Comparison of Motor Outcome in Patients Undergoing Awake vs General Anesthesia Surgery for Brain Tumors Located Within or Adjacent to the Motor Pathways

Awake Craniotomy in Neurosurgery: A Bibliometric Analysis of the Top 100 Most-Cited Articles and Review of Technological Advancements

Awake craniotomy (AC) is a critical neurosurgical technique for maximizing tumor resection in eloquent brain regions while preserving essential neurological functions like speech and motor control. Despite its widespread adoption, no prior bibliometric analysis has evaluated the most influential research in this field. This study analyzed the top 100 most-cited articles on AC to identify key trends, influential works, and authorship demographics. A systematic search of the Web of Science Core Collection on September 17, 2024, yielded 718 publications, with the top 100 ranked by citation count. Analysis revealed a surge in AC research after 2013, peaking in 2021, with the Journal of Neurosurgery contributing significantly (49 articles; 2,611 citations). Themes included functional mapping, anesthetic techniques, and patient outcomes, with technological advancements such as intraoperative MRI and virtual reality enhancing surgical precision. Authorship analysis highlighted a gender disparity, with male authors occupying 77% of first authorship and 88% of senior roles. These findings underscore AC's evolution, foundational studies, and ongoing advancements while emphasizing the need for greater diversity and inclusion in the field.

Awake Versus Asleep Craniotomy for Patients With Eloquent Glioma: A Systematic Review and Meta-Analysis

BACKGROUND AND OBJECTIVES

Awake vs asleep craniotomy for patients with eloquent glioma is debatable. This systematic review and meta-analysis sought to compare awake vs asleep craniotomy for the resection of gliomas in the eloquent regions.

METHODS

MEDLINE and PubMed were searched from inception to December 13, 2022. Primary outcomes were the extent of resection (EOR), overall survival (month), progression-free survival (month), and rates of neurological deficit, Karnofsky performance score, and seizure freedom at the 3-month follow-up. Secondary outcomes were duration of operation (minute) and length of hospital stay (LOS) (day).

RESULTS

Fifteen studies yielded 2032 patients, from which 800 (39.4%) and 1232 (60.6%) underwent awake and asleep craniotomy, respectively. The meta-analysis concluded that the awake group had greater EOR (mean difference [MD] = MD = 8.52 [4.28, 12.76], P < .00001), overall survival (MD = 2.86 months [1.35, 4.37], P = .0002), progression-free survival (MD = 5.69 months [0.75, 10.64], P = .02), 3-month postoperative Karnofsky performance score (MD = 13.59 [11.08, 16.09], P < .00001), and 3-month postoperative seizure freedom (odds ratio = 8.72 [3.39, 22.39], P < .00001). Furthermore, the awake group had lower 3-month postoperative neurological deficit (odds ratio = 0.47 [0.28, 0.78], P = .004) and shorter LOS (MD = -2.99 days [-5.09, -0.88], P = .005). In addition, the duration of operation was similar between the groups (MD = 37.88 minutes [-34.09, 109.86], P = .30).

CONCLUSION

Awake craniotomy for gliomas in the eloquent regions benefits EOR, survival, postoperative neurofunctional outcomes, and LOS. When feasible, the authors recommend awake craniotomy for surgical resection of gliomas in the eloquent regions.

Resection of high-grade glioma involving language areas assisted by multimodal techniques under general anesthesia: a retrospective study

BACKGROUND

Multimodal techniques-assisted resection of glioma under general anesthesia (GA) has been shown to achieve similar clinical outcomes as awake craniotomy (AC) in some studies. In this study, we aim to validate the use of multimodal techniques can achieve the maximal safe resection of high-grade glioma involving language areas (HGILAs) under GA.

METHODS

HGILAs cases were reviewed and collected between January 2009 and December 2020 in our center. Patients were separated into multimodal group (using neuronavigation, intraoperative MRI combined with direct electrical stimulation [DES] and neuromonitoring [IONM]) and conventional group (neuronavigation alone) and clinical outcomes were compared between groups. Studies of HGILAs were reviewed systematically and the meta-analysis results of previous (GA or AC) studies were compared with our results.

