Magnetic Resonance Angiography Study On The Correlation Of Posterior Communicating Artery Variation And Posterior Circulation Infarction

Objective:Feeding arteries in brain include anterior circulation (internal carotid artery systems) and posterior circulation (vertebral basilar arteries system). Posterior Circulation Infarction (PoCI) locates in areas of posterior circulation, and includes upper spinal cord, brain stem, cerebellum, thalamus, occipital lobe, and part of temporal lobe, showing complex and diverse clinical manifestations, with a mortality rate of 3.6% and serious disability rate of 18%. Though early diagnosis and treatment can improve prognosis of PoCI, patients are still highly likely to suffer from neurological deficit or disorder, which affect quality of life and leave a great burden to their family and to the whole society. Thus, research of PoCI is drawing more and more attention. The distribution of lesions in some patients with posterior circulation cerebral infarction do not match with lesions of blood supply arteries, or the imaging of vascular stenosis do not match with clinical manifestations in some patients with posterior circulation infarction, indicating vascular anatomical variations or compensatory collateral circulation influence the distribution of cerebral blood flow, which plays an important role in the pathophysiological process of posterior circulation cerebral infarction. Posterior communicating artery is the most important collateral artery because it communicates the blood of posterior circulation and anterior circulation. The posterior communicating artery influence blood flow compensatory due to variation, which was associated with the occurrence and outcome of posterior circulation cerebral infarction.With the people’s enhancement of health awareness, primary prevention of cerebral infarction has gained more and more importance, with the relationship between vascular morphological variation and cerebral infarction getting more interests from the research field. Using non-invasive examination in ruling out risk factors in vascular morphology has always been the heated research direction. Medical imaging has always been an important way to study morphology of posterior communicating artery. Morphology of posterior communicating artery can be detected by many imaging ways, including Digital Subtraction Angiography (DSA), TCD, X-ray computed tomographic angiography, magnetic resonance angiography, and based on the images, we can analyze lateral branch compensation ability. For Magnetic resonance angiography, there is no interference of ionizing radiation or bony artifact, can be used for accurate diagnosis for posterior circulation infarction after multi-sequence and multi-parameter imaging. Also, MRA examination can be done by various methods, making it the major way in non-invasive, safe and effective study of organization structure in posterior circulation and blood supply in living body, making great improvement of understanding of both areas. At present, there are three major ways in MRA examination of PCoA:three dimensional time of flight (3D-TOF), Phase contrast and contrast enhancement act. For imaging of cerebral vessels, posterior circulation infarction in particular,3D-TOF is the most easy in operation, with the most clear images and best repeatability, and therefore is regarded as the first choice of morphological examination.In the following paper, the author attempts to use noninvasive Three dimensional time-of-flight magnetic resonance angiography (3D-TOF-MRA) in identifying variation of posterior communicating artery (PCoA), so as to study the relationship between variation of PCoA and posterior circulation infarction (PoCI), and find risk factors of vascular form.Materials and Methods:Identified patients were underwent MRI and 3D-T0F-MRA scanning of the brain in affiliated Shunde First People’s Hospital of Southern Medical University between July 1,2014 and June 30,2015. According to the inclusion and exclusion criteria,181 of total of 776 patients were defined as PoCI (research group) based on 2010 Chinese guidelines for the patients with acute ischemic stroke treatment and 595 patients of non PoCI (control group). We detailedly performed to collect the gender, age, drinking, somking, hyperadiposis, hemicranias, hypertension, diabetes and hyperlipidemia and family history of stroke, as well as the outcomes of blood pressure, blood glucose and lipid in patients. All patients received their first MRI examination within 6 hours after onset of the disease. Patients underwent MRI with 3D-TOF-MRA in a 1.5-T system (PHILIPS, Intera Achieva 1.5T). Vascular imaging parameters:use T1-FFE sequence, Repetition time: (TR)26ms, Echo time:(TE) 6.9ms, matrix:576x576, (REC Voxel MPS)(mm):0.31/ 0.31/0.50, and sequence running time:5min30s. Primary dates were performed with graphic reconstruction that was computerized using Extended MR Workspace version. All data are also reconstructed