Postoperative Language Deficits Research Articles

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.

Experience in awake glioma surgery in a South American center. Correlation between intraoperative evaluation, extent of resection and functional outcomes

IntroductionGliomas are the second most frequent primary brain tumors. Surgical resection remains a crucial part of treatment, as well as maximum preservation of neurological function. For this reason awake surgery has an important role.The objectives of this article are to present our experience with awake surgery for gliomas in a South American center and to analyze how intraoperative functional findings may influence the extent of resection and neurological outcomes. Materials and methodsRetrospective single center study of a cohort of adult patients undergoing awake surgery for brain glioma, by the same neurosurgeon, between 2012 and 2022 in the city of Buenos Aires, Argentina. ResultsA total of 71 patients were included (mean age 34 years, 62% males). Seventy seven percent of tumors were low grade, with average extent of resection reaching 94% of preoperative volumetric assessment. At six months follow up, 81.7% of patients presented no motor or language deficit.Further analysis showed that having a positive mapping did not have a negative impact in the extent of resection, but was associated with short term postoperative motor and language deficits, among other variables, with later improvement. ConclusionAwake surgery for gliomas is a safe procedure, with the proper training. In this study it was observed that guiding the resection by negative mapping did not worsen the results and that positive subcortical mapping correlated with short term postoperative neurological deficits with posterior improvement within six months in most cases.

Integrating direct electrical brain stimulation with the human connectome.

Neurological and neurodevelopmental conditions are a major public health concern for which new therapies are urgently needed. The development of effective therapies relies on the precise mapping of the neural substrates causally involved in behaviour generation. Direct electrical stimulation (DES) performed during cognitive and neurological monitoring in awake surgery is currently considered the gold standard for the causal mapping of brain functions. However, DES is limited by the focal nature of the stimulation sites, hampering a real holistic exploration of human brain functions at the network level. We used 4137 DES points derived from 612 glioma patients in combination with human connectome data-resting-state functional MRI, n = 1000 and diffusion weighted imaging, n = 284-to provide a multimodal description of the causal macroscale functional networks subtending 12 distinct behavioural domains. To probe the validity of our procedure, we (i) compared the network topographies of healthy and clinical populations; (ii) tested the predictive capacity of DES-derived networks; (iii) quantified the coupling between structural and functional connectivity; and (iv) built a multivariate model able to quantify single subject deviations from a normative population. Lastly, we probed the translational potential of DES-derived functional networks by testing their specificity and sensitivity in identifying critical neuromodulation targets and neural substrates associated with postoperative language deficits. The combination of DES and human connectome data resulted in an average 29.4-fold increase in whole brain coverage compared to DES alone. DES-derived functional networks are predictive of future stimulation points (97.8% accuracy) and strongly supported by the anatomical connectivity of subcortical stimulations. We did not observe any significant topographical differences between the patients and the healthy population at both group and single subject level. Showcasing concrete clinical applications, we found that DES-derived functional networks overlap with effective neuromodulation targets across several functional domains, show a high degree of specificity when tested with the intracranial stimulation points of a different stimulation technique and can be used effectively to characterize postoperative behavioural deficits. The integration of DES with the human connectome fundamentally advances the quality of the functional mapping provided by DES or functional imaging alone. DES-derived functional networks can reliably predict future stimulation points, have a strong correspondence with the underlying white matter and can be used for patient specific functional mapping. Possible applications range from psychiatry and neurology to neuropsychology, neurosurgery and neurorehabilitation.

