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

Motor Cortex Reorganization in Patients with Glioma Assessed by Repeated Navigated Transcranial Magnetic Stimulation-A Longitudinal Study

OBJECTIVE

Evidence for cerebral reorganization after resection of low-grade glioma has mainly been obtained by serial intraoperative cerebral mapping. Noninvasively collected data on cortical plasticity in tumor patients over a surgery-free period are still scarce. The present study therefore aimed at evaluating motor cortex reorganization by navigated transcranial magnetic stimulation (nTMS) in patients after perirolandic glioma surgery.

METHODS

nTMS was performed preoperatively and postoperatively in 20 patients, separated by 26.1 ± 24.8 months. Further nTMS mapping was conducted in 14 patients, resulting in a total follow-up period of 46.3 ± 25.4 months. Centers of gravity (CoGs) were calculated for every muscle representation area, and Euclidian distances between CoGs over time were defined. Results were compared with data from 12 healthy individuals, who underwent motor cortex mapping by nTMS in 2 sessions.

RESULTS

Preoperatively and postoperatively pooled CoGs from the area of the dominant abductor pollicis brevis muscle and of the nondominant leg area differed significantly compared with healthy individuals (P < 0.05). Most remarkably, during the ensuing follow-up period, a reorganization of all representation areas was observed in 3 patients, and a significant shift of hand representation areas was identified in further 3 patients. Complete functional recovery of postoperative motor deficits was exclusively associated with cortical reorganization.

CONCLUSIONS

Despite the low potential of remodeling within the somatosensory region, long-term reorganization of cortical motor function can be observed. nTMS is best suited for a noninvasive evaluation of this reorganization.

How much is enough-Can resting state fMRI provide a demarcation for neurosurgical resection in glioma?

This study represents a systematic review of the insights provided by resting state functional MRI (rs-fMRI) use in the glioma population. Following PRISMA guidelines, 45 studies were included in the review and were classified in glioma-related neuronal changes (n=28) and eloquent area localization (n=17). Despite the heterogeneous nature of the studies, there is considerable evidence of diffuse functional reorganization occurring in the setting of gliomas with local and interhemispheric functional connectivity alterations involving different functional networks. The studies showed evidence of decreased long distance functional connectivity and increased global local efficiency occurring in the setting of gliomas. The tumour grade seems to correlate with distinct functional connectivity changes. Overall, there is a potential clinical utility of rs-fMRI for identifying the functional brain network disruptions occurring in the setting of gliomas. Further studies utilizing standardized analytical methods are required to elucidate the mechanism through which gliomas induce global changes in brain connectivity.

Functional MRI for Surgery of Gliomas

PURPOSE OF REVIEW

Advanced neuroimaging techniques such as functional MRI (fMRI) and diffusion MR tractography have been increasingly used at every stage of the surgical management of brain gliomas, as a means to improve tumor resection while preserving brain functions. This review provides an overview of the last advancements in the field of functional MRI techniques, with a particular focus on their current clinical use and reliability in the preoperative and intraoperative setting, as well as their future perspectives for personalized multimodal management of patients with gliomas.

RECENT FINDINGS

fMRI and diffusion MR tractography give relevant insights on the anatomo-functional organization of eloquent cortical areas and subcortical connections near or inside a tumor. Task-based fMRI and diffusion tensor imaging (DTI) tractography have proven to be valid and highly sensitive tools for localizing the distinct eloquent cortical and subcortical areas before surgery in glioma patients; they also show good accuracy when compared with intraoperative stimulation mapping data. Resting-state fMRI functional connectivity as well as new advanced HARDI (high angular resolution diffusion imaging) tractography methods are improving and reshaping the role of functional MRI for surgery of gliomas, with potential benefit for personalized treatment strategies. Noninvasive functional MRI techniques may offer the opportunity to perform a multimodal assessment in brain tumors, to be integrated with intraoperative mapping and clinical data for improving surgical management and oncological and functional outcome in patients affected by gliomas.

Reorganization of language centers in patients with brain tumors located in eloquent speech areas - A pre- and postoperative preliminary fMRI study

INTRODUCTION

The aim of this study was to determine in pre- and postsurgical fMRI studies the rearrangement of the Broca's and Wernicke's areas and the lateralization index for these areas in patients with brain tumors located near speech centers. Impact of the surgical treatment on the brain plasticity was evaluated.

MATERIALS AND METHODS

Pre- and postoperative fMRI examinations were performed in 10 patients with low grade glial, left-sided brain tumors located close to the Broca's (5 patients) or Wernicke's area (5 patients). BOLD signal was recorded in regions of interest: Broca's and Wernicke's areas, and their anatomic right-sided homologues.

RESULTS

In the preoperative fMRI study the left Broca's area was activated in all cases. The right Broca's area was activated in all the patients with no speech disorders. In the postoperative fMRI the activation of both Broca's areas increased in two cases. In other two cases activation of one of the Broca's area increased along with the decrease in the contralateral hemisphere. In all patients with temporal lobe tumors, the right Wernicke's area was activated in the pre- and postsurgical fMRI. After the operation, in two patients with speech disorder, the activation of both Broca's areas decreased and the activation of one of the Wernicke's areas increased.

CONCLUSIONS

In the cases of tumors localized near the left Broca's area, a transfer of the function to the healthy hemisphere seems to take place. Resection of tumors located near Broca's or Wernicke's areas may lead to relocation of the brain language centers.

Identifying clinical risk in low grade gliomas and appropriate treatment strategies, with special emphasis on the role of surgery

INTRODUCTION

Diffuse low-grade glioma (DLGG) is a chronic tumoral disease that ineluctably grows, migrates along white matter pathways, and progresses to a higher grade of malignancy. Areas covered: To determine the best individualized treatment attitude for each DLGG patient, and to redefine it over the years, i.e. to optimize the 'onco-functional balance' of serial and multimodal therapies, the understanding of the natural history of this chronic disease is crucial but not sufficient. A paradigmatic shift is to tailor the individual management according to the dynamic relationships between DLGG course and neural remodeling. In this spirit, a better knowledge of brain plasticity in a connectomal account of cerebral processing has enabled a dramatic improvement of both oncological and functional outcomes in DLGG patients, by increasing overall survival while preserving (or even improving) the quality of life. Expert commentary: Here, we propose an individualized and recursive therapeutic strategy in DLGG, leading to the concept of a 'personalized functional neuro-oncology', by emphasizing the role of early and maximal safe surgical resection(s) reliably achieved using intraoperative mapping of cortico-subcortical networks in awake patients.

