Medial loop of v2 segment of vertebral artery causing compression of proximal cervical root

Abstract

Objective: It is rare that the medial loop in the V2 segment of the vertebral artery (VA) causes compression of the proximal cervical root of the spinal cord without leading to bony erosion and an enlarged foramen. We evaluated the clinical significance and incidence of the medial loop in the V2 segment of the VA.

Methods: We reviewed the records from 1000 consecutive patients who had undergone magnetic resonance imaging evaluation of the cervical spine between January 2005 and January 2008. The inclusion criteria were that over a third of the axial aspect of the VA located in the intervertebral foramen was inside the line between the most ventral points of the bilateral lateral mass, and that the ipsilateral proximal root deviated dorsally because of the medial loop of the VA. We excluded cases of bone erosion, a widened foramen at the medial loop of the VA, any bony abnormalities, tumors displacing VA, or vertebral fractures. The medical records were reviewed retrospectively to search for factors of clinical significance.

Results: In six patients (0.6%), the VA formed a medial loop that caused compression of the proximal cervical root. One of these patients had the cervical radiculopathy that developed after minor trauma but the others did not present with cervical radiculopathy related to the medial loop of the VA.

Conclusion: The medial loop of the VA might have a direct effect on cervical radiculopathy. Therefore, this feature should be of critical consideration in preoperative planning and during surgery.

Keywords: Medial loop; Spine; Vertebral artery.

Fig. 1

This picture shows a transaxial section at the level of intervertebral disc. Over a third of the axial aspect of left vertebral artery located in the intervertebral foramen is inside the dotted line between most ventral points of bilateral lateral mass.

Fig. 2

Medial loop of vertebral artery on MRI scans. T2-weight sagittal MRI section shows a disappearance of vertebral artery at the level of the C3-4 foramen (white arrow) (A). T2-weight axial MRI scans show a abnormal position of the vertebral artery leading to compressing of the left C4 root at the level of the C3-4 foramen (white arrow) (B) and normal position of vertebral artery at the level of the C4-5 foramen (white arrow) (C).

Fig. 3

The vertebral arteries form medial loops into intervertebral foramens and compress the proximal cervical roots (arrow). Upper and lower rows indicate the axial and sagittal section of T2 weight image in MRI scans. Fig. 3A to E corresponds with cases 2 to 6.