Neurosurgical Planning Research Articles

A new strategic neurosurgical planning tool for brainstem cavernous malformations using interactive computer graphics with multimodal fusion images

In this study, the authors used preoperative simulation employing 3D computer graphics (interactive computer graphics) to fuse all imaging data for brainstem cavernous malformations. The authors evaluated whether interactive computer graphics or 2D imaging correlated better with the actual operative field, particularly in identifying a developmental venous anomaly (DVA). The study population consisted of 10 patients scheduled for surgical treatment of brainstem cavernous malformations. Data from preoperative imaging (MRI, CT, and 3D rotational angiography) were automatically fused using a normalized mutual information method, and then reconstructed by a hybrid method combining surface rendering and volume rendering methods. With surface rendering, multimodality and multithreshold techniques for 1 tissue were applied. The completed interactive computer graphics were used for simulation of surgical approaches and assumed surgical fields. Preoperative diagnostic rates for a DVA associated with brainstem cavernous malformation were compared between conventional 2D imaging and interactive computer graphics employing receiver operating characteristic (ROC) analysis. The time required for reconstruction of 3D images was 3-6 hours for interactive computer graphics. Observation in interactive mode required approximately 15 minutes. Detailed anatomical information for operative procedures, from the craniotomy to microsurgical operations, could be visualized and simulated three-dimensionally as 1 computer graphic using interactive computer graphics. Virtual surgical views were consistent with actual operative views. This technique was very useful for examining various surgical approaches. Mean (±SEM) area under the ROC curve for rate of DVA diagnosis was significantly better for interactive computer graphics (1.000±0.000) than for 2D imaging (0.766±0.091; p<0.001, Mann-Whitney U-test). The authors report a new method for automatic registration of preoperative imaging data from CT, MRI, and 3D rotational angiography for reconstruction into 1 computer graphic. The diagnostic rate of DVA associated with brainstem cavernous malformation was significantly better using interactive computer graphics than with 2D images. Interactive computer graphics was also useful in helping to plan the surgical access corridor.

Variations of the superior sagittal sinus and bridging veins in human dissections and computed tomography venography

ObjectivesThe aim of the present study was to examine the superior sagittal sinus (SSS) and bridging veins (BVs) from an anatomical, neurosurgical and radiological perspective. MethodsComputed tomography venographies (CTVs) of 30 patients and 9 cadaveric dissections of human SSS were analyzed. ResultsCTV and cadavers showed most BVs emptying into the SSS close by (±3 cm) and distal to the coronary suture (74% in CTV, 62% in cadavers). ConclusionsImportant anatomical information can be drawn from cerebral CTV for neurosurgical preoperative planning.

Functional Magnetic Resonance Imaging for Imaging Neural Activity in the Human Brain: The Annual Progress

Functional magnetic resonance imaging (fMRI) is recently developed and applied to measure the hemodynamic response related to neural activity. The fMRI can not only noninvasively record brain signals without risks of ionising radiation inherent in other scanning methods, such as CT or PET scans, but also record signal from all regions of the brain, unlike EEG/MEG which are biased towards the cortical surface. This paper introduces the fundamental principles and summarizes the research progress of the last year for imaging neural activity in the human brain. Aims of functional analysis of neural activity from fMRI include biological findings, functional connectivity, vision and hearing research, emotional research, neurosurgical planning, pain management, and many others. Besides formulations and basic processing methods, models and strategies of processing technology are introduced, including general linear model, nonlinear model, generative model, spatial pattern analysis, statistical analysis, correlation analysis, and multimodal combination. This paper provides readers the most recent representative contributions in the area.