Relationship Between Perisylvian Essential Language Sites and Arcuate Fasciculus in the Left Hemisphere of Healthy Adults

Essential language sites and the arcuate fasciculus (AF) have been extensively researched. However, the relationship between them remains insufficiently studied, especially in healthy people. Navigated transcranial magnetic stimulation (nTMS) is increasingly used in language mapping. While enjoying the advantage of non-invasiveness, it is also capable of inducing a virtual lesion in the brain. Thus, it offers the possibility of using the virtual-lesion method to study the healthy brain. This study combined nTMS and diffusion tensor imaging (DTI) tractography to investigate the relationship between essential language sites and the AF in 30 healthy right-handed volunteers. A total of 143 essential language sites were identified using nTMS, and a total of 175 AF terminations were identified using DTI tractography. Sixty-six sites had a direct correlation with the AF, accounting for 46% of the total essential language sites. Forty-seven AF terminations harbored essential language sites, accounting for 27% of the total AF terminations. Upon data rendering to the cortical parcellation system, a region-related heterogeneity of the correlation rate was found. This study provides the first data on the relationship between essential language sites and the AF in healthy adults.

Network Plasticity and Intraoperative Mapping for Personalized Multimodal Management of Diffuse Low-Grade Gliomas

Gliomas are the most frequent primary brain tumors and include a variety of different histological tumor types and malignancy grades. Recent achievements in terms of molecular and imaging fields have created an unprecedented opportunity to perform a comprehensive interdisciplinary assessment of the glioma pathophysiology, with direct implications in terms of the medical and surgical treatment strategies available for patients. The current paradigm shift considers glioma management in a comprehensive perspective that takes into account the intricate connectivity of the cerebral networks. This allowed significant improvement in the outcome of patients with lesions previously considered inoperable. The current review summarizes the current theoretical framework integrating the adult human brain plasticity and functional reorganization within a dynamic individualized treatment strategy for patients affected by diffuse low-grade gliomas. The concept of neuro-oncology as a brain network surgery has major implications in terms of the clinical management and ensuing outcomes, as indexed by the increased survival and quality of life of patients managed using such an approach.

Cortical plasticity of motor-eloquent areas measured by navigated transcranial magnetic stimulation in patients with glioma

OBJECTIVE The goal of this study was to obtain a better understanding of the mechanisms underlying cerebral plasticity. Coupled with noninvasive detection of its occurrence, such an understanding has huge potential to improve glioma therapy. The authors aimed to demonstrate the frequency of plastic reshaping, find clues to the patterns behind it, and prove that it can be recognized noninvasively using navigated transcranial magnetic stimulation (nTMS). METHODS The authors used nTMS to map cortical motor representation in 22 patients with gliomas affecting the precentral gyrus, preoperatively and 3-42 months postoperatively. Location changes of the primary motor area, defined as hotspots and map centers of gravity, were measured. RESULTS Spatial normalization and analysis of hotspots showed an average shift of 5.1 ± 0.9 mm (mean ± SEM) on the mediolateral axis, and 10.7 ± 1.6 mm on the anteroposterior axis. Map centers of gravity were found to have shifted by 4.6 ± 0.8 mm on the mediolateral, and 8.7 ± 1.5 mm on the anteroposterior axis. Motor-eloquent points tended to shift toward the tumor by 4.5 ± 3.6 mm if the lesion was anterior to the rolandic region and by 2.6 ± 3.3 mm if it was located posterior to the rolandic region. Overall, 9 of 16 (56%) patients with high-grade glioma and 3 of 6 (50%) patients with low-grade glioma showed a functional shift > 10 mm at the cortical level. CONCLUSIONS Despite the small size of this series, analysis of these data showed that cortical functional reorganization occurs quite frequently. Moreover, nTMS was shown to detect such plastic reorganization noninvasively.

The variability of motor evoked potential latencies in neurosurgical motor mapping by preoperative navigated transcranial magnetic stimulation

Background

Recording of motor evoked potentials (MEPs) is used during navigated transcranial magnetic stimulation (nTMS) motor mapping to locate motor function in the human brain. However, factors potentially underlying MEP latency variability in neurosurgical motor mapping are vastly unknown. In the context of this study, one hundred brain tumor patients underwent preoperative nTMS-based motor mapping of the tumor hemisphere between 2010 and 2013. Fourteen predefined predictor variables were recorded, and MEP latencies of abductor pollicis brevis muscle (APB), abductor digiti minimi muscle (ADM), and flexor carpi radialis muscle (FCR) were analyzed using linear mixed-effect multiple regression analysis with the forward step-wise model comparison approach.

Results

Common factors (relevant to APB, ADM, and FCR) for MEP latency variability were gender, most likely due to body height, and antiepileptic drug (AED) intake. Muscle-specific factors (relevant to APB, ADM, or FCR) for MEP latency variability were resting motor threshold (rMT), tumor side, and tumor location.

Conclusions

Based on a large cohort of neurosurgical patients, this study provides data on a wide range of clinical factors that may underlie MEP latency variability. The factors that significantly contributed to MEP latency variability should be standardly recorded and taken into consideration during neurosurgical motor mapping.

Resection of Motor Eloquent Metastases Aided by Preoperative nTMS-Based Motor Maps-Comparison of Two Observational Cohorts

Introduction

Preoperative mapping of motor areas with navigated transcranial magnetic stimulation (nTMS) has been shown to improve surgical outcomes for peri-Rolandic lesions and, in particular, for gliomas. However, the impact of this technique on surgical outcomes for peri-Rolandic metastatic lesions is yet unknown.

Objective

To investigate the impact of nTMS on surgical outcomes for peri-Rolandic metastatic lesions, various clinical parameters were analyzed in our international study group.

Methods

Two prospectively enrolled cohorts were compared by investigating patients receiving preoperative nTMS (2010–2015; 120 patients) and patients who did not receive preoperative nTMS (2006–2015; 130 patients). Tumor location, pathology, size, and preoperative deficits were comparable.

