Diagnostic benefits of presurgical fMRI in patients with brain tumours in the primary sensorimotor cortex

The new morphologic classification of the hand motor cortex with magnetic resonance imaging in glioma patients

Purpose

The hand motor cortex (HMC) is a reliable anatomical landmark for identifying the precentral gyrus. The current study aimed to investigate the morphology of HMC on axial MRI of glioma patients, propose a new morphological classification of HMC and analyze the effect of tumors on the morphology of HMC.

Methods

A retrospective study of 276 adult right-handed glioma patients was conducted. The morphology of HMC was assessed using T2 axial images. Subsequently, the distribution of morphological subtypes was compared between the bilateral hemispheres and the tumor-affected and healthy hemispheres. Finally, the influence of tumor pathology on the morphology of HMC was investigated.

Results

A new morphological classification of HMC with four subtypes (Ω, ε, Ω-ε and ε-Ω) was proposed. No significant difference was identified in the distribution of morphological subtypes between the bilateral hemispheres (p = 0.0901, Chi-square test), or between the tumor-affected and healthy hemispheres (p = 0.3507, Chi-square test), and the morphology of HMC between the bilateral hemispheres were consistent (p < 0.0001, Kappa test). In addition, a significant difference was identified in the distribution of morphological subtypes between astrocytic and oligodendroglial tumors (p = 0.0135, Chi-square test).

Conclusion

In the current study, we proposed a new morphological classification of HMC, and found that tumor could affect the morphology of HMC in glioma patients. The results can help our clinical practice, enabling us to further understand the spatial structure of the cerebral hemispheres.

Comparative validation of automated presurgical tractography based on constrained spherical deconvolution and diffusion tensor imaging with direct electrical stimulation

OBJECTIVES

Accurate presurgical brain mapping enables preoperative risk assessment and intraoperative guidance. This cross-sectional study investigated whether constrained spherical deconvolution (CSD) methods were more accurate than diffusion tensor imaging (DTI)-based methods for presurgical white matter mapping using intraoperative direct electrical stimulation (DES) as the ground truth.

METHODS

Five different tractography methods were compared (three DTI-based and two CSD-based) in 22 preoperative neurosurgical patients undergoing surgery with DES mapping. The corticospinal tract (CST, N = 20) and arcuate fasciculus (AF, N = 7) bundles were reconstructed, then minimum distances between tractograms and DES coordinates were compared between tractography methods. Receiver-operating characteristic (ROC) curves were used for both bundles. For the CST, binary agreement, linear modeling, and posthoc testing were used to compare tractography methods while correcting for relative lesion and bundle volumes.

RESULTS

Distance measures between 154 positive (functional response, pDES) and negative (no response, nDES) coordinates, and 134 tractograms resulted in 860 data points. Higher agreement was found between pDES coordinates and CSD-based compared to DTI-based tractograms. ROC curves showed overall higher sensitivity at shorter distance cutoffs for CSD (8.5 mm) compared to DTI (14.5 mm). CSD-based CST tractograms showed significantly higher agreement with pDES, which was confirmed by linear modeling and posthoc tests (PFWE < .05).

CONCLUSIONS

CSD-based CST tractograms were more accurate than DTI-based ones when validated using DES-based assessment of motor and sensory function. This demonstrates the potential benefits of structural mapping using CSD in clinical practice.

Functional Magnetic Resonance Imaging and Diffusion Tensor Imaging-Tractography in Resective Brain Surgery: Lesion Coverage Strategies and Patient Outcomes

Diffusion tensor imaging (DTI)-tractography and functional magnetic resonance imaging (fMRI) have dynamically entered the presurgical evaluation context of brain surgery during the past decades, providing novel perspectives in surgical planning and lesion access approaches. However, their application in the presurgical setting requires significant time and effort and increased costs, thereby raising questions regarding efficiency and best use. In this work, we set out to evaluate DTI-tractography and combined fMRI/DTI-tractography during intra-operative neuronavigation in resective brain surgery using lesion-related preoperative neurological deficit (PND) outcomes as metrics. We retrospectively reviewed medical records of 252 consecutive patients admitted for brain surgery. Standard anatomical neuroimaging protocols were performed in 127 patients, 69 patients had additional DTI-tractography, and 56 had combined DTI-tractography/fMRI. fMRI procedures involved language, motor, somatic sensory, sensorimotor and visual mapping. DTI-tractography involved fiber tracking of the motor, sensory, language and visual pathways. At 1 month postoperatively, DTI-tractography patients were more likely to present either improvement or preservation of PNDs (p = 0.004 and p = 0.007, respectively). At 6 months, combined DTI-tractography/fMRI patients were more likely to experience complete PND resolution (p < 0.001). Low-grade lesion patients (N = 102) with combined DTI-tractography/fMRI were more likely to experience complete resolution of PNDs at 1 and 6 months (p = 0.001 and p < 0.001, respectively). High-grade lesion patients (N = 140) with combined DTI-tractography/fMRI were more likely to have PNDs resolved at 6 months (p = 0.005). Patients with motor symptoms (N = 80) were more likely to experience complete remission of PNDs at 6 months with DTI-tractography or combined DTI-tractography/fMRI (p = 0.008 and p = 0.004, respectively), without significant difference between the two imaging protocols (p = 1). Patients with sensory symptoms (N = 44) were more likely to experience complete PND remission at 6 months with combined DTI-tractography/fMRI (p = 0.004). The intraoperative neuroimaging modality did not have a significant effect in patients with preoperative seizures (N = 47). Lack of PND worsening was observed at 6 month follow-up in patients with combined DTI-tractography/fMRI. Our results strongly support the combined use of DTI-tractography and fMRI in patients undergoing resective brain surgery for improving their postoperative clinical profile.

Hemispheric Asymmetry of the Hand Motor Representations in Patients with Highly Malignant Brain Tumors: Implications for Surgery and Clinical Practice

We addressed both brain pre-surgical functional and neurophysiological aspects of the hand representation in 18 right-handed patients harboring a highly malignant brain tumor in the sensorimotor (SM) cortex (10 in the left hemisphere, LH, and 8 in the right hemisphere, RH) and 10 healthy controls, who performed an fMRI hand-clenching task with both hands alternatively. We extracted the main ROI in the SM cortex and compared ROI values and volumes between hemispheres and groups, in addition to their motor neurophysiological measures. Hemispheric asymmetry in the fMRI signal was observed for healthy controls, namely higher signal for the left-hand movements, but not for either patients’ groups. ROI values, although altered in patients vs. controls, did not differ significantly between groups. ROI volumes associated with right-hand movement were lower for both patients’ groups vs. controls, and those associated with left-hand movement were lower in the RH group vs. all groups. These results are relevant to interpret potential preoperative plasticity and make inferences about postoperative plasticity and can be integrated in the surgical planning to increase surgery success and postoperative prognosis and quality of life.

MRI-compatible electromagnetic servomotor for image-guided medical robotics

The soft-tissue imaging capabilities of magnetic resonance imaging (MRI) combined with high precision robotics has the potential to improve the precision and safety of a wide range of image-guided medical procedures. However, functional MRI-compatible robotics have not yet been realized in part because conventional electromagnetic servomotors can become dangerous projectiles near the strong magnetic field of an MRI scanner. Here we report an electromagnetic servomotor constructed from non-magnetic components, where high-torque and controlled rotary actuation is produced via interaction between electrical current in the servomotor armature and the magnetic field generated by the superconducting magnet of the MRI scanner itself. Using this servomotor design, we then build and test an MRI-compatible robot which can achieve the linear forces required to insert a large-diameter biopsy instrument in tissue during simultaneous MRI. Our electromagnetic servomotor can be safely operated (while imaging) in the patient area of a 3 Tesla clinical MRI scanner.

MRI: how to understand it

MRI is a staple of the neurologist's armoury when facing diagnostic challenges. At times, it can reveal or confirm the diagnosis with clarity, at others it brings us no further forwards, or even muddies the water. We rely on the expertise of neuroradiology colleagues to interpret MR images, but the choice of protocol for MR acquisition and its interpretation hinge crucially on the clinical information we provide. Having a degree of understanding about how MRI works, its limitations and pitfalls, can help to optimise what we learn from a scan.

