Intraoperative Electrical Stimulation Mapping Research Articles

Intraoperative seizure outcome of levetiracetam combined with perampanel therapy in patients with glioma undergoing awake brain surgery.

This study aimed to evaluate the efficacy of levetiracetam (LEV) combined with perampanel (PER) therapy for intraoperative seizure treatment to determine whether a combination of LEV and PER can aid in the prevention of intraoperative intractable seizures during awake surgery. The authors performed a retrospective cohort study in 78 consecutive patients with glioma who underwent awake surgery using intraoperative direct electrical stimulation mapping. To prevent intraoperative seizures, 50 patients were treated with the antiepileptic drug LEV only (LEV group) from January 2017 to January 2019, while the remaining 28 patients were treated with LEV plus PER (LEV + PER group) between March 2019 and January 2020. LEV (1000-3000 mg) and/or PER (2-4 mg) were administered before the surgery. Preoperative seizures with International League Against Epilepsy (ILAE) class II-VI occurred in 44% of the patients in the LEV group and in 35.7% of patients in the LEV + PER group, with no significant difference between groups (p = 0.319). Total intraoperative seizures occurred in 18 patients (36.0%) in the LEV therapy group and in 2 patients (7.1%) in the LEV + PER group (p = 0.009). Of these, there were no patients (0%) with intractable seizures in the LEV + PER group. Regarding factors that influence intraoperative seizures in glioma patients during awake brain surgery, multivariate logistic regression models revealed that the occurrence of intraoperative seizures was significantly related to the involvement of motor-related regions (positive vs negative, HR 6.98, 95% CI 1.71-28.56, p = 0.007), preoperative seizure (ILAE class II-VI vs ILAE class I, HR 4.44, 95% CI 1.22-16.11, p = 0.024), and LEV + PER group (positive vs negative, HR 0.07, 95% CI 0.01-0.44, p = 0.005). Treatment-related adverse effects were rare and mild, including sleepiness, tiredness, and dizziness in both treatment groups. This study demonstrates that LEV + PER therapy is significantly associated with a lower risk of intraoperative seizures compared with LEV therapy alone in patients with glioma during awake brain mapping. These findings will help neurosurgeons conduct safe and reliable awake surgeries and reduce the rate of intraoperative intractable seizures during such procedures.

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.

Predicting the Extent of Resection in Low-Grade Glioma by Using Intratumoral Tractography to Detect Eloquent Fascicles Within the Tumor.

An early maximal safe surgical resection is the current treatment paradigm for low-grade glioma (LGG). Nevertheless, there are no reliable methods to accurately predict the axonal intratumoral eloquent areas and, consequently, to predict the extent of resection. To describe the functional predictive value of eloquent white matter tracts within the tumor by using a pre- and postoperative intratumoral diffusion tensor imaging (DTI) tractography protocol in patients with LGG. A preoperative intratumoral DTI-based tractography protocol, using the tumor segmented volume as the only seed region, was used to assess the tracts within the tumor boundaries in 22 consecutive patients with LGG. The reconstructed tracts were correlated with intraoperative electrical stimulation (IES)-based language and motor subcortical mapping findings and the extent of resection was assessed by tumor volumetrics. Identification of intratumoral language and motor tracts significantly predicted eloquent areas within the tumor during the IES mapping: the positive predictive value for the pyramidal tract, the inferior fronto-occipital fasciculus, the arcuate fasciculus and the inferior longitudinal fasciculus positive was 100%, 100%, 33%, and 80%, respectively, whereas negative predictive value was 100% for all of them. The reconstruction of at least one of these tracts within the tumor was significantly associated with a lower extent of resection (67%) as opposed to the extent of resection in the cases with a negative intratumoral tractography (100%) (P<.0001). Intratumoral DTI-based tractography is a simple and reliable method, useful in assessing glioma resectability based on the analysis of intratumoral eloquent areas associated with motor and language tracts within the tumor.

Current strategies for the treatment of malignant gliomas - experience of the Department of Neurosurgery, Brodno Masovian Hospital in Warsaw.

