Journal of neuroimaging : official journal of the American Society of Neuroimaging
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During the past 10 years, conventional magnetic resonance imaging (cMRI) has become an established tool for the assessment of patients with multiple sclerosis (MS) and to monitor treatment trials. This is mainly due to the sensitivity and reproducibility of cMRI in the detection of MS-related damage. ⋯ Despite the fact that the role of cMRI in MS has been profoundly obviated by the advent of modern and quantitative MR techniques, several issues are still unresolved. Technical development in acquisition and postprocessing, as well as the introduction of high-field magnets in the clinical arena, are likely to increase our understanding of disease pathobiology, mainly through an increased ability to quantify the extent of gray matter damage.
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Merrill P Spencer and John M Reid applied the Hagen-Poiseuille law, continuity principle, and cerebrovascular resistance to describe a theoretical model of the relationship between the flow velocity, flow volume, and decreasing size of the residual vessel lumen. The model was plotted in a graph that became widely known as the Spencer's curve. Although derived for a smooth and axis-symmetric arterial stenosis of a short length in a segment with no bifurcations being perfused at stable arterial pressures and viscosity, this model represents a milestone in understanding cerebral hemodynamics with long-lasting practical and research implications. This review summarizes several hemodynamic principles that determine velocity and flow volume changes, explains how the model aids interpretation of cerebrovascular ultrasound studies, and describes its impact on clinical practice and research.
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Review Case Reports
Evidence of acute ischemic tissue change in transient global amnesia in magnetic resonance imaging: case report and literature review.
Transient global amnesia is a benign syndrome of sudden-onset alteration of behavior with temporary dysfunction of anterograde and recent retrograde memory. Its neural substrates remain uncertain. ⋯ The authors report a case of a 62-year-old man with a transient attack of memory disturbance, suggestive of transient global amnesia, in which magnetic resonance imaging performed 48 hours after onset showed left mesial temporal lobe signal changes on diffusion-weighted imaging and fluid-attenuated inversion recovery images. The findings and a literature review lend further support to the ischemic pathogenesis of transient global amnesia as a possible etiology, and underscore the role of diffusion-weighted imaging in the diagnosis of this condition.
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Early and accurate diagnosis of cerebral venous thrombosis (CVT) is possible with the help of computed tomography (CT) scan and magnetic resonance imaging (MRI). Empty delta sign on postcontrast CT is present in only up to 30% of the cases. The role of CT venography is not yet established, but it is emerging as an effective modality for diagnosis of CVT. ⋯ Diffusion-weighted imaging is a relatively new MRI technique that is extremely sensitive in detecting acute arterial strokes and can distinguish cytotoxic and vasogenic edema. The presence of hyperintense signal on diffusion-weighted imaging in the occluded veins or sinuses at the time of diagnosis may predict a low rate of vessel recanalization. Contrast angiography should be strongly considered if isolated cortical vein thrombosis is suspected.
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Multiple sclerosis (MS) is a chronic neurological condition characterized pathologically by axonal loss, demyelination, inflammation, and gliosis. Magnetic resonance imaging (MRI) has had a major impact on diagnosing MS, understanding the condition, and monitoring the effects of treatments. Recently, spinal cord MRI has received increased attention. ⋯ Despite the technical difficulties of performing spinal cord MRI, imaging studies, particularly of the cervical cord, are becoming more common. Significant focus has been placed on measuring cord atrophy, and reproducible techniques have been developed to measure the cervical cord CSA. Spinal cord MRI may provide information about disease progression that is not readily available from brain MRI scans and could be useful in diagnosing MS in some cases, as well as for monitoring the effects of treatments.