RESULTS

Finally, there were 263 patients in multimodal group and 137 patients in conventional group. Compared to the conventional group, the multimodal group achieved the higher median EOR (100% versus 94.32%, P < 0.001) and rate of gross total resection (GTR) (73.8% versus 36.5%, P < 0.001) and the lower incidence of permanent language deficit (PLD) (9.5% versus 19.7%, P = 0.004). The multimodal group achieved the longer median PFS (16.8 versus 10.3 months, P < 0.001) and OS (23.7 versus 15.7 months, P < 0.001) than the conventional group. The multimodal group achieved a higher rate of GTR than the cohorts in previous multimodal studies under GA and AC (73.8% versus 55.7% [95%CI 32.0-79.3%] versus 53.4% [35.5-71.2%]). The multimodal group had a lower incidence of PLD than the cohorts in previous multimodal studies under GA (9.5% versus 14.0% [5.8-22.1%]) and our incidence of PLD was a little higher than that of previous multimodal studies under AC (9.5% versus 7.5% [3.7-11.2%]). Our multimodal group also achieved a relative longer survival than previous studies.

CONCLUSIONS

Surgery assisted by multimodal techniques can achieve maximal safe resection for HGILAs under GA. Further prospective studies are needed to compare GA with AC for HGILAs.

Surgical management of Glioma Grade 4: technical update from the neuro-oncology section of the Italian Society of Neurosurgery (SINch®): a systematic review

PURPOSE

The extent of resection (EOR) is an independent prognostic factor for overall survival (OS) in adult patients with Glioma Grade 4 (GG4). The aim of the neuro-oncology section of the Italian Society of Neurosurgery (SINch®) was to provide a general overview of the current trends and technical tools to reach this goal.

METHODS

A systematic review was performed. The results were divided and ordered, by an expert team of surgeons, to assess the Class of Evidence (CE) and Strength of Recommendation (SR) of perioperative drugs management, imaging, surgery, intraoperative imaging, estimation of EOR, surgery at tumor progression and surgery in elderly patients.

RESULTS

A total of 352 studies were identified, including 299 retrospective studies and 53 reviews/meta-analysis. The use of Dexamethasone and the avoidance of prophylaxis with anti-seizure medications reached a CE I and SR A. A preoperative imaging standard protocol was defined with CE II and SR B and usefulness of an early postoperative MRI, with CE II and SR B. The EOR was defined the strongest independent risk factor for both OS and tumor recurrence with CE II and SR B. For intraoperative imaging only the use of 5-ALA reached a CE II and SR B. The estimation of EOR was established to be fundamental in planning postoperative adjuvant treatments with CE II and SR B and the stereotactic image-guided brain biopsy to be the procedure of choice when an extensive surgical resection is not feasible (CE II and SR B).

CONCLUSIONS

A growing number of evidences evidence support the role of maximal safe resection as primary OS predictor in GG4 patients. The ongoing development of intraoperative techniques for a precise real-time identification of peritumoral functional pathways enables surgeons to maximize EOR minimizing the post-operative morbidity.

Predictive model of language deficit after removing glioma involving language areas under general anesthesia

Purpose

To establish a predictive model to predict the occurrence of language deficit for patients after surgery of glioma involving language areas (GILAs) under general anesthesia (GA).

Methods

Patients with GILAs were retrospectively collected in our center between January 2009 and December 2020. Clinical variables (age, sex, aphasia quotient [AQ], seizures and KPS), tumor-related variables (recurrent tumor or not, volume, language cortices invaded or not, shortest distance to language areas [SDLA], supplementary motor area or premotor area [SMA/PMA] involved or not and WHO grade) and intraoperative multimodal techniques (used or not) were analyzed by univariate and multivariate analysis to identify their association with temporary or permanent language deficits (TLD/PLD). The predictive model was established according to the identified significant variables. Receiver operating characteristic (ROC) curve was used to assess the accuracy of the predictive model.

Results

Among 530 patients with GILAs, 498 patients and 441 patients were eligible to assess TLD and PLD respectively. The multimodal group had the higher EOR and rate of GTR than conventional group. The incidence of PLD was 13.4% in multimodal group, which was much lower than that (27.6%, P<0.001) in conventional group. Three factors were associated with TLD, including SDLA (OR=0.85, P<0.001), preoperative AQ (OR=1.04, P<0.001) and multimodal techniques used (OR=0.41, P<0.001). Four factors were associated with PLD, including SDLA (OR=0.83, P=0.001), SMA/PMA involved (OR=3.04, P=0.007), preoperative AQ (OR=1.03, P=0.002) and multimodal techniques used (OR=0.35, P<0.001). The optimal shortest distance thresholds in detecting the occurrence of TLD/PLD were 1.5 and 4mm respectively. The optimal AQ thresholds in detecting the occurrence of TLD/PLD were 52 and 61 respectively. The cutoff values of the predictive probability for TLD/PLD were 23.7% and 16.1%. The area under ROC curve of predictive models for TLD and PLD were 0.70 (95%CI: 0.65-0.75) and 0.72 (95%CI: 0.66-0.79) respectively.

