Tag: language

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

Neurosurg Focus 53 (6):E3, 2022

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 trueeloquent from false-eloquent tumors in a significant number of cases based on the occurrence of deficits at discharge (p < 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.

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Tumor location and reduction in functional MRI estimates of language laterality

J Neurosurg 135:1674–1684, 2021

Brain tumors located close to the language cortex may distort functional MRI (fMRI)–based estimates of language dominance. The nature of this distortion, and whether this is an artifact of numerous confounders, remains unknown. The authors hypothesized tumor bias based on laterality estimates independent of confounders and that the effects are the greatest for tumors proximal to Broca’s area.

METHODS To answer this question, the authors reviewed more than 1113 patients who underwent preoperative fMRI to match samples on 11 known confounders (tumor location, size, type, and grade; seizure history; prior neurosurgery; aphasia presence and severity; and patient age, sex, and handedness). The samples included 30 patients with left hemisphere tumors (15 anterior and 15 posterior) and 30 with right hemisphere tumors (15 anterior and 15 posterior), thus totaling 60 patients (25 women; 18 left-handed and 4 ambidextrous; mean age 47 [SD 14.1] years). Importantly, the authors matched not only patients with left and right hemisphere tumors but also those with anterior and posterior tumors. Standard fMRI laterality indices (LIs) were calculated using whole-brain and region of interest (ROI) approaches (Broca’s and Wernicke’s areas).

RESULTS Tumors close to Broca’s area in the left hemisphere decreased LIs independently of known confounders. At the whole-brain level, this appeared to reflect a decrease in LI values in patients with left anterior tumors compared with patients with right anterior tumors. ROI analysis replicated these findings. Broca’s area LIs were significantly lower (p = 0.02) in patients with left anterior tumors (mean LI 0.28) when compared with patients with right anterior tumors (mean LI 0.70). Changes in Wernicke’s area–based LIs did not differ as a function of the tumor hemisphere. Therefore, in patients with left anterior tumors, it is essential to assess language laterality using left posterior ROIs. In all remaining tumor groups (left posterior tumors and right hemisphere tumors), language laterality derived from the anterior language ROI was the most robust measure of language dominance.

CONCLUSIONS Patients with tumors close to Broca’s area showed more bilateral fMRI language maps independent of known confounders. The authors caution against the assumption that this reduced language laterality suggests no or little risk to language function following tumor resection in the left inferior frontal gyrus. Their results address how to interpret fMRI data for neurosurgical purposes, along with theoretical questions of contralesional functional compensation and disinhibition.

 

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Central Nervous System Plasticity Influences Language and Cognitive Recovery in Adult Glioma

Neurosurgery 89:539–548, 2021

Gliomas exist within the framework of complex neuronal circuitry in which network dynamics influence both tumor biology and cognition. The generalized impairment of cognition or loss of language function is a common occurrence for glioma patients.

The interface between intrinsic brain tumors such as gliomas and functional cognitive networks are poorly understood. The ability to communicate effectively is critically important for receiving oncological therapies and maintaining a high quality of life.

Although the propensity of gliomas to infiltrate cortical and subcortical structures and disrupt key anatomic language pathways is well documented, there is new evidence offering insight into the network and cellular mechanisms underpinning glioma-related aphasia and aphasia recovery.

In this review, we will outline the current understanding of the mechanisms of cognitive dysfunction and recovery, using aphasia as an illustrative model.

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Incidence and linguistic quality of speech errors: a comparison of preoperative transcranial magnetic stimulation and intraoperative direct cortex stimulation

J Neurosurg 134:1409–1418, 2021

Given the interindividual variance of functional language anatomy, risk prediction based merely on anatomical data is insufficient in language area–related brain tumor surgery, suggesting the need for direct cortical and subcortical mapping during awake surgery. Reliable, noninvasive preoperative methods of language localization hold the potential for reducing the necessity for awake procedures and may improve patient counseling and surgical planning. Repetitive navigated transcranial magnetic stimulation (rnTMS) is an evolving tool for localizing language-eloquent areas. The aim of this study was to investigate the reliability of rnTMS in locating cortical language sites.

