Human basilar artery: morphology & variations

Introduction: Basilar artery is an unpaired medium-sized artery formed by the confluence of right and left vertebral arteries at the pontomedullary junction and extends to the pontomesencephalic junction. It forms the spine of posterior cerebral circulation which is constituted by the vertebrobasilar system and its branches. Normal morphology of the basilar artery forms an essential component of cerebral circulation. The present study aims to measure the level of formation & termination, length, diameter, and angle of formation of the basilar artery. The data presented are relevant to understanding human variations and would be a good anatomical reference for clinicians, anatomists, and medical students. Caliber, length, and angle of bifurcation of the basilar artery help in assessing the feasibility and approach for various surgical procedures and predict cerebro-vascular diseases. Materials & methods: 96 adult human brain specimens were studied. (78 male, 18 female) (Age range: 19–80 y; Average age: 47.66 y). Measurements were taken using Vernier calliper. Data was analysed using Microsoft Excel and SPSS software version 17. Results: The basilar artery was formed by the confluence of two vertebral arteries in all specimens extending from the pontomedullary junction to the pontomesencephalic junction in 2/3rd of the cases. The left vertebral artery was found to be dominant in 62.5% specimens. The basilar artery showed an average length of 3.1 cm (demonstrating positive correlation with age), average diameter of 3.6–3.9 mm at different levels, and average angle of formation as 65.38o in males and 62.22o in females. Fetal type posterior cerebral artery was noticed in 9.4% cases. 3.1% and 6.3% cases were seen on the right and left sides respectively. Basilar artery fenestration was noted in 2 percent specimens. Conclusion: Basilar artery morphology was studied in 96 human adult cadavers. Basilar artery formation and termination was normal in more than 2/3rd cases. Variations were noted in its origin, vessel hypoplasia, presence of fenestrations, and fetal patterns. The data obtained from this study are relevant for anatomists, medical students, interventional radiologists, and neurosurgeons.