Combined EEG-fMRI and tractography to visualise propagation of epileptic activity

In a patient with refractory temporal lobe epilepsy, EEG-fMRI showed activation in association with left anterior temporal interictal discharges, in the left temporal, parietal and occipital lobes. Dynamic causal modelling suggested propagation of neural activity from the temporal focus to the area of occipital activation. Tractography showed connections from the site of temporal lobe activation to the site of occipital activation. This demonstrates the principle of combining EEG-fMRI and tractography to delineate the pathways of propagation of epileptic activity

Fractional Anisotropy and Mean Diffusivity Value in 2nd Grade of Degenerative Cervical Canal Stenosis

Background: By using T2 weighted image (T2WI) of Magnetic Resonance Imaging (MRI), a radiologist can classify degenerative cervical canal stenosis (DCCS) into three grade, but there is no correlation between stenosis classification with clinical symptoms. It means that radiologist need a new parameter to make an early detection for spinal cord injury (SCI). Objective: Proving decrease of FA and increase of MD at the most proximal level of 2nd grade DCCS patient compared with C1-2. Methods: Cervical MR examination with 15-direction DTI sequens was performed on twenty one patient with neurological signs and symptoms of 2nd grade DCCS. Apparent FA and MD maps were generated on axial plane. The FA and MD measurements in each individual were made at the most proximal level of 2nd grade DCCS and C1-2. Wilcoxon rank sump test was used to compare FA and paired t-test was used for MD. Result : There are significant differences for FA (p = 0,00) and MD (p = 0,00) at the most proximal level of 2nd grade DCCS compared with C1-2. Conclusion: This research shows that FA and MD value at DTI sequens can be used for SCI early detection at 2nd grade DCCS patien

In vivo quantitative Magnetisation Transfer in the cervical spinal cord using reduced Field-of-View imaging: a feasibility study

Quantitative Magnetization Transfer (qMT) Imaging techniques offer the possibility to estimate tissue macromolecular fraction, which has been shown to be specific for myelin in the brain and spinal cord. To date, applications of qMT in the spinal cord have been hampered by prohibitive protocol duration. We propose a novel approach for qMT in the spinal cord based on the combination of offresonance saturation a small field-of-view imaging, with the potential of reducing scan time needed to perform qMT in the spinal cord

Characterization and Limitations of Diffusion Tensor Imaging Metrics in the Cervical Spinal Cord in Neurologically Intact Subjects

Purpose To characterize diffusion tensor imaging (DTI) metrics across all levels of the cervical spinal cord (CSC) and to study the impact of age and signal quality on these metrics. Materials and Methods DTI metrics were calculated for gray matter (GM) and white matter (WM) funiculi throughout the CSC (C1–T1) in 25 healthy subjects (22-85 years old). Signal-to-noise ratios (SNRs) and mean DTI metrics were measured for the upper (C1-3), middle (C4-6) and lower (C7-T1) cervical segments. Age-related changes in DTI metrics were analyzed for the individual segment groups. Results Fractional anisotropy (FA), mean diffusivity (MD) and transverse apparent diffusion coefficient (tADC) showed significant differences between GM and WM funiculi. Significant age-related changes were observed in FA in upper and middle CSC segments but not in the lower CSC. The median SNR was significantly lower in the middle and lower segment groups as compared to the upper levels, contributing to poor spatial resolution in these regions. Conclusion This study provides DTI data for GM and WM funiculi throughout the CSC. While DTI metrics may be used to define cord pathology, variations in metrics due to age and signal quality need to be accounted for before making definitive conclusions. J. Magn. Reson

Optic radiation tractography and vision in anterior temporal lobe resection.