Results

The nTMS group showed a lower rate of residual tumor on postoperative magnetic resonance imaging (odds ratio 0.3025; 95% confidence interval 0.1356–0.6749). On long-term follow-up, surgery-related paresis was decreased in the nTMS group (nTMS vs. non-nTMS; improved: 30.8 vs. 13.1%, unchanged: 65.8 vs. 73.8%, worse: 3.4 vs. 13.1% of patients; p = 0.0002). Moreover, the nTMS group received smaller craniotomies (nTMS: 16.7 ± 8.6 cm² vs. non-nTMS: 25.0 ± 17.1 cm²; p < 0.0001). Surgical time differed significantly between the two groups (nTMS: 128.8 ± 49.4 min vs. non-nTMS: 158.0 ± 65.8 min; p = 0.0002).

Conclusion

This non-randomized study suggests that preoperative motor mapping by nTMS may improve the treatment of patients undergoing surgical resection of metastases in peri-Rolandic regions. These findings suggest that further evaluation with a prospective, randomized trial may be warranted.

Clinical Factors Underlying the Inter-individual Variability of the Resting Motor Threshold in Navigated Transcranial Magnetic Stimulation Motor Mapping

Correctly determining individual's resting motor threshold (rMT) is crucial for accurate and reliable mapping by navigated transcranial magnetic stimulation (nTMS), which is especially true for preoperative motor mapping in brain tumor patients. However, systematic data analysis on clinical factors underlying inter-individual rMT variability in neurosurgical motor mapping is sparse. The present study examined 14 preselected clinical factors that may underlie inter-individual rMT variability by performing multiple regression analysis (backward, followed by forward model comparisons) on the nTMS motor mapping data of 100 brain tumor patients. Data were collected from preoperative motor mapping of abductor pollicis brevis (APB), abductor digiti minimi (ADM), and flexor carpi radialis (FCR) muscle representations among these patients. While edema and age at exam in the ADM model only jointly reduced the unexplained variance significantly, the other factors kept in the ADM model (gender, antiepileptic drug intake, and motor deficit) and each of the factors kept in the APB and FCR models independently significantly reduced the unexplained variance. Hence, several clinical parameters contribute to inter-individual rMT variability and should be taken into account during initial and follow-up motor mappings. Thus, the present study adds basic evidence on inter-individual rMT variability, whereby some of the parameters are specific to brain tumor patients.

Awake surgery for hemispheric low-grade gliomas: oncological, functional and methodological differences between pediatric and adult populations

INTRODUCTION

Brain mapping through a direct cortical and subcortical electrical stimulation during an awake craniotomy has gained an increasing popularity as a powerful tool to prevent neurological deficit while increasing extent of resection of hemispheric diffuse low-grade gliomas in adults. However, few case reports or very limited series of awake surgery in children are currently available in the literature.

METHODS

In this paper, we review the oncological and functional differences between pediatric and adult populations, and the methodological specificities that may limit the use of awake mapping in pediatric low-grade glioma surgery.

RESULTS

This could be explained by the fact that pediatric low-grade gliomas have a different epidemiology and biologic behavior in comparison to adults, with pilocytic astrocytomas (WHO grade I glioma) as the most frequent histotype, and with WHO grade II gliomas less prone to anaplastic transformation than their adult counterparts. In addition, aside from the issue of poor collaboration of younger children under 10 years of age, some anatomical and functional peculiarities of children developing brain (cortical and subcortical myelination, maturation of neural networks and of specialized cortical areas) can influence direct electrical stimulation methodology and sensitivity, limiting its use in children.

CONCLUSIONS

Therefore, even though awake procedure with cortical and axonal stimulation mapping can be adapted in a specific subgroup of children with a diffuse glioma from the age of 10 years, only few pediatric patients are nonetheless candidates for awake brain surgery.

Neuroplasticity: Insights from Patients Harboring Gliomas

Neuroplasticity is the ability of the brain to reorganize itself during normal development and in response to illness. Recent advances in neuroimaging and direct cortical stimulation in human subjects have given neuroscientists a window into the timing and functional anatomy of brain networks underlying this dynamic process. This review will discuss the current knowledge about the mechanisms underlying neuroplasticity, with a particular emphasis on reorganization following CNS pathology. First, traditional mechanisms of neuroplasticity, most relevant to learning and memory, will be addressed, followed by a review of adaptive mechanisms in response to pathology, particularly the recruitment of perilesional cortical regions and unmasking of latent connections. Next, we discuss the utility and limitations of various investigative techniques, such as direct electrocortical stimulation (DES), functional magnetic resonance imaging (fMRI), corticocortical evoked potential (CCEP), and diffusion tensor imaging (DTI). Finally, the clinical utility of these results will be highlighted as well as possible future studies aimed at better understanding of the plastic potential of the brain with the ultimate goal of improving quality of life for patients with neurologic injury.

Language pathway tracking: comparing nTMS-based DTI fiber tracking with a cubic ROIs-based protocol

OBJECTIVE Diffusion tensor imaging (DTI) fiber tracking (FT) has been widely used in glioma surgery in recent years. It can provide helpful information about subcortical structures, especially in patients with eloquent space-occupying lesions. This study compared the newly developed navigated transcranial magnetic stimulation (nTMS)-based DTI FT of language pathways with the most reproducible protocol for language pathway tractography, using cubic regions of interest (ROIs) for the arcuate fascicle. METHODS Thirty-seven patients with left-sided perisylvian lesions underwent language mapping by repetitive nTMS. DTI FT was performed using the cubic ROIs-based protocol and the authors' nTMS-based DTI FT approach. The same minimal fiber length and fractional anisotropy were chosen (50 mm and 0.2, respectively). Both protocols were performed with standard clinical tractography software. RESULTS Both methods visualized language-related fiber tracts (i.e., corticonuclear tract, arcuate fascicle, uncinate fascicle, superior longitudinal fascicle, inferior longitudinal fascicle, arcuate fibers, commissural fibers, corticothalamic fibers, and frontooccipital fascicle) in all 37 patients. Using the cubic ROIs-based protocol, 39.9% of these language-related fiber tracts were detected in the examined patients, as opposed to 76.0% when performing nTMS-based DTI FT. For specifically tracking the arcuate fascicle, however, the cubic ROIs-based approach showed better results (97.3% vs 75.7% with nTMS-based DTI FT). CONCLUSIONS The cubic ROIs-based protocol was designed for arcuate fascicle tractography, and this study shows that it is still useful for this intention. However, superior results were obtained using the nTMS-based DTI FT for visualization of other language-related fiber tracts.