Diffusion Tensor Imaging-Based Research on Human White Matter Anatomy

The aim of this study is to investigate the white matter by the diffusion tensor imaging and the Chinese visible human dataset and to provide the 3D anatomical data of the corticospinal tract for the neurosurgical planning by studying the probabilistic maps and the reproducibility of the corticospinal tract. Diffusion tensor images and high-resolution T1-weighted images of 15 healthy volunteers were acquired; the DTI data were processed using DtiStudio and FSL software. The FA and color FA maps were compared with the sectional images of the Chinese visible human dataset. The probability maps of the corticospinal tract were generated as a quantitative measure of reproducibility for each voxel of the stereotaxic space. The fibers displayed by the diffusion tensor imaging were well consistent with the sectional images of the Chinese visible human dataset and the existing anatomical knowledge. The three-dimensional architecture of the white matter fibers could be clearly visualized on the diffusion tensor tractography. The diffusion tensor tractography can establish the 3D probability maps of the corticospinal tract, in which the degree of intersubject reproducibility of the corticospinal tract is consistent with the previous architectonic report. DTI is a reliable method of studying the fiber connectivity in human brain, but it is difficult to identify the tiny fibers. The probability maps are useful for evaluating and identifying the corticospinal tract in the DTI, providing anatomical information for the preoperative planning and improving the accuracy of surgical risk assessments preoperatively.

Biopsy Validation of 18F-FDOPA-PET Uptake and Biodistribution in Gliomas for Neurosurgical Planning and Radiotherapy Target Delineation: Preliminary Results of a Prospective Pilot Study

Biopsy Validation of 18F-FDOPA-PET Uptake and Biodistribution in Gliomas for Neurosurgical Planning and Radiotherapy Target Delineation: Preliminary Results of a Prospective Pilot Study

Impact of Brain Tumor Location on Morbidity and Mortality: A Retrospective Functional MR Imaging Study

fMRI is increasingly used in neurosurgery to preoperatively identify areas of eloquent cortex. Our study evaluated the efficacy of clinical fMRI by analyzing the relationship between the distance from the tumor border to the area of functional activation (LAD) and patient pre- and postoperative morbidity and mortality. The study included patients with diagnosis of primary or metastatic brain tumor who underwent preoperative fMRI-based motor mapping (n=74) and/or language mapping (n=77). The impact of LAD and other variables collected from patient records was analyzed with respect to functional deficits in terms of morbidity (paresis and aphasia) and mortality. Significant relationships were found between motor and language LAD and the existence of either pre- or postoperative motor (P < .001) and language deficits (P=.009). Increasing age was associated with motor and language deficits (P=.02 and P=.04 respectively). Right-handedness was related to language deficits (P=.05). Survival analysis revealed that pre- and postoperative deficits, grade, tumor location, and LAD predicted mortality. Motor deficits increased linearly as the distance from the tumor to the primary sensorimotor cortex decreased. Language deficits increased exponentially as the distance from the tumor to the language areas decreased below 1 cm. Postoperative mortality analysis showed an interaction effect between motor or language LAD and mortality predictors (grade and tumor location, respectively). These findings indicate that tumors may affect language and motor function differently depending on tumor LAD. Overall, the data support the use of fMRI as a tool to evaluate patient prognosis and are directly applicable to neurosurgical planning.

Diffusion Tensor Imaging and Colored Fractional Anisotropy Mapping of the Ventralis Intermedius Nucleus of the Thalamus

The ventralis intermedius (VIM) nucleus of the thalamus is the primary surgical target for treatment of tremor. Most centers rely on indirect targeting based on atlas-defined coordinates rather than patient-specific anatomy, making intraoperative physiological mapping critical. Detailed identification of this target based on patient-specific anatomic features can help optimize the surgical treatment of tremor. To study colored fractional anisotropic images and diffusion tensor imaging (DTI) tractography to identify characteristic magnetic resonance appearances of the VIM nucleus. Four patients undergoing stereotactic surgery for essential tremor (ET) were retrospectively studied with analysis of magnetic resonance imaging-based colored fractional anisotropy (FA) images and fiber tractography. All were scanned with a 1.5-T magnetic resonance imaging unit, and all sequences were obtained before frame placement. Because the goal of this study was to identify the DTI characteristics of physiologically defined VIM nucleus, we selected and studied patients who had undergone DTI and had efficacious tremor control with intraoperative microlesioning effect and tremor reduction with less than 2.0-V stimulation. Analysis of color FA maps, which graphically illustrate fiber directionality, revealed consistent anatomic patterns. The region of the VIM nucleus can be seen as an intermediate region where there is a characteristic transition of color. Presumptive VIM nucleus interconnectivity with sensorimotor cortex and cerebellum was identified via the internal capsule and the superior cerebellar peduncle, respectively. FA maps could also be used to distinguish segments of gray matter, white matter, and gray-white matter boundaries. Analysis of DTI and FA maps on widely available 1.5-T magnetic resonance imaging yields clear identification of various structures key to neurosurgical targeting. Prospective evaluation of integrating DTI into neurosurgical planning may be warranted.