Malignant gliomas (HGG) are the most common primary malignant brain tumors arising from glial cells. Between HGG, glioblastoma is the most common and the most malignant histological subtype with only a 27% 2-year survival rate. Current standard medical treatment of malignant gliomas is still not satisfactory, and may need some development and modification. We presented and discussed the achievements of the Department of Neurosurgery at Brodno Masovian Hospital in the treatment of malignant gliomas. We step by step presented and discussed the policy in the treatment of malignant gliomas. We showed all steps starting from preparation of surgery (eg. neuroimaging) and finishing on the presentation the development of perioperative management - from intraoperative electrical stimulation mapping and monitoring which is nowadays already standard method to convection-enhanced delivery (CED) and gamma knife (GK) which are new and promising methods in the treatment of glioblastoma. All surgical methods described in this manuscript were introduced to achieve maximal and safe resection of malignant glioma. CED and GK are the last resort methods for patients with recurrent HGG. Department of Neurosurgery at Brodno Masovian Hospital deal with all types of brain tumors, including all types of high grade gliomas. As the first Department in Europe with close cooperation with the Department of Neurosurgery in San Francisco, we have started local infusions of drugs directly to the tumor in the real time of magnetic field, and we think that technology may change all approaches to the treatment of high grade gliomas.

A novel effective paradigm of intraoperative electrical stimulation mapping in children.

Resective epilepsy surgery is an established treatment method for children with focal intractable epilepsy, but the use of this method introduces the risk of postsurgical motor deficits. Electrical stimulation mapping (ESM), used to define motor areas and pathways, frequently fails in children. The authors developed and tested a novel ESM protocol in children of all age categories. The ESM protocol utilizes high-frequency electric cortical stimulation combined with continuous intraoperative motor-evoked potential (MEP) monitoring. The relationships between stimulation current intensity and selected presurgical and surgery-associated variables were analyzed in 66 children (aged 7 months to 18 years) undergoing 70 resective epilepsy surgeries in proximity to the motor cortex or corticospinal tracts. ESM elicited MEP responses in all children. Stimulation current intensity was associated with patient age at surgery and date of surgery (F value = 6.81, p < 0.001). Increase in stimulation current intensity predicted postsurgical motor deficits (F value = 44.5, p < 0.001) without effects on patient postsurgical seizure freedom (p > 0.05). The proposed ESM paradigm developed in our center represents a reliable method for preventing and predicting postsurgical motor deficits in all age groups of children. This novel ESM protocol may increase the safety and possibly also the completeness of epilepsy surgery. It could be adopted in pediatric epilepsy surgery centers.

The impact of high functional connectivity network hub resection on language task performance in adult low- and high-grade glioma.

Gliomas are intrinsic brain tumors with the hallmark of diffuse white matter infiltration, resulting in short- and long-range network dysfunction. Preoperative magnetoencephalography (MEG) can assist in maximizing the extent of resection while minimizing morbidity. While MEG has been validated in motor mapping, its role in speech mapping remains less well studied. The authors assessed how the resection of intraoperative electrical stimulation (IES)-negative, high functional connectivity (HFC) network sites, as identified by MEG, impacts language performance. Resting-state, whole-brain MEG recordings were obtained from 26 patients who underwent perioperative language evaluation and glioma resection that was guided by awake language and IES mapping. The functional connectivity of an individual voxel was determined by the imaginary coherence between the index voxel and the rest of the brain, referenced to its contralesional pair. The percentage of resected HFC voxels was correlated with postoperative language outcomes in tasks of increasing complexity: text reading, 4-syllable repetition, picture naming, syntax (SYN), and auditory stimulus naming (AN). Overall, 70% of patients (14/20) in whom any HFC tissue was resected developed an early postoperative language deficit (mean 2.3 days, range 1-8 days), compared to 33% of patients (2/6) in whom no HFC tissue was resected (p = 0.16). When bifurcated by the amount of HFC tissue that was resected, 100% of patients (3/3) with an HFC resection > 25% displayed deficits in AN, compared to 30% of patients (6/20) with an HFC resection < 25% (p = 0.04). Furthermore, there was a linear correlation between the severity of AN and SYN decline with percentage of HFC sites resected (p = 0.02 and p = 0.04, respectively). By 2.2 months postoperatively (range 1-6 months), the correlation between HFC resection and both AN and SYN decline had resolved (p = 0.94 and p = 1.00, respectively) in all patients (9/9) except two who experienced early postoperative tumor progression or stroke involving inferior frontooccipital fasciculus. Imaginary coherence measures of functional connectivity using MEG are able to identify HFC network sites within and around low- and high-grade gliomas. Removal of IES-negative HFC sites results in early transient postoperative decline in AN and SYN, which resolved by 3 months in all patients without stroke or early tumor progression. Measures of functional connectivity may therefore be a useful means of counseling patients about postoperative risk and assist with preoperative surgical planning.