Feasibility, Contrast Sensitivity and Network Specificity of Language fMRI in Presurgical Evaluation for Epilepsy and Brain Tumor Surgery

Language fMRI has become an integral part of the planning process in brain surgery. However, fMRI may suffer from confounding factors both on the patient side, as well as on the provider side. In this study, we investigate how patient-related confounds affect the ability of the patient to perform language fMRI tasks (feasibility), the task sensitivity from an image contrast point of view, and the anatomical specificity of expressive and receptive language fMRI protocols. 104 patients were referred for language fMRI in the context of presurgical procedures for epilepsy and brain tumor surgery. Four tasks were used: (1) a verbal fluency (VF) task to map vocabulary use, (2) a semantic description (SD) task to map sentence formation/semantic integration skills, (3) a reading comprehension (RC) task and (4) a listening comprehension (LC) task. Feasibility was excellent in the LC task (100%), but in the acceptable to mediocre range for the rest of the tasks (SD: 87.50%, RC: 85.57%, VF: 67.30%). Feasibility was significantly confounded by age (p = 0.020) and education level (p = 0.003) in VF, by education level (p = 0.004) and lesion laterality (p = 0.019) in SD and by age (p = 0.001), lesion laterality (p = 0.007) and lesion severity (p = 0.048) in RC. All tasks were comparable regarding sensitivity in generating statistically significant image contrast (VF: 90.00%, SD: 92.30%, RC: 93.25%, LC: 88.46%). The lobe of the lesion (p = 0.005) and the age (p = 0.009) confounded contrast sensitivity in the VF and SD tasks respectively. Both VF and LC tasks demonstrated unilateral lateralization of posterior language areas; only the LC task showed unilateral lateralization of anterior language areas. Our study highlights the effects of patient-related confounding factors on language fMRI and proposes LC as the most feasible, less confounded, and efficiently lateralizing task in the clinical presurgical context.

The utilisation of resting-state fMRI as a pre-operative mapping tool in patients with brain tumours in comparison to task-based fMRI and intraoperative mapping: A systematic review

PURPOSE

Resting-state functional Magnetic Resonance Imaging (rs-fMRI) is suggested to be a viable option for pre-operative mapping for patients with brain tumours. However, it remains an open issue whether the tool is useful in the clinical setting compared to task-based fMRI (T-fMRI) and intraoperative mapping. Thus, a systematic review was conducted to investigate the usefulness of this technique.

METHODS

A systematic literature search of rs-fMRI methods applied as a pre-operative mapping tool was conducted using the PubMed/MEDLINE and Cochrane Library electronic databases following PRISMA guidelines.

RESULTS

Results demonstrated that 50% (six out of twelve) of the studies comparing rs-fMRI and T-fMRI showed good concordance for both language and sensorimotor networks. In comparison to intraoperative mapping, 86% (six out of seven) studies found a good agreement to rs-fMRI. Finally, 87% (twenty out of twenty-three) studies agreed that rs-fMRI is a suitable and useful pre-operative mapping tool.

CONCLUSIONS

rs-fMRI is a promising technique for pre-operative mapping in assessing the functional brain areas. However, the agreement between rs-fMRI with other techniques, including T-fMRI and intraoperative maps, is not yet optimal. Studies to ascertain and improve the sophistication in pre-processing of rs-fMRI imaging data are needed.

Automatic identification of atypical clinical fMRI results

Purpose

Functional MRI is not routinely used for neurosurgical planning despite potential important advantages, due to difficulty of determining quality. We introduce a novel method for objective evaluation of fMRI scan quality, based on activation maps. A template matching analysis (TMA) is presented and tested on data from two clinical fMRI protocols, performed by healthy controls in seven clinical centers. Preliminary clinical utility is tested with data from low-grade glioma patients.

Methods

Data were collected from 42 healthy subjects from seven centers, with standardized finger tapping (FT) and verb generation (VG) tasks. Copies of these “typical” data were deliberately analyzed incorrectly to assess feasibility of identifying them as “atypical.” Analyses of the VG task administered to 32 tumor patients assessed sensitivity of the TMA method to anatomical abnormalities.

Results

TMA identified all atypical activity maps for both tasks, at the cost of incorrectly classifying 3.6 (VG)–6.5% (FT) of typical maps as atypical. For patients, the average TMA was significantly higher than atypical healthy scans, despite localized anatomical abnormalities caused by a tumor.

Conclusion

This study supports feasibility of TMA for objective identification of atypical activation patterns for motor and verb generation fMRI protocols. TMA can facilitate the use and evaluation of clinical fMRI in hospital settings that have limited access to fMRI experts. In a clinical setting, this method could be applied to automatically flag fMRI scans showing atypical activation patterns for further investigation to determine whether atypicality is caused by poor scan data quality or abnormal functional topography.

Presurgical Localization of the Primary Sensorimotor Cortex in Gliomas : When is Resting State FMRI Beneficial and Sufficient?

PURPOSE

Functional magnetic resonance imaging (fMRI) has an established role in neurosurgical planning; however, ambiguity surrounds the comparative value of resting and task-based fMRI relative to anatomical localization of the sensorimotor cortex. This study was carried out to determine: 1) how often fMRI adds to prediction of motor risks beyond expert neuroradiological review, 2) success rates of presurgical resting and task-based sensorimotor mapping, and 3) the impact of accelerated resting fMRI acquisitions on network detectability.

METHODS

Data were collected at 2 centers from 71 patients with a primary brain tumor (31 women; mean age 41.9 ± 13.9 years) and 14 healthy individuals (6 women; mean age 37.9 ± 12.7 years). Preoperative 3T MRI included anatomical scans and resting fMRI using unaccelerated (TR = 3.5 s), intermediate (TR = 1.56 s) or high temporal resolution (TR = 0.72 s) sequences. Task fMRI finger tapping data were acquired in 45 patients. Group differences in fMRI reproducibility, spatial overlap and success frequencies were assessed with t‑tests and χ²-tests.

RESULTS

Radiological review identified the central sulcus in 98.6% (70/71) patients. Task-fMRI succeeded in 100% (45/45). Resting fMRI failed to identify a sensorimotor network in up to 10 patients; it succeeded in 97.9% (47/48) of accelerated fMRIs, compared to only 60.9% (14/23) of unaccelerated fMRIs ([Formula: see text](2) = 17.84, p < 0.001). Of the patients 12 experienced postoperative deterioration, largely predicted by anatomical proximity to the central sulcus.

CONCLUSION

The use of fMRI in patients with residual or intact presurgical motor function added value to uncertain anatomical localization in just a single peri-Rolandic glioma case. Resting fMRI showed high correspondence to task localization when acquired with accelerated sequences but offered limited success at standard acquisitions.

Limitations of functional neuroimaging for patient selection and surgical planning in glioma surgery

The optimal surgical management of gliomas requires a balance between surgical cytoreduction and preservation of neurological function. Preoperative functional neuroimaging, such as functional MRI (fMRI) and diffusion tensor imaging (DTI), has emerged as a possible tool to inform patient selection and surgical planning. However, evidence that preoperative fMRI or DTI improves extent of resection, limits neurological morbidity, and broadens surgical indications in classically eloquent areas is lacking. In this review, the authors describe facets of functional neuroimaging techniques that may limit their impact on neurosurgical oncology and critically evaluate the evidence supporting fMRI and DTI for patient selection and operative planning in glioma surgery. The authors also propose alternative applications for functional neuroimaging in the care of glioma patients.

Intraoperative Use of Functional MRI for Surgical Decision Making after Limited or Infeasible Electrocortical Stimulation Mapping

BACKGROUND AND PURPOSE

Functional magnetic resonance imaging (fMRI) is becoming widely recognized as a key component of preoperative neurosurgical planning, although intraoperative electrocortical stimulation (ECS) is considered the gold standard surgical brain mapping method. However, acquiring and interpreting ECS results can sometimes be challenging. This retrospective study assesses whether intraoperative availability of fMRI impacted surgical decision-making when ECS was problematic or unobtainable.