METHODS Twenty-five patients with brain tumors in speech-related areas were prospectively evaluated with preoperative rnTMS (5 Hz, train of five, average 105% resting motor threshold) and navigated direct cortical stimulation (DCS; bipolar, 50 Hz, 6–8 mA, 200-μsec pulse width) during awake surgeries employing a picture-naming task. Positive and negative stimulation spots within the craniotomy were documented in the same MRI data set. TMS and DCS languagepositive areas were compared with regard to their spatial overlap, their allocation in a cortical parcellation system, and their linguistic qualities.

RESULTS There were over twofold more positive language spots within the exposed area on rnTMS than on DCS. The comparison of positive rnTMS and DCS (ground truth) overlaps revealed low sensitivity (35%) and low positive predictive value (16%) but high specificity (90%) and high negative predictive value (96%). Within the overlaps, there was no correlation in error quality. On DCS, 73% of language-positive spots were located in the pars opercularis and pars triangularis of the frontal operculum and 24% within the supramarginal gyrus and dorsal portion of the superior temporal gyrus, while on rnTMS language positivity was distributed more evenly over a large number of gyri.

CONCLUSIONS The current protocol for rnTMS for language mapping identified language-negative sites with good dependability but was unable to reliably detect language-positive spots. Further refinements of the technique will be needed to establish rnTMS language mapping as a useful clinical tool.

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Protocol for motor and language mapping by navigated TMS in patients and healthy volunteers

Acta Neurochir (2017) 159:1187–1195

Navigated transcranial magnetic stimulation (nTMS) is increasingly used for preoperative mapping of motor function, and clinical evidence for its benefit for brain tumor patients is accumulating. In respect to language mapping with repetitive nTMS, literature reports have yielded variable results, and it is currently not routinely performed for presurgical language localization. The aim of this project is to define a common protocol for nTMS motor and language mapping to standardize its neurosurgical application and increase its clinical value.

Methods: The nTMS workshop group, consisting of highly experienced nTMS users with experience of more than 1500 preoperative nTMS examinations, met in Helsinki in January 2016 for thorough discussions of current evidence and personal experiences with the goal to recommend a standardized protocol for neurosurgical applications.

Results: nTMS motor mapping is a reliable and clinically validated tool to identify functional areas belonging to both normal and lesioned primary motor cortex. In contrast, this is less clear for language-eloquent cortical areas identified by nTMS. The user group agreed on a core protocol, which enables comparison of results between centers and has an excellent safety profile. Recommendations for nTMS motor and language mapping protocols and their optimal clinical integration are presented here.

Conclusion: At present, the expert panel recommends nTMS motor mapping in routine neurosurgical practice, as it has a sufficient level of evidence supporting its reliability. The panel recommends that nTMS language mapping be used in the framework of clinical studies to continue refinement of its protocol and increase reliability.

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Variability of intraoperative electrostimulation parameters in conscious individuals: language cortex

J Neurosurg 126:1641–1652, 2017

Electrostimulation in awake brain mapping is widely used to guide tumor removal, but methodologies can differ substantially across institutions. The authors studied electrostimulation brain mapping data to characterize the variability of the current intensity threshold across patients and the effect of its variations on the number, type, and surface area of the essential language areas detected.

METHODS Over 7 years, the authors prospectively studied 100 adult patients who were undergoing intraoperative brain mapping during resection of left hemisphere tumors. In all 100 cases, the same protocol of electrostimulation brain mapping (a controlled naming task—bipolar stimulation with biphasic square wave pulses of 1-msec duration and 60-Hz trains, maximum train duration 6 sec) and electrocorticography was used to detect essential language areas.

RESULTS The minimum positive thresholds of stimulation varied from patient to patient; the mean minimum intensity required to detect interference was 4.46 mA (range 1.5–9 mA), and in a substantial proportion of sites (13.5%) interference was detected only at intensities above 6 mA. The threshold varied within a given patient for different naming areas in 22% of cases. Stimulation of the same naming area with greater intensities led to slight changes in the type of response in 19% of cases and different types of responses in 4.5%. Naming sites detected were located in subcentimeter cortical areas (50% were less than 20 mm2), but their extent varied with the intensity of stimulation. During a brain mapping session, the same intensity of stimulation reproduced the same type of interference in 94% of the cases. There was no statistically significant difference between the mean stimulation intensities required to produce interfereince in the left inferior frontal lobe (Broca’s area), the supramarginal gyri, and the posterior temporal region.