FMRI-Targeted High-Angular Resolution Diffusion MR Tractography to Identify Functional Language Tracts in Healthy Controls and Glioma Patients.

BackgroundMR Tractography enables non-invasive preoperative depiction of language subcortical tracts, which is crucial for the presurgical work-up of brain tumors; however, it cannot evaluate the exact function of the fibers.PurposeA systematic pipeline was developed to combine tractography reconstruction of language fiber bundles, based on anatomical landmarks (Anatomical-T), with language fMRI cortical activations. A fMRI-targeted Tractography (fMRI-T) was thus obtained, depicting the subsets of the anatomical tracts whose endpoints are located inside a fMRI activation. We hypothesized that fMRI-T could provide additional functional information regarding the subcortical structures, better reflecting the eloquent white matter structures identified intraoperatively.MethodsBoth Anatomical-T and fMRI-T of language fiber tracts were performed on 16 controls and preoperatively on 16 patients with left-hemisphere brain tumors, using a q-ball residual bootstrap algorithm based on High Angular Resolution Diffusion Imaging (HARDI) datasets (b = 3000 s/mm2; 60 directions); fMRI ROIs were obtained using picture naming, verbal fluency, and auditory verb generation tasks. In healthy controls, normalized MNI atlases of fMRI-T and Anatomical-T were obtained. In patients, the surgical resection of the tumor was pursued by identifying eloquent structures with intraoperative direct electrical stimulation mapping and extending surgery to the functional boundaries. Post-surgical MRI allowed to identify Anatomical-T and fMRI-T non-eloquent portions removed during the procedure.ResultsMNI Atlases showed that fMRI-T is a subset of Anatomical-T, and that different task-specific fMRI-T involve both shared subsets and task-specific subsets – e.g., verbal fluency fMRI-T strongly involves dorsal frontal tracts, consistently with the phonogical-articulatory features of this task. A quantitative analysis in patients revealed that Anatomical-T removed portions of AF-SLF and IFOF were significantly greater than verbal fluency fMRI-T ones, suggesting that fMRI-T is a more specific approach. In addition, qualitative analyses showed that fMRI-T AF-SLF and IFOF predict the exact functional limits of resection with increased specificity when compared to Anatomical-T counterparts, especially the superior frontal portion of IFOF, in a subcohort of patients.ConclusionThese results suggest that performing fMRI-T in addition to the ‘classic’ Anatomical-T may be useful in a preoperative setting to identify the ‘high-risk subsets’ that should be spared during the surgical procedure.

Ventral Precentral Fiber Intersection Area: A Central Hub in the Connectivity of Perisylvian Associative Tracts

The ventral part of the precentral gyrus is considered one of the most eloquent areas. However, little is known about the white matter organization underlying this functional hub. To analyze the subcortical anatomy underlying the ventral part of the precentral gyrus, ie, the ventral precentral fiber intersection area (VPFIA). Eight human hemispheres from cadavers were dissected, and 8 healthy hemispheres were studied with diffusion tensor imaging tractography. The tracts that terminate at the ventral part of the precentral gyrus were isolated. In addition, 6 surgical cases with left side gliomas close to the VPFIA were operated awake with intraoperative electrical stimulation mapping. The connections within the VPFIA are anatomically organized along an anteroposterior axis: the pyramidal pathway terminates at the anterior bank of the precentral gyrus, the intermediate part is occupied by the long segment of the arcuate fasciculus, and the posterior bank is occupied by the anterior segment of the arcuate fasciculus. Stimulation of the VPFIA elicited speech arrest in all cases. The present study shows strong arguments to sustain that the fiber organization of the VPFIA is different from the classical descriptions, bringing new light for understanding the functional role of this area in language. The VPFIA is a critical neural epicenter within the perisylvian network that may represent the final common network for speech production, as it is strategically located between the termination of the dorsal stream and the motor output cortex that directly control speech muscles.