METHODS

Records were reviewed for 191 patients who underwent presurgical fMRI with fMRI loaded into the neuronavigation system. Four patients were excluded as a bur-hole biopsy was performed. Imaging was acquired at 3 Tesla and analyzed using the general linear model with significantly activated pixels determined via individually determined thresholds. fMRI maps were displayed intraoperatively via commercial neuronavigation systems.

RESULTS

Seventy-one cases were planned ECS; however, 18 (25.35%) of these procedures were either not attempted or aborted/limited due to: seizure (10), patient difficulty cooperating with the ECS mapping (4), scarring/limited dural opening (3), or dural bleeding (1). In all aborted/limited ECS cases, the surgeon continued surgery using fMRI to guide surgical decision-making. There was no significant difference in the incidence of postoperative deficits between cases with completed ECS and those with limited/aborted ECS.

CONCLUSIONS

Preoperative fMRI allowed for continuation of surgery in over one-fourth of patients in which planned ECS was incomplete or impossible, without a significantly different incidence of postoperative deficits compared to the patients with completed ECS. This demonstrates additional value of fMRI beyond presurgical planning, as fMRI data served as a backup method to ECS.

Modern Treatment of Brain Arteriovenous Malformations Using Preoperative Planning Based on Navigated Transcranial Magnetic Stimulation: A Revisitation of the Concept of Eloquence

BACKGROUND

Navigated transcranial magnetic stimulation (nTMS) provides a reliable identification of "eloquent" cortical brain areas. Moreover, it can be used for diffusion tensor imaging fiber tracking of eloquent subcortical tracts. We describe the use of nTMS-based cortical mapping and diffusion tensor imaging fiber tracking for defining the "eloquence" of areas surrounding brain arteriovenous malformations (BAVMs), aiming to improve patient stratification and treatment.

METHODS

We collected data of BAVMs suspected to be in eloquent areas treated between 2017 and 2019, and submitted to nTMS-based reconstruction of motor, language, and visual pathways for the definition of the eloquence of the surrounding brain areas. We describe the nTMS-based approach and analyze its impact on patient stratification and allocation to treatment in comparison with the standard assessment of eloquence based on anatomical landmarks.

RESULTS

Ten patients were included in the study. Preliminarily, 9 BAVMs were suspected to be located in an eloquent area. After nTMS-based mapping, only 5 BAVMs were confirmed to be close to eloquent structures, thus leading to a change of the score for eloquence and of the final BAVMs grading in 60% of patients. Treatment was customized according to nTMS information, and no cases of neurological worsening were observed. Radiological obliteration was complete in 7 cases microsurgically treated, and accounted for about 70% in the remaining 3 patients 1 year after radiosurgical treatment.

CONCLUSIONS

The nTMS-based information allows an accurate stratification and allocation of patients with BAVMs to the most effective treatment according to a modern, customized, neurophysiological identification of the adjacent eloquent brain networks.

A mixed-effects, spatially varying coefficients model with application to multi-resolution functional magnetic resonance imaging data

Spatial resolution plays an important role in functional magnetic resonance imaging studies as the signal-to-noise ratio increases linearly with voxel volume. In scientific studies, where functional magnetic resonance imaging is widely used, the standard spatial resolution typically used is relatively low which ensures a relatively high signal-to-noise ratio. However, for pre-surgical functional magnetic resonance imaging analysis, where spatial accuracy is paramount, high-resolution functional magnetic resonance imaging may play an important role with its greater spatial resolution. High spatial resolution comes at the cost of a smaller signal-to-noise ratio. This begs the question as to whether we can leverage the higher signal-to-noise ratio of a standard functional magnetic resonance imaging study with the greater spatial accuracy of a high-resolution functional magnetic resonance imaging study in a pre-operative patient. To answer this question, we propose to regress the statistic image from a high resolution scan onto the statistic image obtained from a standard resolution scan using a mixed-effects model with spatially varying coefficients. We evaluate our model via simulation studies and we compare its performance with a recently proposed model that operates at a single spatial resolution. We apply and compare the two models on data from a patient awaiting tumor resection. Both simulation study results and the real data analysis demonstrate that our newly proposed model indeed leverages the larger signal-to-noise ratio of the standard spatial resolution scan while maintaining the advantages of the high spatial resolution scan.

Seed-Based Resting-State Functional MRI for Presurgical Localization of the Motor Cortex: A Task-Based Functional MRI-Determined Seed Versus an Anatomy-Determined Seed

Objective

For localization of the motor cortex, seed-based resting-state functional MRI (rsfMRI) uses the contralateral motor cortex as a seed. However, research has shown that the location of the motor cortex could differ according to anatomical variations. The purpose of this study was to compare the results of rsfMRI using two seeds: a template seed (the anatomically expected location of the contralateral motor cortex) and a functional seed (the actual location of the contralateral motor cortex determined by task-based functional MRI [tbfMRI]).

Materials and Methods

Eight patients (4 with glioma, 3 with meningioma, and 1 with arteriovenous malformation) and 9 healthy volunteers participated. For the patients, tbfMRI was performed unilaterally to activate the healthy contralateral motor cortex. The affected ipsilateral motor cortices were mapped with rsfMRI using seed-based and independent component analysis (ICA). In the healthy volunteer group, both motor cortices were mapped with both-hands tbfMRI and rsfMRI. We compared the results between template and functional seeds, and between the seed-based analysis and ICA with visual and quantitative analysis.

Results

For the visual analysis, the functional seed showed significantly higher scores compared to the template seed in both the patients (p = 0.002) and healthy volunteers (p < 0.001). Although no significant difference was observed between the functional seed and ICA, the ICA results showed significantly higher scores than the template seed in both the patients (p = 0.01) and healthy volunteers (p = 0.005). In the quantitative analysis, the functional seed exhibited greater similarity to tbfMRI than the template seed and ICA.

Conclusion

Using the contralateral motor cortex determined by tbfMRI as a seed could enhance visual delineation of the motor cortex in seed-based rsfMRI.

fMRI data processing in MRTOOL: to what extent does anatomical registration affect the reliability of functional results?

Spatial registration is an essential step in the analysis of fMRI data because it enables between-subject analyses of brain activity, measured either during task performance or in the resting state. In this study, we investigated how anatomical registration with MRTOOL affects the reliability of task-related fMRI activity. We used as a benchmark the results from two other spatial registration methods implemented in SPM12: the Unified Segmentation algorithm and the DARTEL toolbox. Structural alignment accuracy and the impact on functional activation maps were assessed with high-resolution T1-weighted images and a set of task-related functional volumes acquired in 10 healthy volunteers. Our findings confirmed that anatomical registration is a crucial step in fMRI data processing, contributing significantly to the total inter-subject variance of the activation maps. MRTOOL and DARTEL provided greater registration accuracy than Unified Segmentation. Although DARTEL had superior gray matter and white matter tissue alignment than MRTOOL, there were no significant differences between DARTEL and MRTOOL in test-retest reliability. Likewise, we found only limited differences in BOLD activation morphology between MRTOOL and DARTEL. The test-retest reliability of task-related responses was comparable between MRTOOL and DARTEL, and both proved superior to Unified Segmentation. We conclude that MRTOOL, which is suitable for single-subject processing of structural and functional MR images, is a valid alternative to other SPM12-based approaches that are intended for group analysis. MRTOOL now includes a normalization module for fMRI data and is freely available to the scientific community.

How to Build a Neurosurgical Oncology Practice Specializing in Gliomas

For the neurosurgical oncologist, a specialty practice in gliomas represents an intersection of tailored surgical approaches, emerging intraoperative technologies, expanding surgical trial portfolios, and new paradigms in glioma biology. Assembling these disparate pieces into a cohesive career trajectory is a difficult task but ultimately enables the subspecialist to navigate all domains relevant to improving glioma patient outcomes. Within the larger clinical and basic science community, thoughtful integration and intensive collaborations are essential mechanisms when building a multidisciplinary glioma program.

