The Study About The Cerebral Default Mode Network And Cortical Morphology Alteration Of Hypertension Related Cognitive Impairment

Part One The Characteristic Changes of the Default Mode Network in Hypertensive Patients and its Relationship with CognitionBackground and Objectives: Hypertension has a close relationship with brain degeneration and cognitive decline during the ageing process.The default mode network(DMN)is usually affected in various diseases related to cognitive impairment(CI).The present research aimed to explore the alterations in DMN and its subcomponents in hypertensive patients with and those without CI and to investigate the association between cognitive performance and network abnormalities.Methods: From Jan 2017 to Sep 2017,all the subjects were recruited in the Nanjing Drum Tower Hospital.After screen according to the inclusion and exclusion criteria,resting-state functional magnetic resonance imaging and neuropsychological tests were performed in 74 subjects,namely,30 hypertensive patients with normal cognition(HTN-NC),25 hypertensive patients with CI(HTN-CI)and 19 healthy controls.Seed-based functional connectivity(FC)analysis was performed to identify the DMN patterns.Results: The group differences in DMN were mainly shown in brain regions related to the core subsystem and the dorsal medial subsystem of DMN.Post hoc analysis revealed a trend of dissociation among the DMN subsystems in HTN-NC group.In contrast,the HTN-CI group displayed extensively increased FC in both subsystems.Importantly,increased FC of the dorsal medial subsystem in the HTN-CI patients was associated with poor cognitive performance such as scores on Mini-Mental State Examination(? =-0.438,P = 0.029)and Montreal Cognitive Assessment(? =-0.449,P = 0.025).Conclusion: The findings suggested that extensively increased connectivities in the core subsystem and the dorsal media subsystem of DMN may distinguish hypertension with CI from hypertension with normal cognition.The characteristic change in the dorsal medial subsystem may become an early imaging biomarker for the diagnosis and treatment of cognitive impairment associated with hypertension.Part Two The Cerebral Cortical Morphology Alteration and its Relationship with Blood Pressure and Cognition in Hypertensive patientsBackground and Objectives: Hypertension may lead to vascular cognitive impairment(VCI)and even progress into vascular dementia(Va D).The blood pressure(BP)variation would be the cause of brain structural change,although it is still unclear about the relationship between the BP value and brain atrophy,the atrophy of the key structure(gray matter/cortex alteration)is one of the critical reasons which contribute to the cognitive decline.Cortical volume is determined by cortical thickness(CTh)and surface area(SA),CTh and SA could reflect the transformation of cortical morphology in more detailed aspects.The study aimed to explore the change of CTh and SA in hypertensive patients with heterogenous cognitive performance,as well as the correlations among alteration of the cortical morphology,the BP level and cognitive function.It is hopeful that the results of this research can provide some enlightments about the pathogenesis of VCI and Va D in hypertensive patients.Methods: This study recruited 71 subjects in all from Jan 2017 to Dec 2018 in Nanjing Drum Tower Hospital,which including 23 patients in the hypertension with normal cognition(HTN-NC)group,24 patients in the hypertension with cognitive impairment(HTN-CI)group and 24 subjects in the control group with normal cognition.All the subjects performed the magnetic resonance scanning and accept the cognitive scales assessment.The hypertensive patients went through 7 days of successive BP measurement,the related BP indexes were calculated afterwards.In order to find out the group differences,the cortical morphology of the three groups were analyzed by Free Surfer.Meanwhile,the correlation analysis and the mediation analysis among BP,cognition and CTh/SA variations were conducted.Results: When compared with the control group,the CTh of left lingual gyrus increase in the HTN-NC group while the CTh of right postcentral gyrus decrease in the HTN-CI group(Monte Carlo simulation multiple comparison correction,P < 0.05).The SA of left superior frontal gyrus and left inferior parietal lobe were larger in the HTN-CI group than those in the HTN-NC group.The SA of left superior frontal gyrus and the right caudal middle frontal gyrus also enlarged in the HTN-CI group in contrast to the control group.The SA of left superior frontal gyrus in the HTN-CI group showed a positive correlation with the Z score of working memory(r = 0.495,P = 0.037).However,the SA of left superior frontal gyrus in the HTN-NC group related to the Z score of working memory negatively(r =-0.447,P = 0.045),the SA of right caudal middle frontal gyrus also presented a negative correlation with Mini-mental State Examination score(r =-0.438,P = 0.047).The CTh of hypertensive patients were positively correlated with mean BP indexes,the related regions of interests mainly located in the right lateral occipital gyrus.The CTh of right lateral occipital gyrus and right insular lobe became the main mediators of in the mediation analysis of mean arterial pressure and mean diastolic pressure.Conclusion: The variation tendency is different between the hypertensive patients with and without cognitive impairment(CI).The SA of left superior frontal gyrus enlargement may become the characteristic imaging biomarker about the hypertension related CI.The CTh of right lateral occipital gyrus is related to the BP level,the diastolic BP fluctuation could be able to influence the cognitive function through the its effect on the CTh of right lateral occipital gyrus.The low blood pressure in elderly age of hypertensive patients could be one of the risk factor that lead to cognitive impairment.