Intraoperative Identification and Preservation of Verbal Memory in Diffuse Gliomas: A Matched-Pair Cohort Study.

Recent glioma surgery series with intraoperative electrical stimulation (IES) language mapping have demonstrated high rates of postoperative memory impairment, raising a question regarding the efficacy of this approach to preserve memory. To evaluate if intraoperative identification and preservation of verbal memory sites with IES mapping in diffuse gliomas in eloquent areas consistently protect patients from long-term postoperative decline in short-term memory. A cohort of 16 subjects with diffuse low-grade or anaplastic gliomas that were operated with IES and intraoperative evaluation of language and verbal memory (cohort A) was matched by tumor side, pathology, and radiotherapy with a cohort of 16 subjects that were operated with IES and evaluation of language (cohort B). Detailed neuropsychological assessment was performed before and 6 mo after surgery. Intraoperative memory mapping was a strong predictor of verbal memory prognosis. In cohort A, 4 patients (26.7%) had a decline of at least one of the 4 short-term memory tests evaluated. In cohort B, 11 patients (73.3%) had a decline of at least one of the 4 tests. This difference was statistically significant in multivariate analysis (P=.022; odds ratio=9.88; 95% confidence interval=1.39-70.42). Verbal memory areas identified intraoperatively with the current paradigm are critically involved in verbal memory, as memory impairment can be significantly reduced by adapting the resection to avoid those memory areas. Incorporation of verbal memory evaluation in stimulation mapping protocols might assist in reducing postoperative sequelae and preserving the patient's quality of life.

Involvement of the middle frontal gyrus in language switching as revealed by electrical stimulation mapping and functional magnetic resonance imaging in bilingual brain tumor patients

Neural basis of language switching and the cognitive models of bilingualism remain controversial. We explored the functional neuroanatomy of language switching implementing a new multimodal protocol assessing neuropsychological, functional magnetic resonance and intraoperative electrical stimulation mapping results.A prospective series of 9 Spanish–Catalan bilingual candidates for awake brain surgery underwent a specific language switching paradigm implemented both before and after surgery, throughout the electrical stimulation procedure and during functional magnetic resonance both pre- and postoperatively. All patients were harboring left-hemispheric intrinsic brain lesions and were presenting functional language-related activations within the affected hemisphere.Language functional maps were reconstructed on the basis of the intraoperative electrical stimulation results and compared to the functional magnetic resonance findings. Single language-naming sites (Spanish and Catalan), as well as language switching naming sites were detected by electrical stimulation mapping in 8 patients (in one patient only Spanish related sites were detected). Single naming points outnumbered the switching points and did not overlap with each other. Within the frontal lobe, the single language naming sites were found significantly more frequently within the inferior frontal gyrus as compared to the middle frontal gyrus [X2 (1) = 20.3, p < .001]. Contrarily, switching naming sites were distributed across the middle frontal gyrus significantly more often than within the inferior frontal gyrus [X2 (1) = 4.1, p = .043]. Notably, there was not always an overlap between functional magnetic resonance and electrical stimulation mapping findings. After surgery, patients did not report involuntary language switching and their neuropsychological scores did not differ significantly from the pre-surgical examinations. Our results suggest a functional division of the frontal cortex between naming and language switching functions, supporting that non-language specific cognitive control prefrontal regions (middle frontal gyrus) are essential to maintain an effective communication together with the classical language-related sites (inferior frontal gyrus).

Determination of the posterior boundary of Wernicke's area based on multimodal connectivity profiles.

