Neurosurgical Planning Research Articles

Role of virtual modules to supplement neurosurgery education during COVID-19

The advent of the COVID-19 pandemic has disrupted all aspects of neurosurgery education, and it is now challenging to conduct routine sessions. Maintenance of essential standard education among novice neurosurgeons during the pandemic is of paramount importance. The aim of this study was the development of virtual modules and validation of its role to supplement the neurosurgery education program. We developed the virtual modules relevant to neuro-anatomy, neurosurgical procedures, instrumentation, and neurosurgical planning. These modules were virtually demonstrated to twenty-seven resident neurosurgeons through CiscoWebexonline platform. They provided their rating on the aptness of virtual modules for different neurosurgery applications on various parameters using 10 points Likert scale. The parameters included quality, learning, confidence building capacity, usefulness, and overall satisfaction. The results obtained for each module were analysed and the average score was used for the comparison. The highest rating on quality was obtained by the neurosurgical instrumentation module. The highest rating for learning and confidence building capacity was given to neurosurgical procedure animation. The usefulness and overall satisfaction were highly rated for neurosurgical planning module. The results show that developed virtual modules provide an effective method to supplement the neurosurgery education program in the current scenario involving physical distancing and shift rearrangements. These virtual modules help in limiting the visits to operation room, anatomy and surgical training labs, and allow residents to learn online at their pace.

Clinical Utility of Transcranial Magnetic Stimulation (TMS) in the Presurgical Evaluation of Motor, Speech, and Language Functions in Young Children With Refractory Epilepsy or Brain Tumor: Preliminary Evidence.

Accurate presurgical mapping of motor, speech, and language cortices, while crucial for neurosurgical planning and minimizing post-operative functional deficits, is challenging in young children with neurological disease. In such children, both invasive (cortical stimulation mapping) and non-invasive functional mapping imaging methods (MEG, fMRI) have limited success, often leading to delayed surgery or adverse post-surgical outcomes. We therefore examined the clinical utility of transcranial magnetic stimulation (TMS) in young children who require functional mapping. In a retrospective chart review of TMS studies performed on children with refractory epilepsy or a brain tumor, at our institution, we identified 47 mapping sessions in 36 children 3 years of age or younger, in whom upper and lower extremity motor mapping was attempted; and 13 children 5–6 years old in whom language mapping, using a naming paradigm, was attempted. The primary hand motor cortex was identified in at least one hemisphere in 33 of 36 patients, and in both hemispheres in 27 children. In 17 children, primary leg motor cortex was also successfully identified. The language cortices in temporal regions were successfully mapped in 11 of 13 patients, and in six of them language cortices in frontal regions were also mapped, with most children (n = 5) showing right hemisphere dominance for expressive language. Ten children had a seizure that was consistent with their clinical semiology during or immediately following TMS, none of which required intervention or impeded completion of mapping. Using TMS, both normal motor, speech, and language developmental patterns and apparent disease induced reorganization were demonstrated in this young cohort. The successful localization of motor, speech, and language cortices in young children improved the understanding of the risk-benefit ratio prior to surgery and facilitated surgical planning aimed at preserving motor, speech, and language functions. Post-operatively, motor function was preserved or improved in nine out of 11 children who underwent surgery, as was language function in all seven children who had surgery for lesions near eloquent cortices. We provide feasibility data that TMS is a safe, reliable, and effective tool to map eloquent cortices in young children.

875 Use of Oriented Priors Through Magnetic Tractography (MAGNET) In Deliniation Of Meyer's Loop and Correlation with Visual Field Deficit In Temporal Lobe Epilepsy (TLE) Surgery: A Pilot Study

