Placement accuracy of external ventricular drain when comparing freehand insertion to neuronavigation guidance in severe traumatic brain injury.

BACKGROUND: External ventricular drain (EVD) placement is a frequently performed neurosurgical procedure. Inaccuracies in drain positioning and the need for multiple passes using the classic freehand insertion technique is well reported in the literature, especially in the traumatic brain injury (TBI) population. The purpose of this study was to evaluate if electromagnetic neuronavigation guidance for EVD insertion improves placement accuracy and minimizes the number of passes in severe TBI patients. METHODS: Navigation was applied prospectively for all new severe TBI patients who required ventricular catheter placement over a period of 1 year, and compared with a retrospective cohort of severe TBI patients who had EVD inserted freehand in the preceding year. The placement accuracy was evaluated using the Kakarla grading system; the number of passes was also compared. RESULTS: Fifty-four cases were recruited: 35 (64.8%) had their EVD placed using the freehand technique and 19 (35.2%) using navigation guidance. In the navigation group, the placement accuracy was: 94.7% (18/19) grade 1, 5.3% (1/19) grade 2, and none at grade 3. In comparison, freehand placement was associated with misplacement (grades 2 and 3) in 42.9% of the cases (p value = 0.009). The number of passes was significantly lower in the navigation group (mean of 1.16 ± 0.38), compared with the freehand group (mean of 1.63 ± 0.88) (p value = 0.018). CONCLUSIONS: Using the navigation to guide EVD placement was associated with a significantly better accuracy and a lower number of passes in severe TBI patients.

Sub-diffuse interstitial optical tomography to improve the safety of brain needle biopsies: a proof-of-concept study.

The extraction of tissue samples during brain needle biopsy can cause life-threatening hemorrhage because of significant blood vessel injury during the procedure. Vessel rupture can have significant consequences for patient health, ranging from transient neurological deficits to death. Here, we present a sub-diffuse optical tomography technique that can be integrated into neurosurgical workflow to detect the presence of blood vessels. A proof-of-concept study performed on a realistic brain tissue phantom is presented and demonstrates that interstitial optical tomography (iOT) can detect several 1 mm diameter high-contrast absorbing objects located <2 mm from the needle.

Pathologic substrates of focal epilepsy influence the generation of high-frequency oscillations.

OBJECTIVE: Although a clear correlation has been observed between high-frequency oscillations (HFOs) and the seizure-onset zone in distinct lesions, the role of the underlying pathologic substrates in the generation of HFOs is not well established. We aimed to investigate HFO correlates of different pathologic substrates in patients with drug-resistant epilepsy, and to examine the relation of HFOs with the anatomic location of the dysplastic lesion and surrounding tissue in patients with focal cortical dysplasia (FCD). METHODS: We studied consecutive patients with drug-resistant epilepsy who underwent intracranial electroencephalography (iEEG) investigations with depth electrodes at the Montreal Neurological Institute and Hospital, between November 2004 and May 2013. Inclusion criteria were the following: a focal lesion documented by magnetic resonance imaging (MRI); EEG recording at a 2,000 Hz sampling rate; and seizures starting from depth electrode contacts placed in lesion and perilesional tissue. RESULTS: Thirty-seven patients (13 FCD, 12 mesial temporal sclerosis, five cortical atrophy, three polymicrogyria, three nodular heterotopia, and one tuberous sclerosis) were included; 18 were women (median age 34). Ripples and fast ripples were found in all lesion types, except tuberous sclerosis, which showed no fast ripples. There was a significant difference in rates of ripples and fast ripples across different lesions (p < 0.001), with higher rates in FCD, mesial temporal sclerosis, and nodular heterotopia than in atrophy, polymicrogyria, and tuberous sclerosis. Regarding patients with FCD, HFOs rates differed significantly across the three types of tissue (lesional, perilesional, and nonlesional; p < 0.001), being higher within the borders of the MRI-visible dysplastic lesion, followed by the surrounding area, and rare in the remote cortex. SIGNIFICANCE: Our findings suggest that in patients who are all intractable, the HFO rates vary with different pathologies, and reflect different types of neuronal derangements. Our results also emphasize the potential usefulness of HFOs as an additional method to better define the extent of the epileptogenic dysplastic tissue in FCD.

Atypical speech activations: PET results of 92 patients with left-hemispheric epilepsy.