NIMG-63. GAMMA-BAND MODULATIONS OF ELECTROCORTICOGRAM (ECOG) INDUCED BY COGNITIVE-LINGUISTIC TASKS DURING AWAKE CRANIOTOMY FOR FEASIBLE FUNCTIONAL LANGUAGE MAPPING

Abstract INTRODUCTION Intraoperative functional language mapping has uncertainty in predicting language function and post-surgical outcomes. We study the feasibility of functional mapping using electrocorticogram (ECoG) gamma-band modulations induced by linguistic tasks having different complexity levels. METHODS Five subjects with left temporal lobe glioma underwent resection involving awake language mapping using a 4x8 ECoG electrode grid. A MATLAB/Simulink based real-time software system was used to map task-induced gamma-band modulations as 2D heat maps. Tasks included verbally responding to single word/tone categorization; object, action, written descriptive and auditory naming respectively. Auditory stimuli were provided during word/tone categorization (duration 300~500ms) and auditory naming tasks ( &amp;gt; 1s). Other tasks provided visual stimuli (line drawings or written phrases). Bipolar DCS (2~6 mA, 60Hz, 2s) was applied at different electrode pairs while repeating the naming tasks. RESULTS Cortical regions activated by word stimuli and the auditory naming task were similar; superior, middle temporal gyri (STG, MTG). Visual naming tasks modulated posterior MTG (pMTG) and STG (written naming). Reproducible speech arrests occurred during different naming tasks while stimulating specific electrode pairs, even though not all electrodes had strong task-specific activations. Considerable inter-personal variability of language areas identified with DCS was observed, despite the similarity of task-specific gamma-band modulated regions across subjects. Post-operative decline in language score was observed in one subject, with resection boundary covering gamma modulated regions during auditory processing tasks but no DCS identified region. CONCLUSION Intraoperative language mapping guided by gamma-band ECoG modulations induced by simple word/tone categorization task exhibited similar patterns to more complex naming tasks, suggesting this task may be a viable approach to localize functional cortex, especially in patients unable to reliably perform more difficult paradigms. Utilizing this method in conjunction with DCS mapping guided by visual naming tasks, eloquent cortical language areas may be better preserved reducing post-operative language deficits.

Structural connectome combining DTI features predicts postoperative language decline and its recovery in glioma patients.

A decline in language function is a common complication after glioma surgery, affecting patients' quality of life and survival. This study predicts the postoperative decline in language function and whether it can be recovered based on the preoperative white matter structural network. Eighty-one right-handed patients with glioma involving the left hemisphere were retrospectively included. Their language function was assessed using the Western Aphasia Battery before and 1 week and 3 months after surgery. Structural connectome combining DTI features was selected to predict postoperative language decline and recovery. Nested cross-validation was used to optimize the models, evaluate the prediction performance of the models, and identify the most predictive features. Five, seven, and seven features were finally selected as the predictive features in each model and used to establish predictive models for postoperative language decline (1 week after surgery), long-term language decline (3 months after surgery), and language recovery, respectively. The overall accuracy of the three models in nested cross-validation and overall area under the receiver operating characteristic curve were 0.840, 0.790, and 0.867, and 0.841, 0.778, and 0.901, respectively. We used machine learning algorithms to establish models to predict whether the language function of glioma patients will decline after surgery and whether postoperative language deficit can recover, which may help improve the development of treatment strategies. The difference in features in the non-language decline or the language recovery group may reflect the structural basis for the protection and compensation of language function in gliomas. Models can predict the postoperative language decline and whether it can recover in glioma patients, possibly improving the development of treatment strategies. The difference in selected features may reflect the structural basis for the protection and compensation of language function. • Structural connectome combining diffusion tensor imaging features predicted glioma patients' language decline after surgery. • Structural connectome combining diffusion tensor imaging features predicted language recovery of glioma patients with postoperative language disorder. • Diffusion tensor imaging and connectome features related to language function changes imply plastic brain regions and connections.