The Role of Navigated Transcranial Magnetic Stimulation Motor Mapping in Adjuvant Radiotherapy Planning in Patients With Supratentorial Brain Metastases

Purpose: In radiotherapy (RT) of brain tumors, the primary motor cortex is not regularly considered in target volume delineation, although decline in motor function is possible due to radiation. Non-invasive identification of motor-eloquent brain areas is currently mostly restricted to functional magnetic resonance imaging (fMRI), which has shown to lack precision for this purpose. Navigated transcranial magnetic stimulation (nTMS) is a novel tool to identify motor-eloquent brain areas. This study aims to integrate nTMS motor maps in RT planning and evaluates the influence on dosage modulations in patients harboring brain metastases.

Materials and Methods: Preoperative nTMS motor maps of 30 patients diagnosed with motor-eloquent brain metastases were fused with conventional planning imaging and transferred to the RT planning software. RT plans of eleven patients were optimized by contouring nTMS motor maps as organs at risk (OARs). Dose modulation analyses were performed using dose-volume histogram (DVH) parameters.

Results: By constraining the dose applied to the nTMS motor maps outside the planning target volume (PTV) to 15 Gy, the mean dose (Dmean) to the nTMS motor maps was significantly reduced by 18.1% from 23.0 Gy (16.9–30.4 Gy) to 18.9 Gy (13.5–28.8 Gy, p < 0.05). The Dmean of the PTV increased by 0.6 ± 0.3 Gy (1.7%).

Conclusion: Implementing nTMS motor maps in standard RT planning is feasible in patients suffering from intracranial metastases. A significant reduction of the dose applied to the nTMS motor maps can be achieved without impairing treatment doses to the PTV. Thus, nTMS might provide a valuable tool for safer application of RT in patients harboring motor-eloquent brain metastases.

Clinical Long-Term Follow-Up Evaluation of Functional Neuronavigation in Adult Cerebral Gliomas

OBJECTIVE

To assess the application of functional neuronavigation in surgeries of adult cerebral gliomas.

METHODS

We performed a retrospective analysis of 375 cases of adult cerebral glioma patients who underwent microsurgical treatment between 2011 and 2017 in our department. Among them, 142 patients underwent surgery using functional neuronavigation (group A), and the other 233 patients were operated on without the help of functional neuronavigation (group B). For both groups, we categorized them into several subgroups according to the lesion locations.

RESULTS

A significant difference in the gross total resection rate was observed between group A and group B (P = 0.001 for overall; P = 0.036 for EO area; and P = 0.004 for BBT area). The postoperative complication rate of group A was much lower than that of group B (P = 0.003 for overall; and P = 0.016 for BBT area). The postoperative 6-month Karnofsky Performance Scale score of all patients in group A was significantly higher than that of group B. Kaplan-Meier survival analyses showed significant increases in the median survival time of group A compared with that of group B (P < 0.001 for overall; P = 0.012 for EO area; P = 0.006 for BBT area), and the Cox proportional regression analysis estimated the hazard ratio of the functional neuronavigation to be 0.533, helping reduce the risk of death by 46.7%.

CONCLUSIONS

This study confirmed that the application of neuronavigation in adult glioma surgery can improve postoperative quality of life and lengthen the survival time of patients, especially in cases involving the brainstem and the eloquent area.

Chaperonology: The Third Eye on Brain Gliomas

The European Organization for Research and Treatment of Cancer/National Cancer Institute of Canada Phase III trial has validated as a current regimen for high-grade gliomas (HGG) a maximal safe surgical resection followed by radiotherapy with concurrent temozolamide. However, it is essential to balance maximal tumor resection with preservation of the patient&rsquo;s neurological functions. Important developments in the fields of pre-operative and intra-operative neuro-imaging and neuro-monitoring have ameliorated the survival rate and the quality of life for patients affected by HGG. Moreover, even though the natural history remains extremely poor, advancement in the molecular and genetic fields have opened up new potential frontiers in the management of this devastating brain disease. In this review, we aim to present a comprehensive account of the main current pre-operative, intra-operative and molecular approaches to HGG with particular attention to specific chaperones, also called heat shock proteins (Hsps), which represent potential novel biomarkers to detect and follow up HGG, and could also be therapeutic agents.

The reliability of identifying the Omega sign using axial T2-weighted magnetic resonance imaging

Preoperative identification of the eloquent brain is important for neurosurgical planning. One common method of finding the motor cortex is by localizing "the Omega sign." No studies have tested the reliability of imaging to identify the Omega sign. We identified 40 recent and consecutive patients who had undergone preoperative functional magnetic resonance imaging for identification of the hand motor area prior to tumor resection. We recruited 11 neurosurgical residents of various levels of training and one board-certified neurosurgeon to identify the hand motor cortex Omega. Testees were given axial images of T2-weighted MRI and placed marks where they expected to find the Omega. Two board-certified radiologists graded and quantified the localization attempts. Inter-rater reliability was assessed using the kappa statistic, and Rao-Scott chi-square tests were used to examine the relationship between clinical factors and testees' experience with correct identification of the Omega sign. The overall correct identification rate was 69.9% (95% CI = 63.4-75.7), ranging from 36.6% to 92.7% among all raters for the tumor side and from 46.2% to 97.4% for the non-tumor side. Anatomic distortion greatly affected correct identification ( p < 0.005). Senior residents had a significantly higher rate of identification of the Omega than junior residents ( p < 0.001). Overall, inter-rater reliability for the Omega sign is poor, with a Fleiss kappa of 0.23. We concluded that correct identification of the Omega sign is affected by tumor distortion and experience but overall is not reliable. This underscores the limitations of anatomic landmarks and the importance of utilizing multiple scanning planes and preoperative fMRI for appropriate localization.

PreSurgMapp: a MATLAB Toolbox for Presurgical Mapping of Eloquent Functional Areas Based on Task-Related and Resting-State Functional MRI

The main goal of brain tumor surgery is to maximize tumor resection while minimizing the risk of irreversible postoperative functional sequelae. Eloquent functional areas should be delineated preoperatively, particularly for patients with tumors near eloquent areas. Functional magnetic resonance imaging (fMRI) is a noninvasive technique that demonstrates great promise for presurgical planning. However, specialized data processing toolkits for presurgical planning remain lacking. Based on several functions in open-source software such as Statistical Parametric Mapping (SPM), Resting-State fMRI Data Analysis Toolkit (REST), Data Processing Assistant for Resting-State fMRI (DPARSF) and Multiple Independent Component Analysis (MICA), here, we introduce an open-source MATLAB toolbox named PreSurgMapp. This toolbox can reveal eloquent areas using comprehensive methods and various complementary fMRI modalities. For example, PreSurgMapp supports both model-based (general linear model, GLM, and seed correlation) and data-driven (independent component analysis, ICA) methods and processes both task-based and resting-state fMRI data. PreSurgMapp is designed for highly automatic and individualized functional mapping with a user-friendly graphical user interface (GUI) for time-saving pipeline processing. For example, sensorimotor and language-related components can be automatically identified without human input interference using an effective, accurate component identification algorithm using discriminability index. All the results generated can be further evaluated and compared by neuro-radiologists or neurosurgeons. This software has substantial value for clinical neuro-radiology and neuro-oncology, including application to patients with low- and high-grade brain tumors and those with epilepsy foci in the dominant language hemisphere who are planning to undergo a temporal lobectomy.

Reducing task-based fMRI scanning time using simultaneous multislice echo planar imaging

PURPOSE

To maintain alertness and to remain motionless during scanning represent a substantial challenge for patients/subjects involved in both clinical and research functional magnetic resonance imaging (fMRI) examinations. Therefore, availability and application of new data acquisition protocols allowing the shortening of scan time without compromising the data quality and statistical power are of major importance.

METHODS

Higher order category-selective visual cortical areas were identified individually, and rapid event-related fMRI design was used to compare three different sampling rates (TR = 2000, 1000, and 410 ms, using state-of-the-art simultaneous multislice imaging) and four different scanning lengths to match the statistical power of the traditional scanning methods to high sampling-rate design.

RESULTS

The results revealed that ~ 4 min of the scan time with 1 Hz (TR = 1000 ms) sampling rate and ~ 2 min scanning at ~ 2.5 Hz (TR = 410 ms) sampling rate provide similar localization sensitivity and selectivity to that obtained with 11-min session at conventional, 0.5 Hz (TR = 2000 ms) sampling rate.