Conclusion

The use of multimodal techniques can reduce the risk of postoperative TLD/PLD after removing GILAs under general anesthesia. The established predictive model based on clinical variables can predict the probability of occurrence of TLD and PLD, and it had a moderate predictive accuracy.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Clinical and prognostic implications of rim restriction following glioma surgery

Rim restriction surrounding the resection cavity of glioma is often seen on immediate post-op diffusion-weighted imaging (DWI). The etiology and clinical impact of rim restriction are unknown. We evaluated the incidence, risk factors and clinical consequences of this finding. We evaluated patients that underwent surgery for low-grade glioma (LGG) and glioblastoma (GBM) without stroke on post-operative imaging. Analyses encompassed pre- and postoperative clinical, radiological, intraoperative monitoring, survival, functional and neurocognitive outcomes. Between 2013 and 2017, 63 LGG and 209 GBM patients (272 in total) underwent surgical resection and were included in our cohort. Post-op rim restriction was demonstrated in 68 patients, 32% (n = 20) of LGG and 23% (n = 48) of GBM patients. Risk factors for restriction included temporal tumors in GBM (p = 0.025) and insular tumors in LGG (p = 0.09), including longer surgery duration in LGG (p = 0.008). After a 1-year follow-up, LGG patients operated on their dominant with post-op restriction had a higher rate of speech deficits (46 vs 9%, p = 0.004). Rim restriction on postoperative imaging is associated with longer duration of glioma surgery and potentially linked to brain retraction. It apparently has no direct clinical consequences, but is linked to higher rates of speech deficits in LGG dominant-side surgeries.

Impact of awake mapping on overall survival and extent of resection in patients with adult diffuse gliomas within or near eloquent areas: a retrospective propensity score-matched analysis of awake craniotomy vs. general anesthesia

PURPOSE

Awake craniotomy (AC) with intraoperative mapping is the best approach to preserve neurological function for glioma surgery in eloquent or near eloquent areas, but whether AC improves the extent of resection (EOR) and overall survival (OS) is controversial. This study aimed to compare the long-term clinical outcomes of glioma resection under AC with those under general anesthesia (GA).

METHODS

Data of 335 patients who underwent surgery with intraoperative magnetic resonance imaging for newly diagnosed gliomas of World Health Organization (WHO) grades II-IV between 2000 and 2013 were reviewed. EOR and OS were quantitatively compared between the AC and GA groups after 1:1 propensity score matching. The two groups were matched for age, preoperative Karnofsky performance status (KPS), tumor location, and pathology.

RESULTS

After propensity score matching, 91 pairs were obtained. The median EOR was 96.1% (interquartile range [IQR] 7.3) and 97.4% (IQR 14.4) in the AC and GA groups, respectively (p = 0.31). Median KPS score 3 months after surgery was 90 (IQR 20) in both groups (p = 0.384). The median survival times were 163.3 months (95% confidence interval [CI] 77.9-248.7) and 143.5 months (95% CI 94.4-192.7) in the AC and GA groups, respectively (p = 0.585).

CONCLUSION

Even if the glioma was within or close to the eloquent area, AC was comparable with GA in terms of EOR and OS. In case of difficulties in randomizing patients with eloquent or near eloquent glioma, our propensity score-matched analysis provides retrospective evidence that AC can obtain EOR and OS equivalent to removing glioma under GA.

Personalized fMRI delineates functional regions preserved within brain tumors

Objective

Methods

Results

Interpretation

Understanding Variable Motor Responses to Direct Electrical Stimulation of the Human Motor Cortex During Brain Surgery

Direct electrical stimulation of the brain is the gold standard technique used to define functional-anatomical relationships during neurosurgical procedures. Areas that respond to stimulation are considered “critical nodes” of circuits that must remain intact for the subject to maintain the ability to perform certain functions, like moving and speaking. Despite its routine use, the neurophysiology underlying downstream motor responses to electrical stimulation of the brain, such as muscle contraction or movement arrest, is poorly understood. Furthermore, varying and sometimes counterintuitive responses can be seen depending on how and where the stimulation is applied, even within the human primary motor cortex. Therefore, here we review relevant neuroanatomy of the human motor system, provide a brief historical perspective on electrical brain stimulation, explore mechanistic variations in stimulation applications, examine neurophysiological properties of different parts of the motor system, and suggest areas of future research that can promote a better understanding of the interaction between electrical stimulation of the brain and its function.