Abstract Introduction Pre-operative white matter tract reconstruction of the Meyer’s loop (ML) of the optic radiation using diffusion MRI (tractography) can be used to prevent post-operative visual-field deficit. Due to its complex anatomy, precise reconstruction of the ML is challenging and often underestimated. Previous work has suggested that an innovative tractography technique using oriented priors called MAGNET better approximates reconstruction to reported histological prosections. This proof-of-context study validates the MAGNET methodology in predicting visual-field deficits in patients undergoing TLE surgery. Method Diffusion MRI datasets were used to reconstruct pre-operative ML using MAGNET in five patients. These were overlaid on post-operative T2-MRI series demonstrating the surgically resected area to measure overlap between resection and reconstructed ML. A correlation with post-operative visual-field defects was established. Results There was no evidence of visual field deficit in the cases where there was no overlap between the reconstructed ML and the resected region. In the cases with overlap with reconstructed ML and resection, there was visual deficit found. There was no correlation between proportion of resected ML and visual deficit. Conclusions This pilot demonstrates that MAGNET accurately reconstructs ML in pre-surgical TLE cases compared to standard tractography techniques and can be used to augment neurosurgical planning and resection.

Functional Magnetic Resonance Imaging and Applications in Dermatology

As a noninvasive imaging modality able to show the dynamic changes in neurologic activity, functional magnetic resonance imaging has revolutionized the ability to both map and further understand the functional regions of the brain. Current applications range from neurosurgical planning to an enormous variety of investigational applications across many diverse specialties. The main purpose of this article is to provide a foundational understanding of how functional magnetic resonance imaging is being used in research by outlining the underlying basic science, specific methods, and direct investigational and clinical applications. In addition, the use of functional magnetic resonance imaging in current dermatological research, especially in relation to studies concerning the skin‒brain axis, is explicitly addressed. This article also touches on the advantages and limitations concerning functional magnetic resonance imaging in comparison with other similar techniques.

Patient-specific prediction of SEEG electrode bending for stereotactic neurosurgical planning

Purpose Electrode bending observed after stereotactic interventions is typically not accounted for in either computer-assisted planning algorithms, where straight trajectories are assumed, or in quality assessment, where only metrics related to entry and target points are reported. Our aim is to provide a fully automated and validated pipeline for the prediction of stereo-electroencephalography (SEEG) electrode bending.Methods We transform electrodes of 86 cases into a common space and compare features-based and image-based neural networks on their ability to regress local displacement (mathbf{lu} ) or electrode bending (hat{mathbf{eb }}). Electrodes were stratified into six groups based on brain structures at the entry and target point. Models, both with and without Monte Carlo (MC) dropout, were trained and validated using tenfold cross-validation.Results mage-based models outperformed features-based models for all groups, and models that predicted mathbf{lu} performed better than for hat{mathbf{eb }}. Image-based model prediction with MC dropout resulted in lower mean squared error (MSE) with improvements up to 12.9% (mathbf{lu} ) and 39.9% (hat{mathbf{eb }}), compared to no dropout. Using an image of brain tissue types (cortex, white and deep grey matter) resulted in similar, and sometimes better performance, compared to using a T1-weighted MRI when predicting mathbf{lu} . When inferring trajectories of image-based models (brain tissue types), 86.9% of trajectories had an MSEle 1 mm.Conclusion An image-based approach regressing local displacement with an image of brain tissue types resulted in more accurate electrode bending predictions compared to other approaches, inputs, and outputs. Future work will investigate the integration of electrode bending into planning and quality assessment algorithms.

Utility of Preoperative Blood-Oxygen-Level-Dependent Functional MR Imaging in Patients with a Central Nervous System Neoplasm.

Functional neuroimaging provides means to understand the relationship between brain structure and associated functions. Functional MR (fMR) imaging can offer a unique insight into preoperative planning for central nervous system (CNS) neoplasms by identifying areas of the brain effected or spared by the neoplasm. BOLD (blood-oxygen-level-dependent) fMR imaging can be reliably used to map eloquent cortex presurgically and is sufficiently accurate for neurosurgical planning. In patients with brain tumors undergoing neurosurgical intervention, fMR imaging can decrease postoperative morbidity. This article discusses the applications, significance, and interpretation of BOLD fMR imaging, and its applications in presurgical planning for CNS neoplasms.