Anterior temporal lobe resection (ATLR) is an effective treatment for refractory temporal lobe epilepsy but may result in a contralateral superior visual field deficit (VFD) that precludes driving in the seizure-free patient. Diffusion tensor imaging (DTI) tractography can delineate the optic radiation preoperatively and stratify risk. It would be advantageous to incorporate display of tracts into interventional magnetic resonance imaging (MRI) to guide surgery

FRACTIONAL ANISOTROPY IN DEGENERATIVE CERVICAL STENOSIS SURGERY PROGNOSTIC: A SYSTEMATIC REVIEW

ABSTRACT Cervical spondylotic myelopathy (CSM) is a common disease with an increased anticipated burden to health systems worldwide. Methods to predict outcomes in these patients are needed so physicians can provide more effective care. Fractional anisotropy (FA) analysis is a promising technique used to quantify how preserved the diffusion is in neural pathways. A systematic review and meta-analysis were performed using the PRISMA guidelines. Full articles available online were searched for correlation coefficients between FA values and mJOA scores. Average FA values, preoperative mJOA, and postoperative mJOA scores were gathered to perform a correlation analysis. A total of 5 articles presented correlations between FA and mJOA change and were included in the correlation meta-analysis. Correlation coefficients varied from -0.42 and 0.55. The number of patients in each study varied from 15 to 95. The Random effects model resulted in a non-significant correlation coefficient of 0.1315 (95% CI: -0.2575 to 0.4839; p= 0.5124). Spearman's correlation analysis was significant for preoperative vs postoperative mJOA (r = 0.79, p = 0.02), while preoperative FA did not correlate significantly with preoperative or postoperative mJOA. At this point, the data available in the literature is insufficient to determine a real correlation between FA and mJOA scores. More studies are necessary for a better understanding of this matter. Level of Evidence III; Study Review

Defining Meyer's loop-temporal lobe resections, visual field deficits and diffusion tensor tractography

Anterior temporal lobe resection is often complicated by superior quadrantic visual field deficits (VFDs). In some cases this can be severe enough to prohibit driving, even if a patient is free of seizures. These deficits are caused by damage to Meyer's loop of the optic radiation, which shows considerable heterogeneity in its anterior extent. This structure cannot be distinguished using clinical magnetic resonance imaging sequences. Diffusion tensor tractography is an advanced magnetic resonance imaging technique that enables the parcellation of white matter. Using seed voxels antero-lateral to the lateral geniculate nucleus, we applied this technique to 20 control subjects, and 21 postoperative patients. All patients had visual fields assessed with Goldmann perimetry at least three months after surgery. We measured the distance from the tip of Meyer's loop to the temporal pole and horn in all subjects. In addition, we measured the size of temporal lobe resection using postoperative T1-weighted images, and quantified VFDs. Nine patients suffered VFDs ranging from 22% to 87% of the contralateral superior quadrant. In patients, the range of distance from the tip of Meyer's loop to the temporal pole was 24–43 mm (mean 34 mm), and the range of distance from the tip of Meyer's loop to the temporal horn was –15 to +9 mm (mean 0 mm). In controls the range of distance from the tip of Meyer's loop to the temporal pole was 24–47 mm (mean 35 mm), and the range of distance from the tip of Meyer's loop to the temporal horn was –11 to +9 mm (mean 0 mm). Both quantitative and qualitative results were in accord with recent dissections of cadaveric brains, and analysis of postoperative VFDs and resection volumes. By applying a linear regression analysis we showed that both distance from the tip of Meyer's loop to the temporal pole and the size of resection were significant predictors of the postoperative VFDs. We conclude that there is considerable variation in the anterior extent of Meyer's loop. In view of this, diffusion tensor tractography of the optic radiation is a potentially useful method to assess an individual patient's risk of postoperative VFDs following anterior temporal lobe resection

Diffusion Tensor Imaging of the Spinal Cord: Insights From Animal and Human Studies

Diffusion tensor imaging (DTI) provides a measure of the directional diffusion of water molecules in tissues. The measurement of DTI indexes within the spinal cord provides a quantitative assessment of neural damage in various spinal cord pathologies. DTI studies in animal models of spinal cord injury indicate that DTI is a reliable imaging technique with important histological and functional correlates. These studies demonstrate that DTI is a noninvasive marker of microstructural change within the spinal cord. In human studies, spinal cord DTI shows definite changes in subjects with acute and chronic spinal cord injury, as well as cervical spondylotic myelopathy. Interestingly, changes in DTI indexes are visualized in regions of the cord, which appear normal on conventional magnetic resonance imaging and are remote from the site of cord compression. Spinal cord DTI provides data that can help us understand underlying microstructural changes within the cord and assist in prognostication and planning of therapies. In this article, we review the use of DTI to investigate spinal cord pathology in animals and humans and describe advances in this technique that establish DTI as a promising biomarker for spinal cord disorders