| Objective: (1) To investigate the clinical features of cognitive impairment in patients with carotid artery stenosis; (2) To evaluate the characteristics of magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI) and perfusion-weighted imaging (PWI) of the patients with carotid artery stenosis; (3) To make an approach to the relationship between the cognitive impairments and changes of regional cerebral blood flow and metabolism in patients with carotid artery stenosis, offer clues to better understand the pathophysiological mechanisms of cognitive impairments and promote the clinical diagnosis and treatment of cognitive impairment in patients with carotid artery stenosis.Methods: (1) Thirty–one patients with symptomatic carotid artery stenosis or occlusion (stenosis) and 14 patients without carotid and intracranial vascular stenosis or occlusion (no-stenosis) identified by cerebral angiography were tested with a set of neuropsychological scales, including Wisconsin Card Sorting Test (WCST), Verbal Fluency Test (VFT), Trail Making Test (TMT), Symbol Digit Modalities Test (SDMT), Mini-Mental State Examination(MMSE), National Institute of Health Stroke Scale(NIHSS), and Instrumental Activity of Daily Living (IADL). (2) Single voex 1H-MRS was operated on 22 stenosis patients and the 12 no-stenosis patients in non-infarcted bilateral frontal white matter and occipio-parietal gray matter, simultaneously DTI and PWI were also performed in all patients to obtain parameters of fractional anisotropy (FA), apparent diffusion coefficient (ADC), relative time to peak (rTTP), relative mean transit time (rMTT), relative regional cerebral blood flow (rrCBF) and relative regional cerebral blood volume (rrCBV) in frontal white matter, centrum semiovale and posterior cortical watershed. The rMTT, rTTP , rrCBV and rrCBF ratio were calculated as stenosis side against contralateral side or right side against left side. (3) Correlation analysis was performed between the scores of neuropsychological scaling and the measurements of functional magnetic resonance imaging . Results: (1) Cognitive impairments with various degrees were found in all patients with stenosis after analyzing the results of all the neuropsychological scaling adopted. Thirty patients(96.8%) were diagnosed as cognitive impairment depending on the score of VFT. Twenty-one patients(67.7 %) were presumed cognitive impairment depending on the score of preservative responses(Rp) in WCST. But only 5 patients (26.3%) were considered as cognitive impairment depending on the score of MMSE. (2) They both have significant differences in the scores of Rp, SDMT and VFT between the stenosis and no-stenosis groups and the scores of Rp, VFT, NIHSS and IADL between the moderate stenosis and severe stenosis patients(p<0.05).No significant difference of the scores of the neurop -sychological tests was found between the patients with left and the patients with right carotid artery stenosis(p>0.05).The VFT scores correlated with SDMT(r=0.3642, P=0.0139) and Rp(r=-0.3316, P=0.0261). (3) N-acetyl aspartate/creatine (NAA/Cr) in the frontal white matter on the side of carotid artery stenosis obviously decreased(p<0.05),yet choline-related compounds/creatine ( Cho/cr) and myo-inositol/ creatine( mI/cr) in frontal white matter, NAA/cr, Cho/cr and mI/cr in occipio-parietal gray matter changed a little(p>0.05). (4) FA in frontal and centrum semiovale white matter on the side of carotid artery stenosis decreased significantly by comparison with the average FA in both sides in the corresponding regions of no-stenosis group(p<0.05), ADC values had no significant differences between stenosis and no-stenosis groups(p>0.05). (5) Eleven patients(50%) with stenosis had inadequate perfusion in the frontal lobe, centrum semiovale or posterior cortical watershed. No significant difference of the ratio for rrCBF,rrCBV,rMTT,rTTP was found among the patients with severe carotid stenosis, the patients with moderate carotid stenosis, and the no-stenosis patients(p>0.05). (6) A positive correlation was formed between the NAA/Cr of frontal white matter on the stenosis side and the rrCBF ratio(r=0.4899, P=0.0081) of frontal lobe,while no significant dependability was formed between the value of FA, NAA/Cr and rrCBF ratio(p>0.05). The NAA/Cr of frontal white matter on the stenosis side positively correlated with scores of MMSE(r=0.4094, P=0.0421) and VFT(r=0.5335, P=0.0060), while negatively correlated with scores of NIHSS(r= -0.6500, P=0.0004), Rp(r=-0.4594, P=0.0209) and TMT(r=-0.4015, P=0.0467). The FA value of centrum semiovale on the stenosis side positively correlated with scores of VFT(r=0.4455, P=0.0154) and SDMT(r=0.3892, P=0.0369), while negatively correlated with scores of TMT(r=-0.4228, P=0.0223).Conclusion: (1) Patients with carotid artery stenosis have definite cognitive impairment, prominently in cognitive conversion, executive function, and attention.The VFT is a very sensitive test to detect cognitive impairment in patients with carotid artery stenosis. Cognitive impairment in patients with carotid artery stenosis can be definitely identified by WCST. (2) The reduction of cerebral blood flow and consequently the change of regional metabolism in the frontal white matter are the main reasons leading to cognitive impairment in the patients with carotid artery stenosis. (3) The NAA/cr and FA of frontal white matter on the stenosis side may drop mainly not because of the neuron loss, but mainly because of nerve axons and myelin damage in patients with carotid artery stenosis . (4) The functional magnetic resonance imaging, especially the NAA/Cr and the FA, might be as the diagnostic tools to detect the basis of pathological damage while managing the cognitive impairment patients with carotid artery stenosis . (5) The evaluation of the structure and function integrity of the frontal lobe-subcortex neural circuits should be attached more importance while making an approach to the pathophysiological mechanisms of cognitive impairment in patients with carotid artery stenosis.
|
PDF Full Text Request