Multimodal Risk-Based Path Planning for Neurosurgical Interventions

AbstractImage-guided neurosurgical interventions are challenging due to the complex anatomy of the brain and the inherent risk of damaging vital structures. This paper presents a neurosurgical planning tool for safe and effective neurosurgical interventions, minimizing the risk through optimized access planning. The strengths of the proposed system are the integration of multiple risk structures combined into a holistic model for fast and intuitive user interaction, and a modular architecture. The tool is intended to support neurosurgeons to quickly determine the most appropriate surgical entry point and trajectory through the brain with minimized risk. The user interface guides a user through the decision-making process and may save planning time of neurosurgical interventions. The navigation tool has been interfaced to the Robot Operating System, which allows the integration into automated workflows and the planning of linear and nonlinear trajectories. Determined risk structures and trajectories can be visualized intuitively as a projection map on the skin or cortical surface. Two risk calculation modes (strict and joint) are offered to the neurosurgeons, depending on the intracranial procedure's type and complexity. A qualitative evaluation with clinical experts shows the practical relevance, while a quantitative performance and functionality analysis proves the robustness and effectiveness of the system.

Role of Diffusion Tensor Imaging and Motor Functional MRI in Preoperative Assessment of Brain Tumors

Diffusion tensor imaging is a non-invasive magnetic resonance imaging technique that describe the orientation and location of white matter tracts in vivo, it guides the surgeon regarding the relationship of the intra-axial tumor to adjacent white matter tracts in different planes. Routine pre-surgical FMRI allows for assessment of the relationship between brain tumor and motor cortex to facilitate function-preserving surgery and reduce postoperative morbidity. The purpose of this study is to evaluate role of diffusion tensor magnetic resonance imaging, fiber tractography and motor functional MRI in assessment of white matter tracts affected by the tumor, and to utilize this information in guiding surgeons. Fifty patients with different types of brain tumors were enrolled in this study. Fiber tracts involvement were classified into four categories (edema, displacement, infiltration and disruption), comparison between benign and malignant tumors groups as regards to the patterns of fiber tracts involvement were done. The prevalence of edema and displacement was higher among the benign group while prevalence of infiltration and disruption was higher among the malignant group. Localization of the primary motor hand area with functional MRI was done, The relation of it to the tumor was measured. Treatment plans before and after DTI & functional MR imaging differed in 35 patients as regard to surgical approach and in 17 patients as regard to modification of extent of resection with significant relation. Diffusion tensor imaging DTI represents recent important progress in the field of diagnostic imaging. It is the only technique that is able to visualize in vivo white-matter tracts so that it is of great help in pre-operative neurosurgical planning.

Revisiting almost forgotten two ends of the central sulcus of cerebral hemisphere in brains of cadavers

: The central sulcus also known as Rolandic Fissure separates the sensory cortex in front from motor cortex behind. The central sulcus starts in or near the superomedial border of the cerebral hemisphere, and ends usually a little above the posterior ramus of the lateral sulcus. The central sulcus is the only sulcus that divides the brain at its superior surface. The objective of the present study was to analyse the various types of the central sulcus of cerebral hemisphere with respect to its two ends in the cadavers. A total of 44 cadaveric brains (88 cerebral hemispheres) were studied. The variations at upper end of the central sulcus with respect to the superomedial border of the hemisphere and at its lower end with respect to the posterior ramus of the Sylvian fissure were noted. At the upper end, we found three types of central sulcus – type 1= 68% (those cutting the border and extending on the medial surface), type 2= 23% (those just reaching the border but not reaching the medial surface) and type 3 =9% (those falling short of the border). At the lower end of the fissure, we observed two types of the central sulcus – type 2=83% (those falling short of the posterior ramus of the Sylvian fissure) and type 1=17% (those reaching the posterior ramus of the Sylvian fissure). The variability in the morphology of the cortical gyri and sulci including size, shape and spatial pattern has been previously reported. Such variability raises methodological issues for functional brain mapping1 as well as for lesion localization in neurosurgical planning. This finding will be useful to anatomists, neurosurgeons, radiologists etc. Compared to Chinese population, the percentage of type 2 of the upper end was almost half in our study which represents central India population. Further clinical research is required by radiological examination of the two ends of the central sulcus to determine any association with functional anatomy as well as any correlation with various diseases of the brain.