CONCLUSIONS Intrasubject and intersubject variations of the minimum thresholds of positive naming areas and changes in the type of response and in the size of these areas according to the intensity used may limit the interpretation of data from electrostimulation in awake brain mapping. To optimize the identification of language areas during electrostimulation brain mapping, it is important to use different intensities of stimulation at the maximum possible currents, avoiding afterdischarges. This could refine the clinical results and scientific data derived from these mapping sessions.

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Passive language mapping combining real-time oscillation analysis with cortico-cortical evoked potentials for awake craniotomy

J Neurosurg 125:1580–1588, 2016

Electrocortical stimulation (ECS) is the gold standard for functional brain mapping; however, precise functional mapping is still difficult in patients with language deficits. High gamma activity (HGA) between 80 and 140 Hz on electrocorticography is assumed to reflect localized cortical processing, whereas the cortico-cortical evoked potential (CCEP) can reflect bidirectional responses evoked by monophasic pulse stimuli to the language cortices when there is no patient cooperation. The authors propose the use of “passive” mapping by combining HGA mapping and CCEP recording without active tasks during conscious resections of brain tumors.

Methods Five patients, each with an intraaxial tumor in their dominant hemisphere, underwent conscious resection of their lesion with passive mapping. The authors performed functional localization for the receptive language area, using real-time HGA mapping, by listening passively to linguistic sounds. Furthermore, single electrical pulses were delivered to the identified receptive temporal language area to detect CCEPs in the frontal lobe. All mapping results were validated by ECS, and the sensitivity and specificity were evaluated.

Results Linguistic HGA mapping quickly identified the language area in the temporal lobe. Electrical stimulation by linguistic HGA mapping to the identified temporal receptive language area evoked CCEPs on the frontal lobe. The combination of linguistic HGA and frontal CCEPs needed no patient cooperation or effort. In this small case series, the sensitivity and specificity were 93.8% and 89%, respectively.

Conclusions The described technique allows for simple and quick functional brain mapping with higher sensitivity and specificity than ECS mapping. The authors believe that this could improve the reliability of functional brain mapping and facilitate rational and objective operations. Passive mapping also sheds light on the underlying physiological mechanisms of language in the human brain.

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Mapping of cortical language function by functional magnetic resonance imaging and repetitive navigated transcranialmagnetic stimulation in 40 healthy subjects

Mapping of cortical language function by functional magnetic resonance imaging and repetitive navigated transcranial magnetic stimulation in 40 healthy subjects

Acta Neurochir (2016) 158:1303–1316

Functional magnetic resonance imaging (fMRI) is considered to be the standard method regarding noninvasive language mapping. However, repetitive navigated transcranial magnetic stimulation (rTMS) gains increasing importance with respect to that purpose. However, comparisons between both methods are sparse.

Methods We performed fMRI and rTMS language mapping of the left hemisphere in 40 healthy, right-handed subjects in combination with the tasks that are most commonly used in the neurosurgical context (fMRI: word-generation=WGEN task; rTMS: object-naming=ON task). Different rTMS error rate thresholds (ERTs) were calculated, and Cohen’s kappa coefficient and the cortical parcellation system (CPS) were used for systematic comparison of the two techniques.

Results Overall, mean kappa coefficients were low, revealing no distinct agreement. We found the highest agreement for both techniques when using the 2-out-of-3 rule (CPS region defined as language positive in terms of rTMS if at least 2 out of 3 stimulations led to a naming error). However, kappa for this threshold was only 0.24 (kappa of <0, 0.01–0.20, 0.21– 0.40, 0.41–0.60, 0.61–0.80 and 0.81–0.99 indicate less than chance, slight, fair, moderate, substantial and almost perfect agreement, respectively).

Conclusions Because of the inherent differences in the underlying physiology of fMRI and rTMS, the different tasks used and the impossibility of verifying the results via direct cortical stimulation (DCS) in the population of healthy volunteers, one must exercise caution in drawing conclusions about the relative usefulness of each technique for language mapping. Nevertheless, this study yields valuable insights into these two mapping techniques for the most common language tasks currently used in neurosurgical practice.