PURPOSE: Language lateralization and factors that may influence language lateralization were investigated using positron emission tomography. METHODS: Ninety-two right-handed patients who had left-sided lesions (tumors, focal cortical dysplasia, and vascular lesions) and 19 right-handed normal subjects were included and synonym generation task was used for evaluation of language lateralization. RESULTS: As expected, the majority of individuals in both groups showed left hemisphere dominance. Lesions in the vicinity of language-related areas did not alter patterns of activation responses. However, atypical inferior frontal gyrus (IFG) activations (33.6%) were more commonly observed in the patient group than in the control group (21%). There were no clear right-sided IFG activations in the control group but almost 28% of the patients showed clear right-sided IFG activations. Atypical language lateralization was strongly correlated with duration of seizure (p = 0.01) and early age at onset (p = 0.03). CONCLUSIONS: Our data provide evidence for inter-hemispheric plasticity related to language function as a response to lesions involving the left hemisphere. A better understanding of the dynamic organization of the brain and about the interaction between the lesion and reactional plasticity will lead to changes in surgical strategy, which will enable us to perform a total removal of the lesion involving eloquent brain areas with improved functional outcome.

Atypical language lateralization in patients with left hippocampal sclerosis: does the hippocampus affect language lateralization?

AIM: To provide information related to atypical language activations (right or bilateral) in positron emission tomography in patients with left clear-cut hippocampal sclerosis. MATERIAL AND METHODS: Twelve right-handed patients who had been operated on left-sided hippocampal sclerosis and 12 right-handed normal subjects were included and the synonym generation task was used for evaluation of language lateralization. RESULTS: Atypical language activations were frequently found in the patients compared to the controls. A total of 3 (25%) subjects in the controls showed atypical activations: 2 bilateral with right and 1 bilateral with left-sided activations. There were no clear right-sided Broca activations in the control group but almost 25% of the patients showed clear right-sided Broca activations. In the patients the incidence of atypical language activations was 91.6% (11 patients). CONCLUSION: From the present study, it is clear that functional reorganization of the language-related neuronal network is modified in patients with left hippocampal sclerosis. Although the lesion is far from the primary language-related areas, atypical language lateralization is common in these patients and this should be considered in preoperative period.

MRI Based Brain-Specific 3D-Printed Model Aligned to Stereotactic Space for Registering Histology to MRI.

Studies that seek to predict the brain microstructure based on MRI require precise alignment of processed brain histology slices to the corresponding 3D MRI data. However, achieving such alignment is a challenging problem, due to tissue distortions and the different contrasts seen in MRI and the processed tissue. Here we present a pipeline for aligning a histology volume to the MRI data of the tissue and to a stereotaxic brain atlas. To this end, we segment the volume of the brain from ex-vivo MRI data, align the MRI data obtained in the native space to an MRI stereotaxic template and create a 3D printed model (a mold or cradle) that precisely fits the brain. The pipeline then makes it possible to create grooves in the 3D model, for guiding blades for cutting slabs of tissue. Placing the brain in the brain-specific 3D printed model aligns the tissue to the MRI data by default. Aligning the MRI data to an MRI stereotaxic template makes it possible to section histology slices parallel to the standard stereotaxic axes of the atlas. This facilitates comparisons to other MRI contrasts and to images of processed tissue aligned to the standard space, while maintaining the high-resolution of the tissue images along the standard stereotaxic plane. Guiding the positioning of the grooves according to species-specific anatomical information from the co-registered atlas facilitates region-specific histology. The pipeline we introduce can be used to create brain-specific sectioning models for a variety of species, including humans, primates, and rodents. To demonstrate the generalizability of the pipeline across species, we show models generated for macaques and rats.

An Open Resource for Non-human Primate Imaging.

Non-human primate neuroimaging is a rapidly growing area of research that promises to transform and scale translational and cross-species comparative neuroscience. Unfortunately, the technological and methodological advances of the past two decades have outpaced the accrual of data, which is particularly challenging given the relatively few centers that have the necessary facilities and capabilities. The PRIMatE Data Exchange (PRIME-DE) addresses this challenge by aggregating independently acquired non-human primate magnetic resonance imaging (MRI) datasets and openly sharing them via the International Neuroimaging Data-sharing Initiative (INDI). Here, we present the rationale, design, and procedures for the PRIME-DE consortium, as well as the initial release, consisting of 25 independent data collections aggregated across 22 sites (total = 217 non-human primates). We also outline the unique pitfalls and challenges that should be considered in the analysis of non-human primate MRI datasets, including providing automated quality assessment of the contributed datasets.