Unique challenges faced by pediatric neurosurgeon Harvey Cushing in 1909 at Johns Hopkins: a choroid plexus tumor of the lateral ventricle mimicking a cerebellar lesion

At the turn of the twentieth century, diagnosis of pediatric intracranial lesions frequently relied exclusively on the subtle, nonspecific signs associated with these pathologies. In absence of detailed neuroimaging, erroneous diagnoses and misdirected operative explorations were common within pediatric populations. Following institutional review board approval, and through the courtesy of the Alan Mason Chesney Archives, we reviewed the surgical files from the Johns Hopkins Hospital for the years 1896-1912. Harvey Cushing's neurosurgical cases were collected and further analyzed. A 9-year-old boy presented with a year-long history of headaches and blindness. His neurological examination was remarkable for focal cranial nerve deficits and cerebellar signs. Cushing diagnosed a cerebellar tumor with hydrocephalus and performed two suboccipital explorations with negative results. The patient died prior to further operative intervention, and the postmortem examination revealed a large choroid plexus tumor within the left lateral ventricle. Early neurosurgical diagnosis and operative planning was fraught with difficulties, and surgeons relied solely on history and physical examination for localization of intracranial lesions. Here we report a case of a choroid plexus tumor of the lateral ventricle, which was misdiagnosed by Cushing. This case serves to emphasize the unique challenges faced by pediatric neurosurgeons at the turn of the twentieth century, who relied solely on history and examination to localize intracranial lesions.

Interactive Diffusion Tensor Tractography Visualization for Neurosurgical Planning

Diffusion tensor imaging (DTI) infers the trajectory and location of large white matter tracts by measuring the anisotropic diffusion of water. DTI data may then be analyzed and presented as tractography for visualization of the tracts in 3 dimensions. Despite the important information contained in tractography images, usefulness for neurosurgical planning has been limited by the inability to define which are critical structures within the mass of demonstrated fibers and to clarify their relationship to the tumor. To develop a method to allow the interactive querying of tractography data sets for surgical planning and to provide a working software package for the research community. The tool was implemented within an open source software project. Echo-planar DTI at 3 T was performed on 5 patients, followed by tensor calculation. Software was developed that allowed the placement of a dynamic seed point for local selection of fibers and for fiber display around a segmented structure, both with tunable parameters. A neurosurgeon was trained in the use of software in < 1 hour and used it to review cases. Tracts near tumor and critical structures were interactively visualized in 3 dimensions to determine spatial relationships to lesion. Tracts were selected using 3 methods: anatomical and functional magnetic resonance imaging-defined regions of interest, distance from the segmented tumor volume, and dynamic seed-point spheres. Interactive tractography successfully enabled inspection of white matter structures that were in proximity to lesions, critical structures, and functional cortical areas, allowing the surgeon to explore the relationships between them.

「最近の脳科学」拡散テンソルの臨床応用

Over the past decade, diffusion tensor imaging (DTI) has offered researchers and clinicians a new noninvasive window into the human brain. DTI infers the trajectory and location of large white matter tracts by measuring anisotropic diffusion of water. DTI data may then be analyzed and presented as fractional anisotropy (FA) mapping, vector map, Ellipsoid image, and 3D fiber tractography. Three-dimensional fiber tractography based on DTI is useful for neurosurgical planning, and stereotactic radiotherapy, which present relationship between tumor and white matter tracts. Furthermore, several studies have suggested disorganization of the specific tract in Alzheimer disease, schizophrenia,and amyotrophic lateral sclerosis, etc. In this article, first,we briefly explain the basic physics of diffusion-weighted imaging (DWI) and DTI, and then present some clinical applications.

