilitate practical intra-operative brain mapping. In the future, this method may be helpful for pre-operatively or intra-operatively predicting brain function.

A valid alternative for in-person language assessments in brain tumor patients: feasibility and validity measures of the new TeleLanguage test

BACKGROUND

Although language deficits after awake brain surgery are usually milder than post-stroke, postoperative language assessments are needed to identify these. Follow-up of brain tumor patients in certain geographical regions can be difficult when most patients are not local and come from afar. We developed a short telephone-based test for pre- and postoperative language assessments.

METHODS

The development of the TeleLanguage Test was based on the Dutch Linguistic Intraoperative Protocol and existing standardized English batteries. Two parallel versions were composed and tested in healthy native English speakers. Subsequently, the TeleLanguage Test was administered in a group of 14 tumor patients before surgery and at 1 week, 1 month, and 3 months after surgery. The test includes auditory comprehension, repetition, semantic selection, sentence or story completion, verbal naming, and fluency tests. It takes less than 20 minutes to administer.

RESULTS

Healthy participants had no difficulty performing any of the language tests via the phone, attesting to the feasibility of a phone assessment. In the patient group, all TeleLanguage test scores significantly declined shortly after surgery with a recovery to preoperative levels at 3 months postsurgery for naming and fluency tasks and a recovery to normal levels for the other language tasks. Analysis of the in-person language assessments (until 1 month) revealed a similar profile.

CONCLUSION

The use of the TeleLanguage battery to conduct language assessments from afar can provide convenience, might optimize patient care, and enables longitudinal clinical research. The TeleLanguage is a valid tool for various clinical and scientific purposes.

Brain Mapping as Helpful Tool in Brain Glioma Surgical Treatment-Toward the "Perfect Surgery"?

Gliomas are the most common primary malignant brain tumours in adults, representing nearly 80%, with poor prognosis in their high-grade forms. Several variables positively affect the prognosis of patients with high-grade glioma: young age, tumour location, radiological features, recurrence, and the opportunity to perform post-operative adjuvant therapy. Low-grade gliomas are slow-growing brain neoplasms of adolescence and young-adulthood, preferentially involving functional areas, particularly the eloquent ones. It has been demonstrated that early surgery and higher extent rate ensure overall longer survival time regardless of tumour grading, but nowadays, functional preservation that is as complete as possible is imperative. To achieve the best surgical results, along with the best functional results, intraoperative mapping and monitoring of brain functions, as well as different anaesthesiology protocols for awake surgery are nowadays being widely adopted. We report on our experience at our institution with 28 patients affected by malignant brain tumours who underwent brain mapping-aided surgical resection of neoplasm: 20 patients underwent awake surgical resection and 8 patients underwent asleep surgical resection. An analysis of the results and a review of the literature has been performed.