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Title: Serial magnetic resonance spectroscopy imaging in the acute stroke and the relationship with diffusion and perfusion parameters
Author: Cvoro, Vera
Awarding Body: University of Edinburgh
Current Institution: University of Edinburgh
Date of Award: 2013
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The aim of this thesis is to investigate the changes in brain metabolite concentration in the acute stroke across the whole of the diffusion lesion and their relationship with the parameters that measure diffusion and perfusion. 51 patients with cortical strokes of mean (+SD) age 75 ± 15 years, and mean NIHSS 11 ± 8 were imaged within 24 hours of onset, mean of 11 ± 7 hours for the first, and 5 ± 1, 12 ± 2, 31 ± 2, and 95 ± 6 days for each of the subsequent scans. Follow-up scanning was not possible in all cases. From the 51 initial patients, 26 (51%) were scanned up to 1 month and 23 (45%) at 3 months. All patients had structural T2 imaging, diffusion weighted (DWI) imaging, perfusion weighted (PWI) imaging and spectroscopy (MRS) as well as full initial clinical assessment and functional outcome at 3 months (Rankin score, Barthel index and extended Nothingam ADL scale). (1) Distribution of the metabolites within 24 h of stroke onset (region of interest (ROI) and MRS grid analysis). The metabolites were measured in the diffusion lesion classified according to its appearance on visual inspection (grid analysis). NAA differentiated 'definitely' from 'possibly abnormal', and 'possibly abnormal' from 'mismatch' (both comparisons p < 0.01) voxels, but not 'mismatch' from 'normal' voxels. Lactate was highest in 'definitely abnormal', and progressively lower in 'possibly abnormal', 'mismatch', then 'normal' voxels (all differences p < 0.01). There was no correlation between NAA and ADC or PWI values, but high lactate correlated with low ADC (Spearman q=-0.41, p=0.02) and prolonged MTT (Spearman q=0.42, p=0.02). The ROI analysis showed similar correlations. Conclusion: ADC and MTT indicate the presence of ischemia (lactate) but not cumulative total neuronal damage (NAA) in acute ischemic stroke, suggesting that caution is required if using ADC and PWI parameters to differentiate salvageable from non-salvageable tissue. (2) Choline and creatine are not reliable denominators for calculating metabolite ratios in acute ischemic stroke. Choline and creatine concentrations were measured by MR S in 51 patients at 5 times up to 3 months after stroke. Choline and creatine levels changed significantly in the ischemic region. Choline was significantly reduced during the first 2 weeks after stroke onset (P=0.034). Creatine was significantly reduced during the whole period of the study (P=0.011). Choline and creatine concentrations are not reliable denominators for metabolite ratios in acute stroke because their levels vary significantly in ischemic brain regions. (3) Changes in NAA and lactate over 3 months in the ischaemic lesion. NAA was significantly reduced from admission in definitely and possibly abnormal (p=0.01) compared to contralateral normal voxels, reaching a nadir by 2 weeks and remaining reduced at 3 months. Lactate was significantly increased in definitely and possibly abnormal voxels (p=0.01) during the first 5 days, falling to normal at 2 weeks, rising again later in these voxels. (4) Correlation with functional outcome. In the ROI analysis there was no association between any of the metabolites and the NIHSS score. There was no correlation between the metabolites, ADC, MTT or CBF and three month Rankin score. However, the clinical parameter of NIHSS (measured at baseline) was associated with the three month Rankin score (Spearman's p= 0.665, p=0.0001), in keeping with the known strong association between stroke severity and functional outcome.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (M.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available