Journal of neuroimaging : official journal of the American Society of Neuroimaging
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The authors investigate the reproducibility of metabolite signals measured with proton magnetic resonance spectroscopy (1H-MRS) acquired from the human hippocampus in controls and in a phantom. Two 1H-MRS studies separated by 3 weeks were performed in 8 healthy volunteers and in a phantom. N-acetyl compounds (NA), choline (Ch), and creatine (Cr) peak areas and ratios were measured and compared using percentage variation, and Pearson Correlation Coefficient at the level of every voxel, the level of 1 hippocampus (5 voxels), and the level of 2 hippocampi (10 voxels). ⋯ Left-right asymmetry indices showed similar and limited inter-hemispheric asymmetry in repeated examination. This study suggests that 1H-MRS reproducibility performance is adequate for the study and monitoring of human hippocampus function when NA ratios and the sum of multiple voxels are considered. Individual metabolite peaks and single-voxel measurements have low reproducibility at 1.5 T and should be used only with clearly established statistical parameters.
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Cortical processing involved in seemingly similar tasks may differ in important ways. The authors mapped cortical regions engaged in a commonly performed picture naming task, seeking differences by semantic category. Functional magnetic resonance imaging was used during presentation of standardized line drawings in 18 healthy right-handed female participants, comparing living versus nonliving entities. ⋯ Activation of right inferior temporal cortex (BA19 and BA37) was greater during naming of living versus nonliving category items. No category differences in activation strength in the left temporal lobe were observed. The authors conclude that visual semantic operations may involve visual association cortex in the right temporal lobe in women.
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Although anterior circulation transient ischemic attacks (TIAs) tend to be more common in patients with extra- cranial carotid arterial disease than in those with intracranial carotid or middle cerebral arterial disease, the authors recently encountered 4 patients with both recurrent, stereotypical TIAs as well as isolated stenosis of their petrous internal carotid artery (ICA). While the gold standard for establishing the diagnosis of intracranial large-artery disease has always been conventional angiography, magnetic resonance angiography changes, confirmed with intra-arterial digital subtraction angiography in 2 of these patients, were quite sufficient to define the occlusive disease in each of the cases. Petrous ICA stenosis is not uncommon, but it has often been overshadowed by the search for extracranial ICA disease that might be amenable to surgical reconstruction.
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Case Reports
Transcranial color-coded sonography of a vein of Galen arteriovenous malformation in an adult.
The case of an adult harboring a vein of Galen arteriovenous malformation (VGAM) is reported. Diagnosis was established by computed tomography (CT) and digital subtraction angiography and confirmed afterwards by transcranial color-coded sonography (TCCS). ⋯ The results of TCCS were validated by angiography, with which they showed good correlation. Thus, it can be concluded that TCCS may be a useful adjunct to CT and angiography to noninvasively monitor adults with VGAM.
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Intravenous recombinant tissue plasminogen activator (rt-PA) is the only therapy of proven value for patients with acute ischemic stroke (AIS). Controversy exists with regard to the prognostic significance of early computed tomography (CT) changes in patients receiving rt-PA for AIS. The authors retrospectively reviewed all cases of AIS who received intravenous rt-PA for AIS in University of South Alabama hospitals between January 1996 and May 1999. ⋯ The frequency of specific findings were as follows: SE in 13 patients (36%), LGWD in 12 patients (33%), PH in 9 patients (25%), HMCA in 4 patients (11%), and IRS in 3 patients (8%) patients. There was no statistically significant association between the occurrence of these imaging findings and subsequent functional outcome after thrombolysis. The data suggest that the presence of subtle acute CT changes in AIS patients is not predictive of clinical outcome following administration of rt-PA as per National Institute of Neurological Disorders and Stroke protocol.