Study On The CTA Feature And Clinical Implication Of Accessory Middle Cerebral Artery

Objective : To investigate the Computed Tomography Angiography(CTA)findings of the accessory middle cerebral artery(AMCA) and to discuss its image classification, gender difference, the relationship between the AMCA and the leptomeningeal anastomoses(LMAs), and the clinical value. To investigate and analyze the epidemiology of the AMCA. To estimate the diagnostic value and clinical significance of AMCA with CTA.Methods:45 patients with AMCA(group AMCA)were enrolled in a total of 2489 patients, who had been examined by CTA in our hospital between January 2011 and December 2014. At the other hand, 65 patients associated with LMAs(group LMAs) and severe stenosis or occlusion of ipsilateral middle cerebral artery( IMCA) diagnosed by CTA were enrolled. All of them examined by CT scan or MRI. Retrospectively analyzed the image and clinical data of the 45 cases(group AMCA).The original raw data were post-processed to obtain the 3D reconstruction images with volume rendering(VR) and maximal intensity projection(MIP) techniques. The imaging characteristics of the artery were analyzed by two senior doctors observing the images blindly. Firstly we reviewed the diagnosis, secondly, we investigated epidemiological study(including the point of origin,incidence, gender,classification and so on),at last,we analyzed the divergence and occasions. Analyzing whether there was difference between male and female associated with the AMCA,when the middle cerebral artery was stenotic at different degrees, and then discussing the occasions. Analyzing whether there were AMCA associated with the LMAs, when the middle cerebral artery were steno-occlusive lesions, and then discussing the reasons. Finally, to discuss the relation between group AMCA or group LMAs and the cerebral infarction. The data were analyzed by using SPSS 16.0. Presence percentage comparison between different groups were made by using the test, the significance level is 0.05。Result:1 2489 cases of patients with 47 AMCAs found in 45 cases(one patient had two AMCAs on each side and one patient had two AMCAs on the left), 31 men and 14 woman,representing an incidence of 1.80%.There were 27 cases at the left side and 18 at the right. 5 cases of these arteries arised from the ICA at the proximal point of bifurcation, 18 cases arised from the proximal portion of the ACA,4 cases arised from the distal portion of the A1 segment of the ACA near the anterior communicating artery(ACo A),whereas 20 cases arised from the proximal portion of the A2 segment of the ACA.2 All AMCAs followed a course parallel to the main middle cerebral artery(MCA),and reaching the parietal lobe at last with the artery of cortical territory originates from the MCA. The AMCA supplied the cortical territory of the orbitofrontal and/or prefrontal arteries,while the DMCAs supplied the cortical territory of the temporopolar and the anterior temporal and/or middle temporal arteries.3 32 cases of these arteries were slim,including 8 cases associated with severe stenosis of IMCAs,17 cases associated with occlusion of IMCAs which involved in 1 cases of moyamoya disease;2 cases with IMCAs aplasia, including one patient had two AMCAs arises from the ICA at the proximal point of bifurcation and the proximal portion of the A2 segment of the ACA;5cases with usual caliber and smooth vessels of IMCA, one patient had two slim AMCAs originates from the proximal portion of the A2 segment of the ACA at each side. 13 cases of these arteries were not slim, including 2 cases associated with occlusion of IMCAs. On the other hand,8 cases in 45 cases associated with occlusion of the distal portion of the M1 segment of the IMCAs,while the M3 segment of the IMCA were unobstructed, and AMCAs appeared but no LMAs. Both AMCAs and LMAs can be seen in the other cases with severe stenosis or occlusion of IMCAs.4 AMCAs appeared 15 cases with the fenestration located on the anterior communicating artery,including the three variants of the anterior cerebral artery associated with moyamoya.5 By using fourfold table chi-square test, there was significant statistically difference between male and female(P<0.05), when the rate of stenosis of MCA is greater than70%, the incidence of male was 77.4% which was significantly higher than the group of stenosis of MCA less than 70%(22.6%).6 We divided 29 patients of group AMCA into severe stenosis group(70≤stenosis rate≤99%) and occlusion group(stenosis rate=100%),comparing the emergence rates of LMAs. There was significant statistically difference, by using fourfold table chi-square test. When the rate of stenosis of MCA is 100%, the incidence of LMAs was 90.5% which was significantly higher than the group of severe stenosis of MCA(25%).7 94 patients with severe stenosis or occlusion of MCA,dividing into group AMCA and group LMAs,observing whether there was cerebral infarction in territory of MCA.compared.Cerebral infarction cases between AMCA( including simple AMCA and AMCA coexist with LMAs) and LMAs. P<0.05 was statistically significant.AMCA open group compared with LM open group,the incidence of cerebral infarction decreaced.Conclusions:1 CTA has high research value of AMCA,it can be used as AMCA large sample surveys and research methods.2 The clinical manifestation and collateral circulation have a close relationship in the patients who had severe stenosis or occlusion of MCA.Secondary collateral circulation may play a compensatory role. Compensatory blood that came from AMCA and LMAs can reduce the incidence of cerebral infarction.3 General epidemiological survey of AMCA at home and abroad are not consistent. When IMCA was severe stenosis or occlusion that AMCA commonly occured in our study, while it appeared when the aneurysmruptured at abroad.We need additional investigation to get closer to the real epidemiological data.