Cortical plasticity catalyzed by prehabilitation enables extensive resection of brain tumors in eloquent areas

OBJECTIVE The extent of resection is the most important prognostic factor following brain glioma surgery. However, eloquent areas within tumors limit the extent of resection and, thus, critically affect outcomes. The authors hypothesized that presurgical suppression of the eloquent areas within a tumor by continuous cortical electrical stimulation, coupled with appropriate behavioral training ("prehabilitation"), would induce plastic reorganization and enable a more extensive resection. METHODS The authors report on 5 patients harboring gliomas involving eloquent brain areas within tumors as identified on intraoperative stimulation mapping. A grid of electrodes was placed over the residual tumor, and continuous cortical electrical stimulation was targeted to the functional areas. The stimulation intensity was adjusted daily to provoke a mild functional impairment while the function was intensively trained. RESULTS The stimulation intensity required to impair function increased progressively in all patients, and all underwent another operation a mean of 33.6 days later (range 27-37 days), when the maximal stimulation voltage in all active contacts induced no functional deficit. In all cases, a substantially more extensive resection of the tumor was possible. Intraoperative mapping and functional MRI demonstrated a plastic reorganization, and most previously demonstrated eloquent areas within the tumor were silent, while there was new functional activation of brain areas in the same region or toward the contralateral hemisphere. CONCLUSIONS Prehabilitation with continuous cortical electrical stimulation and appropriate behavioral training prior to surgery in patients with WHO Grade II and III gliomas affecting eloquent areas accelerate plastic changes. This can help maximize tumor resection and, thus, improve survival while maintaining function.

Intraoperative mapping during repeat awake craniotomy reveals the functional plasticity of adult cortex

OBJECT

To avoid iatrogenic injury during the removal of intrinsic cerebral neoplasms such as gliomas, direct electrical stimulation (DES) is used to identify cortical and subcortical white matter pathways critical for language, motor, and sensory function. When a patient undergoes more than 1 brain tumor resection as in the case of tumor recurrence, the use of DES provides an unusual opportunity to examine brain plasticity in the setting of neurological disease.

METHODS

The authors examined 561 consecutive cases in which patients underwent DES mapping during surgery forglioma resection. “Positive” and “negative” sites—discrete cortical regions where electrical stimulation did (positive) or did not (negative) produce transient sensory, motor, or language disturbance—were identified prior to tumor resection and documented by intraoperative photography for categorization into functional maps. In this group of 561 patients, 18 were identified who underwent repeat surgery in which 1 or more stimulation sites overlapped with those tested during the initial surgery. The authors compared intraoperative sensory, motor, or language mapping results between initial and repeat surgeries, and evaluated the clinical outcomes for these patients.

RESULTS

A total of 117 sites were tested for sensory (7 sites, 6.0%), motor (9 sites, 7.7%), or language (101 sites, 86.3%) function during both initial and repeat surgeries. The mean interval between surgical procedures was 4.1 years. During initial surgeries, 95 (81.2%) of 117 sites were found to be negative and 22 (18.8%) of 117 sites were found to be positive. During repeat surgeries, 103 (88.0%) of 117 sites were negative and 14 (12.0%) of 117 were positive. Of the 95 sites that were negative at the initial surgery, 94 (98.9%) were also negative at the repeat surgery, while 1 (1.1%) site was found to be positive. Of the 22 sites that were initially positive, 13 (59.1%) remained positive at repeat surgery, while 9 (40.9%) had become negative for function. Overall, 6 (33.3%) of 18 patients exhibited loss of function at 1 or more motor or language sites between surgeries. Loss of function at these sites was not associated with neurological impairment at the time of repeat surgery, suggesting that neurological function was preserved through neural circuit reorganization or activation of latent functional pathways.

CONCLUSIONS

The adult central nervous system reorganizes motor and language areas in patients with glioma. Ultimately, adult neural plasticity may help to preserve motor and language function in the presence of evolving structural lesions. The insight gained from this subset of patients has implications for our understanding of brain plasticity in clinical settings.

Feasibility of nTMS-based DTI fiber tracking of language pathways in neurosurgical patients using a fractional anisotropy threshold

BACKGROUND

Navigated transcranial magnetic stimulation (nTMS) provides language maps in brain tumor patients. Yet, corresponding data on the visualization of language-related subcortical pathways is lacking. Therefore, this study evaluates the feasibility of nTMS-based diffusion tensor imaging fiber tracking (DTI FT) for subcortical language pathways by a fractional anisotropy (FA) protocol.

NEW METHOD

DTI FT was performed in 37 patients suffering from left-sided perisylvian brain lesions based on nTMS data exclusively, using the FA-based protocol originally established for the corticospinal tract (CST) by Frey et al. (2012): minimum fiber length was 110mm and the highest individual FA value leading to visualization of white matter tracts was determined as the FA threshold (FAT). Then, deterministic DTI FT using an FA value of 100%, 75%, 50%, and 25% of the individual FAT (with 25% as an additional setting to the original protocol) was performed.

RESULTS

Our approach visualized 9 language-related subcortical white matter pathways. By using 100% FAT, the mean percentage of visualized tracts was 13.5%, whereas DTI FT performed with 75%, 50%, and 25% FAT detected 30.6%, 61.3%, and 93.7% of language-related fiber tracts, respectively.

COMPARISON WITH EXISTING METHODS

nTMS language mapping alone is not able to visualize subcortical language-related pathways.

CONCLUSIONS

This study shows that nTMS language maps are feasible for DTI FT of language-related pathways within the scope of a FAT-based protocol. Although this approach is novel and might be helpful during scientific neuroimaging and tumor resection, intraoperative validation is needed to go beyond the level of feasibility.