Tumor location-based classification of surgery-related language impairments in patients with glioma

INTRODUCTION

Many patients with glioma experience surgery-related language impairment. This study developed a classification system to predict postoperative language prognosis.

METHODS

Sixty-eight patients were retrospectively reviewed. Based on their location, tumors were subtyped as follows: (I) inferior frontal lobe or precentral gyrus; (II) posterior central gyrus or supramarginal gyrus (above the lateral fissure level); (III) posterior region of the superior or middle temporal gyri or supramarginal gyrus (below the lateral fissure level); and (IV) insular lobe. The distance from the tumor to the superior longitudinal fasciculus/arcuate fasciculus was calculated. The recovery of language function was assessed using the Western Aphasia Battery before surgery, and a comprehensive language test was conducted on the day of surgery; 3, 7, and 14 days after surgery. Our follow-up information of was the comprehensive language test from telephone interviews in 3 months after surgery.

RESULTS

Thirty-three patients experienced transient language impairment within 1 week of surgery. Fourteen patients had permanent language impairment. Type II tumors, shorter distance from the tumor to the posterior superior longitudinal fasciculus/arcuate fasciculus, and isocitrate dehydrogenase mutations were risk factors for surgery-related language impairment. Regarding the presence or absence of permanent surgery-related language impairments, the cut-off distance between the tumor and posterior superior longitudinal fasciculus/arcuate fasciculus was 2.75 mm.

CONCLUSIONS

According to our classification, patients with type II tumors had the worst language prognosis and longest recovery time. Our classification, based on tumor location, can reliably predict postoperative language status and may be used to guide tumor resection.

Intra-operative mapping and language protection in glioma

ABSTRACT

The demand for acquiring different languages has increased with increasing globalization. However, knowledge of the modification of the new language in the neural language network remains insufficient. Although many details of language function have been detected based on the awake intra-operative mapping results, the language neural network of the bilingual or multilingual remains unclear, which raises difficulties in clinical practice to preserve patients' full language ability in neurosurgery. In this review, we present a summary of the current findings regarding the structure of the language network and its evolution as the number of acquired languages increased in glioma patients. We then discuss a new insight into the awake intra-operative mapping protocol to reduce surgical risks during the preservation of language function in multilingual patients with glioma.

Awake craniotomy for auditory brainstem implant in patients with neurofibromatosis type 2: Four case reports

BACKGROUND

The auditory brainstem implant (ABI) is a significant treatment to restore hearing sensations for neurofibromatosis type 2 (NF2) patients. However, there is no ideal method in assisting the placement of ABIs. In this case series, intraoperative cochlear nucleus mapping was performed in awake craniotomy to help guide the placement of the electrode array.

CASE SUMMARY

We applied the asleep-awake-asleep technique for awake craniotomy and hearing test via the retrosigmoid approach for acoustic neuroma resections and ABIs, using mechanical ventilation with a laryngeal mask during the asleep phases, utilizing a ropivacaine-based regional anesthesia, and sevoflurane combined with propofol/remifentanil as the sedative/analgesic agents in four NF2 patients. ABI electrode arrays were placed in the awake phase with successful intraoperative hearing tests in three patients. There was one uncooperative patient whose awake hearing test needed to be aborted. In all cases, tumor resection and ABI were performed safely. Satisfactory electrode effectiveness was achieved in awake ABI placement.

CONCLUSION

This case series suggests that awake craniotomy with an intraoperative hearing test for ABI placement is safe and well tolerated. Awake craniotomy is beneficial for improving the accuracy of ABI electrode placement and meanwhile reduces non-auditory side effects.

Clinical Pearls and Methods for Intraoperative Motor Mapping

Resection of brain tumors involving motor areas and pathways requires the identification and preservation of various cortical and subcortical structures involved in motor control at the time of the procedure, in order to maintain the patient's full motor capacities. The use of brain mapping techniques has now been integrated into clinical practice for many years, as they help the surgeon to identify the neural structures involved in motor functions. A common definition of motor function, as well as knowledge of its neural organization, has been continuously evolving, underlining the need for implementing intraoperative strategies at the time of the procedure. Similarly, mapping strategies have been subjected to continuous changes, enhancing the likelihood of preservation of full motor capacities. As a general rule, the motor mapping strategy should be as flexible as possible and adapted strictly to the individual patient and clinical context of the tumor. In this work, we present an overview of current knowledge of motor organization, indications for motor mapping, available motor mapping, and monitoring strategies, as well as their advantages and limitations. The use of motor mapping improves resection and outcomes in patients harboring tumors involving motor areas and pathways, and should be considered the gold standard in the resection of this type of tumor.