CONCLUSION

Our findings suggest that task-based fMRI examination of clinical population prone to distress such as presurgical mapping experiments might substantially benefit from the reduced (20-40%) scanning time that can be achieved by the application of simultaneous multislice sequences.

The Impact of Diffusion Tensor Imaging Fiber Tracking of the Corticospinal Tract Based on Navigated Transcranial Magnetic Stimulation on Surgery of Motor-Eloquent Brain Lesions

BACKGROUND

Navigated transcranial magnetic stimulation (nTMS) enables preoperative mapping of the motor cortex (M1). The combination of nTMS with diffusion tensor imaging fiber tracking (DTI-FT) of the corticospinal tract (CST) has been described; however, its impact on surgery of motor-eloquent lesions has not been addressed.

OBJECTIVE

To analyze the impact of nTMS-based mapping on surgery of motor-eloquent lesions.

METHODS

In this retrospective case-control study, we reviewed the data of patients operated for suspected motor-eloquent lesions between 2012 and 2015. The patients underwent nTMS mapping of M1 and, from 2014, nTMS-based DTI-FT of the CST. The impact on the preoperative risk/benefit analysis, surgical strategy, craniotomy size, extent of resection (EOR), and outcome were compared with a control group.

RESULTS

We included 35 patients who underwent nTMS mapping of M1 (group A), 35 patients who also underwent nTMS-based DTI-FT of the CST (group B), and a control group composed of 35 patients treated without nTMS (group C). The patients in groups A and B received smaller craniotomies (P = .01; P = .001), had less postoperative seizures (P = .02), and a better postoperative motor performance (P = .04) and Karnofsky Performance Status (P = .009) than the controls. Group B exhibited an improved risk/benefit analysis (P = .006), an increased EOR of nTMS-negative lesions in absence of preoperative motor deficits (P = .01), and less motor and Karnofsky Performance Status worsening in case of preoperative motor deficits (P = .02, P = .03) than group A.

CONCLUSION

nTMS-based mapping enables a tailored surgical approach for motor-eloquent lesions. It may improve the risk/benefit analysis, EOR and outcome, particularly when nTMS-based DTI-FT is performed.

Surgery for dysembryoplastic neuroepithelial tumors and gangliogliomas in eloquent areas. Functional results and seizure control

INTRODUCTION

Dysembryoplastic neuroepithelial tumors and gangliogliomas are developmental glioneuronal tumors usually revealed by partial epilepsy. High epileptogenicity, childhood epilepsy onset, drug-resistance, temporal location, and seizure freedom after complete resection are common characteristics of both tumors. We report the specificity of surgical management, functional results and seizure outcome in cases of a tumor location in eloquent areas.

METHODS

Among 150 patients (88 males, 3-55 years) operated on for refractory epilepsy due to a glioneuronal tumor (1990-2015), 30 (20%, dysembryoplastic neuroepithelial tumors=21; gangliogliomas=9) had a tumor located in an eloquent cortex (sensory-motor, insular or language areas). Surgery was performed after a preoperative work-up, including stereo-electroencephalography in 48 patients (26%) and functional MRI in 100 (67%). MRI-guided lesionectomy was mainly performed in extra-temporal location, whereas an additional corticectomy was performed in a temporal location. Tumor microsurgical resections were guided using neuronavigation and cortical/subcortical electrical stimulations. Multiple stereotactic thermocoagulations were performed in two insular tumors.

RESULTS

New motor/language deficits related to eloquent areas occurred postoperatively in 6/30 patients (20%) without any major permanent disability. Minor sensorimotor (n=2) and moderate language disturbance (n=1) persisted in three of them. Postoperative seizure-free outcome (mean follow-up>5 years) was obtained in 81% of the entire series, but significantly decreased to 60% in eloquent areas. Incomplete tumor resection was the main cause of surgical failure. However, unfavorable seizure outcome was also observed despite complete tumor resection. Malignant transformation occurred in one ganglioglioma.

CONCLUSION

Epilepsy surgery for benign glioneuronal tumors in eloquent areas provides acceptable results regarding the functional risks. Complete tumor resection is crucial for long-term favorable outcome.

7T-fMRI: Faster temporal resolution yields optimal BOLD sensitivity for functional network imaging specifically at high spatial resolution

Recent developments in accelerated imaging methods allow faster acquisition of high spatial resolution images. This could improve the applications of functional magnetic resonance imaging at 7 Tesla (7T-fMRI), such as neurosurgical planning and Brain Computer Interfaces (BCIs). However, increasing the spatial and temporal resolution will both lead to signal-to-noise ratio (SNR) losses due to decreased net magnetization per voxel and T₁-relaxation effect, respectively. This could potentially offset the SNR efficiency gains made with increasing temporal resolution. We investigated the effects of varying spatial and temporal resolution on fMRI sensitivity measures and their implications on fMRI-based BCI simulations. We compared temporal signal-to-noise ratio (tSNR), observed percent signal change (%∆S), volumes of significant activation, Z-scores and decoding performance of linear classifiers commonly used in BCIs across a range of spatial and temporal resolution images acquired during an ankle-tapping task. Our results revealed an average increase of 22% in %∆S (p=0.006) and 9% in decoding performance (p=0.015) with temporal resolution only at the highest spatial resolution of 1.5×1.5×1.5mm³, despite a 29% decrease in tSNR (p<0.001) and plateaued Z-scores. Further, the volume of significant activation was indifferent (p>0.05) across spatial resolution specifically at the highest temporal resolution of 500ms. These results demonstrate that the overall BOLD sensitivity can be increased significantly with temporal resolution, granted an adequately high spatial resolution with minimal physiological noise level. This shows the feasibility of diffuse motor-network imaging at high spatial and temporal resolution with robust BOLD sensitivity with 7T-fMRI. Importantly, we show that this sensitivity improvement could be extended to an fMRI application such as BCIs.

Functional Magnetic Resonance Imaging for Preoperative Planning in Brain Tumour Surgery

BACKGROUND

Functional magnetic resonance imaging (fMRI) is being increasingly used for the preoperative evaluation of patients with brain tumours.

METHODS

The study is a retrospective chart review investigating the use of clinical fMRI from 2002 through 2013 in the preoperative evaluation of brain tumour patients. Baseline demographic and clinical data were collected. The specific fMRI protocols used for each patient were recorded.

RESULTS

Sixty patients were identified over the 12-year period. The tumour types most commonly investigated were high-grade glioma (World Health Organization grade III or IV), low-grade glioma (World Health Organization grade II), and meningioma. Most common presenting symptoms were seizures (69.6%), language deficits (23.2%), and headache (19.6%). There was a predominance of left hemispheric lesions investigated with fMRI (76.8% vs 23.2% for right). The most commonly involved lobes were frontal (64.3%), temporal (33.9%), parietal (21.4%), and insular (7.1%). The most common fMRI paradigms were language (83.9%), motor (75.0%), sensory (16.1%), and memory (10.7%). The majority of patients ultimately underwent a craniotomy (75.0%), whereas smaller groups underwent stereotactic biopsy (8.9%) and nonsurgical management (16.1%). Time from request for fMRI to actual fMRI acquisition was 3.1±2.3 weeks. Time from fMRI acquisition to intervention was 4.9±5.5 weeks.

CONCLUSIONS

We have characterized patient demographics in a retrospective single-surgeon cohort undergoing preoperative clinical fMRI at a Canadian centre. Our experience suggests an acceptable wait time from scan request to scan completion/analysis and from scan to intervention.

The "White Gray Sign" Identifies the Central Sulcus on 3T High-Resolution T1-Weighted Images

BACKGROUND AND PURPOSE

The central sulcus is an important anatomic landmark, but most methods of identifying it rely on variable gyral and sulcal patterns. We describe and assess the accuracy of reduced gray-white contrast along the central sulcus, an observation we term the "white gray sign."

