| Objective:Vertebrobasilar system is the important portion of the intracranial blood supply system and the blood supply region of the vertebrobasilar system includes the occipital lobes,the posterior part of the temporal lobes,the cerebellum and the brainstem.The purpose of the study is to analyze the normal anatomical features,variations,diameter of the branches of intracalvarium of vertebrobasilar system and relation of the branches between different levels of age and gender with 3D-TOF MRA.Methods:1 120 normal volunteers underwent brain 3.0T MR T2-FLAIR examination and 3D-TOF MRA and the intracalvarium of vertebrobasilar vasculature of them were analyzed.In order to show the shape and relationship between the distribution of the blood vessels and vascular clearly,we made the MIP reconstruction and observed and recorded the normal anatomical features and variations of intracalvarium of vertebrobasilar system.2 The diameter of bilateral distal vertebral arteries,posterior inferior cerebellar arteries,anterior inferior cerebellar arteries,superior cerebellar arteries and posterior cerebral arteries were measured,and we analyzed significant statistical differences of the diameter of the vertebrobasilar system branches between different gender and levels of age(group 1 <45 years old,group 2 ≥45 years old).3 Dividing the basilar artery into proximal,middle and distal segment,the diameter of the proximal,middle and distal segment of basilar artery were measured and we analyzed significant statistical differences of the diameter between the three segments and the differences between gender.4 The PICA and AICA were classifed into 3 groups according to thediameters.For PICA,diamerters equal to or over 2mm,between 1 and 2mm,and equal to or lower than 1 mm were determined as well,moderate,and poorly developed,respectively.For AICA,diameters equal to or over 1.4 mm,between 1.4 and 0.9 mm,and equal to or lower than 0.9mm were determined as well,moderately and poorly developed,respectively.The development situation of PICA or AICA between absence and existence of ipsilateral AICA or PICA were analyzed.5 Vertebral artery hypoplasia(VAH)was defined by a diameter of <2mm or less 50% than the contralateral vertebral artery.The significant statistical differences of the VAH between left and right and different gender were analyzed.6 The patency of the bilateral posterior communicating arteries ratios were anaylzed between different gender and levels of age(group 1 <45 years old,group 2 ≥45 years old).Results:1 Our analysis results show that,the prevalence of anatomical variations of the intracalvarium of vertebrobasilar system was high.The most frequent variations was absence of the PICA,and there was no PICA in 25%(30/120)and 37.5%(45/120)of the cases on the left and right side,respectively.There was statistically significant different between absence of PICA on the left and right(P=0.037),and absence of right PICA was more frequent.There was no statistically significant different between absence of the left and right PICA in males and females(P =0.395,P =0.849).The second most frequent variations was absence of the AICA,and there was no AICA in 11.7%(14/120)and10.8%(13/120)of the cases on the left and right side,respectively.Some of the volunteers were abesenc of bilateral PICA(8 cases,6.7%)and AICA(5cases,4.2%).The duplication was found on the bilateral AICA and SCA,and we also found a case of double origin of the left PICA.In all of the cases,there were bilateral SCA and PCA.We found 3 cases and 1 case of the eraly bifurcation of SCA and anomalous origin of SCA,respectively.In 4 cases(3.3%)P1 segments of right PCA were absence and in these 4 cases PCA withfetal origin were demonstrated.At the same time,there were 9 cases(7.5%)and 5cases(4.2%)partial embryonic PCA on the left and right side,respectively.In 21cases(17.5%)and in 12 cases(10%)there were no left PCoA and right PCoA,respectively,and in 36 cases(30%)there were no bilateral PCoA.In our study,we demonstrated fenstration of the basilar artery in 8 cases(6.7%).2 There was no statistically significant difference between diameters of the distal VA,PICA,AICA,SCA,PCA in different gender and in different levels of age(P>0.05).3 There was stastically significant differece between diameters of basilar artery in distal segment,middle segment and proximal segment.The diameters of basilar arteries of males is bigger than females(P<0.05).4 In cases with absenct PICA or AICA on either side,there was ststistically significant moderately or well-developed ipsilateral AICA or PICA(P<0.05).5 Vertebral artery hypoplasia(VAH)was common(11.7%,14/120).There were 2 cases VAH on the left side and 12 cases VAH on the right side,respectively.The VAH was more frequent on the right side(P =0.006)and there was no stastically significant differece in males and females(P =0.540).6 The patency rate of bilateral PCoA in males and females was of no statistically difference,while there was statistically difference in different levels of age.The patency rate of bilateral PCoA in group 1(<45 years old)is bigger than in group 2(≥45 years old).Conclusion:1 The prevalence of anatomical variations of the intracalvarium of vertebrobasilar system was high and there were many types of variation.Only25% of the normal volunters met the well-known normal anatomy.The most frequent variations was absence of the right PICA.2 There was no statistically fignificant difference between diameters of the distal VA,PICA,AICA,SCA,PCA in different gender and in different levels of age.3 The diameters of basilar artery decrease from the proximal segement to the distal segment gradually and it is bigger in males than in females.4 In cases with absenct PICA or AICA on either side,the ipsilateral AICA or PICA had a certain amount of compensatory function.5 The VAH was more frequent on the right side and there was no stastically significant differece in males and females.6 The patency rate of bilateral PCoA is lower in the older people and there was no stastically significant differece in males and females. |
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