Measurement of basilar artery bending and elongation by magnetic resonance cerebral angiography: relationship to age, sex and vertebral artery dominance.

Elongation and bending of the basilar artery are frequently observed in both normal and pathological subjects. However, their mechanism of generation remain unclear. In the present study, we measured basilar arteries in patients and normal subjects using magnetic resonance angiography (MRA) and estimated the relationships between these anatomical changes and some factors such as age, sex and vertebral artery dominance. A total of 510 subjects underwent MRA. Basilar artery length (BAL), bending length (BL), or side of bending of basilar artery was estimated on the plain images including the basilar artery in two groups with and without vertebral union. BAL was longer in males than in females (P = 0.0009) and correlated with age (P < 0.0001) in the population with vertebral union, while BL did not differ between genders and was not correlated with age in this population. Both BAL and BL were longer in subjects with vertebral artery dominance than in subjects with equivalent-sized vertebral arteries in the population with vertebral union (P < 0.0001 and P = 0.0005). No difference in the frequency of basilar artery bending was observed between males and females and no correlation was observed between the frequency of basilar artery bending and ages in subjects without vertebral artery union. A significant negative correlation between the side of bending of the basilar artery and dominant side of vertebral arteries was found for group of all patients (P < 0.0001). BAL growth may mainly depend on aging, and the presence of vertebral artery dominance may contribute to the growth of BAL while BL growth may depend on vertebral artery dominance mainly in the contralateral direction.