Interhemispheric connectivity revealed by diffusion tensor imaging fiber tracking derived from navigated transcranial magnetic stimulation maps as a sign of language function at risk in patients with brain tumors

OBJECTIVE Resection of brain tumors in language-eloquent areas entails the risk of postoperative aphasia. It has been demonstrated via navigated transcranial magnetic stimulation (nTMS) that language function can partially shift to the unaffected hemisphere due to tumor-induced plasticity. Therefore, this study was designed to evaluate whether interhemispheric connectivity (IC) detected by nTMS-based diffusion tensor imaging-fiber tracking (DTI-FT) can be used to predict surgery-related aphasia in patients with brain tumors. METHODS Thirty-eight patients with left-sided perisylvian brain lesions underwent cortical language mapping of both hemispheres by nTMS prior to awake surgery. Then, nTMS-based DTI-FT was conducted with a fractional anisotropy (FA) of 0.01 and 0.2 to visualize nTMS-based IC. Receiver operating characteristics were calculated for the prediction of a postoperative (irrespective of the preoperative state) and a new surgery-related aphasia by the presence of detectable IC. RESULTS Language mapping by nTMS was possible in all patients. Seventeen patients (44.7%) suffered from surgery-related worsening of language performance (transient aphasia according to 3-month follow-up in 16 subjects [42.1%]; new permanent aphasia according to 3-month follow-up in 1 patient [2.6%]). Regarding the correlation of aphasia to nTMS-based IC, statistically significant differences were revealed for both evaluated FA values. However, better results were observed for tractography with an FA of 0.2, which led to a specificity of 93% (postoperative aphasia) and 90% (surgery-related aphasia). For postoperative aphasia, the corresponding OR was 0.1282 (95% CI 0.0143-1.1520), and for surgery-related aphasia the OR was 0.1184 (95% CI 0.0208-0.6754). CONCLUSIONS According to these results, IC detected by preoperative nTMS-based DTI-FT might be regarded as a risk factor for surgery-related aphasia, with a specificity of up to 93%. However, because the majority of enrolled patients suffered from transient aphasia postoperatively, it has to be evaluated whether this approach distinctly leads to similar results among patients with permanent language deficits. Despite this restriction, this approach might contribute to individualized patient consultation prior to tumor resection in clinical practice.

A two-level model of interindividual anatomo-functional variability of the brain and its implications for neurosurgery

The classical dogma of localizationism implicitly resulted in the principle of a similar brain functional anatomy between individuals, as for example the pars opercularis of the left "dominant" hemisphere corresponding to the speech area. This fixed "single brain" model led neurosurgeons to define a set of "eloquent" areas, for which injury would induce severe and persistent neurological worsening, making their surgical resections impossible. Therefore, numerous patients with a cerebral lesion justifying surgery were a priori not selected for resection and lost a chance to be treated. In fact, advances in brain mapping showed a considerable inter-individual variability explained by a networking organization of the brain, in which one function is not underpinned by one specific region, but by interactions between dynamic large-scale delocalized sub-circuits. Indeed, using non-invasive neuroimaging, a variability of both structural and functional anatomy was demonstrated in healthy volunteers. Moreover, intraoperative electrical stimulation mapping of cortex and white matter tracts in awake patients who underwent surgery for tumor or epilepsy also showed an important anatomo-functional variability. However, a remarkable observation is that this variability is huge at the cortical level, while it is very low at the subcortical level. Based upon these intrasurgical findings, the goal of this review is to propose a two-level model of inter-individual variability (high cortical variation, low subcortical variation), breaking with the traditional rigid workframe, and making neurosurgery in traditionally presumed "eloquent" areas feasible without permanent deficits, on condition nonetheless to preserve the "invariant common core" of the brain.

Post-Surgical Language Reorganization Occurs in Tumors of the Dominant and Non-Dominant Hemisphere

PURPOSE

Surgical resection of brain tumors may shift the location of cortical language areas. Studies of language reorganization primarily investigated left-hemispheric tumors irrespective of hemispheric language dominance. We used functional magnetic resonance imaging (fMRI) to investigate how tumors influence post-surgical language reorganization in relation to the dominant language areas.

METHODS

A total of, 17 patients with brain tumors (16 gliomas, one metastasis) in the frontotemporal and lower parietal lobes planned for awake surgery underwent pre-surgical and post-surgical language fMRI. Language activation post-to-pre surgery was evaluated visually and quantitatively on the statistically thresholded images on patient-by-patient basis. Results were qualitatively compared between three patient groups: temporal, with tumors in the dominant temporal lobe, frontal, with tumors in the dominant frontal lobe and remote, with tumors in the non-dominant hemisphere.

RESULTS

Post-to-pre-surgical distributions of activated voxels changed in all except the one patient with metastasis. Changes were more pronounced in the dominant hemisphere for all three groups, showing increased number of activated voxels and also new activation areas. Tumor resection in the dominant hemisphere (frontal and temporal) shifted the activation from frontal towards temporal, whereas tumor resection in the non-dominant hemisphere shifted the activation from temporal towards frontal dominant areas.

CONCLUSION

Resection of gliomas in the dominant and in the non-dominant hemisphere induces postsurgical shifts and increase in language activation, indicating that infiltrating gliomas have a widespread influence on the language network. The dominant hemisphere gained most of the language activation irrespective of tumor localization, possibly reflecting recovery of pre-surgical tumor-induced suppression of these activations.

Re-do Craniotomy for Recurrent Grade IV Glioblastomas: Impact and Outcomes from the National Neuroscience Institute Singapore

AIM

We hypothesize that re-do craniotomy for recurrent grade IV glioblastomas improves survival while preserving outcome in selected patients.

METHODS

A retrospective analysis was conducted of 141 patients, from a prospectively collected database from 2004-2014, with grade IV glioblastomas who underwent craniotomy and excision. Sixty-five patients were included in our analysis. Twenty patients underwent re-do craniotomy at recurrence and were compared with 45 patients who received nonsurgical therapy for recurrences. Primary end point was overall survival from time of diagnosis. Demographic and disease factors were analyzed using Cox regression analysis for significance.

RESULTS

The median survival for those with re-do craniotomy was 25.4 months compared with 11.6 months (P < 0.001) in the group that underwent nonsurgical therapy. The mean age for this group was 53.5 years. This group had a higher postsurgical/treatment median Karnofsky performance scale (KPS) of 80 compared with 60 (P < 0.001) showing better functional outcome. A Cox regression analysis of factors determined that age, KPS at recurrence, extent of resection at initial surgery and re-do craniotomy were significant for positive outcomes.

CONCLUSION

Our results show that in a select group of patients with recurrent grade IV glioblastomas, repeated excision, aiming for gross total resection where safely possible, has significant survival benefit without severely compromising functionality and should be considered.

