Vertebral artery position in the setting of cervical degenerative disease: implications for selective cervical transforaminal epidural injections

Abstract

Cervical transforaminal epidural injections (C-TfEI) are commonly performed in patients with cervical radiculopathy/pain. C-TfEIs are typically performed without incident but adverse events can occur. Using CT-fluoroscopy-guided C-TfEI, we commonly observe the vertebral artery in proximity to the target injection site. The purpose of this study was to assess the position of the vertebral artery relative to the typical C-TfEI injection point. CT-fluoroscopy-guided C-TfEIs were performed at 70 levels in 68 patients with radiculopathy/neck pain (age range 19-83 yrs, mean 50.6 yrs). Degenerative neural foraminal narrowing at each level was characterized (normal-to-mild, moderate, severe). Vertebral artery position was categorized as: anterior (normal), partially covering neural foramen, complete/near-complete covering the neural foramen. Additional measured variables included angle of needle trajectory, foraminal angle, and whether or not needle trajectory intersected with the vertebral artery. Foraminal vertebral artery covering correlated with severity of foraminal degenerative narrowing (p=0.003). Complete/near-complete covering was seen in: 65% severely narrowed foramina, 30% moderately narrowed foramina and 10% normal/mildly-narrowed foramina. Needle trajectory intersected with the vertebral artery in 30 of 70 injections (46%) by CT-fluoroscopy, frequently associated with shallow (lateral) approaches. Foraminal angle, approximating oblique fluoroscopic technique, suggests needle trajectory intersection with the vertebral artery in 27 of 70 foramina (39%). Vertebral artery position is commonly displaced into the foramen in patients with advanced cervical degenerative disease. Operator awareness of altered vertebral artery position is important for determination of optimal needle trajectory and tip placement prior to injection in patients undergoing C-TfEI.

Keywords: cervical nerve root block; cervical radiculopathy; cervical spine; cervical transforaminal epidural injection; computed tomography; neck pain.

Figure 1

Axial non-enhanced CT images in three patients demonstrating examples of neural foraminal grading. A) Normal to mild degenerative narrowing. B) Moderate degenerative narrowing. C) Severe degenerative narrowing.

Figure 2

Axial non-enhanced CT images in three patients prior to CNRB illustrating vertebral artery position. A) Normal vertebral position. B) Partial coverage of the lateral aperture of the foramen. C) Complete/near-complete coverage of the foramen.

Figure 3

43-year-old woman with right neck pain radiating to the proximal right upper extremity referred for right C5 NRB. Axial CT image during the process of CT-fluoroscopy guided needle placement at the level of the right C4/5 neural foramen demonstrates intersection of the needle trajectory with the vertebral artery as demonstrated by streak artifact (solid arrow). Of note, the position of the carotid sheath (dashed arrow) influences the available trajectory angle such that avoidance of the sheath requires a more shallow approach.