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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Case Reports
In vivo 1H magnetic resonance spectroscopic measurement of brain glycine levels in nonketotic hyperglycinemia.
Nonketotic hyperglycinemia (NKH) is an autosomal recessive disorder of glycine metabolism. Defective glycine cleavage causes elevated concentrations of glycine in plasma, urine, and cerebrospinal fluid. A longitudinal study using magnetic resonance imaging (MRI) and single-voxel 1H magnetic resonance spectroscopy (MRS) was performed on an infant with the typical clinical picture of NKH. ⋯ At the age of 10 months, MRI showed normal brain structure, while MRS detected a prominent glycine peak in the brain. Repeat MRS at the age of 13 months showed a small increase in glycine peak and a prominent glutamate/glutamine peak not previously detected. The MRS measurements were consistent with the slight increase in blood glycine level and the elevation in glutamine level, indicating that 1HMRS can be a valuable tool in the diagnosis and monitoring of treatment effects in patients with NKH.
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There has been limited data on the frequency of microembolic signals in patients with middle cerebral artery (MCA) stenosis, especially during the acute phase of stroke. Using transcranial Doppler, the authors prospectively monitored the MCA segments distal to stenosis in 4 groups of patients for 30 minutes: (1) symptomatic patients with acute ischemic stroke and MCA stenosis, (2) asymptomatic group patients with asymptomatic MCA stenosis, (3) control patients with acute ischemic stroke of undetermined etiology, and (4) normal people. A total of 60 patients completed the study. ⋯ Among 20 patients in the symptomatic group, microembolic signals were detected in 3 patients (15%). The number of emboli ranged from 1 to 6 per 30 minutes. This is the first report of the presence of microembolic signals in acute stroke patients with MCA stenosis.
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The objective of this study was to examine cerebral hemodynamics changes during hypothermic circulatory arrest (HCA) with and without retrograde cerebral perfusion (RCP). Thirteen colony-bred hound dogs were placed on cardiopulmonary bypass (CPB) and cooled to 18 degrees C. Five dogs underwent 2 hours of HCA without RCP and 8 with RCP. ⋯ During hypothermic circulatory arrest, RCP provides CBFV in the MCA comparable to MCA CBFV during CPB. HCA dogs without RCP showed immediate hyperemia on reperfusion. The decreased CBFV and increased PI at 1 hour after postarrest CPB could be an indicator of progressive ischemic injury due to the increased intracranial pressure despite the implementation of RCP.
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To test the hypothesis that syndrome X is a systemic vascular disorder, the authors studied 40 patients with this diagnosis using technetium-99m hexamethylpropylene amine oxime and single photon emission computed tomography (SPECT) brain images. Twenty-three of 25 cases with definite myocardial perfusion defects diagnosed by thallium-201 myocardial perfusion SPECT also had multiple hypoperfusion areas in the brain versus 2 of 15 patients without thallium myocardial defects. The parietal lobes were the most common hypoperfusion areas, and cerebellum was the least common. Syndrome X is a systemic vascular disorder with a high incidence of hypoperfusion lesions of the brain and is usually coincident with myocardial defects.