Wernicke's area is one of the most important language regions and has been widely studied in both basic research and clinical neurology. However, its exact anatomy has been controversial. In this study, we proposed to address the anatomy of Wernicke's area by investigating different connectivity profiles. First, the posterior superior temporal gyrus (STG), traditionally called "Wernicke's area", was parcellated into three component subregions with diffusion MRI. Then, whole-brain anatomical connectivity, resting-state functional connectivity (RSFC) and meta-analytic connectivity modeling (MACM) analyses were used to establish the anatomical, resting-state and task-related coactivation network of each subregion to identify which subregions participated in the language network. In addition, behavioral domain analysis, meta-analyses of semantics, execution speech, and phonology and intraoperative electrical stimulation were used to determine which subregions were involved in language processing. Anatomical connectivity, RSFC and MACM analyses consistently identified that the two anterior subregions in the posterior STG primarily participated in the language network, whereas the most posterior subregion in the temporoparietal junction area primarily participated in the default mode network. Moreover, the behavioral domain analyses, meta-analyses of semantics, execution speech and phonology and intraoperative electrical stimulation mapping also confirmed that only the two anterior subregions were involved in language processing, whereas the most posterior subregion primarily participated in social cognition. Our findings revealed a convergent posterior anatomical border for Wernicke's area and indicated that the brain's functional subregions can be identified on the basis of its specific structural and functional connectivity patterns.

Cost-utility of maximal safe resection of WHO grade II gliomas within eloquent areas

Despite the growing use of intraoperative electrical stimulation (IES) mapping for resection of WHO grade II gliomas (GIIG) located within eloquent areas, some authors claim that this is a complex, time-consuming and expensive approach, and not well tolerated by patients, so they rely on other mapping techniques. Here we analyze the health related quality of life, direct and indirect costs of surgeries with and without intraoperative electrical stimulation (IES) mapping for resection of GIIG within eloquent areas. A cohort of 11 subjects with GIIG within eloquent areas who had IES while awake (group A) was matched by tumor side and location to a cohort of 11 subjects who had general anesthesia without IES (group B). Direct and indirect costs (measured as loss of labor productivity) and utility (measured in quality adjusted life years, QALYs), were compared between groups. Total mean direct costs per patient were $38,662.70 (range $19,950.70 to $61,626.40) in group A, and $32,116.10 (range $22,764.50 to $46,222.50) in group B (p = 0.279). Total mean indirect costs per patient were $10,640.10 (range $3,010.10 to $86,940.70) in group A, and $48,804.70 (range $3,340.10 to $98,400.60) in group B (p = 0.035). Mean costs per QALY were $12,222.30 (range $3,801.10 to $47,422.90) in group A, and $31,927.10 (range $6,642.90 to $64,196.50) in group B (p = 0.023). Asleep-awake-asleep craniotomies with IES are associated with an increase in direct costs. However, these initial expenses are ultimately offset by medium and long-term costs averted from a decrease in morbidity and preservation of the patient's professional life. The present study emphasizes the importance to switch to an aggressive and safer surgical strategy in GIIG within eloquent areas.

Eficacia y seguridad del mapeo por estimulación eléctrica intraoperatoria para la extirpación de gliomas OMS grado ii y iii en áreas cerebrales elocuentes

Despite the growing use of intraoperative electrical stimulation (IES) mapping for the resection of WHO grade ii and iii gliomas (GGII and GGIII) in eloquent areas, few studies have compared 2 series with and without IES. The present study compares 2 series of patients operated with and without IES at the same institution, analyzing the extent of resection, neurological morbidity, epilepsy prognosis and quality of life. The surgical results in 2 series of patients with GGII and GGIII within eloquent were compared. Period A (2004-2009): 17 patients operated without IES. Period B (2009-2010): 19 patients operated with IES. The extent of tumor resection was 54.7% in group A and 79.9% in group B (P=.006). Six months after surgery, neurological morbidity was present in 8 patients of group A and one patient of group B (P=.015; odds ratio [OR] 16, 95% confidence interval [95% CI] 1.7-148.3). Two patients of group A with refractory epilepsy, and 8 patients of group B improved epilepsy control (P=.05; OR 42, 95% CI 2.1-825.7). Nine patients of group A and 18 patients of group B returned to the same socio-professional situation as before surgery (P=.015; OR 16, 95% CI 1.7-148.4). The comparison of IES mapping surgery to conventional surgery revealed that the former enables to: increase in 25.2% the extent of tumor resection, decrease in 48.1% the risk of permanent sequelae, improve epilepsy control and preserve quality of life.