A novel tailored immune gene pairs signature for overall survival prediction in lower-grade gliomas

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The Immune-related gene pairs (IRGPs) pronostic signature for LGG is correlated with immune cells infiltration.

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WGCNA presented a gene set correlating with immune cells infiltration and genes co-expression relationships were visualized.

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The nomogram constrcted by three IRGPs and clinical factors is a novel tailored tool for individual-level prediction.

Lower-grade gliomas (LGGs) have a good prognosis with a wide range of overall survival (OS) outcomes. An accurate prognostic system can better predict survival time. An RNA-Sequencing (RNA-seq) prognostic signature showed a better predictive power than clinical predictor models. A signature constructed using gene pairs can transcend changes from biological heterogeneity, technical biases, and different measurement platforms. RNA-seq coupled with corresponding clinical information were extracted from The Cancer Genome Atlas (TCGA) and the Chinese Glioma Genome Atlas (CGGA). Immune-related gene pairs (IRGPs) were used to establish a prognostic signature through univariate and multivariate Cox proportional hazards regression. Weighted gene co-expression network analysis (WGCNA) was used to evaluate module eigengenes correlating with immune cell infiltration and to construct gene co-expression networks. Samples in the training and testing cohorts were dichotomized into high- and low-risk groups. Risk score was identified as an independent predictor, and exhibited a closed relationship with prognosis. WGCNA presented a gene set that was positively correlated with age, WHO grade, isocitrate dehydrogenase (IDH) mutation status, 1p/19 codeletion, risk score, and immune cell infiltrations (CD4 T cells, B cells, dendritic cells, and macrophages). A nomogram comprising of age, WHO grade, 1p/19q codeletion, and three gene pairs (BIRC5|SSTR2, BMP2|TNFRSF12A, and NRG3|TGFB2) was established as a tool for predicting OS. The IPGPs signature, which is associated with immune cell infiltration, is a novel tailored tool for individual-level prediction.

Postcentral gyrus resection of opercular gliomas is a risk factor for motor deficits caused by damaging the radiologically invisible arteries supplying the descending motor pathway

BACKGROUND

Postoperative motor deficits are among the worst morbidities of glioma surgery. We aim to investigate factors associated with postoperative motor deficits in patients with frontoparietal opercular gliomas.

METHODS

Thirty-four patients with frontoparietal opercular gliomas were retrospectively investigated. We examined the postoperative ischemic changes and locations obtained from MRI.

RESULTS

Twenty-one patients (62%) presented postoperative ischemic changes. Postoperative MRI was featured with ischemic changes, all located at the subcortical area of the resection cavity. Six patients had postoperative motor deficits, whereas 28 patients did not. Compared to those without motor deficits, those with motor deficits were associated with old age, pre- and postcentral gyri resection, and postcentral gyrus resection (P = 0.023, 0,024, and 0.0060, respectively). A merged image of the resected cavity and T1-weighted brain atlas of the Montreal Neurological Institute showed that a critical area for postoperative motor deficits is the origin of the long insular arteries (LIAs) and the postcentral gyrus. Detail anatomical architecture created by the Human Connectome Project database and T2-weighted images showed that the subcortical area of the operculum of the postcentral gyrus is where the medullary arteries supply, and the motor pathways originated from the precentral gyrus run.

CONCLUSIONS

We verified that the origin of the LIAs could damage the descending motor pathways during the resection of frontoparietal opercular gliomas. Also, we identified that motor pathways run the subcortical area of the operculum of the postcentral gyrus, indicating that the postcentral gyrus is an unrecognized area of damaging the descending motor pathways.

Correlation between localization of supratentorial glioma to the precentral gyrus and difficulty in identification of the motor area during awake craniotomy

OBJECTIVE

Identification of the motor area during awake craniotomy is crucial for preservation of motor function when resecting gliomas located within or close to the motor area or the pyramidal tract. Nevertheless, sometimes the surgeon cannot identify the motor area during awake craniotomy. However, the factors that influence failure to identify the motor area have not been elucidated. The aim of this study was to assess whether tumor localization was correlated with a negative cortical response in motor mapping during awake craniotomy in patients with gliomas located within or close to the motor area or pyramidal tract.

METHODS

Between April 2000 and May 2019 at Tokyo Women's Medical University, awake craniotomy was performed to preserve motor function in 137 patients with supratentorial glioma. Ninety-one of these patients underwent intraoperative cortical motor mapping for a primary glioma located within or close to the motor area or pyramidal tract and were enrolled in the study. MRI was used to evaluate whether or not the tumors were localized to or involved the precentral gyrus. The authors performed motor functional mapping with electrical stimulation during awake craniotomy and evaluated the correlation between identification of the motor area and various clinical characteristics, including localization to the precentral gyrus.