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Identifying preoperative language tracts and predicting postoperative functional recovery using HARDI q-ball fiber tractography in patients with gliomas

Identifying preoperative language tracts and predicting postoperative functional recovery using HARDI q-ball ber tractography in patients with gliomas

J Neurosurg 125:33–45, 2016

Diffusion MRI has uniquely enabled in vivo delineation of white matter tracts, which has been applied to the segmentation of eloquent pathways for intraoperative mapping. The last decade has also seen the development from earlier diffusion tensor models to higher-order models, which take advantage of high angular resolution diffusion-weighted imaging (HARDI) techniques. However, these advanced methods have not been widely implemented for routine preoperative and intraoperative mapping. The authors report on the application of residual bootstrap q-ball fiber tracking for routine mapping of potentially functional language pathways, the development of a system for rating tract injury to evaluate the impact on clinically assessed language function, and initial results predicting long-term language deficits following glioma resection.

Methods: The authors have developed methods for the segmentation of 8 putative language pathways including dorsal phonological pathways and ventral semantic streams using residual bootstrap q-ball fiber tracking. Furthermore, they have implemented clinically feasible preoperative acquisition and processing of HARDI data to delineate these pathways for neurosurgical application. They have also developed a rating scale based on the altered fiber tract density to estimate the degree of pathway injury, applying these ratings to a subset of 35 patients with pre- and postoperative fiber tracking. The relationships between specific pathways and clinical language deficits were assessed to determine which pathways are predictive of long-term language deficits following surgery.

Results: This tracking methodology has been routinely implemented for preoperative mapping in patients with brain gliomas who have undergone awake brain tumor resection at the University of California, San Francisco (more than 300 patients to date). In this particular study the authors investigated the white matter structure status and language correlation in a subcohort of 35 subjects both pre- and postsurgery. The rating scales developed for fiber pathway damage were found to be highly reproducible and provided significant correlations with language performance. Preservation of the left arcuate fasciculus (AF) and the temporoparietal component of the superior longitudinal fasciculus (SLF-tp) was consistent in all patients without language deficits (p < 0.001) at the long-term follow-up. Furthermore, in patients with short-term language deficits, the AF and/or SLF-tp were affected, and damage to these 2 pathways was predictive of a long-term language deficit (p = 0.005).

Conclusions: The authors demonstrated the successful application of q-ball tracking in presurgical planning for language pathways in brain tumor patients and in assessing white matter tract integrity postoperatively to predict long-term language dysfunction. These initial results predicting long-term language deficits following tumor resection indicate that postoperative injury to dorsal language pathways may be prognostic for long-term clinical language deficits. Study results suggest the importance of dorsal stream tract preservation to reduce language deficits in patients undergoing glioma resection, as well as the potential prognostic value of assessing postoperative injury to dorsal language pathways to predict long-term clinical language deficits.

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Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

Combined noninvasive language mapping by navigated transcranial magnetic stimulation and functional MRI and its comparison with direct cortical stimulation

 

J Neurosurg 123:212–225, 2015

Repetitive navigated transcranial magnetic stimulation (rTMS) is now increasingly used for preoperative language mapping in patients with lesions in language-related areas of the brain. Yet its correlation with intraoperative direct cortical stimulation (DCS) has to be improved. To increase rTMS’s specificity and positive predictive value, the authors aim to provide thresholds for rTMS’s positive language areas. Moreover, they propose a protocol for combining rTMS with functional MRI (fMRI) to combine the strength of both methods.

Methods The authors performed multimodal language mapping in 35 patients with left-sided perisylvian lesions by using rTMS, fMRI, and DCS. The rTMS mappings were conducted with a picture-to-trigger interval (PTI, time between stimulus presentation and stimulation onset) of either 0 or 300 msec. The error rates (ERs; that is, the number of errors per number of stimulations) were calculated for each region of the cortical parcellation system (CPS). Subsequently, the rTMS mappings were analyzed through different error rate thresholds (ERT; that is, the ER at which a CPS region was defined as language positive in terms of rTMS), and the 2-out-of-3 rule (a stimulation site was defined as language positive in terms of rTMS if at least 2 out of 3 stimulations caused an error). As a second step, the authors combined the results of fMRI and rTMS in a predefined protocol of combined noninvasive mapping. To validate this noninvasive protocol, they correlated its results to DCS during awake surgery.