Controversias en el tratamiento de los gliomas OMS grado II localizados en áreas elocuentes: revisión de la bibliografía reciente

Recent studies have shown that diffuse grade II gliomas (GGII) located in eloquent brain areas represent over 80% of all GGII. The optimal management of these tumours is still controversial. It has long been considered that surgery is not an option for GGII within eloquent areas, due to the high risk of inducing postoperative sequelae in patients with normal neurological explorations. However, the safety of these surgeries has significantly improved in recent years due to the rapid development of techniques enabling a precise mapping of brain functions. Noninvasive functional neuroimaging techniques have been recently developed, enabling cortical mapping of the entire brain prior to surgical procedures. Such precise data provide a preoperative estimation of the location of eloquent areas in relation to the tumour, which is essential for surgical planning and preoperative assessment of morbidity for various surgical approaches. The intraoperative electrical stimulation (IES) mapping technique consists in the application of a bipolar electrode on the brain tissue, enabling an accurate location of brain functions. This provides unique assistance in GGII resection, as it generates a discrete and transient "virtual" lesion within the eloquent tissue. Tumour removal is then tailored according to functional boundaries in order to optimise the quality of resection and to minimise the risk of postoperative sequelae, preserving quality of life. For patients with a GGII in an eloquent area, the possibility of an early resection should be evaluated by a multidisciplinary neuro-oncology team specialising in the management of such tumours.

Language monitoring in multilingual patients undergoing awake craniotomy: A case study of a German–English–French trilingual patient with a WHO grade II glioma

In this paper, we report a case study of a 31-year-old multilingual female (LK) who presented with a left prefrontal brain tumour (WHO grade II glioma). LK is a late trilingual person whose first language is German. She had been learning English and French for 10 years when she moved to France at the age of 20 and now mostly uses French. German (L1) and French (L3) were assessed using a selection of sub-tests taken from the MT 86, the French version of the BDAE, the ECOSSE, the MEC, the German BAT, and, a non-standardized German adaptation of parts of the MEC. Preoperatively, LK had no language deficit. She was operated on under awake craniotomy, and both languages were mapped. Direct intraoperative electrical stimulation mapping showed that i) L1 and L3 were represented by both distinct and overlapping areas within the left (dominant) inferior frontal cortex, but shared the same subcortical tracts, and ii) the left dorsolateral prefrontal cortex was engaged when switching from one language to another. Since surgery, the patient has been followed longitudinally, with six-monthly assessments of her language skills using the same test battery. Her L1 and L3 language skills have been intact for 24 months postoperatively. After presenting the behavioural and brain mapping data, we discuss their relevance with respect to the organization of language skills within the frontal cortex and deep frontal structures.

Preoperative assessment of language areas in epileptic patients using functional MR imaging

ObjectiveTo determine the role of functional magnetic resonance imaging (fMRI) in assessing hemispheric language dominance in patients with epilepsy who are candidates for surgical treatment. Patients and methodsThis study was conducted on (14) consecutively enrolled epileptic patients (12 males, 2 females; mean age, 21years; range 16–58years) who were prospectively examined by the neurologist. Eleven (78.6%) patients were dominantly right handed, three (21.4%) were dominantly left handed. All of them underwent language assessment with fMRI and the results were compared with the intraoperative direct electrical stimulation mapping recordings. ResultsIn all the 14 epilepsy cases, language mapping data was concordant between fMRI and intraoperative direct electrocortical stimulation recordings for language dominance. However, fMRI mapping allowed for discrete, focal localization of regions involved in language processes whereas electrical recordings only delineated hemispheric dominance. ConclusionfMRI is considered as a powerful pre-surgical planning tool that has the potential to replace invasive and costly conventional methods. FMRI maps can easily be uploaded and used intra-operatively during stereotactic neurosurgery for accurate localization of complex brain functions.

Resting functional connectivity in patients with brain tumors in eloquent areas

Resection of brain tumors adjacent to eloquent areas represents a challenge in neurosurgery. If maximal resection is desired without inducing postoperative neurological deficits, a detailed knowledge of the functional topography in and around the tumor is crucial. The aim of the present work is to evaluate the value of preoperative magnetoencephalography (MEG) imaging of functional connectivity to predict the results of intraoperative electrical stimulation (IES) mapping, the clinical gold standard for neurosurgical localization of functional areas. Resting-state whole-cortex MEG recordings were obtained from 57 consecutive subjects with focal brain tumors near or within motor, sensory, or language areas. Neural activity was estimated using adaptive spatial filtering algorithms, and the mean imaginary coherence between the rest of the brain and voxels in and around brain tumors were compared to the mean imaginary coherence between the rest of the brain and contralesional voxels as an index of functional connectivity. IES mapping was performed in all subjects. The cortical connectivity pattern near the tumor was compared to the IES results. Maps with decreased resting-state functional connectivity in the entire tumor area had a negative predictive value of 100% for absence of eloquent cortex during IES. Maps showing increased resting-state functional connectivity within the tumor area had a positive predictive value of 64% for finding language, motor, or sensory cortical sites during IES mapping. Preoperative resting state MEG connectivity analysis is a useful noninvasive tool to evaluate the functionality of the tissue surrounding tumors within eloquent areas, and could potentially contribute to surgical planning and patient counseling.