450 A Shared Cortical Language Network for Multimodal Naming

INTRODUCTION: Surgical resections for epilepsy or neoplasms often result in naming deficits. While various brain regions are hypothesized to support separable processes, the language network and its functional mapping to naming remain unclear. However, such knowledge could improve the localization of critical brain regions to preserve language function. METHODS: Data were obtained from epilepsy patients who underwent invasive electrophysiology. Recordings were acquired during three cued-naming tasks using pictures (n = 120), auditory descriptions (n = 82), and orthographic descriptions (n = 68). High-gamma power (65-115Hz) was used to measure activity, and group-level activity was estimated using surface-based mixed-effects multilevel analysis. RESULTS: Analyses showed left-lateralized heteromodal activity in the inferior frontal gyrus (IFG), the middle fusiform gyrus (mFus), and the intraparietal sulcus (IPS) following sensory processing. Activation of mFus peaked 150ms before stimulus offset for auditory (15.2%, p &lt; 10-6) and orthographic (21.4%, p &lt; 10-6) naming and 350ms after picture onset (39.0%, p &lt; 10-6) for visual naming. IPS activation peaked just before stimulus offset for auditory (38.1%, p = 7.7*10-5) and orthographic (27.5%, p = 0.008) naming and 450ms following picture onset (43.0%, p &lt; 10-6) for visual naming. IFG activation peaked just before stimulus offset for auditory (30.1%, p &lt; 10-6) and orthographic (40.1%, p = 10-6) naming and 500ms after picture onset (36.4%, p &lt; 10-6) for visual naming. The left posterior middle temporal gyrus (pMTG) showed heteromodal activity for auditory and orthographic but not visual stimuli with peak activation occurring before convergence of all tasks 250ms before stimulus offset (auditory = 34.1%, p &lt; 10-6;orthographic = 25.5%, p = 0.0035). CONCLUSIONS: These results reveal a heteromodal network of IFG, mFus, and IPS supporting lexical access. Our findings also implicate the role of pMTG in phonological access. Altogether, this work characterizes the roles of key regions within language networks, which could influence surgical approaches to minimize postoperative language deficits.

Critical role of the ventral temporal lobe in naming.

Lexical retrieval deficits are characteristic of a variety of different neurological disorders. However, the exact substrates responsible for this are not known. We studied a large cohort of patients undergoing surgery in the dominant temporal lobe for medically intractable epilepsy (n= 95) to localize brain regions that were associated with anomia. We performed a multivariate voxel-based lesion-symptom mapping analysis to correlate surgical lesions within the temporal lobe with changes in naming ability. Additionally, we used a surface-based mixed-effects multilevel analysis to estimate group-level broadband gamma activity during naming across a subset of patients with electrocorticographic recordings and integrated these results with lesion-deficit findings. We observed that ventral temporal regions, centered around the middle fusiform gyrus, were significantly associated with a decline in naming. Furthermore, we found that the ventral aspect of temporal lobectomies was linearly correlated to a decline in naming, with a clinically significant decline occurring once the resection extended 6cm from the anterior tip of the temporal lobe on the ventral surface. On electrocorticography, the majority of these cortical regions were functionally active following visual processing. These loci coincide with the sites of susceptibility artifacts during echoplanar imaging, which may explain why this region has been previously underappreciated as the locus responsible for postoperative naming deficits. Taken together, these data highlight the crucial contribution of the ventral temporal cortex in naming and its important role in the pathophysiology of anomia following temporal lobe resections. As such, surgical strategies should attempt to preserve this region to mitigate postoperative language deficits.

Personalized surgery of brain tumors in language areas: the role of preoperative brain mapping in patients not eligible for awake surgery