MATERIALS AND METHODS

We conducted a retrospective review of 51 fMRIs with a T1-weighted 3D inversion recovery fast-spoiled gradient-echo and concomitant hand-motor fMRI, which served as confirmation for the location of the central sulcus. To measure gray-white contrast across the central and adjacent sulci, we performed a quantitative analysis of 25 normal hemispheres along the anterior and posterior cortices and intervening white matter of the pre- and postcentral gyri. 3D inversion recovery fast-spoiled gradient-echo axial images from 51 fMRIs were then evaluated by 2 raters for the presence of the white gray sign as well as additional established signs of the central sulcus: the bracket, cortical thickness, omega, and T signs.

RESULTS

The mean gray-white contrast along the central sulcus was 0.218 anteriorly and 0.237 posteriorly, compared with 0.320 and 0.295 along the posterior precentral and anterior postcentral sulci, respectively (P < .001). Both raters correctly identified the central sulcus in all 35 normal and 16 abnormal hemispheres. The white gray sign had the highest agreement of all signs between raters and was rated as present the most often among all the signs.

CONCLUSIONS

Reduced gray-white contrast around the central sulcus is a reliable sign for identification of the central sulcus on 3D inversion recovery fast-spoiled gradient-echo images.

Functional MRI vs. navigated TMS to optimize M1 seed volume delineation for DTI tractography. A prospective study in patients with brain tumours adjacent to the corticospinal tract

BACKGROUND

DTI-based tractography is an increasingly important tool for planning brain surgery in patients suffering from brain tumours. However, there is an ongoing debate which tracking approaches yield the most valid results. Especially the use of functional localizer data such as navigated transcranial magnetic stimulation (nTMS) or functional magnetic resonance imaging (fMRI) seem to improve fibre tracking data in conditions where anatomical landmarks are less informative due to tumour-induced distortions of the gyral anatomy. We here compared which of the two localizer techniques yields more plausible results with respect to mapping different functional portions of the corticospinal tract (CST) in brain tumour patients.

METHODS

The CSTs of 18 patients with intracranial tumours in the vicinity of the primary motor area (M1) were investigated by means of deterministic DTI. The core zone of the tumour-adjacent hand, foot and/or tongue M1 representation served as cortical regions of interest (ROIs). M1 core zones were defined by both the nTMS hot-spots and the fMRI local activation maxima. In addition, for all patients, a subcortical ROI at the level of the inferior anterior pons was implemented into the tracking algorithm in order to improve the anatomical specificity of CST reconstructions. As intra-individual control, we additionally tracked the CST of the hand motor region of the unaffected, i.e., non-lesional hemisphere, again comparing fMRI and nTMS M1 seeds. The plausibility of the fMRI-ROI- vs. nTMS-ROI-based fibre trajectories was assessed by a-priori defined anatomical criteria. Moreover, the anatomical relationship of different fibre courses was compared regarding their distribution in the anterior-posterior direction as well as their location within the posterior limb of the internal capsule (PLIC).

RESULTS

Overall, higher plausibility rates were observed for the use of nTMS- as compared to fMRI-defined cortical ROIs (p < 0.05) in tumour vicinity. On the non-lesional hemisphere, however, equally good plausibility rates (100%) were observed for both localizer techniques. fMRI-originated fibres generally followed a more posterior course relative to the nTMS-based tracts (p < 0.01) in both the lesional and non-lesional hemisphere.

CONCLUSION

NTMS achieved better tracking results than fMRI in conditions when the cortical tract origin (M1) was located in close vicinity to a brain tumour, probably influencing neurovascular coupling. Hence, especially in situations with altered BOLD signal physiology, nTMS seems to be the method of choice in order to identify seed regions for CST mapping in patients.

Sources of Variation Influencing Concordance between Functional MRI and Direct Cortical Stimulation in Brain Tumor Surgery

Object: Preoperative functional magnetic resonance imaging (fMRI) remains a promising method to aid in the surgical management of patients diagnosed with brain tumors. For patients that are candidates for awake craniotomies, surgical decisions can potentially be improved by fMRI but this depends on the level of concordance between preoperative brain maps and the maps provided by the gold standard intraoperative method, direct cortical stimulation (DCS). There have been numerous studies of the concordance between fMRI and DCS using sensitivity and specificity measures, however the results are variable across studies and the key factors influencing variability are not well understood. Thus, the present work addresses the influence of technical factors on fMRI and DCS concordance. Methods: Motor and language mapping data were collected for a group of glioma patients (n = 14) who underwent both preoperative fMRI and intraoperative DCS in an awake craniotomy procedure for tumor removal. Normative fMRI data were also acquired in a healthy control group (n = 12). The fMRI and DCS mapping data were co-registered; true positive (TP), true negative (TN), false positive (FP), and false negative (FN) occurrences were tabulated over the exposed brain surface. Sensitivity and specificity were measured for the total group, and for the motor and language sub-groups. The influence of grid placement, fMRI statistical thresholding, and task standardization were assessed. Correlations between proportions of agreement and error were also carefully scrutinized to evaluate concordance in more detail. Results: Concordance was significantly better for motor vs. language mapping. There was an inverse relationship between TP and TN with increasing statistical threshold, and FP dominated the total error. Sensitivity and specificity were reduced when tasks were not standardized across fMRI and DCS. Conclusions: Although the agreement between fMRI and DCS is good, variability is introduced by technical factors that can diminish the quality of patient data. Neurosurgeons should evaluate the usefulness of fMRI data while considering that (a) discordance arises primarily from FP fMRI results; (b) there is an inherent trade-off between sensitivity and specificity with fMRI statistical threshold; and

Presurgical motor, somatosensory and language fMRI: Technical feasibility and limitations in 491 patients over 13 years

OBJECTIVES

To analyse the long-term feasibility and limitations of presurgical fMRI in a cohort of tumour and epilepsy patients with different MR-scanners at 1.5 and 3.0 T.

METHODS

Four hundred and ninety-one consecutive patients undergoing presurgical fMRI between 2000 and 2012 on five different MR-scanners using established paradigms and semi-automated data processing were included. Success rates of task performance and BOLD-activation were determined for motor and somatosensory somatotopic mapping and language localisation. Procedural success, failures and imaging artifacts were analysed. MR-field strengths were compared.

RESULTS

Two thousand three hundred fifteen of 2348 (98.6 %) attempted paradigms (1033 motor, 1220 speech, 95 somatosensory) were successfully performed. 100 paradigms (4.3 %) were repetition runs. 23 speech, 6 motor and 2 sensory paradigms failed for non-compliance and technical issues. Most language paradigm failures were noted in overt sentence generation. Average significant BOLD-activation was higher for motor than language paradigms (95.8 vs. 81.6 %). Most language paradigms showed significantly higher activation rates at 3 T compared to 1.5 T, whereas no significant difference was found for motor paradigms.

CONCLUSIONS

fMRI proved very robust for the presurgical localisation of the different motor and somatosensory body representations, as well as Broca's and Wernicke's language areas across different MR-scanners at 1.5 and 3.0 T over 13 years.

KEY POINTS

• Standardised presurgical motor and language fMRI is robust across various MRI platforms. • Motor fMRI is less dependent on field strength than language fMRI. • fMRI task failures are relatively low and are reduced by paradigm repetition.

Presurgical functional magnetic resonance imaging in patients with brain tumors

BACKGROUND

Clinical functional magnetic resonance imaging (fMRI) is still an upcoming diagnostic tool because it is time-consuming to perform the post-scan calculations and interpretations. A standardized and easily used method for the clinical assessment of fMRI scans could decrease the workload and make fMRI more attractive for clinical use.

PURPOSE

To evaluate a standardized clinical approach for distance measurement between benign brain tumors and eloquent cortex in terms of the ability to predict pre- and postoperative neurological deficits after intraoperative neuronavigation-assisted surgery.

MATERIAL AND METHODS

A retrospective study of 34 patients. The fMRI data were reanalyzed using a standardized distance measurement procedure combining data from both fMRI and three-dimensional T1 MRI scans. The pre- and postoperative neurological status of each patient was obtained from hospital records. Data analysis was performed using logistic regression analysis to determine whether the distance measured between the tumor margin and fMRI activity could serve as a predictor for neurological deficits.

