Cervical transforaminal injection and the radicular artery: Variation in anatomical location within the cervical intervertebral foramina

Background: Recent articles have detailed the adverse events associated with transforaminal steroid injections into the radicular arteries. Guidelines on strict transforaminal epidural techniques have been described to limit complications. There remains limited information regarding the cervical level of entry, location within the intervertebral foramina, and prevalence of the radicular arteries within the population. Methods: With the aid of premortem angiography and postmortem latex-injected vasculature, a single detailed cadaveric dissection was performed to elucidate the specific anatomic location of the radicular arteries within the intervertebral foramina and the anastomoses of the arteries to the anterior spinal artery. Results: Five radicular arteries (C5, C6, two at C7, C8) were traced entering the foramina either anteriorly or posteriorly to supply the anterior and posterior spinal arteries. Radicular arteries received blood supply from either the deep cervical (C8) or vertebral arteries. The C8 radicular artery entered the lateral aspect of the foramen and penetrated the dural sleeve within the inferior portion of the foramen, directly inferior to the exiting spinal nerve, to supply the anterior spinal artery. This artery was of a large enough caliber to be entered by a 22-gauge needle. Conclusions: A larger population is necessary to characterize the range of anatomic variations in arterial supply within the foramina. Available studies support the current technique of fluoroscopic needle insertion. Yet, there is wide anatomic variation in the origin and location of these vessels, and even with strict adherence to technique, it is feasible that a properly placed needle could penetrate a radicular artery.