New Protocol for Skin Landmark Registration in Image-Guided Neurosurgery: Technical Note.

BACKGROUND: Newer versions of the commercial Medtronic StealthStation allow the use of only 8 landmark pairs for patient-to-image registration as opposed to 9 landmarks in older systems. The choice of which landmark pair to drop in these newer systems can have an effect on the quality of the patient-to-image registration. OBJECTIVE: To investigate 4 landmark registration protocols based on 8 landmark pairs and compare the resulting registration accuracy with a 9-landmark protocol. METHODS: Four different protocols were tested on both phantoms and patients. Two of the protocols involved using 4 ear landmarks and 4 facial landmarks and the other 2 involved using 3 ear landmarks and 5 facial landmarks. Both the fiducial registration error and target registration error were evaluated for each of the different protocols to determine any difference between them and the 9-landmark protocol. RESULTS: No difference in fiducial registration error was found between any of the 8-landmark protocols and the 9-landmark protocol. A significant decrease (P < .05) in target registration error was found when using a protocol based on 4 ear landmarks and 4 facial landmarks compared with the other protocols based on 3 ear landmarks. CONCLUSION: When using 8 landmarks to perform the patient-to-image registration, the protocol using 4 ear landmarks and 4 facial landmarks greatly outperformed the other 8-landmark protocols and 9-landmark protocol, resulting in the lowest target registration error.

Characterization of a Raman spectroscopy probe system for intraoperative brain tissue classification.

A detailed characterization study is presented of a Raman spectroscopy system designed to maximize the volume of resected cancer tissue in glioma surgery based on in vivo molecular tissue characterization. It consists of a hand-held probe system measuring spectrally resolved inelastically scattered light interacting with tissue, designed and optimized for in vivo measurements. Factors such as linearity of the signal with integration time and laser power, and their impact on signal to noise ratio, are studied leading to optimal data acquisition parameters. The impact of ambient light sources in the operating room is assessed and recommendations made for optimal operating conditions. In vivo Raman spectra of normal brain, cancer and necrotic tissue were measured in 10 patients, demonstrating that real-time inelastic scattering measurements can distinguish necrosis from vital tissue (including tumor and normal brain tissue) with an accuracy of 87%, a sensitivity of 84% and a specificity of 89%.

Augmented reality in neurovascular surgery: feasibility and first uses in the operating room.

PURPOSE: The aim of this report is to present a prototype augmented reality (AR) intra-operative brain imaging system. We present our experience of using this new neuronavigation system in neurovascular surgery and discuss the feasibility of this technology for aneurysms, arteriovenous malformations (AVMs), and arteriovenous fistulae (AVFs). METHODS: We developed an augmented reality system that uses an external camera to capture the live view of the patient on the operating room table and to merge this view with pre-operative volume-rendered vessels. We have extensively tested the system in the laboratory and have used the system in four surgical cases: one aneurysm, two AVMs and one AVF case. RESULTS: The developed AR neuronavigation system allows for precise patient-to-image registration and calibration of the camera, resulting in a well-aligned augmented reality view. Initial results suggest that augmented reality is useful for tailoring craniotomies, localizing vessels of interest, and planning resection corridors. CONCLUSION: Augmented reality is a promising technology for neurovascular surgery. However, for more complex anomalies such as AVMs and AVFs, better visualization techniques that allow one to distinguish between arteries and veins and determine the absolute depth of a vessel of interest are needed.

Intraoperative brain cancer detection with Raman spectroscopy in humans.

Cancers are often impossible to visually distinguish from normal tissue. This is critical for brain cancer where residual invasive cancer cells frequently remain after surgery, leading to disease recurrence and a negative impact on overall survival. No preoperative or intraoperative technology exists to identify all cancer cells that have invaded normal brain. To address this problem, we developed a handheld contact Raman spectroscopy probe technique for live, local detection of cancer cells in the human brain. Using this probe intraoperatively, we were able to accurately differentiate normal brain from dense cancer and normal brain invaded by cancer cells, with a sensitivity of 93% and a specificity of 91%. This Raman-based probe enabled detection of the previously undetectable diffusely invasive brain cancer cells at cellular resolution in patients with grade 2 to 4 gliomas. This intraoperative technology may therefore be able to classify cell populations in real time, making it an ideal guide for surgical resection and decision-making.