A Practical Approach to Imaging of the Supplementary Motor Area and Its Subcortical Connections.

First, an anatomical and functional review of these cortical areas and subcortical connections with T-fMRI and tractography techniques; second, to demonstrate the value of this approach in neurosurgical planning in a series of patients with tumors close to the SMA. Implications in language and cognitive networks with a clear hemispheric lateralization of these SMA/pre-SMA. The recommendation of the use of the advanced neuroimaging studies for surgical planning and preservation of these areas. The SMA/pre-SMA and their subcortical connections are functional areas to be taken into consideration in neurosurgical planning. These areas would be involved in the control/inhibition of movement, in verbal expression and fluency and in tasks of cognitive control capacity. Its preservation is key to the patient's postsurgical cognitive and functional evolution.

Patterns and predictors of language representation and the influence of epilepsy surgery on language reorganization in children and young adults with focal lesional epilepsy.

Mapping brain functions is crucial for neurosurgical planning in patients with drug-resistant seizures. However, presurgical language mapping using either functional or structural networks can be challenging, especially in children. In fact, most of the evidence on this topic derives from cross-sectional or retrospective studies in adults submitted to anterior temporal lobectomy. In this prospective study, we used fMRI and DTI to explore patterns of language representation, their predictors and impact on cognitive performances in 29 children and young adults (mean age at surgery: 14.6 ± 4.5 years) with focal lesional epilepsy. In 20 of them, we also assessed the influence of epilepsy surgery on language lateralization. All patients were consecutively enrolled at a single epilepsy surgery center between 2009 and 2015 and assessed with preoperative structural and functional 3T brain MRI during three language tasks: Word Generation (WG), Rhyme Generation (RG) and a comprehension task. We also acquired DTI data on arcuate fasciculus in 24 patients. We first assessed patterns of language representation (relationship of activations with the epileptogenic lesion and Laterality Index (LI)) and then hypothesized a causal model to test whether selected clinical variables would influence the patterns of language representation and the ensuing impact of the latter on cognitive performances. Twenty out of 29 patients also underwent postoperative language fMRI. We analyzed possible changes of fMRI and DTI LIs and their clinical predictors. Preoperatively, we found atypical language lateralization in four patients during WG task, in one patient during RG task and in seven patients during the comprehension task. Diffuse interictal EEG abnormalities predicted a more atypical language representation on fMRI (p = 0.012), which in turn correlated with lower attention (p = 0.036) and IQ/GDQ scores (p = 0.014). Postoperative language reorganization implied shifting towards atypical language representation. Abnormal postoperative EEG (p = 0.003) and surgical failures (p = 0.015) were associated with more atypical language lateralization, in turn correlating with worsened fluency. Neither preoperative asymmetry nor postoperative DTI LI changes in the arcuate fasciculus were observed. Focal lesional epilepsy associated with diffuse EEG abnormalities may favor atypical language lateralization and worse cognitive performances, which are potentially reversible after successful surgery.

Automatic identification of atypical clinical fMRI results

PurposeFunctional 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.MethodsData 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.ResultsTMA 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.ConclusionThis 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.

A MRI-Based Toolbox for Neurosurgical Planning in Nonhuman Primates.

In this paper, we outline a method for surgical preparation that allows for the practical planning of a variety of neurosurgeries in NHPs solely using data extracted from magnetic resonance imaging (MRI). This protocol allows for the generation of 3D printed anatomically accurate physical models of the brain and skull, as well as an agarose gel model of the brain modeling some of the mechanical properties of the brain. These models can be extracted from MRI using brain extraction software for the model of the brain, and custom code for the model of the skull. The preparation protocol takes advantage of state-of-the-art 3D printing technology to make interfacing brains, skulls, and molds for gel brain models. The skull and brain models can be used to visualize brain tissue inside the skull with the addition of a craniotomy in the custom code, allowing for better preparation for surgeries directly involving the brain. The applications of these methods are designed for surgeries involved in neurological stimulation and recording as well as injection, but the versatility of the system allows for future expansion of the protocol, extraction techniques, and models to a wider scope of surgeries.