Residual Postoperative Tumour Volume Predicts Outcome after High-dose Radiotherapy for Chordoma and Chondrosarcoma of the Skull Base and Spine

Aims High-dose radiotherapy after surgical debulking is the treatment of choice for chordomas and chondrosarcomas. This study reviewed our outcomes, in relation to residual tumour volume and radiation dose, in order to inform our future practice. Patients and methods Nineteen patients referred to the Neuro-Oncology Unit at Addenbrooke’s Hospital (Cambridge, UK) between 1996 and 2009 and treated with photon radiotherapy were reviewed. Seventeen of the 19 were treated with curative intent. The median follow-up was 53 months. The tumours in the study had a mean gross tumour volume (GTV) of 17.2 cm 3 (median 10.5 cm 3) and a range of 0–76.3 cm 3. The median dose was 65 Gy in 39 fractions. Results The 5 year cause-specific survival for radically treated patients with chordomas was 92% and the 5 year local control rate was 83%. The 5 year cause-specific survival and local control rates with chondrosarcomas were both 100%. A planning target volume (PTV) below 90 cm 3 is predictive of local control, but volumes above this are not. The GTV seems to be a better predictor of outcome: among the 17 of 19 patients treated curatively, a GTV threshold of 30 cm 3 distinguished local failures from the 15 patients with local control, with sensitivity to detect local control of 100% (95% confidence interval 78–100%), specificity 100% (95% confidence interval 16–100%) and positive predictive value 100% (95% confidence interval 78–100%). Conclusions Our results show a high level of efficacy for fractionated photon radiotherapy after surgery, in keeping with other series. In addition, we found that although surgical debulking is essential, a small residual tumour volume may still be controlled with high-dose photon radiotherapy. This information may be relevant during neurosurgical planning, possibly allowing a reduction in risk of serious neurological deficits. This should encourage the further development of sophisticated photon radiotherapy, for patients unsuitable for proton therapy.

Hierarchical Density-Based Clustering of White Matter Tracts in the Human Brain

Diffusion tensor magnetic resonance imaging (DTI) provides a promising way of estimating the neural fiber pathways in the human brain non-invasively via white matter tractography. However, it is difficult to analyze the vast number of resulting tracts quantitatively. Automatic tract clustering would be useful for the neuroscience community, as it can contribute to accurate neurosurgical planning, tract-based analysis, or white matter atlas creation. In this paper, the authors propose a new framework for automatic white matter tract clustering using a hierarchical density-based approach. A novel fiber similarity measure based on dynamic time warping allows for an effective and efficient evaluation of fiber similarity. A lower bounding technique is used to further speed up the computation. Then the algorithm OPTICS is applied, to sort the data into a reachability plot, visualizing the clustering structure of the data. Interactive and automatic clustering algorithms are finally introduced to obtain the clusters. Extensive experiments on synthetic data and real data demonstrate the effectiveness and efficiency of our fiber similarity measure and show that the hierarchical density-based clustering method can group these tracts into meaningful bundles on multiple scales as well as eliminating noisy fibers.

Brain Surgery in a Stereoscopic Virtual Reality Environment

A comprehensive understanding of the spatial relationships between intracranial anatomy and pathological features is a crucial element in neurosurgical planning. To assess our clinical experiences using a novel approach, stereoscopic virtual reality environment, to help neurosurgeons with both surgical training and surgical strategic planning purposes. Patient-specific digital imaging data obtained from a variety of different diagnostic sources (computed tomography, computed tomographic angiography, magnetic resonance, functional magnetic resonance, magnetic resonance-diffusion tensor imaging) were collected and then transferred to a workstation setting. These clinical data were obtained from 100 patients who were suffering from either brain vascular malformations or tumors that were located in difficult brain sites. A 3-dimensional volume rendering was produced for each of the 100 clinical cases, which were then subjected to data coregistration and fusion. By using different head positioning systems and craniotomy options, we simulated microscopic visualizations of the lesion through numerous surgical approaches and from various angles of view. This simulation strategy enabled us to carry out an approach selection and eventually to identify the optimum angle of lesion visualization. These virtual craniotomies successfully simulated a sampling of different operative environments that have the potential to play a significant role in neurosurgical training and operative planning worthy of further exploration and development.

