Study On Cerebral Autoregulation In Patients With Alzheimer’s Disease

BACKGROUNDAlzheimer’s disease is a degenerative disease of the nervous system with outstanding performance such as memory loss,aphasia,apraxia,misrecognition,impairment of visual space function,executive dysfunction,and personality and behavioral changes.It seriously affects the quality of patients’ daily life,and brings a heavy burden to the society and the family.As the aging population increase continually,the prevalence of AD increases significantly as a result.Nowadays,the diagnosis of AD is mainly based on clinical diagnosis,which is mainly assisted by various auxiliary examinations such as neuropsychology scale,imaging examination,neuroelectrophysiological examination,biomarker measurement,and genetic testing,etc.The current study confirms that the main pathological features of cerebral small vessel lesions in AD are cerebral amyloid angiopathy and microvascular degeneration.Therefore,changes in CA function caused by cerebral microvascular disease may be involved in the pathogenesis of AD.Usually,50-60 ml/min blood is needed in every 100 g brain tissue,although the brain only accounts for 2%of the total brain weight,but cerebral blood flow accounts for about 15%of cardiac output even at rest,and oxygen consumption accounts for 20%of total body oxygen demands.Brain is a high metabolic demand tissue,and in order to maintain a state of consciousness,it must obtain enough blood flow to ensure that energy and oxygen needs are met.Cerebral autoregulation(CA)is a mechanism of self-protection in the brain.It refers to the ability of maintaining the relative stability of cerebral blood flow via vasomotion of the cerebral blood vessels when the arterial blood pressure and cerebral perfusion pressure changes.Cerebral small vessels,especially small arteries,participate in the regulation of CA.Currently there are diverse methods in CA function researching,such as Kety-Schmidt,PET,SPECT,CT perfusion imaging,MRI perfusion imaging,Transcranial Dopple(TCD),etc.However,whether the change of CA function caused by cerebral small vessel disease is involved in the study of the incidence of AD is less.Currently,the function of CA is mainly detected by inducing changes in blood pressure,via TCD,in which the original method called thigh-sleeve bag compression method.The trouble is that the operation procedure is complicated and most patients are reluctant to accept.Fortunately,Supine-to-standing transcranial Doppler test is relatively simple and easy,non-invasive,more safety,and good patient coordination,especially suitable for the elderly population.As a result,this project intends to use Supine-to-standing transcranial Doppler test to evaluate the changes of CA function in AD patients.OBJECTIVETo evaluate the ability of autoregulation of cerebral blood flow in patients with AD by Supine-to-standing transcranial Doppler test.METHODS31 patients,aged over 65 years,who were diagnosed as very high risk of AD(according to the 2011 NINDS-ADRDA diagnostic criteria)in Qilu Hospital of Shandong University were enrolled in the test group.As a control,31 healthy individuals without cognitive impairment,aged 65 years or older,were enrolled at the same time.The general statistics of all subjects were collected,including gender,age,years of education,Mini-Mental state examina(MMSE)scores,and so on.All subjects underwent TCD examinations,Supine-to-standing transcranial Doppler test,and Supine-to-standing blood pressure monitoring test(brachial artery blood pressures were measured).All relevant parameters were recorded,including:cerebral blood flow velocity(CBFV)、cerebral blood flow velocity(PI)、Resistance index(RI)、time and W waves.SPSS24.0 data software was used for sample analysis.RESULTS(1)The maximum blood flow velocity,mean blood flow velocity,and minimum blood velocity of AD group and control group were used to calculate the rate of change of W-wave descending branch rate and the rate of change of W-wave rising branch rate which represent the ascending and descending branch slopes respectively.Statistical analysis showed significant differences(P<0.05).(2)There was no significant difference in blood flow velocity,pulse index(PI)and resistance index(RI)between the AD group and the control group in the supine position(P ≥ 0.05).(3)The W waves of the CBFV curves of the AD group and the control group all appeared.There was no significant difference in the Supine-to-standing blood pressure between the two groups(P ≥ 0.05).CONCLUSIONS(1)There is a difference in the curve of the velocity of cerebellar blood flow between the two groups of people.Consider the differences in the autoregulation function of cerebral blood flow between the two groups.The rate of change of W wave decline rate and the rate of change of W wave rising rate in patients with AD were significantly lower than those in the normal population.It is proved that the autoregulation of cerebral blood flow in patients with AD is different from that in the normal population,and it also shows that small blood vessels in the brain participate in the pathogenesis.(2)W wave time and the curve shape were normal in two groups,so the influence of autonomic nerves which may affect the results of this study is small.(3)Supine-to-standing transcranial Doppler test is a better way to assess the ability of cerebral autoregulation.