A MRI-Based Toolbox for Neurosurgical Planning in Nonhuman Primates

A MRI-Based Toolbox for Neurosurgical Planning in Nonhuman Primates

Combined Isoflurane-Remifentanil Anaesthesia Permits Resting-State fMRI in Children with Severe Epilepsy and Intellectual Disability.

Head motion is a significant barrier to functional MRI (fMRI) in patients who are unable to tolerate awake scanning, including young children or those with cognitive and behavioural impairments. General anaesthesia minimises motion and ensures patient comfort, however the optimal anaesthesia regimen for fMRI in the paediatric setting is unknown. In this study, we tested the feasibility of anaesthetised fMRI in 11 patients (mean age = 9.8 years) with Lennox-Gastaut syndrome, a severe form of childhood-onset epilepsy associated with intellectual disability. fMRI was acquired during clinically-indicated MRI sessions using a synergistic anaesthesia regimen we typically administer for epilepsy neurosurgery: combined low-dose isoflurane (≤ 0.8% end-tidal concentration) with remifentanil (≤ 0.1 mcg/kg/min). Using group-level independent component analysis, we assessed the presence of resting-state networks by spatially comparing results in the anaesthetised patients to resting-state network templates from the 'Generation R' study of 536 similarly-aged non-anaesthetised healthy children (Muetzel et al. in Hum Brain Mapp 37(12):4286-4300, 2016). Numerous resting-state networks commonly studied in non-anaesthetised healthy children were readily identifiable in the anaesthetised patients, including the default-mode, sensorimotor, and frontoparietal networks. Independent component time-courses associated with these networks showed spectral characteristics suggestive of a neuronal origin of fMRI signal fluctuations, including high dynamic range and temporal frequency power predominantly below 0.1 Hz. These results demonstrate the technical feasibility of anaesthetised fMRI in children, suggesting that combined isoflurane-remifentanil anaesthesia may be an effective strategy to extend the emerging clinical applications of resting-state fMRI (for example, neurosurgical planning) to the variety of patient groups who may otherwise be impractical to scan.

Letter to the Editor: ‘Neurosurgical Planning in Patients' Management During the COVID-19 Pandemic? Our Early Experience in Bangladesh’

Letter to the Editor: ‘Neurosurgical Planning in Patients' Management During the COVID-19 Pandemic? Our Early Experience in Bangladesh’

Alterations of functional and structural connectivity in patients with brain metastases.

Metastases are the most prevalent tumors in the brain and are commonly associated with high morbidity and mortality. Previous studies have suggested that brain tumors can induce a loss of functional connectivity and alter the brain network architecture. Little is known about the effect of brain metastases on whole-brain functional and structural connectivity networks. In this study, 14 patients with brain metastases and 16 healthy controls underwent resting state functional magnetic resonance imaging (rs-fMRI) and diffusion tensor imaging (DTI). We constructed functional connectivity network using rs-fMRI signal correlations and structural connectivity network using DTI tractography. Graph theoretical analysis was employed to calculate network properties. We further evaluated the performance of brain networks after metastases resection by a simulated method. Compared to healthy controls, patients with brain metastases showed an altered “small-world” architecture in both functional and structural connectivity networks, shifting to a more randomness organization. Besides, the coupling strength of functional-structural connectivity was decreased in patients. After removing nodes infiltrated by metastases, aggravated disruptions were found in both functional and structural connectivity networks, and the alterations of network properties correlated with the removed hubs number. Our findings suggest that brain metastases interfere with the optimal network organization and relationship of functional and structural connectivity networks, and tumor resection involving hubs could cause a worse performance of brain networks. This study provides neuroimaging guidance for neurosurgical planning and postoperative assessment of brain metastases from the aspect of brain networks.

Automated neurosurgical stereotactic planning for intraoperative use: a comprehensive review of the literature and perspectives.