Computed tomographic angiography of the superior sagittal sinus and bridging veins

The primary aim of our paper was to describe typical anatomical patterns of the superior sagittal sinus (SSS) and bridging veins (BV) using cerebral venous computed tomographic angiography (CTA) with a focus on the direction of the BV entering the SSS. We retrospectively analyzed venous CTA of 30 patients to estimate the total number and direction of the BV entering the SSS. Maximum intensive projections were analyzed for length, diameter and cross-sectional area of the SSS. Thee hundred and fifty-four BV were assessed. The mean total length of the SSS was 25.6±1.6cm (mean±1SD). The mean horizontal diameter at the level of the coronary suture was 6.7±2.0mm, and the mean vertical diameter at the coronary suture measured 5.3±1.8mm. Most BV emptied into the SSS, at the level of or distal to the coronary suture (74%). The BV draining into the SSS at the level of the coronary suture typically joined into a lacunar formation (43%). Veins draining into the sinus more than 3cm distal from the coronary suture presented a predominantly retrograde inflow direction (77%). Despite large variations in the location and course of BV, typical anatomical patterns were noted especially in relation to the direction of BV entering the SSS. The present anatomical analysis of the cerebral convexity veins by cerebral venous CTA provides an overview of the configuration of these veins which is useful information in neurosurgical preoperative planning.

A pipeline for interactive cortex segmentation

In various clinical or research scenarios, such as neurosurgical intervention planning, diagnostics, or clinical studies concerning neurological diseases, cortex segmentation can be of great value. As, e.g., the visualization of the cortical surface along with target and risk structures enables conservative access planning and gives context information about the patient-specific anatomy. We present an interactive cortex segmentation pipeline (CSP) for T1-weighted MR images, utilizing watershed and level set methods. It is designed to allow the user to adjust the intermediate results at any stage of the segmentation process. Particular attention is paid to the appropriate visualization of the segmentation in the context of the original data for verification and to different interaction methods (manual editing, parameter tuning, morphological operations). Evaluation of the interactive CSP is performed with the Segmentation Validation Engine (SVE) by Shattuck et al. (NeuroImage 45(2):431---439, 2009). The segmentation quality of our method is comparable to the best results of three different established methods: the brain extraction tool (BET), brain surface extractor (BSE), and hybrid watershed algorithm (HWA). Being designed for interaction, the CSP integrates the users' expertise by allowing him to perform correction at any stage of the pipeline, enabling him to easily achieve a segmentation fulfilling his specific needs.

A BOLD move

Since its first discovery in the early 1990s, the blood oxygenation level–dependent (BOLD) effect as measured by fMRI has been increasingly used in the neuroscientific study of brain activity. Similar to PET, it is based on the coupling of neuronal firing with increases in blood flow, but instead it relies upon magnetic field changes consequent to endogenous blood oxygenation rather than injected radioactivity. It is thus noninvasive and repeatable, relatively low in cost, with high spatial and temporal resolution. Consequently, there have been growing efforts to implement fMRI in clinical practice, successfully in some areas, such as neurosurgical preoperative planning.1 In this issue of Neurology ®, O'Brien et al.2 present evidence suggesting that fMRI may be useful in the early detection of functional brain changes that ultimately lead to Alzheimer disease (AD). The authors measured hippocampal BOLD signals during an associative memory paradigm, combined with clinical assessment of 51 older subjects without dementia with follow-up after 2 years. Study participants were divided based on their Clinical Dementia Rating (CDR) scores of 0 or 0.5 (the …

Organisation topographique du corps calleux chez l’homme. Étude cartographique en imagerie par résonance magnétique fonctionnelle (f-IRM)

The concept of a topographical map of the corpus callosum (CC) has emerged from lesion studies in humans and from anatomical tracing investigations in other mammals. We conducted the first in vivo study aimed at outlining the topographical organization of the normal human CC, using non-invasive functional magnetic resonance imaging (fMRI). We tested cortical and callosal activation by the BOLD effect during simple sensory stimulation (tactile, gustatory and visual) and simple motor tasks in 38 volunteers. The axonal organization of callosal white matter was also studied in 16/38 subjects, using diffusion tensor imaging (DTI) and diffusion tensor tractography (DTT). Activation foci evoked by taste stimuli were detected in most subjects in the anterior part of the CC, those elicited by motor tasks lay in the central portion of the body of the CC, and those elicited by tactile stimulation of different body regions lay in the posterior part of the body. Activation foci evoked by visual stimulation were seen in the splenium of the CC. Callosal fibers interconnecting the primary cortical areas activated by taste stimulation, motor tasks, and tactile and visual stimuli were shown by DTT. Anatomical correlates of the BOLD activation foci were demonstrated in the CC, with fibers crossing it at the level of the genu, anterior and posterior body, and splenium, respectively. This study demonstrates for the first time that the functional topographical organization of the human CC can be explored by fMRI in vivo. Our findings may have clinical implications, especially for neurosurgical planning.

