Abstract
PurposeTo investigate cortical thickness and cortical quantitative T2 values as imaging markers of microstructural tissue damage in patients with unilateral high-grade internal carotid artery occlusive disease (ICAOD).MethodsA total of 22 patients with ≥70% stenosis (mean age 64.8 years) and 20 older healthy control subjects (mean age 70.8 years) underwent structural magnetic resonance imaging (MRI) and high-resolution quantitative (q)T2 mapping. Generalized linear mixed models (GLMM) controlling for age and white matter lesion volume were employed to investigate the effect of ICAOD on imaging parameters of cortical microstructural integrity in multivariate analyses.ResultsThere was a significant main effect (p < 0.05) of the group (patients/controls) on both cortical thickness and cortical qT2 values with cortical thinning and increased cortical qT2 in patients compared to controls, irrespective of the hemisphere. The presence of upstream carotid stenosis had a significant main effect on cortical qT2 values (p = 0.01) leading to increased qT2 in the poststenotic hemisphere, which was not found for cortical thickness. The GLMM showed that in general cortical thickness was decreased and cortical qT2 values were increased with increasing age (p < 0.05).ConclusionUnilateral high-grade carotid occlusive disease is associated with widespread cortical thinning and prolongation of cortical qT2, presumably reflecting hypoperfusion-related microstructural cortical damage similar to accelerated aging of the cerebral cortex. Cortical thinning and increase of cortical qT2 seem to reflect different aspects and different pathophysiological states of cortical degeneration. Quantitative T2 mapping might be a sensitive imaging biomarker for early cortical microstructural damage.
Highlights
Atherosclerotic large vessel stenosis is one of the leading causes for ischemic stroke worldwide [1]
Reconstruction of the cortical surface and computation of cortical thickness failed in one healthy control subject for technical reasons, while qT2 maps could be analyzed for all subjects included in the study
The Generalized linear mixed models (GLMM) analyses showed a significant main effect of the group on both cortical thickness (p = 0.034) and cortical qT2 values (p = 0.023) with reduced cortical thickness and increased cortical qT2 in patients compared to controls (Tables 1 and 2; Fig. 3a,b)
Summary
Atherosclerotic large vessel stenosis is one of the leading causes for ischemic stroke worldwide [1]. Quantitative (q)MRI with qT2 mapping is sensitive to pathological tissue alterations, such as increase of tissue water content due to extracellular and intracellular edema, gliosis, demyelination and axonal damage, which typically lead to a prolongation of qT2 values [13, 14]. Given these underlying pathophysiological mechanisms, increases of cortical qT2 in general should be associated with cortical thinning but may be assessable before reduction of cortical thickness occurs. A group of control subjects was used for comparison to assess potential bilateral changes of cortical microstructure in ICAOD
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