OBJECTIVE Awake surgery represents the gold standard for resection of brain tumors close to the language network. However, in some cases patients may be considered not eligible for awake craniotomy. In these cases, a personalized brain mapping of the language network may be achieved by navigated transcranial magnetic stimulation (nTMS), which can guide resection in patients under general anesthesia. Here the authors describe their tailored nTMS-based strategy and analyze its impact on the extent of tumor resection (EOR) and language outcome in a series of patients not eligible for awake surgery. METHODS The authors reviewed data from all patients harboring a brain tumor in or close to the language network who were considered not eligible for awake surgery and were operated on during asleep surgery between January 2017 and July 2022, under the intraoperative guidance of nTMS data. The authors analyzed the effectiveness of nTMS-based mapping data in relation to 1) the ability of the nTMS-based mapping to stratify patients according to surgical risks, 2) the occurrence of postoperative language deficits, and 3) the EOR. RESULTS A total of 176 patients underwent preoperative nTMS cortical language mapping and nTMS-based tractography of language fascicles. According to the nTMS-based mapping, tumors in 115 patients (65.3%) were identified as true-eloquent tumors because of a close spatial relationship with the language network. Conversely, tumors in 61 patients (34.7%) for which the nTMS mapping disclosed a location at a safer distance from the network were identified as false-eloquent tumors. At 3 months postsurgery, a permanent language deficit was present in 13 patients (7.3%). In particular, a permanent deficit was observed in 12 of 115 patients (10.4%) with true-eloquent tumors and in 1 of 61 patients (1.6%) with false-eloquent lesions. With nTMS-based mapping, neurosurgeons were able to distinguish true-eloquent from false-eloquent tumors in a significant number of cases based on the occurrence of deficits at discharge (p &lt; 0.0008) and after 3 months from surgery (OR 6.99, p = 0.03). Gross-total resection was achieved in 80.1% of patients overall and in 69.5% of patients with true-eloquent lesions and 100% of patients with false-eloquent tumors. CONCLUSIONS nTMS-based mapping allows for reliable preoperative mapping of the language network that may be used to stratify patients according to surgical risks. nTMS-guided asleep surgery should be considered a good alternative for personalized preoperative brain mapping of the language network that may increase the possibility of safe and effective resection of brain tumors in the dominant hemisphere whenever awake mapping is not feasible.

Speech and Language Errors during Awake Brain Surgery and Postoperative Language Outcome in Glioma Patients: A Systematic Review.

Awake craniotomy with direct electrical stimulation (DES) is the standard treatment for patients with gliomas in eloquent areas. Even though language is monitored carefully during surgery, many patients suffer from postoperative aphasia, with negative effects on their quality of life. Some perioperative factors are reported to influence postoperative language outcome. However, the influence of different intraoperative speech and language errors on language outcome is not clear. Therefore, we investigate this relation. A systematic search was performed in which 81 studies were included, reporting speech and language errors during awake craniotomy with DES and postoperative language outcomes in adult glioma patients up until 6 July 2020. The frequencies of intraoperative errors and language status were calculated. Binary logistic regressions were performed. Preoperative language deficits were a significant predictor for postoperative acute (OR = 3.42, p &lt; 0.001) and short-term (OR = 1.95, p = 0.007) language deficits. Intraoperative anomia (OR = 2.09, p = 0.015) and intraoperative production errors (e.g., dysarthria or stuttering; OR = 2.06, p = 0.016) were significant predictors for postoperative acute language deficits. Postoperatively, the language deficits that occurred most often were production deficits and spontaneous speech deficits. To conclude, during surgery, intraoperative anomia and production errors should carry particular weight during decision-making concerning the optimal onco-functional balance for a given patient, and spontaneous speech should be monitored. Further prognostic research could facilitate intraoperative decision-making, leading to fewer or less severe postoperative language deficits and improvement of quality of life.

Association of homotopic areas in the right hemisphere with language deficits in the short term after tumor resection.