RESULTS

Thirty-four of the 91 patients had tumors that were localized to the precentral gyrus. The mean extent of resection was 89.4%. Univariate analyses revealed that identification of the motor area correlated significantly with age and localization to the precentral gyrus. Multivariate analyses showed that older age (≥ 45 years), larger tumor volume (> 35.5 cm3), and localization to the precentral gyrus were significantly correlated with failure to identify the motor area (p = 0.0021, 0.0484, and 0.0015, respectively). Localization to the precentral gyrus showed the highest odds ratio (14.135) of all regressors.

CONCLUSIONS

Identification of the motor area can be difficult when a supratentorial glioma is localized to the precentral gyrus. The authors' findings are important when performing awake craniotomy for glioma located within or close to the motor area or the pyramidal tract. A combination of transcortical motor evoked potential monitoring and awake craniotomy including subcortical motor mapping may be needed for removal of gliomas showing negative responses in the motor area to preserve the motor-related subcortical fibers.

Predictors of stimulation-induced seizures during perirolandic glioma resection using intraoperative mapping techniques

BACKGROUND

Intraoperative mapping techniques maximize safety and efficacy during perirolandic glioma resection but may induce seizures and limit the procedure. We aim to report the incidence and predictors of stimulation-induced seizures during mapping either patient is awake or under general anesthesia (GA).

METHODS

Retrospective analysis of 64 patients (40 awake and 24 GA) with perirolandic glioma underwent resection using intraoperative mapping techniques between 2014 and 2019. Preoperative data, operative details, postoperative neurological status, and extent of resection (EOR) were analyzed. Predictors of intraoperative seizures were assessed.

RESULTS

The mean cortical and subcortical stimulation intensities needed to evoke motor responses were significantly lower in awake cases than in GA patients (4.9 ± 0.42 vs. 8.9 ± 1.2 mA) and (8.3 ± 0.62 vs. 12.1 ± 1.1 mA), respectively (P = 0.01). Incidence of intraoperative seizures was lower but statistically non-significant in awake cases (10% vs. 12.5%) (P = 0.76). Preoperative multiple antiepileptic drugs (AEDs) (P = 0.03) and low-grade glioma (P = 0.04) were statistically significant predictors for intraoperative seizures. Mean EOR in awake cases was 92.03% and 90.05% in GA cases (P = 0.23). Postoperative deficits were permanent after 3 months only in 5% of awake patients versus 8.3% of GA group (P = 0.59).

CONCLUSION

Awake craniotomy with intraoperative mapping can be done safely for perirolandic gliomas with lower but statistically nonsignificant incidence of intraoperative seizures and this could be attributed to statistically significant lower stimulation intensities required for mapping. Preoperative multiple AEDs and low-grade glioma are significant predictors for intraoperative seizures.

Incidence and impact of stroke following surgery for low-grade gliomas

OBJECTIVE

Ischemic complications are a common cause of neurological deficits following low-grade glioma (LGG) surgeries. In this study, the authors evaluated the incidence, risk factors, and long-term implications of intraoperative ischemic events.

METHODS

The authors retrospectively evaluated patients who had undergone resection of an LGG between 2013 and 2017. Analysis included pre- and postoperative demographic, clinical, radiological, and anesthetic data, as well as intraoperative neurophysiology data, overall survival, and functional and neurocognitive outcomes.

RESULTS

Among the 82 patients included in the study, postoperative diffusion-weighted imaging showed evidence of acute ischemic strokes in 19 patients (23%), 13 of whom (68%) developed new neurological deficits. Infarcts were more common in recurrent and insular surgeries (p < 0.05). Survival was similar between the patients with and without infarcts. Immediately after surgery, 27% of the patients without infarcts and 58% of those with infarcts experienced motor deficits (p = 0.024), decreasing to 16% (p = 0.082) and 37% (p = 0.024), respectively, at 1 year. Neurocognitive functions before and 3 months after surgery were generally stable for the two groups, with the exception of a decline in verbal rhyming ability among patients with infarcts. Confusion during awake craniotomy was a strong predictor of the occurrence of an ischemic stroke. Mean arterial pressure at the beginning of surgery was significantly lower in the infarct group.

CONCLUSIONS

Recurrent surgeries and insular tumor locations are risk factors for intraoperative strokes. Although they do not affect survival, these strokes negatively affect patient activity and performance status, mainly during the first 3 postoperative months, with gradual functional improvement over 1 year. Several intraoperative parameters may suggest the impending development of an infarct.