Second Surgery in Insular Low-Grade Gliomas

Background. Given the technical difficulties, a limited number of works have been published on insular gliomas surgery and risk factors for tumor recurrence (TR) are poorly documented. Objective. The aim of the study was to determine TR in adult patients with initial diagnosis of insular Low-Grade Gliomas (LGGs) that subsequently underwent second surgery. Methods. A consecutive series of 53 patients with insular LGGs was retrospectively reviewed; 23 patients had two operations for TR. Results. At the time of second surgery, almost half of the patients had experienced progression into high-grade gliomas (HGGs). Univariate analysis showed that TR is influenced by the following: extent of resection (EOR) (P < 0.002), ΔVT2T1 value (P < 0.001), histological diagnosis of oligodendroglioma (P = 0.017), and mutation of IDH1 (P = 0.022). The multivariate analysis showed that EOR at first surgery was the independent predictor for TR (P < 0.001). Conclusions. In patients with insular LGG the EOR at first surgery represents the major predictive factor for TR. At time of TR, more than 50% of cases had progressed in HGG, raising the question of the oncological management after the first surgery.

Functional preoperative and intraoperative mapping and monitoring: increasing safety and efficacy in glioma surgery

Greater extent of resection (EOR) of low-grade gliomas is associated with improved survival. Proximity to eloquent cortical regions often limits resectability and elevates the risk of surgery-related deficits. Therefore, functional localization of eloquent cortex or subcortical fiber tracts can enhance the EOR and functional outcome. Imaging techniques such as functional MRI and diffusion tensor imaging fiber tracking, and neurophysiological methods like navigated transcranial magnetic stimulation and magnetoencephalography, make it possible to identify eloquent areas prior to resective surgery and to tailor indication and surgical approach but also to assess the surgical risk. Intraoperative monitoring with direct cortical stimulation and subcortical stimulation enables surgeons to preserve essential functional tissue during surgery. Through tailored pre- and intraoperative mapping and monitoring the EOR can be maximized, with reduced rates of surgery-related deficits.

Impairment of preoperative language mapping by lesion location: a functional magnetic resonance imaging, navigated transcranial magnetic stimulation, and direct cortical stimulation study

OBJECT

Language mapping by repetitive navigated transcranial magnetic stimulation (rTMS) is increasingly used and has already replaced functional MRI (fMRI) in some institutions for preoperative mapping of neurosurgical patients. Yet some factors affect the concordance of both methods with direct cortical stimulation (DCS), most likely by lesions affecting cortical oxygenation levels. Therefore, the impairment of the accuracy of rTMS and fMRI was analyzed and compared with DCS during awake surgery in patients with intraparenchymal lesions.

METHODS

Language mapping was performed by DCS, rTMS, and fMRI using an object-naming task in 27 patients with left-sided perisylvian lesions, and the induced language errors of each method were assigned to the cortical parcellation system. Subsequently, the receiver operating characteristics were calculated for rTMS and fMRI and compared with DCS as ground truth for regions with (w/) and without (w/o) the lesion in the mapped regions.

RESULTS

The w/ subgroup revealed a sensitivity of 100% (w/o 100%), a specificity of 8% (w/o 5%), a positive predictive value of 34% (w/o: 53%), and a negative predictive value (NPV) of 100% (w/o: 100%) for the comparison of rTMS versus DCS. Findings for the comparison of fMRI versus DCS within the w/ subgroup revealed a sensitivity of 32% (w/o: 62%), a specificity of 88% (w/o: 60%), a positive predictive value of 56% (w/o: 62%), and a NPV of 73% (w/o: 60%).

CONCLUSIONS

Although strengths and weaknesses exist for both rTMS and fMRI, the results show that rTMS is less affected by a brain lesion than fMRI, especially when performing mapping of language-negative cortical regions based on sensitivity and NPV.

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

OBJECT

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.

Current and potential utility of transcranial magnetic stimulation in the diagnostics before brain tumor surgery

This article describes the evolution and state-of-the-art of navigated transcranial magnetic stimulation for evaluation of patients with brain tumors in presumed eloquent location. Alternative noninvasive technologies for functional brain mapping are described and assessed in the context of their usability and clinical needs. In addition to the description of the current validation level and clinical application of navigated transcranial magnetic stimulation for motor and language mapping, the manuscript highlights ongoing research efforts and provides an outlook on upcoming developments in the field of noninvasive brain mapping. Finally, the clinical rationale for presurgical noninvasive brain mapping is discussed in the light of current developments in neurosurgery.

Microsurgical anatomy of the central lobe

OBJECT

Central Lobe consists of the pre- and postcentral gyri on the lateral surface and the Paracentral Lobule on the medial surface and corresponds to the sensorimotor cortex. The objective of the present study was to define the neural features, craniometric relationships, arterial supply, and venous drainage of the central lobe.

METHODS

Cadaveric hemispheres dissected using microsurgical techniques provided the material for this study.

RESULTS

The coronal suture is closer to the precentral gyrus and central sulcus at its lower rather than at its upper end, but they are closest at a point near where the superior temporal line crosses the coronal suture. The arterial supply of the lower two-thirds of the lateral surface of the central lobe was from the central, precentral, and anterior parietal branches that arose predominantly from the superior trunk of the middle cerebral artery. The medial surface and the superior third of the lateral surface were supplied by the posterior interior frontal, paracentral, and superior parietal branches of the pericallosal and callosomarginal arteries. The venous drainage of the superior two-thirds of the lateral surface and the central lobe on the medial surface was predominantly through the superior sagittal sinus, and the inferior third of the lateral surface was predominantly through the superficial sylvian veins to the sphenoparietal sinus or the vein of Labbé to the transverse sinus.

CONCLUSIONS

The pre- and postcentral gyri and paracentral lobule have a morphological and functional anatomy that differentiates them from the remainder of their respective lobes and are considered by many as a single lobe. An understanding of the anatomical relationships of the central lobe can be useful in preoperative planning and in establishing reliable intraoperative landmarks.

Intraoperative functional mapping and monitoring during glioma surgery

Glioma surgery represents a significant advance with respect to improving resection rates using new surgical techniques, including intraoperative functional mapping, monitoring, and imaging. Functional mapping under awake craniotomy can be used to detect individual eloquent tissues of speech and/or motor functions in order to prevent unexpected deficits and promote extensive resection. In addition, monitoring the patient’s neurological findings during resection is also very useful for maximizing the removal rate and minimizing deficits by alarming that the touched area is close to eloquent regions and fibers. Assessing several types of evoked potentials, including motor evoked potentials (MEPs), sensory evoked potentials (SEPs) and visual evoked potentials (VEPs), is also helpful for performing surgical monitoring in patients under general anesthesia (GA). We herein review the utility of intraoperative mapping and monitoring the assessment of neurological findings, with a particular focus on speech and the motor function, in patients undergoing glioma surgery.