It is important to identify language deficit and recovery in the week following a tumor resection procedure. The homotopic Broca's area and the superior longitudinal fasciculus in the right hemisphere participate in language functional compensation. However, the nodes in these structures, as well as their contributions to language rehabilitation, remain unknown. In this study, the authors investigated the association of homotopic areas in the right hemisphere with language deficit. The authors retrospectively reviewed the records of 50 right-handed patients with left hemispheric lower-grade glioma that had been surgically treated between June 2020 and May 2022. The patients were divided into normal and aphasia groups based on their postoperative aphasia quotient (AQ) from the Western Aphasia Battery. Preoperative (within 24 hours before surgery) and postoperative (7 days after tumor resection) diffusion tensor images were used to reveal alterations of structural networks by using graphic theory analysis. The shortest distance between the glioma and the nodes belonging to the language network (SDTN) was quantitatively assessed. Pearson's correlation and causal mediation analyses were used to identify correlations and mediator factors among SDTN, topological properties, and AQs. Postoperative nodal local efficiency of the node dorsal Brodmann area (BA) 44 (A44d; p = 0.0330), nodal clustering coefficient of the nodes A44d (p = 0.0402) and dorsal lateral BA6 (A6dl; p = 0.0097), and nodal degree centrality (p = 0.0058) of the node medial BA7 (A7m) were higher in the normal group than in the aphasia group. SDTN was positively correlated with postoperative AQ (r = 0.457, p = 0.0009) and ΔAQ (r = 0.588, p < 0.0001). The nodal local efficiency of node A44d and the nodal efficiency, nodal betweenness centrality, and degree centrality of node A7m were mediators of SDTN and postoperative AQs. The decreased ability of nodes A44d, A6dl, and A7m to convey information in the right hemisphere was associated with short-term language deficits after tumor resection. A smaller SDTN induced a worsened postoperative language deficit through a significant decrease in the ability to convey information from these three nodes.

Grading scale based on arcuate fasciculus segmentation to predict postoperative language outcomes of brain arteriovenous malformations

ObjectiveThe long-term postoperative language outcomes for brain arteriovenous malformations (bAVMs) have not been well characterised. With fibres scattered in the Broca’s, Wernicke’s and Geschwind’s area, the arcuate fasciculus (AF) is...

Interventional neurorehabilitation for promoting functional recovery post-craniotomy: a proof-of-concept

The human brain is a highly plastic ‘complex’ network—it is highly resilient to damage and capable of self-reorganisation after a large perturbation. Clinically, neurological deficits secondary to iatrogenic injury have very few active treatments. New imaging and stimulation technologies, though, offer promising therapeutic avenues to accelerate post-operative recovery trajectories. In this study, we sought to establish the safety profile for ‘interventional neurorehabilitation’: connectome-based therapeutic brain stimulation to drive cortical reorganisation and promote functional recovery post-craniotomy. In n = 34 glioma patients who experienced post-operative motor or language deficits, we used connectomics to construct single-subject cortical networks. Based on their clinical and connectivity deficit, patients underwent network-specific transcranial magnetic stimulation (TMS) sessions daily over five consecutive days. Patients were then assessed for TMS-related side effects and improvements. 31/34 (91%) patients were successfully recruited and enrolled for TMS treatment within two weeks of glioma surgery. No seizures or serious complications occurred during TMS rehabilitation and 1-week post-stimulation. Transient headaches were reported in 4/31 patients but improved after a single session. No neurological worsening was observed while a clinically and statistically significant benefit was noted in 28/31 patients post-TMS. We present two clinical vignettes and a video demonstration of interventional neurorehabilitation. For the first time, we demonstrate the safety profile and ability to recruit, enroll, and complete TMS acutely post-craniotomy in a high seizure risk population. Given the lack of randomisation and controls in this study, prospective randomised sham-controlled stimulation trials are now warranted to establish the efficacy of interventional neurorehabilitation following craniotomy.

Impacting the Treatment of Highly Eloquent Supratentorial Cerebral Cavernous Malformations by Noninvasive Functional Mapping-An Observational Cohort Study.

Cerebral cavernous malformations (CCM) may cause cavernoma-related epilepsy (CRE) and intracranial hemorrhage (ICH). Functional mapping has shown its usefulness during the resection of eloquent lesions including the treatment of brain arteriovenous malformations. To evaluate the impact of noninvasive functional mapping on decision-making and resection of eloquently located CCM. Of 126 patients with intracranial cavernomas, we prospectively included 40 consecutive patients (31.7%) with highly eloquent CCM between 2012 and 2020. We performed functional mapping via navigated transcranial magnetic stimulation (nTMS) motor mapping in 30 cases and nTMS language mapping in 20 cases. Twenty patients suffered from CRE. CCM caused ICH in 18 cases. We used functional mapping data including function-based tractography in all cases. Indication toward (31 cases) or against (9 cases) CCM resection was influenced by noninvasive functional mapping in 36 cases (90%). We resected CCMs in 24 cases, and 7 patients refused the recommendation for surgery. In 19 and 4 cases, we used additional intraoperative neuromonitoring and awake craniotomy, respectively. Patients suffered from transient postoperative motor or language deficits in 2 and 2 cases, respectively. No patient suffered from permanent deficits. After 1 yr of follow-up, anti-epileptic drugs could be discontinued in all patients who underwent surgery but 1 patient. Surgery-related deficit rates are low even for highly eloquent CCM and seizure outcome is excellent. The present results show that noninvasive functional mapping and function-based tractography is a useful tool for the decision-making process and during microsurgical resection of eloquently located CCM.

