| Watershed infarction is a cerebral infarction occurred between the areas adjacent to the marginal zone. The incidence of it accounts for 10% of all cerebral infarctions. As the ischemic neurological symptoms induced by WSI are more minor or asymptoms, therefore the rate of treatment is lower, the real incidence may be greater.The occurrence of WSI has multiple relative factors. In recent years, studies have shown that the occurrence of watershed infarction is no longer the result of one single factor, but rather the interaction between the various factors, the formation of a variety of factors have led to occurrence of hemodynamic. What are the most fundamental role in the occurrence and development of WSI are that the most fundamental low blood perfusion caused by vascular stenosis and micro-emboli. The changes of cerebral hemodynamic might cause compensatory changes in blood flow of adjacent zone , it is known as the establishment of collateral circulation. when the collateral circulation is sufficient to maintain the cerebral perfusion ,no cerebral lesions can happen,whereas when the collateral circulation compensatory capacity is poor, the cerebral vascular regulatory function of this imbalance will lead to the occurrence of ischemic lesions. The degree of stenosis and collateral circulation will affect the location and degree of ischemia occurred. Ischemic cerebro- vascular risk factors play different roles in the occurrence and development course of WSI through different mechanisms.Intracranial hemodynamic instability can lead to the repeated occurrence of WSI, causing worse symptoms of neurological impairment, resulting in higher nervous functions such as computing power, memory, intelligence decreased, the result affects people's quality of life. We can produce better treatment and prognosis assessment through monitoring the intracranial hemodynamics of patients with WSI. However, ongoing monitoring methods of intracranial hemodynamic parameters, such as the objective examination PET, SPECT, DSA and others have not yet fully universal in our country, and subjecting to economic conditions, these methods can not be widely accepted. In contrast, TCD and the CDFI are the important non-invasive detection methods of hemodynamic assessment, indicators for monitoring blood flow velocity and blood flow spectrum and changes in lumen can reflects the degree of blood vessels narrow, plaques and hemodynamic changes after the existence of collateral circulation caused by vascular leisions. Therefore ,it can assess and describe the severity and location of ?the lesion accurately in the early stage of the disease. It can also reflect the compensatory likelihood and type of collateral circulation, and thus to an objective evaluation of the intracranial self-regulatory mechanisms. For the current days, it is an universal application of a simple and convenient way.91 cases with WSI in our hospital in from March 2009 to December 2009 and 20 casea with a large area cerebral infarction or brain stem infarction and 32 cases with asymptoms of lacunar infarction during the same period are chosen in our study. The gende and age of the patients are similar. All of them carried out on the TCD and CDFI examination, at the same time according to the need account for CTA, MRA, DSA and so on. The basic characters of their blood vessels, such as blood vessels narrow, small plaques, Willis ring compensatory hemodynamics and collateral circulation and then opening them up a statistical analysis, all of the data apply SPSS16.0 package for processing, x±s is applied for quantitative data, t test is applied in the test of significance of mean number, frequency distribution using X2 test. the correlation between the establishment of collateral circulation and stroke risk factors (hypertension, high blood lipids, high blood sugar, etc.), aortic stenosis, plaque and so on ,using Logistic regression analysis.Studies have shown that: the incidence of stenosis with WSI is 81.3%, which is greater than the incidence of stenosis with non-WSI ,38.5%. The incidence of vascular steosis of cortical and subcortical watershed infarct were 90.3%, 75.0%, the occurrence of watershed infarction is significantly related with the vascular stenosis (P <0.01), the blood vessels narrow and different infarction formation type of WSI are no correlation (P> 0.05), Willis ring compensatory collateral circulation and the formation of the watershed is no correlation, but associated with the sub-type of WSI. the rate of atherosclerotic plaques in the WSI is 75.8%, the occurrence of watershed infarction is related with the formation of tiny plaques (P <0.05), high blood sugar is the most risk factor with the occurrence of WSI, atherosclerotic plaque is the major risk factors with arterial stenosis,.Normally, left and right anterior cerebral artery, middle cerebral artery, and posterior cerebral artery blood flow velocity was no difference (P> 0.05), in WSI patients with internal carotid artery or middle cerebral artery stenosis, cerebral artery blood flow velocity of the anterior cerebral artery middle cerebral artery, posterior cerebral artery blood flow velocity on the lesion side are significantly higher than the contralateral lesions (P <0.05), also,in the affected side, the posterior cerebral artery blood flow velocity is higher than the contralateral (P <0.01).To sum up, the following conclusions can be drawn: low blood perfusion caused by vascular stenosis, and minimal plaque formation are correlative factors in the occurrence of watershed infarction. Willis ring compensatory hemodynamic is the first collateral circulation after ischemia with carotid artery or middle cerebral artery stenosis .it doesnot has relative with the occurrence of watershed infarction , but with its sub-type. Among the many cerebrovascular risk factors, high blood glucose has high relevance with the watershed infarction. After the intracranial arterial stenosis or occlusion, the establishment of intracranial collateral circulation may lead to compensatory blood flow to add the cerebral perfusion. When the vascular blood velocity difference of collateral circulation between affected side and contrallateral side is smaller,it presents that the capacity of collateral circulation is strong, whereas the difference is larger, the collateral circulation is on behalf of the poor compensation. we can use TCD and CDFI apply objective assessment of intracranial collateral circulation and the compensatory ability of them, then we can better use them to guide clinical diagnosis and treatment. |