Resection of supratentorial gliomas: the need to merge microsurgical technical cornerstones with modern functional mapping concepts. An overview

Although surgery is not curative for the majority of intracranial gliomas, radical resection has been demonstrated to influence survival and delay tumor progression. Because gliomas are very frequently located in eloquent or more generally critical areas, surgeons must always balance the maximizing resection with the need to preserve neurological function. In this overview, we tried to summarize the recent literature and our personal experience about (1) the benefits and limits of using preoperative anatomical and functional neuroimaging (anatomical MRI, DTI fiber tracking, and functional MRI), (2) the issues to consider in planning the surgical strategy, (3) the need to thoroughly understand microsurgical techniques that enable a maximal resection (subpial dissection, vascular manipulation, etc.), (4) the importance of individualizing surgical strategy especially in patients with gliomas in eloquent areas (the role of neuropsychological evaluation in redefining eloquent and non-eloquent areas), and (5) how to use intraoperative mapping techniques and understand why and when to use them. Through this paper, the reader should become more familiar with a comprehensive panel of techniques and methodologies but more importantly become aware that these recent technical advances facilitate a conceptual change from classical surgical paradigms toward a more patient-specific approach.

Navigated Transcranial Magnetic Stimulation for “Somatotopic” Tractography of the Corticospinal Tract

BACKGROUND:

Diffusion tensor imaging tractography provides 3-dimensional reconstruction of principal white matter tracts, but its spatial accuracy has been questioned. Navigated transcranial magnetic stimulation (nTMS) enables somatotopic mapping of the motor cortex.

OBJECTIVE:

We used motor maps to reconstruct the corticospinal tract (CST) by integrating elements of its somatotopic organization. We analyzed the accuracy of this method compared with a standard technique and verified its reliability with intraoperative subcortical stimulation.

METHODS:

We prospectively collected data from patients who underwent surgery between January 2012 and October 2013 for lesions involving the CST. nTMS-based diffusion tensor imaging tractography was compared with a standard technique. The reliability and accuracy between the 2 techniques were analyzed by comparing the number of fibers, the concordance in size, and the location of the cortical end of the CST and the motor area. The accuracy of the technique was assessed by using direct subcortical stimulation.

RESULTS:

Twenty patients were enrolled in the study. nTMS-based tractography provided a detailed somatotopic reconstruction of the CST. This nTMS-based reconstruction resulted in a decreased number of fibers (305.1 ± 231.7 vs 1024 ± 193, P &lt; .001) and a significantly greater overlap between the motor cortex and the cortical end-region of the CST compared with the standard technique (90.5 ± 8.8% vs 58.3 ± 16.6%, P &lt; .001). Direct subcortical stimulation confirmed the CST location and the somatotopic reconstruction in all cases.

CONCLUSION:

These results suggest that nTMS-based tractography of the CST is more accurate and less operator dependent than the standard technique and provides a reliable anatomic and functional characterization of the motor pathway.

Integration of navigated brain stimulation data into radiosurgical planning: potential benefits and dangers

BACKGROUND

Radiosurgical treatment of brain lesions near motor or language eloquent areas requires careful planning to achieve the optimal balance between effective dose prescription and preservation of function. Navigated brain stimulation (NBS) is the only non-invasive modality that allows the identification of functionally essential areas by electrical stimulation or inhibition of cortical neurons analogous to the gold-standard of intraoperative electrical mapping.

OBJECTIVE

To evaluate the feasibility of NBS data integration into the radiosurgical environment, and to analyze the influence of NBS data on the radiosurgical treatment planning for lesions near or within motor or language eloquent areas of the brain.

METHODS

Eleven consecutive patients with brain lesions in presumed motor or language eloquent locations eligible for radiosurgical treatment were mapped with NBS. The radiosurgical team prospectively analyzed the data transfer and classified the influence of the functional NBS information on the radiosurgical treatment planning using a standardized questionnaire.

RESULTS

The semi-automatized data transfer to the radiosurgical planning workstation was flawless in all cases. The NBS data influenced the radiosurgical treatment planning procedure as follows: improved risk-benefit balancing in all cases, target contouring in 0 %, dose plan modification in 81.9 %, reduction of radiation dosage in 72.7 % and treatment indication in 63.7 % of the cases.

CONCLUSIONS

NBS data integration into radiosurgical treatment planning is feasible. By mapping the spatial relationship between the lesion and functionally essential areas, NBS has the potential to improve radiosurgical planning safety for eloquently located lesions.

Awake surgery between art and science. Part II: language and cognitive mapping

Direct cortical and subcortical stimulation has been claimed to be the gold standard for exploring brain function. In this field, efforts are now being made to move from intraoperative naming-assisted surgical resection towards the use of other language and cognitive tasks. However, before relying on new protocols and new techniques, we need a multi-staged system of evidence (low and high) relating to each step of functional mapping and its clinical validity. In this article we examine the possibilities and limits of brain mapping with the aid of a visual object naming task and various other tasks used to date. The methodological aspects of intraoperative brain mapping, as well as the clinical and operative settings, were discussed in Part I of this review.

Functional brain mapping of patients with arteriovenous malformations using navigated transcranial magnetic stimulation: first experience in ten patients

BACKGROUND

Intracranial arteriovenous malformations (AVM) are known to be potent inductors of functional plasticity, and their vasculature makes standard functional imaging difficult. Here we conducted functional mapping of both primary motor cortex and speech related areas in patients with AVM using navigated transcranial magnetic stimulation (nTMS), which has been recently proven as a reliable noninvasive modality of preoperative functional brain mapping.

METHOD

nTMS mapping was performed in ten patients with unruptured intracranial AVMs located in or near eloquent areas. Motor mapping was conducted for six patients with AVMs near the rolandic region, and speech mapping was performed for four patients with left perisylvian AVMs. After the examination, all patients were treated with surgery, radiosurgery or observed with best medical treatment on case-by-case basis.

RESULTS

Motor mapping allowed for delineation of the primary motor cortex, even if the anatomy was severely obscured by the AVM in all cases with rolandic AVMs. No plastic relocation of the primary motor cortex was observed. Repetitive stimulation of the left ventral precentral gyrus led to speech impairments in all four cases that underwent speech mapping. Right hemispheric involvement was observed in one out of four cases and potentially indicated plastic changes. No side effects were observed.