BRMP-02. Feasibility and evaluation of a novel language paradigm for intraoperative language testing

Abstract INTRODUCTION Mapping language during direct cortical stimulation (DCS) in the stetting of awake craniotomy might be challenging without using more than one language paradigm. Applying several language tasks leads to increasing surgery times and to patient’s exhaustion. Additionally, a single language trial must be performed in less than 4 seconds to avoid DCS-induced seizures. Therefore, we aimed to design a single language paradigm which pictures highly relevant language functions and simultaneously restrains the assessment time of single language trials up to 4 seconds. METHOD The intraoperative language task comprised a combination of picture naming and verb generation. During DCS patients should generate correct sentences according to the language stimulus by not exceeding 4 seconds. To assess the intraoperative feasibility of the language task we included 30 healthy subjects in a pilot study to measure subjects’ speed of performing a single language task trial and to evaluate the language paradigm according to its language sensitivity by using the paradigm as a task for functional MRI. Intraoperatively, 21 patients with brain tumors in language associated brain areas were included. Patients received neuropsychological testing before and after surgery. RESULTS The pilot study showed in healthy subjects that by applying the novel paradigm during fMRI there is activation in a left accentuated network of inferior frontal and parietal regions and the superior and middle temporal gyrus (p&amp;lt;.05, FEW). It was feasible to conduct a single language trial of the novel paradigm in a time frame of 4s (performance speed 2.53 s; SD=.32s). Intraoperatively, tumor patients showed DCS-associated language errors while conducting the language task. Postoperatively, mild language but no other neuropsychological deteriorations compared to presurgical assessment were observed (p&amp;lt;.05). CONCLUSION We present a novel language paradigm which safely pictures and monitors highly relevant language functions and consequently can minimize postoperative language deficits.

Intraoperative brain stimulation during awake craniotomy in aphasia prevention

Abstract Objective: Surgical treatment of tumors located in close proximity to the eloquent areas carry a risk of postsurgical cognitive deficits, e.g. aphasia, which prevent patients from fully returning to their previous lifestyle. Therefore, in case of the risk of postoperative language deficits, it is important to plan the surgery in a way that will increase the safety of the procedure and spare brain regions crucial for speech functions. The most effective and accurate way of brain mapping in order to prevent damage of the key regions for particular functions is awake craniotomy with intraoperative brain stimulation and neuropsychological assessment. Aim of the study was to present the protocol of language assessment during brain stimulation performed in our center and to analyze the frequency of postoperative verbal deficits. Methods: Forty-six awake craniotomies were performed in patients with lesions of the left dominant hemisphere. In 44 cases with lesion in the frontal (n=14), temporal (n=12), parietal (n=12) and insular areas (6), verbal functions were studied due to the close proximity of tumor to the areas responsible for these processes. The stimulation was performed with a bipolar electrode. Depending on the location of lesions, the following abilities were tested: spontaneous speech, naming, speech understanding, reading, writing and repetition. Results: In all patients, areas responsible for language functions were found using intraoperative brain stimulation. In some cases is resulted in altering the manner, direction, and / or extent of tumor removal. After the surgery 21 (48%) patients had no deficits, 17 (38.5%) had minor short-term deficits (withdrawing spontaneously or with neuropsychological rehabilitation within 2 weeks) and 6 (13.5%) had moderate deficits lasting more than 2 weeks. Conclusion: After awake surgery long-standing aphasia was very rare, therefore it should be considered as effective procedure for removing lesions located close to functionally important brain areas. Keywords: aphasia, awake craniotomy, intraoperative brain stimulation

