Toward improving the safety of transforaminal injection.

James P. Rathmell, MD*† Transforaminal injection of steroids has emerged as a common technique for the treatment of acute radicular pain associated with intervertebral disk herniation. In contrast to placing steroid in the epidural space using a standard, midline approach between adjacent laminae (the “interlaminar” approach), the transforaminal technique uses a needle that approaches the posterolateral aspect of the intervertebral foramen and places the steroid directly adjacent to the affected spinal nerve at the site of inflammation. The concept is to inject the steroid solution directly at the target site in high concentration. There are limited data suggesting that the efficacy of steroid placed via a transforaminal approach is superior to that of the same steroid placed via an interlaminar approach. In recent years, catastrophic neurologic complications have been reported after transforaminal injection of steroids. After cervical transforaminal injection: spinal cord infarction resulting in quadriplegia, cortical blindness, and fatal strokes in the territory of the posterior cerebral circulation; after lumbar transforaminal injection: paraplegia resulting from infarction of the conus medullaris. The clinical suspicion has been that the mechanism of injury is ischemia caused by end-arteriolar occlusion after the inadvertent intraarterial injection of particulate steroid, which has been recently confirmed in a convincing study performed in large animals. It follows that the only safe manner to perform transforaminal injection using the common particulate formulations of steroid that have been used for this application is to devise a means to detect intravascular needle position before particulate steroid is injected, allowing the needle position to be adjusted to avoid intraarterial injection of even a portion of the injected steroid. Experts have recommended the use of radiographic contrast injected under continuous or “live” fluoroscopy with or without digital subtraction to detect intravascular needle position. In this issue, Kim et al. prospectively examined the frequency of intravascular injection using radiographic contrast injected under continuous fluoroscopy. What is most striking is that the incidence of intravascular injection that Kim et al. report is frighteningly high: 56 of 182 injections (30.8%) overall, 45 of 71 (63%) cervical, 11 of 110 (10%) lumbar with no blood flashback through the 21-gauge needle in 45 of 56 (80%) these cases. The incidence is markedly higher during cervical injections when compared with lumbar injections. Static fluoroscopic injections performed during and immediately after injection do not reliably detect intravascular injection in more than half of the cases. Simultaneous perineural spread and intravascular uptake frequently occurred (23 of 45 [52%] in cervical and 1 of 11 [9%] in lumbar injections), whereas pure vascular uptake occurred in 11.3% of cervical and 0.9% of lumbar injections, underscoring the need for a continuous fluoroscopy. However, something is curious: the authors tell us that they cannot distinguish between IV (benign) and arterial (potentially catastrophic) uptake. A previous report also did not discern between IV and intraarterial injection, finding a somewhat lower incidence of intravascular injection during cervical transforaminal injection (19.4% of 504 injections) and a similar rate during lumbar transforaminal injection (11.2% in a series of 761 injections). Clinical practice and a few sporadic observations suggest that From the *Division of Pain Medicine, Department of Anesthesia and Critical Care, and Pain Medicine, Massachusetts General Hospital; and †Department of Anesthesia, Harvard Medical School, Boston, Massachusetts. Accepted for publication March 9, 2009. Address correspondence and reprint requests to James P. Rathmell, MD, Department of Anesthesia and Critical Care, Massachusetts General Hospital, 55 Fruit St., GRB 444, Boston, MA 02114. Address e-mail to jrathmell@partners.org. Copyright © 2009 International Anesthesia Research Society