The Evolution of Clinical Functional Imaging during the Past 2 Decades and Its Current Impact on Neurosurgical Planning

BOLD fMRI has, during the past decade, made a major transition from a purely research imaging technique to a viable clinical technique used primarily for presurgical planning in patients with brain tumors and other resectable brain lesions. This review article briefly examines the history and evolution of clinical functional imaging, with particular emphasis on how the use of BOLD fMRI for neurosurgical planning has changed during the past 2 decades. Even more important, this article describes the many published studies during that same period that have examined the overall clinical impact that BOLD and DTI have made on surgical planning.

Augmented reality neurosurgical planning and navigation for surgical excision of parasagittal, falcine and convexity meningiomas

Objective. To assess the utility of pre-operative 3-dimension (3D) visualisation and surgical planning with the Dextroscope™ in combination with the use of DEX-Ray—a novel augmented reality surgical navigation platform for resection of meningiomas in the falcine, convexity and parasagittal regions.Methods and Results. Magnetic resonance imaging (MRI) and magnetic resonance venogram (MRV) images of the patients were reconstructed in 3D using the Dextroscope workstation. Using a variety of available tools, we were able to view the tumour in various surgical angles and appreciate the intricate relationship of the tumour with respect to the surrounding structures and venous anatomy. Critical draining veins both superficial and deep to the tumour were well visualised. By varying the transparency of the overlying scalp and bone we were able to preoperatively determine the ideal size of our scalp flap and bone window for surgical approach. The Dextroscope enabled us to simulate surgical opening and various trajectories of approach while the DexRay virtual reality navigation system enabled the transfer of the Dextroscope 3D planning data into the operating by displaying it in real-time video-augmented mode which further enhanced the appreciation of the tumour's location in 3D space. Four patients underwent total excision of their meningioma while one patient had near total excision with a small residual remnant left behind at the medial third of the superior sagittal sinus. All 5 patients had good neurological recovery post-operatively.Conclusion. The use of the Dextroscope for pre-operative surgical planning allows for appreciation of complex anatomical relationships in 3D. This appreciation is further translated for use during surgical navigation utilizing the DEX-Ray platform that provided us with the superior advantage of allowing fast and accurate surgical resection confidently.

Appliance of preoperative diffusion tensor imaging and fiber tractography in patients with brainstem lesions

Surgical resection of brainstem lesions has a high risk of morbidity, because vital fasciculi in the brainstem can be damaged along the entry routes. Diffusion tensor imaging (DTI) is an in vivo method for mapping white matter fiber tracts in the brain. To summarize the experience of surgical treatment of brainstem lesions with the assistance of DTI and fiber tractography. A retrospective analysis clinical data of nine patients with brainstem lesions were investigated between July 2007 and September 2009. The analysis included age distribution, clinical presentation, pre- and postoperative modified Rankin score (mRS), and surgical approach. DTI and fiber tractography were used to reconstruct the corticospinal tracts and the medial lemnisci. DTI and fiber tractography showed that most of the corticospinal tracts were compressed anteriorly or anterolaterally, except for one case (posteriorly). All the medial lemnisci were displaced posteriorly or posterolaterally. Individualized surgical approaches were designed according to the information provided by DTI and fiber tractography. Total resection was achieved in two patients with brainstem cavernomas and two patients with pilocytic astrocytoma. Partial resection was performed in the other patients. The neurological functional status was better than preoperative period in eight patients, one patient with medulla oblongata astrocytoma deteriorated. The preoperative average mRS score was 2.22 points. At the time of the last follow-up, the average postoperative score had improved by 0.56 to 1.66 points. DTI and fiber tractography can provide valuable information regarding the relationship between the principal fiber tracts and brainstem lesions, which is useful in neurosurgical planning.