RESULTS

An odds ratio of 0.89 mm(-1) (P = 0.03) was found between the risk of preoperative neurological motor deficits and the tumor-fMRI distance. An odds ratio of 0.82 mm(-1) (P = 0.04) was found between the risk of additional postoperative neurological motor deficits and the tumor-fMRI distance. The tumor was radically removed in 10 cases; five patients experienced additional postoperative motor deficits (tumor-fMRI distance <18 mm) and five did not (tumor-fMRI distance >18 mm) (P = 0.008).

CONCLUSION

This study indicates that the distance measured between the tumor margin and fMRI activation could serve as a valuable predictor of neurological motor deficits.

Challenges in Identifying the Foot Motor Region in Patients with Brain Tumor on Routine MRI: Advantages of fMRI

BACKGROUND AND PURPOSE

Accurate localization of the foot/leg motor homunculus is essential because iatrogenic damage can render a patient wheelchair- or bed-bound. We hypothesized the following: 1) Readers would identify the foot motor homunculus <100% of the time on routine MR imaging, 2) neuroradiologists would perform better than nonradiologists, and 3) those with fMRI experience would perform better than those without it.

MATERIALS AND METHODS

Thirty-five attending-level raters (24 neuroradiologists, 11 nonradiologists) evaluated 14 brain tumors involving the frontoparietal convexity. Raters were asked to identify the location of the foot motor homunculus and determine whether the tumor involved the foot motor area and/or motor cortex by using anatomic MR imaging. Results were compared on the basis of prior fMRI experience and medical specialty by using Mann-Whitney U test statistics.

RESULTS

No rater was 100% correct. Raters correctly identified whether the tumor was in the foot motor cortex 77% of the time. Raters with fMRI experience were significantly better than raters without experience at foot motor fMRI centroid predictions (13 ± 6 mm versus 20 ± 13 mm from the foot motor cortex center, P = 2 × 10(-6)) and arrow placement in the motor gyrus (67% versus 47%, P = 7 × 10(-5)). Neuroradiologists were significantly better than nonradiologists at foot motor fMRI centroid predictions (15 ± 8 mm versus 20 ± 14 mm, P = .005) and arrow placement in the motor gyrus (61% versus 46%, P = .008).

CONCLUSIONS

The inability of experienced readers to consistently identify the location of the foot motor homunculus on routine MR imaging argues for using fMRI in the preoperative setting. Experience with fMRI leads to improved accuracy in identifying anatomic structures, even on routine MR imaging.

Process of the Functional Reorganization of the Cortical Centers for Movement in GBM Patients: fMRI Study

Purpose

The aim of this study was to verify whether the functional reorganization of motor cortex is associated with the increase in the size of WHO type IV glioma lesion, that is, disease duration and development, and whether surgical treatment has an impact on cerebral plasticity.

Methods

The study included 16 patients with primary tumors of the brain located at the region of central sulcus. The clinical status of patients and tumor volume was determined. Functional magnetic resonance imaging examinations were performed before and 3 months after operation.

Results

The activity of all cortical centers, both contralateral and ipsilateral, was observed in a group of small as well as large tumors. The intensity of activation and the number of activated clusters of small tumors were almost always higher as compared with the large tumors. The frequency of the activity of contralateral areas was similar during the first and the second examination. In the case of ipsilateral centers, the frequency of activation during the second examination was lower. Mean values of t-statistics during the first examination were higher than during the second examination. Supplementary motor area (SMAa) was the only center for which the mean values of activation intensity remained similar.

Conclusions

SMAa seems to play the most important role in the processes of motor cortex plasticity in high-grade glioma patients. Surgery seems not having a significant influence on the pattern of functional reorganization of the cortical centers for movement. Identification of the individual patterns of the reorganization of motor centers plays an important role in clinical practice.

Objective Bayesian fMRI analysis-a pilot study in different clinical environments

Functional MRI (fMRI) used for neurosurgical planning delineates functionally eloquent brain areas by time-series analysis of task-induced BOLD signal changes. Commonly used frequentist statistics protect against false positive results based on a p-value threshold. In surgical planning, false negative results are equally if not more harmful, potentially masking true brain activity leading to erroneous resection of eloquent regions. Bayesian statistics provides an alternative framework, categorizing areas as activated, deactivated, non-activated or with low statistical confidence. This approach has not yet found wide clinical application partly due to the lack of a method to objectively define an effect size threshold. We implemented a Bayesian analysis framework for neurosurgical planning fMRI. It entails an automated effect-size threshold selection method for posterior probability maps accounting for inter-individual BOLD response differences, which was calibrated based on the frequentist results maps thresholded by two clinical experts. We compared Bayesian and frequentist analysis of passive-motor fMRI data from 10 healthy volunteers measured on a pre-operative 3T and an intra-operative 1.5T MRI scanner. As a clinical case study, we tested passive motor task activation in a brain tumor patient at 3T under clinical conditions. With our novel effect size threshold method, the Bayesian analysis revealed regions of all four categories in the 3T data. Activated region foci and extent were consistent with the frequentist analysis results. In the lower signal-to-noise ratio 1.5T intra-operative scanner data, Bayesian analysis provided improved brain-activation detection sensitivity compared with the frequentist analysis, albeit the spatial extents of the activations were smaller than at 3T. Bayesian analysis of fMRI data using operator-independent effect size threshold selection may improve the sensitivity and certainty of information available to guide neurosurgery.

Improved nTMS- and DTI-derived CST tractography through anatomical ROI seeding on anterior pontine level compared to internal capsule

Imaging of the course of the corticospinal tract (CST) by diffusion tensor imaging (DTI) is useful for function-preserving tumour surgery. The integration of functional localizer data into tracking algorithms offers to establish a direct structure–function relationship in DTI data. However, alterations of MRI signals in and adjacent to brain tumours often lead to spurious tracking results. We here compared the impact of subcortical seed regions placed at different positions and the influences of the somatotopic location of the cortical seed and clinical co-factors on fibre tracking plausibility in brain tumour patients.

The CST of 32 patients with intracranial tumours was investigated by means of deterministic DTI and neuronavigated transcranial magnetic stimulation (nTMS). The cortical seeds were defined by the nTMS hot spots of the primary motor area (M1) of the hand, the foot and the tongue representation. The CST originating from the contralesional M1 hand area was mapped as intra-individual reference. As subcortical region of interests (ROI), we used the posterior limb of the internal capsule (PLIC) and/or the anterior inferior pontine region (aiP). The plausibility of the fibre trajectories was assessed by a-priori defined anatomical criteria. The following potential co-factors were analysed: Karnofsky Performance Scale (KPS), resting motor threshold (RMT), T1-CE tumour volume, T2 oedema volume, presence of oedema within the PLIC, the fractional anisotropy threshold (FAT) to elicit a minimum amount of fibres and the minimal fibre length.

The results showed a higher proportion of plausible fibre tracts for the aiP-ROI compared to the PLIC-ROI. Low FAT values and the presence of peritumoural oedema within the PLIC led to less plausible fibre tracking results. Most plausible results were obtained when the FAT ranged above a cut-off of 0.105. In addition, there was a strong effect of somatotopic location of the seed ROI; best plausibility was obtained for the contralateral hand CST (100%), followed by the ipsilesional hand CST (>95%), the ipsilesional foot (>85%) and tongue (>75%) CST. In summary, we found that the aiP-ROI yielded better tracking results compared to the IC-ROI when using deterministic CST tractography in brain tumour patients, especially when the M1 hand area was tracked. In case of FAT values lower than 0.10, the result of the respective CST tractography should be interpreted with caution with respect to spurious tracking results. Moreover, the presence of oedema within the internal capsule should be considered a negative predictor for plausible CST tracking.

•

Somatotopic CST tractography was done in 32 patients with eloquent brain tumours.

•

Seeding ROIs were defined by navigated TMS of the M1 hot spot (hand, foot, tongue).

•

Using the anterior pons as a second ROI yielded more plausible tracts than the PLIC.

•

Low FAT and oedema of the internal capsule were negative predictors.

Localizing hand motor area using resting-state fMRI: validated with direct cortical stimulation

BACKGROUND

Resting-state functional magnetic resonance imaging (R-fMRI) is a promising tool in clinical application, especially in presurgical mapping for neurosurgery. This study aimed to investigate the sensitivity and specificity of R-fMRI in the localization of hand motor area in patients with brain tumors validated by direct cortical stimulation (DCS). We also compared this technique to task-based blood oxygenation level-dependent (BOLD) fMRI (T-fMRI).