Clinical Pearls and Methods for Intraoperative Awake Language Mapping

Intraoperative language mapping of tumor and peritumor tissue is a well-established technique for avoiding permanent neurological deficits and maximizing extent of resection. Although there are several components of language that may be tested intraoperatively (eg, naming, writing, reading, and repetition), there is a lack of consistency in how patients are tested intraoperatively as well as the techniques involved to ensure safety during an awake procedure. Here, we review appropriate patient selection, neuroanesthetic techniques, cortical and subcortical language mapping stimulation paradigms, and selection of intraoperative language tasks used during awake craniotomies. We also expand on existing language mapping reviews by considering how intensity and timing of electrical stimulation may impact interpretation of mapping results.

Preoperative Prediction of Communication Difficulties during Awake Craniotomy in Glioma Patients: A Retrospective Evaluation of 136 Cases at a Single Institution

Awake craniotomy has been widely performed in patients with glioma in eloquent areas to minimize postoperative brain dysfunction. However, neurological examination in awake craniotomy is sometimes problematic due to communication difficulties during the intraoperative awake period. We evaluated preoperative predictors of these difficulties in awake craniotomy for patients with glioma. In all, 136 patients with glioma who underwent awake craniotomy at our institution between January 2012 and January 2020 were retrospectively evaluated. Patients were divided into two groups (appropriately awake group and inappropriately awake group) depending on their state during the intraoperative awake period, and the relationship between communication difficulties in awake craniotomy and both clinical and radiological characteristics were assessed. The appropriately awake group included 110 patients, and the inappropriately awake group included 26 patients. Reasons for inclusion in the inappropriately awake group were insufficient wakefulness in 15 patients, restless state in 6, and intraoperative seizures in 5. In multivariate analysis, the likelihood of being inappropriately awake was inversely correlated with preoperative seizures (odds ratio [OR], 0.23; 95% confidence interval [CI], 0.06–0.89; p = 0.033) and positively correlated with left-sided lesions (OR, 7.31; 95% CI, 1.54–34.62; p = 0.012). Both lack of preoperative seizures and left-sided lesions were identified as risk factors for intraoperative difficulties in awake craniotomy for patients with glioma. Understanding these risk factors may lead to more appropriate determination of eligibility for awake craniotomy.

Intraoperative Direct Stimulation Identification and Preservation of Critical White Matter Tracts During Brain Surgery

The study of brain connectomics has led to a rapid evolution in the understanding of human brain function. Traditional localizationist theories are being replaced by more accurate network, or hodologic, approaches that model brain function as widespread processes dependent on cortical and subcortical structures, as well as the white matter tracts (WMTs) that link these areas. Recent surgical literature suggests that WMTs may be more critical to preserve than cortical structures because of the comparably lower capacity of recovery of the former when damaged. Given the relevance of eloquent WMTs to neurologic function and thus quality of life, neurosurgical interventions must be tailored to maximize their preservation. Direct electric stimulation remains a vital tool for identification and avoidance of these critical tracts. Neurosurgeons therefore require proper understanding of the anatomy and function of WMTs, as well as the reported contemporary tasks used during intraoperative stimulation. We review the relevant tracts involved in language, visuospatial, and motor networks and the updated direct electric stimulation-based mapping tasks that aid in their preservation. The dominant-hemisphere language WMTs have been mapped using picture naming, semantic association, word repetition, reading, and writing tasks. For monitoring of vision and spatial functions, the modified picture naming and line bisection tasks, as well as the recording of visual evoked potentials, have been used. Repetitive movements and monitoring of motor evoked potentials and involuntary movements have been applied for preservation of the motor networks.

Glioma surgery with awake language mapping versus generalized anesthesia: a systematic review

Awake craniotomy with language mapping is being increasingly applied to avoid postoperative language dysfunctions worldwide. However, the effectiveness and reliability of this technique remain unclear due to the paucity of studies comparing the awake craniotomy with general anesthesia. To determine the benefit of awake craniotomy for language, motor, and neurological functions, as well as other clinical outcomes, we searched Medline, Embase, the Cochrane Library, and the Chinese Biomedical Literature Database up to December 2019. Gray literatures were also searched. We included randomized and non-randomized controlled studies comparing awake craniotomy versus general anesthetic resection and reporting the language and neurological outcomes. Ten studies with 833 patients were included in the meta-analysis. The pooled risk ratio (RR) suggested no significant differences in language and neurological outcomes between general anesthesia group and awake craniotomy group without electrical stimulation. Awake craniotomy with electrical stimulation, however, was associated with improved late language and neurological outcomes (≥ 3 months) versus general anesthesia with pooled RR of 0.44 (95% CI = 0.20-0.96) and 0.49 (95% CI = 0.30-0.79), respectively. Awake craniotomy with electrical stimulation was also associated with better extent of resection with the pooled RR of 0.81 (95%CI = 0.71-0.92) and shorter hospital stay duration with the pooled weighted mean difference (WMD) of - 1.14 (95%CI = - 1.80 to - 0.48). This meta-analysis suggested that the application of awake craniotomy with electrical stimulation during glioma resection is associated with lower risks of long-term neurological and language deficits and higher extent of tumor resection, as well as shorter hospital stay duration.