Aspectos controvertidos en el manejo de gliomas hemisféricos OMS grado II: revisión de la bibliografía reciente

The optimal management of WHO grade II gliomas (GIIG) is currently one of the most controversial issues in neuro-oncology. This paper discusses the most controversial aspects of management of these tumors, based on a review of the literature of the last 20 years. Patients with GIIG often suffer cognitive and emotional disorders that go unnoticed in daily clinic, which significantly affect the quality of life. These tumors do not remain stable, as they grow slowly and steadily. In fact, growth rate is a reliable marker of their biological behaviour, with rapid growth being a marker of malignancy. Current neuro-imaging studies and stereotactic biopsy are not reliable enough for diagnosis of GIIG, thus many authors consider that a definitive diagnosis can only be obtained with a detailed histological examination after extensive surgical resection. An increasing number of studies support the prognostic impact of surgery, as it delays malignant transformation and increases survival. GIIG are frequently located in eloquent brain areas; intraoperative electrical stimulation mapping is now considered the gold standard to remove these tumors with a low risk of sequelae. There is growing scientific evidence against a 'wait-and-see' management of GIIG. Surgery is considered nowadays by most authors as the first step in the diagnosis and treatment of these tumors.

Re-operation is a safe and effective therapeutic strategy in recurrent WHO grade II gliomas within eloquent areas

To analyze the functional and oncological results after re-operation for recurrent WHO grade II Glioma located in eloquent regions. We reviewed a consecutive series of 19 patients with GIIG within functional areas who underwent two operations separated by at least 1 year. Intraoperative electrical stimulation mapping was used in all operations for recurrence and in 14 of the initial procedures. A specific rehabilitation was provided. At the first operation, we performed 14 subtotal and 5 partial resections. Eighteen patients returned to a normal socio-professional life. Nine patients received adjuvant treatment. At the second operation, we performed 1 total, 13 subtotal and 5 partial resections. Three patients with a preoperative neurological deficit improved, 13 remained unchanged, and 3 slight new deficits appeared. In 14 of the 17 patients with preoperative chronic epilepsy, the seizures were reduced or disappeared. Sixteen patients returned to a normal socio-professional life. Pathohistological examination showed that 11 tumours had progressed to high-grade glioma. The median time between the two operations was 4.1 years (range 1 to 7.8 years) and the median follow-up from initial diagnosis was 6.6 years (range 2.3 to 14.3 years). No deaths occurred during the follow-up period. Repeat operations guided by intra-operative electrical stimulation is an efficacious treatment for recurrent grade II glioma in an eloquent area.

Long-term brain plasticity allowing a multistage surgical approach to World Health Organization Grade II gliomas in eloquent areas

Although the goal of surgery for World Health Organization Grade II gliomas is maximal extent of resection, complete tumor removal is not always possible when the glioma involves eloquent areas. The authors propose a multistage surgical approach to highly crucial areas that are classically considered inoperable, enabling optimization of the extent of resection while avoiding permanent cognitive deficits due to induced functional reshaping in the interim between the 2 consecutive operations. To demonstrate such plasticity, the authors used a combination of sequential functional MR imaging and intraoperative electrical stimulation mapping before and during surgeries spaced by several years in 2 patients who each underwent 2 separate resections of Grade II gliomas located in the left dominant premotor area. During several years of follow-up after the first procedure, both patients had unremarkable examination results and normal socioprofessional lives. There was no malignant transformation. Based on their experience with these cases, the authors suggest that in cases of incomplete glioma removal, a second operation before anaplasia should be considered, made possible by brain reorganization after the first operation.