METHODS

R-fMRI and T-fMRI were acquired from 17 patients with brain tumors. The cortex sites of the hand motor area were recorded by DCS. Site-by-site comparisons between R-fMRI/T-fMRI and DCS were performed to calculate R-fMRI and T-fMRI sensitivity and specificity using DCS as a "gold standard". R-fMRI and T-fMRI performances were compared statistically

RESULTS

A total of 609 cortex sites were tested with DCS and compared with R-fMRI findings in 17 patients. For hand motor area localization, R-fMRI sensitivity and specificity were 90.91 and 89.41 %, respectively. Given that two subjects could not comply with T-fMRI, 520 DCS sites were compared with T-fMRI findings in 15 patients. The sensitivity and specificity of T-fMRI were 78.57 and 84.76 %, respectively. In the 15 patients who successfully underwent both R-fMRI and T-fMRI, there was no statistical difference in sensitivity or specificity between the two methods (p = 0.3198 and p = 0.1431, respectively)

CONCLUSIONS

R-fMRI sensitivity and specificity are high for localizing hand motor area and even equivalent or slightly higher compared with T-fMRI. Given its convenience for patients, R-fMRI is a promising substitute for T-fMRI for presurgical mapping.

Correlation between anatomic landmarks and fMRI in detection of the sensorimotor cortex in patients with structural lesions

BACKGROUND

Structural lesions in/near the sensorimotor cortex may cause distortion/obscuration of the anatomic landmarks.

PURPOSE

To compare the localization of the sensorimotor cortex using anatomical landmarks and fMRI in the clinical setting in patients with structural lesions in/near the central sulcus.

MATERIAL AND METHODS

We analyzed the anatomic and fMRI data of 68 consecutive patients (42 tumors, 15 gliotic lesions, 11 focal cortical dysplasias [FCD]) who underwent MRI to assess the relationship of these lesions to the sensorimotor cortex. Anatomical data was analyzed on conventional two- and three-dimensional sequences. BOLD fMRI was performed with block design hand/leg or lip movement paradigm and general linear model was used for detecting the activated cortex. fMRI was considered as a valid method for identifying the sensorimotor cortex based on previously reported literature.

RESULTS

The sensorimotor cortex could not be identified with anatomical landmarks in 9/68 (13.2%) patients. fMRI detected activation in areas different from that predicted by anatomical landmarks in 11/68 (16.2%) cases. This occurred in 5/42 (11.9%) tumors, 6/15 (40%) gliotic lesions, and 0/11 (0%) FCDs. The kappa value for concordance between fMRI and anatomic landmarks was 0.883 overall, 1.0 for tumors, 0.721 for gliotic lesions, and in none of the patients with focal cortical dysplasias.

CONCLUSION

In patients with lesions that obscure normal cerebral landmarks, fMRI supplies the information that is not available from the anatomic images. In patients with landmarks that can be recognized, the location of the rolandic cortex may be misjudged in some cases if functional imaging is not used. Anatomic landmarks may not correlate with the area of functional activation in gliotic lesions and tumors. Determining the risk of a postoperative neurologic defect from surgery is likely to be more reliable with functional imaging than with conventional anatomic imaging.

Cerebrovascular reactivity mapping in patients with low grade gliomas undergoing presurgical sensorimotor mapping with BOLD fMRI

PURPOSE

(i) to validate blood oxygenation level dependent (BOLD) breathhold cerebrovascular reactivity (BH CVR) mapping as an effective technique for potential detection of neurovascular uncoupling (NVU) in a cohort of patients with perirolandic low grade gliomas undergoing presurgical functional MRI (fMRI) for sensorimotor mapping, and (ii) to determine whether NVU potential, as assessed by BH CVR mapping, is prevalent in this tumor group.

MATERIALS AND METHODS

We retrospectively evaluated 12 patients, with histological diagnosis of grade II glioma, who performed multiple motor tasks and a BH task. Sensorimotor activation maps and BH CVR maps were compared in two automatically defined regions of interest (ROIs), ipsilateral to the lesion (i.e., ipsilesional) and contralateral to the lesion (i.e., contralesional).

RESULTS

Motor task mean T-value was significantly higher in the contralesional ROIs (6.00 ± 1.74 versus 4.34 ± 1.68; P = 0.00004) as well as the BH mean T-value (4.74 ± 2.30 versus 4.09 ± 2.50; P = 0.009). The number of active voxels was significantly higher in the contralesional ROIs (Z = 2.99; P = 0.03). Actual NVU prevalence was 75%.

CONCLUSION

Presurgical sensorimotor fMRI mapping can be affected by NVU-related false negative activation in low grade gliomas (76% of analyzed tasks).

Quantification of primary motor pathways using diffusion MRI tractography and its application to predict postoperative motor deficits in children with focal epilepsy

As a new tool to quantify primary motor pathways and predict postoperative motor deficits in children with focal epilepsy, the present study utilized a maximum a posteriori probability (MAP) classification of diffusion weighted imaging (DWI) tractography combined with Kalman filter. DWI was performed in 31 children with intractable focal epilepsy who underwent epilepsy surgery. Three primary motor pathways associated with "finger," "leg," and "face" were classified using DWI-MAP classifier and compared with the results of invasive electrical stimulation mapping (ESM) via receiver operating characteristic (ROC) curve analysis. The Kalman filter analysis was performed to generate a model to determine the probability of postoperative motor deficits as a function of the proximity between the resection margin and the finger motor pathway. The ROC curve analysis showed that the DWI-MAP achieves high accuracy up to 89% (finger), 88% (leg), 89% (face), in detecting the three motor areas within 20 mm, compared with ESM. Moreover, postoperative reduction of the fiber count of finger pathway was associated with postoperative motor deficits involving the hand. The prediction model revealed an accuracy of 92% in avoiding postoperative deficits if the distance between the resection margin and the finger motor pathway seen on preoperative DWI tractography was 19.5 mm. This study provides evidence that the DWI-MAP combined with Kalman filter can effectively identify the locations of cortical motor areas even in patients whose motor areas are difficult to identify using ESM, and also can serve as a reliable predictor for motor deficits following epilepsy surgery.

Stereotactic iodine-125 brachytherapy for the treatment of WHO grades II and III gliomas located in the central sulcus region

BACKGROUND

Resection of gliomas located in eloquent brain areas remains a neurosurgical challenge. The reported incidence of transient or permanent neurological deficits after microsurgery in eloquent brain ranges 20%-100%, or 0%-47% among contemporary neurosurgical series. The aim of this study was to assess the feasibility of stereotactic brachytherapy (SBT) as a local treatment alternative to microsurgical resection for patients with gliomas in highly eloquent areas, located in the central sulcus region (CSR).

METHOD

Between 1997 and 2010, 60 patients with World Health Organization (WHO) grades II and III gliomas located in the CSR were treated with SBT (iodine-125 seeds; cumulative therapeutic dose, 50-65 Gy). Following SBT, WHO grade III glioma patients additionally received percutaneous radiotherapy (median boost dose, 25.2 Gy). We evaluated procedure-related complications, clinical outcome, and progression-free survival.

RESULTS

Procedure-related mortality was zero. Within 30 days of SBT, 3 patients (5%) had transient neurological deficits, and 8 patients (13%) had temporarily increased seizure activity. One patient (1.6%) deteriorated permanently. Space-occupying cysts (6 patients) and radiation necrosis (1 patient) developed after a median of 38 months and required surgical intervention. Seizure activity, rated 12 months following SBT, decreased in 82% of patients (Engel classes I-III). Median progression-free survivals were 62.2 ± 19.7 months (grade II gliomas) and 26.1 ± 17.9 months (grade III gliomas).

CONCLUSIONS

Compared with microsurgical resection, SBT harbors a low risk of procedural complications, is minimally invasive, and seems to be an effective local treatment option for patients with inoperable, eloquent WHO grade II and III gliomas in the CSR. However, the value of SBT for treating gliomas still needs to be determined in prospective, randomized studies.