The creation of intracranial stereotactic trajectories, from entry point to target point, is still mostly done manually by the neurosurgeon. The development of automated stereotactic planning tools has been described in the literature. This systematic review aims to assess the effectiveness of stereotactic planning procedure automation and develop tools for patients undergoing neurosurgical stereotactic procedures. PubMed/MEDLINE, EMBASE, Google Scholar, CINAHL, PsycINFO, and Cochrane Register of Controlled Trials databases were searched from inception to September 1, 2019, at the exception of Google Scholar (from 1 January 2010 to September 1, 2019) in French and English. Eligible studies included all studies proposing automated stereotactic planning. A total of 1543 studies were screened. Forty-two studies were included in the systematic review, including 18 (42.9%) conference papers. The surgical procedures planned automatically were mainly deep brain stimulation (n = 14, 33.3%), stereoelectroencephalography (n = 12, 28.6%), and not specified (n = 10, 23.8%). The most frequently used surgical constraints to plan the trajectory were blood vessels (n = 32, 76.2%), cerebral sulci (n = 27, 64.3%), and cerebral ventricles (n = 23, 54.8%). The distance from blood vessels ranged from 1.96 to 4.78 mm for manual trajectories and from 2.47 to 7.0 mm for automated trajectories. At least one neurosurgeon was involved in 36 studies (85.7%). The automated stereotactic trajectory was preferred in 75.4% of the studied cases (range 30-92.9). Only 3 (7.1%) studies were multicentric. No study reported prospective use of the planning software. Stereotactic planning automation is a promising tool to provide valuable stereotactic trajectories for clinical applications.

UK neurosurgical workforce planning. What changes have occurred in the consultant body 2014–2018?

Introduction: The British Neurosurgery Trainee Association aimed to investigate the amount of trainees qualifying through the British national training scheme and the rate at which potential consultant posts became available from 2014 to 2018.Methodology: A survey was sent to representatives from each neurosurgical unit and deanery across the United Kingdom to ask about the changes in consultant numbers and those who had attained CCT (Completion of Certificate of Training) over 5 years.Results: At the end of 2018, there were 416.5 full-time equivalent consultants in neurosurgical posts, 388.5 in substantive posts; a median of 11 per unit. The rate of vacating substantive posts was 3.04% per year, with 60% doing so due to retirement. There were 119 substantive appointments, 74 of which were expansion posts (an expansion rate of 4.31% per year). 66% of the appointments went to those with a British CCT. 107 trainees achieved CCT over the 5 years. Five separate scenarios are presented to show the potential variation in the future. If current trends continue there will be 666 consultants by 2031 and 102 too few UK-trained trainees to fill consultant posts. If expansion slows to 467 consultants by 2031, there will potentially be 211 post-CCT trainees more than available consultant posts.Conclusion: There is a wide range of outcomes for workforce planning, greatly impacted upon by retirement rates and consultant body expansion; therefore, a workforce planning committee has been created to monitor and respond to the ongoing situation, with representation from the SBNS, BNTA and SAC.

Mapping tracts in the human subthalamic area by 11.7T ex vivo diffusion tensor imaging.

The cortico-basal ganglia-thalamo-cortical feedback loops that consist of distinct white matter pathways are important for understanding in vivo imaging studies of functional and anatomical connectivity, and for localizing subthalamic white matter structures in surgical approaches for movement disorders, such as Parkinson's disease. Connectomic analysis in animals has identified fiber connections between the basal ganglia and thalamus, which pass through the fields of Forel, where other fiber pathways related to motor, sensory, and cognitive functions co-exist. We now report these pathways in the human brain on ex vivo mesoscopic (250μm) diffusion tensor imaging and on tractography. The locations of the tracts were identified relative to the adjacent gray matter structures, such as the internal and external segments of the globus pallidus; the zona incerta; the subthalamic nucleus; the substantia nigra pars reticulata and compacta; and the thalamus. The connectome atlas of the human subthalamic region may serve as a resource for imaging studies and for neurosurgical planning.