CONCLUSION

nTMS allowed for detailed delineation of eloquent areas even within hypervascularized cortical areas. Our observations indicate that nTMS functional mapping is feasible not only in tumorous brain lesions, but also in AVMs.

Surgical strategies for nonenhancing slow-growing gliomas with special reference to functional reorganization: review with own experience

Nonenhancing intrinsic brain tumors have been empirically treated with a strategy that has been adopted for World Health Organization (WHO) grade II gliomas (low-grade gliomas: LGGs), even though small parts of the tumors might have been diagnosed as WHO grade III gliomas after surgery. However, the best surgical strategy for nonenhancing gliomas, including LGGs, is still debatable. LGGs have the following features: slow growth, high possibility of histologically malignant transformation, and no clear border between the tumor and adjacent normal brain. We retrospectively examined 26 consecutive patients with nonenhancing gliomas who were surgically treated at Kanazawa University Hospital between January 2006 and May 2012, with special reference to functional reorganization, extent of resection (EOR), and functional mapping during awake surgery. These categories are closely related with the features of LGG, i.e. functional reorganization due to slow-growing nature, EOR with related malignant transformation, and functional mapping for delineating the unclear tumor border. Finally, we discuss surgical strategies for slow-growing gliomas that are represented by LGGs and nonenhancing gliomas. In conclusion, slow-growing gliomas tend to undergo functional reorganization, and the functional reorganization affects the presurgical evaluation for resectability based on tumor location related to eloquence. In the clinical setting, to definitely identify the reorganized functional regions, awake surgery is recommended. Therefore, awake surgery could increase the extent of the resection of the tumor without deficits, resulting in the delay of malignant transformation and increase in overall survival.

Functional plasticity of language confirmed with intraoperative electrical stimulations and updated neuronavigation: case report of low-grade glioma of the left inferior frontal gyrus

Removal of glioma from the dominant side of the inferior frontal gyrus (IFG) is associated with a risk of permanent language dysfunction. While intraoperative cortical and subcortical electrical stimulations can be used for functional language mapping in an effort to reduce the risk of postoperative neurological impairment, the extent of resection is limited by the functional boundaries. Recent reports proposed that a two-stage surgical approach for low-grade glioma in eloquent areas could avoid permanent deficits via the functional plasticity that occurs between the two operations. The report describes a patient with World Health Organization (WHO) grade II oligoastrocytoma in the left IFG, in functional plasticity of language occurred in the interval between two consecutive surgeries. Intraoperative electrical stimulations suggested that a language area and related subcortical fiber crossed the pre-central sulcus during tumor progression owing to functional plasticity. In the present case, we integrated neurophysiological data into the intraoperative neuronavigation system. We also confirmed the peri-lesional shift of language area and related subcortical fiber on image findings. Consequently, the tumor was sub-totally removed with two separate resections. Permanent language disturbance did not occur, and this favorable outcome was attributed to functional plasticity. The present experience sustains the multistage approach for low-grade gliomas in the language area. A combination of intraoperative electrical stimulations and updated neuronavigation may facilitate the characterization of brain functional plasticity.

Preoperative motor mapping by navigated transcranial magnetic brain stimulation improves outcome for motor eloquent lesions

BACKGROUND

Navigated transcranial magnetic stimulation (nTMS) has been proven to influence surgical indication and planning. Yet there is still no clear evidence how these additional preoperative functional data influence the clinical course and outcome. Thus, this study aimed to compare patients with motor eloquently located supratentorial lesions investigated with or without preoperative nTMS in terms of clinical outcome parameters.

METHODS

A prospectively enrolled cohort of 100 patients with supratentorial lesions located in motor eloquent areas was investigated by preoperative nTMS (2010-2013) and matched with a control of 100 patients who were operated on without nTMS data (2006-2010) by a matched pair analysis.

RESULTS

Patients in the nTMS group showed a significantly lower rate of residual tumor on postoperative MRI (OR 0.3828; 95% CI 0.2062-0.7107). Twelve percent of patients in the nTMS and 1% of patients in the non-nTMS group improved while 75% and 81% of the nTMS and non-nTMS groups, respectively, remained unchanged and 13% and 18% of patients in the nTMS and non-nTMS groups, respectively, deteriorated in postoperative motor function on long-term follow-up (P = .0057). Moreover, the nTMS group showed smaller craniotomies (nTMS 22.4 ± 8.3 cm(2); non-nTMS 26.7 ± 11.3 cm(2); P = .0023).

CONCLUSIONS

This work increases the level of evidence for preoperative motor mapping by nTMS for rolandic lesions in a group comparison study. We therefore strongly advocate nTMS to become increasingly used for these lesions. However, a randomized trial on the comparison with the gold standard of intraoperative mapping seems mandatory.

Tailoring neurophysiological strategies with clinical context enhances resection and safety and expands indications in gliomas involving motor pathways

BACKGROUND

Resection of motor pathway gliomas requires the intraoperative recognition of essential cortical-subcortical motor structures. The degree of involvement of motor structures is variable, and increases as result of treatments patients are submitted to. Intraoperative neurophysiology offers various stimulation modalities, which efficiency is based on the ability to recognize essential sites with the highest possible resolution in most clinical conditions. Two stimulation paradigms evolved for intraoperative guidance of motor tumors removal: the 60 Hz-technique [low frequency (LF)] and the pulse-technique [high frequency-(HF)], delivered by bipolar or monopolar probe respectively. Most surgical teams rely on to either of the 2 techniques. The key point is the integration of the choice of the stimulation modality with the clinical context.

METHODS

In 591 tumors involving the corticospinal tract, the use of HF and LF was tailored to the clinical context defined by patient clinical history and tumor features (by imaging). The effect was evaluated on the feasibility of mapping, the impact on immediate and permanent morbidity, the extent of resection, and the number of patients treated.

RESULTS

By integrating the choice of the probe and the stimulation protocol with patient clinical history and tumor characteristics, the best probe-frequency match was identified for the different sets of clinical conditions. This integrative approach allows increasing the extent of resection and patient functional integrity, and greatly expands the number of patients who could benefit from surgery.

CONCLUSIONS

The integration of stimulation modalities with clinical context enhances the extent and safety of resection and expands the population of patients who could benefit from surgical treatment.