Age of language learning shapes brain structure: a cortical thickness study of bilingual and monolingual individuals.

We examined the effects of learning a second language (L2) on brain structure. Cortical thickness was measured in the MRI datasets of 22 monolinguals and 66 bilinguals. Some bilingual subjects had learned both languages simultaneously (0-3 years) while some had learned their L2 after achieving proficiency in their first language during either early (4-7 years) or late childhood (8-13 years). Later acquisition of L2 was associated with significantly thicker cortex in the left inferior frontal gyrus (IFG) and thinner cortex in the right IFG. These effects were seen in the group comparisons of monolinguals, simultaneous bilinguals and early and late bilinguals. Within the bilingual group, significant correlations between age of acquisition of L2 and cortical thickness were seen in the same regions: cortical thickness correlated with age of acquisition positively in the left IFG and negatively in the right IFG. Interestingly, the monolinguals and simultaneous bilinguals did not differ in cortical thickness in any region. Our results show that learning a second language after gaining proficiency in the first language modifies brain structure in an age-dependent manner whereas simultaneous acquisition of two languages has no additional effect on brain development.

Pedicle violation and Navigational errors in pedicle screw insertion using the intraoperative O-arm: A preliminary report.

BACKGROUND: Use of computer-assisted insertion of pedicle screws has some advantages owing to the reportedly decreased incidence of pedicle breach and clinical events. Registration-based methods based on preoperative computed tomography imaging, 2D fluoroscopy, and 3D fluoroscopy are the most popular, however each has its limitations. O-arm-based navigation, which uses intraoperative acquisition and registration of navigated images, may overcome many of these disadvantages. We set out to study the clinical accuracy and navigational accuracy for pedicle screw insertion using our recently acquired O-arm and present our preliminary findings. METHODS: The first 26 patients operated consecutively for L4-5 fusion were included in the study. O-arm-based navigation was used to insert the pedicle screws. Postoperative computed tomography images were acquired and assessed for pedicle breach and anterior cortical perforation. Planned trajectories of each screw were compared with the actual trajectories in the postoperative images to assess navigational accuracy in both axial and sagittal planes. RESULTS: A total of 104 screws were inserted. One screw (1%) breached the pedicle laterally. Nonsignificant anterolateral cortical perforations were noted in 7 screws (6.7%), all of which occurred at L5 level. The mean axial and sagittal navigational error was 2.3° (±1.7) and 3.1° (±2.3), respectively. There were no significant differences in the errors between L4 or L5 level. The occurrence of anterior perforation correlated with the degree of axial (P = .02) but not sagittal (P = .12) navigational error. There were no clinical events related to the screw insertion. CONCLUSION: Use of O-arm-guided pedicle screw insertion was associated with low incidence of pedicle breach (1%) and a low range of navigational error in both sagittal and axial planes. Anterolateral vertebral body perforation was higher at L5 without any negative clinical events. Despite the high need for technical support, we found that O-arm was a very efficient tool for accurate pedicle screw insertion.

Brain reorganization after endovascular treatment in a patient with a large arteriovenous malformation: the role of diagnostic and functional neuroimaging techniques.

We describe a case of brain cortical reorganization after embolization of a large right temporal arteriovenous malformation. A comprehensive imaging protocol, including functional magnetic resonance imaging (fMRI), cortical thickness analysis and 320-row computed tomography (CT) perfusion was used to provide information on brain plasticity and potential steal phenomenon. A 25-year-old man known for a right temporal grade V Spetzler-Martin classification arteriovenous malformation (AVM) presented with left progressive hemiparesis. He underwent functional 3T magnetic resonance imaging (fMRI), cortical thickness analysis, and CT perfusion (CT 320 row, Aquilion ONE, Toshiba, Tokyo, Japan) before and after endovascular treatment. The results were compared to look for modifications in brain perfusion and organization. An improvement in the left hemiparesis and a reorganization of motor function were observed after endovascular treatment. Modifications in the angioarchitecture and perfusion of an extensive AVM may be accompanied by a functional and structural reorganization of the brain. The location in the so-called eloquent regions may not be sufficient to explain the wide spectrum of symptoms that these patients can present. A more comprehensive approach considering a global involvement of the brain in patients with large AVMs is suggested to achieve the best treatment strategy and to stage treatment in incurable AVMs.

