The morphometric analysis of the V2 and V3 segments of the vertebral artery: Normal values on MDCT
A potential hazard in midline posterior fossa craniectomy may be the injury of vertebral artery. That's why vertebral artery evaluation prior to surgery may prevent dangerous complications. Advancements in multidetector computed tomography (MDCT) have provided detailed demonstration of the vertebral artery at the craniocervical junction and its relationships with atlas and axis. We aimed to define the normal anatomic relationship of the V2 and V3 part of the vertebral artery on MDCT. In total, 33 patients underwent MDCT angiography scan with suspected cranial aneurysm. V2 and V3 segments of vertebral artery were evaluated. Eight measurements (B, C, D, E, G, H, X, and Y line) were taken from MDCT images. For B and C, a line initially passing through the body of axis and spinous process and determining the midline was formed. Then, the vertical distance of vertebral artery from the level of transverse foramen of axis and loop to this midline was measured. For D and G, the vertical distance of vertebral artery to the midline from the upper and lower margin levels of transverse foramen of atlas was measured after a line establishing the midline passing through the anterior and posterior tubercles of atlas was drawn first. For E, transverse diameter of vertebral artery was measured at the loop level of V2 segment. For H, the vertical distance at the point where vertebral artery entered dura in the line passing from the midline of foramen magnum at anteriorposterior plane was measured. For X and Y, two different points of horizontal part of the vertebral artery were determined. One of these two points was the lateral one which was the origin of the horizontal part in the transverse foramen, the other was the intersection point on atlas. Average distances for both sides from transverse foramen of the axis, the loop of axoatlantal part and the lower border of the atlas of the vertebral artery to the midline were 20.97mm on the right, 22.29mm on the left; 27.19mm on the right, 28.34mm on the left; and 25.75mm on the right and 27.21mm on the left, respectively. Average distances for both sides from the upper border of the atlas, and at its penetration through dura were 27.40mm on the right, 28.94mm on the left; and 10.90mm on the right and 10.93mm on the left, respectively. Distances between spinous process and intersection of vertebral artery with horizontal part were 35.79mm on the right and 36.63mm on the left laterally, and 22.27mm on the right and 22.62mm on the left medially. MDCT angiography is a powerful test to demonstrate the vasculature of the head and neck. Bony structures and adjacent vessel morphology can be evaluated by this technique. The evaluation of craniocervical region prior to surgery with MDCT may be helpful to avoid intraoperative vascular injuries.
morphometric analysis v3 segment vertebral artery mdct craniocervical junction v2 segment