P03.05 The use of subcortical intraoperative electrical stimulation mapping for assessment of executive functions: A summary of the evidence so far

Abstract BACKGROUND Over the past years, the functional subcortical architecture of the brain has been increasingly acknowledged in neurosurgical planning. A method to study anatomo-functional correlations is direct electrical stimulation (DES). DES is widely used by neurosurgeons and considered as a reliable tool to minimize the occurrence of permanent postoperative motor, language and visual deficits. In recent years, DES has also been used for mapping of other cognitive functions, such as executive functions. MATERIAL AND METHODS We systematically summarized the evidence so far from DES studies on subcortical pathways that are involved in the following three executive functions: (1) inhibitory control, (2) working memory and (3) cognitive flexibility. RESULTS We only found twelve articles that reported on intraoperative electrical stimulation of white matter pathways to map executive functions and explicitly clarified which subcortical tract was stimulated. The results indicate that the second branch of the right superior longitudinal fasciculus (SLF-II) is involved in inhibitory control, the first branch of the right superior longitudinal fasciculus (SLF-I) and the third branch of the left superior longitudinal fasciculus (SLF-III) are involved in working memory and the cingulum is involved in cognitive flexibility. CONCLUSION We were unable to draw any specific conclusions, nor unequivocally established the pathways involved in executive functions due to heterogenous study characteristics, methods and tasks, and the limited number of studies that assessed these relationships. Clearly, neurosurgical groups are exploring novel methods to assess cognition during awake neurosurgery, but are far from consensus on indications and protocols, which complicated the comparison and summarization of findings. We will discuss possible approaches for future research to obtain converging and more definite evidence for the involvement of subcortical pathways in specific executive functions.

Intraoperative Corticocortical Evoked Potentials for Language Monitoring in Epilepsy Surgery

To evaluate the applicability of corticocortical evoked potentials (CCEP) for intraoperative monitoring of the language network in epilepsy surgery under general anesthesia. To investigate the clinical relevance on language functions of intraoperative changes of CCEP recorded under these conditions. CCEP monitoring was performed in 14 epileptic patients (6 females, 4 children) during resections in the left perisylvian region under general anesthesia. Electrode strips were placed on the anterior language area (AL) and posterior language area (PL), identified by structural and functional magnetic resonance imaging. Single-pulse electric stimulations were delivered to pairs of adjacent contacts in a bipolar fashion. During resection, we monitored the integrity of the dorsal language pathway by stimulating either AL by recording CCEP from PL or vice versa, depending on stability and reproducibility of CCEP. We evaluated the first negative (N1) component of CCEP before, during, and after resection. All procedures were successfully completed without adverse events. The best response was obtained from AL during stimulation of PL in 8 patients and from PL during stimulation of AL in 6 patients. None of 12 patients with a postresection N1 amplitude decrease of 0%-15% from baseline presented postoperative language impairment. Decreases of 28% and 24%, respectively, of the N1 amplitude were observed in 2 patients who developed transient postoperative speech disturbances. The application of CCEP monitoring is possible and safe in epilepsy surgery under general anesthesia. Putative AL and PL can be identified using noninvasive presurgical neuroimaging. Decrease of N1 amplitude >15% from baseline may predict postoperative language deficits.

Language Mapping Using Stereo Electroencephalography: A Review and Expert Opinion.