Optimizing the onco-functional balance in supratentorial brain tumour surgery: A single institution's initial experience with intraoperative cortico-subcortical mapping and monitoring in Singapore

Intraoperative cortical mapping provides functional information that permits the safe and maximal resection of supratentorial lesions infiltrating the so-called eloquent cortex or subcortical white matter tracts. Primary and secondary brain tumours located in eloquent cortex can render surgical treatment ineffective if it results in new or worsening neurology. A cohort of forty-six consecutive patients with supratentorial tumours of variable pathology involving eloquent cortical regions and aided with intraoperative neurophysiology were included for retrospective analysis at a single-centre tertiary institution. Intraoperative neurophysiological data has been related to immediate post-operative neurologic status as well as 3-month follow-up in patients that underwent awake or asleep surgical resection. Patients that experienced new or worsening neurologic symptoms post-operatively demonstrated a high incidence of recovery at 3-months. Those without new neurologic symptoms post-operatively demonstrated little to no worsening at 3-months. Our study explored the extent to which cortical mapping permitted safe surgical resection whilst preserving neurologic function. To the authors' knowledge this is the first documented case series in Singapore that has incorporated a systematic and individually tailored multimodal workflow to cortico-subcortical mapping and monitoring for the safe resection of infiltrative lesions of the supratentorial region.

Pre- and Intraoperative Mapping for Tumors in the Primary Motor Cortex: Decision-Making Process in Surgical Resection

BACKGROUND

 Lesions within the primary motor cortex (M1) and the corticospinal tract (CST) represent a significant surgical challenge with a delicate functional trade-off that should be integrated in the overall patient-centered treatment plan.

METHODS

 Patients with lesions within the M1 and CST with preoperative cortical and subcortical mapping (navigated transcranial magnetic stimulation [nTMS] and tractography), intraoperative mapping, and intraoperative provisional histologic information (smear with and without 5-aminolevulinic acid [5-ALA]) were included. This independently acquired information was integrated in a decision-making process model to determine the intraoperative extent of resection.

RESULTS

 A total of 10 patients (6 patients with metastatic precentral tumor; 1 patient with grade III and 2 patients with grade IV gliomas; 1 patient with precentral cavernoma) were included in the study. Most of the patients (60%) had a preoperative motor deficit. The nTMS documented M1 invasion in all cases, and in eight patients, the lesions were embedded within the CST. Overall, 70% of patients underwent gross total resection; 20% of patients underwent near-total resection of the lesions. In only one patient was no surgical resection possible after both preoperative and intraoperative mapping. Overall, 70% of patients remained stable postoperatively, and previous motor weakness improved in 20%.

CONCLUSION

 The independently acquired anatomical (anatomical MRI) and functional (nTMS and tractography) tests in patients with CST lesions provide a useful guide for resection. The inclusion of histologic information (smear with or without 5-ALA) further allows the surgical team to balance the potential functional risks within the global treatment plan. Therefore, the patient is kept at the center of the informed decision-making process.

Awake glioma surgery: technical evolution and nuances

INTRODUCTION

Multiple studies have demonstrated that improved extent of resection is associated with longer overall survival for patients with both high and low grade glioma. Awake craniotomy was developed as a technique for maximizing resection whilst preserving neurological function.

METHODS

We performed a comprehensive review of the literature describing the history, indications, techniques and outcomes of awake craniotomy for patients with glioma.

RESULTS

The technique of awake craniotomy evolved to become an essential tool for resection of glioma. Many perceived contraindications can now be managed. We describe in detail our preferred technique, the testing paradigms utilized, and critically review the literature regarding functional and oncological outcome.

CONCLUSIONS

Awake craniotomy with mapping has become the gold standard for safely maximizing extent of resection for tumor in or near eloquent brain. Cortical and subcortical mapping methods have been refined and the technique is associated with an extremely low rate of complications.