Results The analysis by different rTMS ERTs obtained the highest correlation regarding sensitivity and a low rate of false positives for the ERTs of 15%, 20%, 25%, and the 2-out-of-3 rule. However, when comparing the combined fMRI and rTMS results with DCS, the authors observed an overall specificity of 83%, a positive predictive value of 51%, a sensitivity of 98%, and a negative predictive value of 95%.

Conclusions In comparison with fMRI, rTMS is a more sensitive but less specific tool for preoperative language mapping than DCS. Moreover, rTMS is most reliable when using ERTs of 15%, 20%, 25%, or the 2-out-of-3 rule and a PTI of 0 msec. Furthermore, the combination of fMRI and rTMS leads to a higher correlation to DCS than both techniques alone, and the presented protocols for combined noninvasive language mapping might play a supportive role in the language-mapping assessment prior to the gold-standard intraoperative DCS.

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A Comparison of Language Mapping by Preoperative Navigated Transcranial Magnetic Stimulation and Direct Cortical Stimulation During Awake Surgery

A_Comparison_of_Language_Mapping_by_Preoperative

Neurosurgery 72:808–819, 2013

Navigated transcranial magnetic stimulation (nTMS) is increasingly used in presurgical brain mapping. Preoperative nTMS results correlate well with direct cortical stimulation (DCS) data in the identification of the primary motor cortex. Repetitive nTMS can also be used for mapping of speech-sensitive cortical areas.

OBJECTIVE: The current cohort study compares the safety and effectiveness of preoperative nTMS with DCS mapping during awake surgery for the identification of language areas in patients with left-sided cerebral lesions.

METHODS: Twenty patients with tumors in or close to left-sided language eloquent regions were examined by repetitive nTMS before surgery. During awake surgery, language-eloquent cortex was identified by DCS. nTMS results were compared for accuracy and reliability with regard to DCS by projecting both results into the cortical parcellation system.

RESULTS: Presurgical nTMS maps showed an overall sensitivity of 90.2%, specificity of 23.8%, positive predictive value of 35.6%, and negative predictive value of 83.9% compared with DCS. For the anatomic Broca’s area, the corresponding values were a sensitivity of 100%, specificity of 13.0%, positive predictive value of 56.5%, and negative predictive value of 100%, respectively.

CONCLUSION: Good overall correlation between repetitive nTMS and DCS was observed, particularly with regard to negatively mapped regions. Noninvasive inhibition mapping with nTMS is evolving as a valuable tool for preoperative mapping of language areas. Yet its low specificity in posterior language areas in the current study necessitates further research to refine the methodology.

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Noninvasive Language Mapping in Patients With Epilepsy or Brain Tumors

Noninvasive_Language_Mapping_in_Patients_With

Neurosurgery 72:555–565, 2013

Functional magnetic resonance imaging (fMRI) has become part of routine brain mapping in patients with epilepsy or tumor undergoing resective surgery. However, robust localization of crucial functional areas is required.

OBJECTIVE: To establish a simple, short fMRI task that reliably localizes crucial language areas in individual patients who undergo respective surgery.

METHODS: fMRI was measured during an 8-minute auditory semantic decision task in 28 healthy controls and 35 consecutive patients who had focal epilepsy or a brain tumor. Nineteen underwent resective surgery. Group and individual analyses were performed. Results in patients were compared with postsurgical language outcome and electrocortical stimulation when available.

RESULTS: fMRI activations concordant with the anterior and posterior language areas were found in 96% and 89% of the controls, respectively. The anterior and posterior language areas were both activated in 93% of the patients. These results were concordant with electrocortical stimulation results in 5 patients. Transient postsurgical language deficits were found in 2 patients in whom surgery was performed in the vicinity of the fMRI activations or who had postsurgical complications implicating areas of fMRI activations.

