Vertebral artery anatomical variations as they relate to cervical transforaminal epidural steroid injections

Objective: To identify and categorize anatomical anomalies of the vertebral artery and determine the relationship of these unexpected variations to the site for cervical transforaminal epidural steroid injections (CTESI). Design: The cervical region and course of the vertebral arteries was dissected in 10 cadavers. Anatomical anomalies of the vertebral arteries were identified and documented. Those that could increase the risk of intra-arterial injection during fluoroscopically guided procedures are detailed. Results: Twenty percent of vertebral arteries were found to have anatomical variations including accessory vessels and lateral loops. These variations placed arterial segments in a portion of the posterior neural foramen where they could be at risk for cannulation during CETSI. In addition, 20% of the vertebral arteries entered the transverse foraminal column at a level other than C6. Discussion: CTESI have become a mainstay in the treatment algorithm for painful cervical radiculopathy. Described techniques take extreme care to avoid cannulation of the vertebral artery during this procedure. Unexpected deviation of the artery, or an arterial segment, into the posterior neural foramen, the target zone for CTESI, increases the risk of intra-arterial cannulation during injection. Accordingly, the practitioner must be aware of variant anatomy of the vertebral artery and take all precautions to avoid potential complications that may arise as a consequence.