Journal of neuroimaging : official journal of the American Society of Neuroimaging
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The authors' aim was to evaluate the time course of the basal vein's (BVR) mean flow velocity (VBVR) in patients after traumatic brain injury and its relation to intracranial pressure (ICP), cerebral perfusion pressure (CPP), and the clinical outcome. ⋯ Repetitive Doppler examination of the basal cerebral veins may add new aspects to the monitoring of head-injured patients.
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High-intensity transient signals (HITS) are frequently detected by transcranial Doppler (TCD) ultrasound in patients with mechanical prosthetic heart valves (PHVs), but published data about their clinical relevance are controversial. This study was undertaken to determine the clinical relevance of HITS in patients with mechanical PHVs. ⋯ Only age was a significant predictor of HITS in patients with mechanical PHVs. The lack of association between HITS, clinical symptoms, and cognitive functioning suggests that most of these signals represent harmless epiphenomena, and only HITS detected after O2 inhalation have any clinical relevance.
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Despite good clinical criteria for diagnosing optic neuritis (ON), only a few techniques can precisely assess its impact on visual brain function. The authors studied whether functional magnetic resonance imaging (fMRI) of visual activation reliably reflects the cerebral consequences of acute unilateral ON, and how fMRI correlates with clinical function and visual evoked potentials (VEPs). Twenty ON patients, before and after steroid treatment, were compared to 20 controls. ⋯ The higher stimulation frequencies yielded greater fMRI responses from unaffected eyes, but not from affected eyes, in controls. The fMRI responses were quantifiable in every subject, whereas in 11 ON eyes, no VEPs were obtained during the acute stage. The authors conclude that fMRI is sensitive to the cerebral response alteration during ON and might therefore contribute to evaluating the temporal evolution of the visual functional deficit during recovery or therapy.
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Case Reports
Diffusion magnetic resonance imaging in intermediate form of maple syrup urine disease.
An 8-year-old boy with the intermediate variant of maple syrup urine disease is reported. On b = 1000 s/mm2 (heavily diffusion weighted) images of diffusion magnetic resonance imaging, there was symmetric high signal in the globus pallidus, mesencephalon, dorsal pons, and nucleus dentatus, consistent with restriction of the mobility of water molecules. Apparent diffusion coefficient (ADC) maps revealed low ADC values ranging from 0.42 to 0.56 x 10(-3) mm2/s in these regions, compared to those of apparently unaffected regions in the brain parenchyma ranging from 0.63 to 0.97 x 10(-3) mm2/s. It is suggested that the areas of increased signal (and low ADC values) are the result of dysmyelination as a reflection of disorganized tissue integrity.
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Although conventional magnetic resonance imaging (cMRI) is widely used for diagnosing multiple sclerosis (MS) and monitoring disease activity and evolution, the correlation between cMRI and clinical findings is far from strict. Among the reasons for this "clinical-MRI paradox," a major role has been attributed to the limited specificity of cMRI to the heterogeneous pathological substrates of MS and to its inability to quantify the extent of damage in the normal-appearing tissue. Modern quantitative MRI techniques have the potential to overcome some of the limitations of cMRI. ⋯ Magnetic resonance spectroscopy can add information on the biochemical nature of such changes, with the potential to improve significantly our ability to monitor inflammatory demyelination and axonal injury. Finally, functional MRI might provide new insights into the role of cortical adaptive changes in limiting the clinical consequences of white-matter structural damage. This review outlines the major contributions given by MRI-based techniques to the diagnostic work-up of MS patients, to the understanding of the pathobiology of the disease, and to the assessment of the effects of new experimental treatments.