with maximum intensity projection, and rotated 180°around horizontal and vertical axes for multi-angle observation.Vascular diameter and form were analyzed in PACS of affiliated Shunde First People’s Hospital of Southern Medical University. Evaluation and measurement of posterior communicating artery:in 3D TOF MRA image with maximum intensity projection, if there is clear starting and ending points in posterior communicating artery, the whole artery is judged to be normal. If there is no starting or ending points, or there are intermittent vascular images, it can be viewed as dysplasia when starting and ending points and the whole vascular image can be seen in raw image. If there is no image of the vessels or no starting or ending points can be seen, it is believed that there is no such a vessel. Posterior communicating arterie which was judged as normal had been measured only. The narrowing, starting and ending points of Posterior communicating arterie had been measure. Record mean as the measurements. Statistical analyses were calculated using software SPSS version 13.0. From images of 3D TOF MRA, PCoA can be divided into 6 anatomical subtypes and later summarized into 4 clinical subtypes. The four subtypes include:(1) Type A:unilateral and bilateral PCoA, with blood in such arteries flow not only to ipsilateral PCA, but also to opposite PCA or basilar artery under certain condition. Difference between unilateral and bilateral PCoA lies only in the size of effective shunt passage. (2) Type B:unilateral and bilateral embryonic PCoA with blood flow mainly comes from internal carotid artery and participation of different degree of vertebra-basilar artery. (3) Type C:normal PCoA, with its blood flows to ipsilateral PCA or BA, but not able to effectively compensate opposite PCA when unilateral embryonic PCA joins with opposite PCoA. (4) Type D:No PCoA or embryonic posterior artery exist with only BA supplies blood in posterior circulation and no blood exchange in anterior and posterior circulation. Microanatomy of cadavers show that Type D is the most common type and therefore used as reference group in the definition of categorical variables in the analysis of effects of other variation subtypes of PCoA on posterior circulation infarction.Use Pearson χ2 to compare gender distribution and morphological constitution of patients in both groups. Because the age distributions of patients in two groups are non-normality distributed and missing variance, Wilcoxon rank sum test is used here. Using ENTER, apply Logistic regression to analyze risk factors of posterior circulation cerebral infarction with clinical subtypes of PCoA, gender, age, hypertension, diabetes and hyperlipidemia as independent variables, and lesions of PoCI as dependent variables. When use clinical subtypes of PCoA as categorical variable, Type D (without either PCoA or FTP) is used as reference group in definition of categorical variables and compare using Indicator. Two-sided test is used in statistical inference, with P<0.05 being considered as statistically significant.Results:Study group (181 cases):age (67.1±11.61), median age 68, youngest 40 and oldest 90; 109 male patients and 72 female patients; 133 patients with hypertension,147 with hyperlipidemia and 108 with diabetes mellitus. When study group is compared to reference group, ratio difference of patients complicated with hypertension shows statistical significance, (χ2=19.725, P<0.001), with no statistical significance of age distribution, sex ratio, ratio difference of patients with hyperlipidemia or ratio difference of patients with diabetes mellitus is showed in the study. The total PCoA (included fetal origin of the posterior cerebral artery, FTP) from 776 patients was 581, with a mean of 1.67±0.47 mm (minimal,0.5mm) and 1.73±0.47 mm (minimal,0.6mm) in diameter of left and right, respectively. The constituent ratio of PCoA clinical subtypes between research group and control group was statistically significant difference (χ2=13.399, P=0.004). For the PoCI, hypertension (χ2=21.085, P<0.001) and hyperlipidemia (χ2=5.876, P=0.015), as well as the clinical subtypes of PCoA (χ2=11.406, P=0.010) are the risk factor. We further concluded that the clinical subtypes of PCoA, of which only type B (single or double sides of fetal origin of the posterior cerebral artery) as risk factor (χ2=4.233, P=0.040) that has more 65.4% risk of the PoCI than type D (neither has PCoA, nor fetal origin of the posterior cerebral artery).Conclusion:The 3D-TOF-MRA could be an effective and noninvasive method for identifying variation of PCoA, especially have a promotion value for sub-healthy crowd. Previous research studies have often shown that PCoA image characteristic can be systematically divided into 4 clinical subtypes. For risk factors of PoCI, FTP has more 65.4% than neither has PCoA; as did hypertension and hyperlipidemia could be an important risk factor of PoCI and primary prevention of PoCI must be done actively.