CONCLUSION: The proposed fast fMRI language protocol reliably localized the most relevant language areas in individual subjects. It appears to be a valuable complementary tool for surgical planning of epileptogenic foci and of brain tumors.

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A Detailed Analysis of Functional Magnetic Resonance Imaging in the Frontal Language Area: A Comparative Study With Extraoperative Electrocortical Stimulation

Neurosurgery 69:590–597, 2011 DOI: 10.1227/NEU.0b013e3182181be1

Functional magnetic resonance imaging (fMRI) is a less invasive way of mapping brain functions. The reliability of fMRI for localizing language-related function is yet to be determined.

OBJECTIVE: We performed a detailed analysis of language fMRI reliability by comparing the results of 3-T fMRI with maps determined by extraoperative electrocortical stimulation (ECS).

METHODS: This study was performed on 8 epileptic patients who underwent subdural electrode placement. The tasks performed during fMRI included verb generation, abstract/ concrete categorization, and picture naming. We focused on the frontal lobe, which was effectively activated by these tasks. In extraoperative ECS, 4 tasks were combined to determine the eloquent areas: spontaneous speech, picture naming, reading, and comprehension. We calculated the sensitivity and specificity with different Z score thresholds for each task and appropriate matching criteria. For further analysis, we divided the frontal lobe into 5 areas and investigated intergyrus variations in sensitivity and specificity.

RESULTS: The abstract/concrete categorization task was the most sensitive and specific task in fMRI, whereas the picture naming task detected eloquent areas most efficiently in ECS. The combination of the abstract/concrete categorization task and a 3-mm matching criterion gave the best tradeoff (sensitivity, 83%; specificity, 61%) when the Z score was 2.24. As for intergyrus variation, the posterior inferior frontal gyrus showed the best tradeoff (sensitivity, 91%; specificity, 59%), whereas the anterior middle frontal gyrus had low specificity.

CONCLUSION: Despite different tasks for fMRI and extraoperative ECS, the relatively low specificity might be caused by a fundamental discrepancy between the 2 techniques. Reliability of language fMRI activation might differ, depending on the brain region.

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Functional outcome after language mapping for insular WHO Grade II gliomas in the dominant hemisphere: experience with 24 patients

Neurosurg Focus 27 (2):E7, 2009
Despite the report of recent experiences of insular surgery in the past decade, there has been no series specifically dedicated to studying functional outcome following resection of insular WHO Grade II gliomas involving the dominant hemisphere, in patients with no or only mild preoperative language deficit. In this article, the authors analyze the contribution of awake mapping for preservation of brain function, especially language, in a homogeneous series of 24 patients who underwent surgery for insular Grade II gliomas within the dominant insular lobe.

Methods
Twenty-four patients underwent surgery for an insular Grade II glioma involving the dominant hemisphere (22 left, 2 right), revealed by seizures in all but 1 case. The preoperative neurological examination result was normal in 17 patients (71%), whereas 7 patients presented with language disorders detected using an accurate language assessment performed by a speech therapist. All surgeries were performed on awake patients utilizing intra-operative language mapping involving cortical and subcortical stimulation.

Results
There were no intrasurgical complications or postsurgical sensorimotor deficits. Despite an immediate postoperative language worsening in 12 cases (50%), all patients recovered to a normal status within 3 months, and 6 cases even improved in comparison with their preoperative examination results. The 24 patients returned to normal social and professional lives. Moreover, the surgery had a favorable impact on epilepsy in all but 4 cases (83%). On control MR imaging, 62.5% of resections were total or subtotal. Three patients underwent a second or third awake surgery, with no additional deficit. All but 2 patients (92%) are alive after a mean follow-up of 3 years (range 3–133 months).

Conclusions
Although insular surgery was long believed to be too risky, the present results show that the rate of permanent deficit, especially dysphasia, following resection of Grade II gliomas involving the dominant insula has been dramatically reduced (none in this patient series), thanks to the systematic use of intraoperative awake mapping, even in cases of repeated operations. Furthermore, patient quality of life may be improved due to a decrease of epilepsy after surgery. Thus, the authors suggest systematically considering resection when an insular Grade II glioma is diagnosed after seizures in a patient with no or mild deficit, even a glioma invading the dominant hemisphere.

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