Automatic trajectory planning of DBS neurosurgery from multi-modal MRI datasets.

We propose an automated method for preoperative trajectory planning of deep brain stimulation image-guided neurosurgery. Our framework integrates multi-modal MRI analysis (T1w, SWI, TOF-MRA) to determine an optimal trajectory to DBS targets (subthalamic nuclei and globus pallidus interna) while avoiding critical brain structures for prevention of hemorrhages, loss of function and other complications. Results show that our method is well suited to aggregate many surgical constraints and allows the analysis of thousands of trajectories in less than 1/10th of the time for manual planning. Finally, a qualitative evaluation of computed trajectories resulted in the identification of potential new constraints, which are not addressed in the current literature, to better mimic the decision-making of the neurosurgeon during DBS planning.

Comparison between manual and semiautomated volumetric measurements of pituitary adenomas.

Linear measurements have many limitations. The aim of this study is to compare manual and semiautomated volumetric measurements of pituitary adenomas. Magnetic resonance imaging (MRI) scans of 38 patients with pituitary adenomas were analyzed. Preoperative MRI was acquired on a 1.5 T. MRI volumes of the pituitary adenomas were obtained by two methods: manual (MA) and semiautomated (SA). The concurrent validity for SA and MA methods on 38 patients in the form of correlation coefficient was 0.97 (p < 0.0001). The intraobserver and the interobserver correlation coefficients for SA volumes were both 0.98, as for the intraobserver MA volumes were 0.98. Although the results of both methods are comparable, analysis of volumetric measurements by SA method is more time-efficient than MA segmentation. Precision in volumetric measurement techniques is likely to increase reliability of posttherapeutic monitoring of pituitary adenomas.

Tractography of the amygdala and hippocampus: anatomical study and application to selective amygdalohippocampectomy.

OBJECT: The aim of this study was to evaluate, using diffusion tensor tractography, the white matter fibers crossing the hippocampus and the amygdala, and to perform a volumetric analysis and an anatomical study of the connections of these 2 structures. As a second step, the authors studied the white matter tracts crossing a virtual volume of resection corresponding to a selective amygdalohippocampectomy. METHODS: Twenty healthy right-handed individuals underwent 3-T MR imaging. Volumetric regions of interest were manually created to delineate the amygdala, the hippocampus, and the volume of resection. White matter fiber tracts were parcellated using the fiber assignment for continuous tracking tractography algorithm. All fibers were registered with the anatomical volumes. RESULTS: In all participants, the authors identified fibers following the hippocampus toward the fornix, the splenium of the corpus callosum, and the dorsal hippocampal commissure. With respect to the fibers crossing the amygdala, the authors identified the stria terminalis and the uncinate fasciculus. The virtual resection disrupted part of the fornix, fibers connecting the 2 hippocampi, and fibers joining the orbitofrontal cortex. The approach created a theoretical frontotemporal disconnection and also interrupted fibers joining the temporal pole and the occipital area. CONCLUSIONS: This diffusion tensor tractography study allowed for good visualization of some of the connections of the amygdala and hippocampus. The authors observed that the virtual selective amygdalohippocampectomy disconnected a large number of fibers connecting frontal, temporal, and occipital areas.

An indexed atlas for content-based retrieval and analysis of mammograms.

We describe the development of an indexed atlas of digital mammograms to facilitate content-based retrieval and comparative analysis of mammograms for computer-aided diagnosis (CAD) of breast cancer. Specifically, the requirements and the design of the components of the indexed archival and retrieval system are examined. In order to facilitate search by categories, the mammograms in the atlas are indexed by case number, year of acquisition, category (normal, benign disease, and malignant disease that could be screen-detected or interval cancer), and the presence of signs of disease such as masses, calcifications, bilateral asymmetry, and architectural distortion. In the initial phase of the project, mammograms with masses have been indexed with objective diagnostic features related to their shape, edge definition, and texture. Interfaces to the atlas provide tools for selection and retrieval of cases by text-based or content-based indices. The system should assist radiologists and clinical specialists in CAD of breast cancer.