Stereo-electroencephalography (sEEG) is a method that uses stereotactically implanted depth electrodes for extra-operative mapping of epileptogenic and functional networks. sEEG derived functional mapping is achieved using electrical cortical stimulations (ECS) that are currently the gold standard for delineating eloquent cortex. As this stands true especially for primary cortices (e.g., visual, sensitive, motor, etc.), ECS applied to higher order brain areas determine more subtle behavioral responses. While anterior and posterior language areas in the dorsal language stream seem to share characteristics with primary cortices, basal temporal language area (BTLA) in the ventral temporal cortex (VTC) behaves as a highly associative cortex. After a short introduction and considerations about methodological aspects of ECS using sEEG, we review the sEEG language mapping literature in this perspective. We first establish the validity of this technique to map indispensable language cortices in the dorsal language stream. Second, we highlight the contrast between the growing empirical ECS experience and the lack of understanding regarding the fundamental mechanisms underlying ECS behavioral effects, especially concerning the dispensable language cortex in the VTC. Evidences for considering network architecture as determinant for ECS behavioral response complexities are discussed. Further, we address the importance of designing new research in network organization of language as this could enhance ECS ability to map interindividual variability, pathology driven reorganization, and ultimately identify network resilience markers in order to better predict post-operative language deficit. Finally, based on a whole body of available studies, we believe there is strong evidence to consider sEEG as a valid, safe and reliable method for defining eloquent language cortices although there have been no proper comparisons between surgical resections with or without extra-operative or intra-operative language mapping.

Risk Assessment by Pre-surgical Tractography in Left Hemisphere Low-Grade Gliomas.

Background: Tracking the white matter principal tracts is routinely typically included during the pre-surgery planning examinations and has revealed to limit functional resection of low-grade gliomas (LGGs) in eloquent areas.Objective: We examined the integrity of the Superior Longitudinal Fasciculus (SLF) and Inferior Fronto-Occipital Fasciculus (IFOF), both known to be part of the language-related network in patients with LGGs involving the temporo-insular cortex. In a comparative approach, we contrasted the main quantitative fiber tracking values in the tumoral (T) and healthy (H) hemispheres to test whether or not this ratio could discriminate amongst patients with different post-operative outcomes.Methods: Twenty-six patients with LGGs were included. We obtained quantitative fiber tracking values in the tumoral and healthy hemispheres and calculated the ratio (HIFOF–TIFOF)/HIFOF and the ratio (HSLF–TSLF)/HSLF on the number of streamlines. We analyzed how these values varied between patients with and without post-operative neurological outcomes and between patients with different post-operative Engel classes.Results: The ratio for both IFOF and SLF significantly differed between patient with and without post-operative neurological language deficits. No associations were found between white matter structural changes and post-operative seizure outcomes.Conclusions: Calculating the ratio on the number of streamlines and fractional anisotropy between the tumoral and the healthy hemispheres resulted to be a useful approach, which can prove to be useful during the pre-operative planning examination, as it gives a glimpse on the potential clinical outcomes in patients with LGGs involving the left temporo-insular cortex.

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

Neurosurgeons adopt several different surgical approaches to deal with glioblastomas (GB) located in or near eloquent areas. Some attempt maximal safe resection by awake craniotomy (AC), but doubts persist concerning the real benefits of this type of surgery in this situation. We performed a retrospective study to evaluate the extent of resection (EOR), functional and survival outcomes after AC of patients with GB in critical locations. Forty-six patients with primary GB treated with the Stupp regimen between 2004 and 2019, for whom brain mapping was feasible, were included. We assessed EOR, postoperative language and/or motor deficits three months after AC, progression-free survival (PFS) and overall survival (OS). Complete resection was achieved in 61% of the 46GB patients. The median PFS was 6.8months (CI 6.1; 9.7) and the median OS was 17.6months (CI 14.8; 34.1). Three months after AC, more than half the patients asymptomatic before surgery remained asymptomatic, and one third of patients with symptoms before surgery experienced improvements in language, but not motor functions. The risk of postoperative deficits was higher in patients with preoperative deficits or incomplete resection. Furthermore, the presence of postoperative deficits was an independent predictive factor for shorter PFS. AC is an option for the resection of GB in critical locations. The observed survival outcomes are typical for GB patients in the Stupp era. However, the success of AC in terms of the recovery or preservation of language and/or motor functions cannot be guaranteed, given the aggressiveness of the tumor.