E LETTERS TO THE EDITOR Section Editor: Lawrence Saidman
Safety of Interlaminar and Transforaminal Epidural Steroid Injections To the Editor
B
ased on the results of their study comparing the efficacy of lumbar epidural steroid injection via a parasagittal interlaminar approach with that following a midline interlaminar approach, Ghai et al.1 concluded that a lumbar transforaminal epidural steroid injection (TFESI) targeting the “safe triangle” does not guarantee safety due to potential radiculomedullary artery (Adamkiewicz artery) injury. While we agree with this conclusion, we respectfully disagree with the authors’ implied opinion that the parasagittal interlaminar approach may be safer than the approach following traditional TFESIs. At least 3 cases of lumbar paraplegia have been reported after interlaminar lumbar epidural steroid injections.2 The proposed mechanism is similar to that for paraplegia from a lumbar TFESI in which the epidural needle injured or penetrated the radiculomedullary artery and particulate corticosteroid was injected into the spinal canal with resultant spinal cord embolism and subsequent paraplegia. In fact, anatomic studies have demonstrated that after the radiculomedullary arteries enter the neuroforamina near the anterior aspect of the dorsal root ganglion and exiting nerve root,3,4 they often travel a distance superiorly and laterally in the lateral epidural space joining the anterior spinal artery which ultimately supplies the anterior 2/3 of the spinal cord. In addition, in about 63% of cadavers studied, there is a posterior branch of the radiculomedullary artery which supplies the dorsal aspect of the cauda equina.5 It is conceivable that the epidural needle might encounter the radiculomedullary artery in the lateral or in the midline posterior epidural space. In light of the radiculomedullary artery anatomical positions inside the spinal canal as described above, neither midline nor parasagittal interlaminar lumbar epidural steroid injections are completely risk-free with respect to potential needle vascular injury and paraplegia, particularly if particulate corticosteroids are used, as has been determined for TFESIs. Furthermore, Kambin’s triangle approach for TFESIs might be the safest of all approaches.6–8 Boqing Chen, MD, PhD Todd P. Stitik, MD Patrick M. Foye, MD Physical Medicine and Rehabilitation New Jersey Medical School Metuchen, New Jersey [email protected] REFERENCES 1. Ghai B, Vadaje KS, Wig J, Dhillon MS. Lateral parasagittal versus midline interlaminar lumbar epidural steroid injection for management of low back pain with lumbosacral radicular pain: a double-blind, randomized study. Anesth Analg 2013;117:219–27
236 www.anesthesia-analgesia.org
2. Thefenne L, Dubecq C, Zing E, Rogez D, Soula M, Escobar E, Defuentes G, Lapeyre E, Berets O. A rare case of paraplegia complicating a lumbar epidural infiltration. Ann Phys Rehabil Med 2010;53:575–83 3. Kroszczynski AC, Kohan K, Kurowski M, Olson TR, Downie SA. Intraforaminal location of thoracolumbar anterior medullary arteries. Pain Med 2013;14:808–12 4. Murthy NS, Maus TP, Behrns CL. Intraforaminal location of the great anterior radiculomedullary artery (artery of Adamkiewicz): a retrospective review. Pain Med 2010;11:1756–64 5. Rodriguez-Baeza A, Muset-Lara A, Rodriguez-Pazos M, Domenech-Mateu JM. The arterial supply of the human spinal cord: a new approach to the arteria radicularis magna of Adamkiewicz. Acta Neurochir (Wien) 1991;109:57–62 6. Park JW, Nam HS, Cho SK, Jung HJ, Lee BJ, Park Y. Kambin’s Triangle Approach of Lumbar Transforaminal Epidural Injection with Spinal Stenosis. Ann Rehabil Med 2011;35:833–43 7. Glaser SE, Shah RV. Root cause analysis of paraplegia following transforaminal epidural steroid injections: the ‘unsafe’ triangle. Pain Physician 2010;13:237–44 8. Zhu J, Falco FJ, Formoso F, Onyewu O, Irwin FL. Alternative approach for lumbar transforaminal epidural steroid injections. Pain Physician 2011;14:331–41 DOI: 10.1213/ANE.0000000000000009
In Response
W
e agree with Chen et al.1 that neither midline interlaminar nor parasaggital interlaminar approaches of epidural steroid injection are completely risk free with respect to potential needle-related vascular injury because of wide variation of spinal vascular anatomy. While we did conclude that the administration of epidural steroid injection was without complication with both parasaggital interlaminar and midline interlaminar approaches in our study subjects,2 this does not imply that complications cannot occur with these procedures. Our study was not powered to detect vascular complications with these procedures. What we implied in our article was that transforaminal epidural steroid injection is associated with higher incidence of catastrophic complication, and this is supported by literature. At least 18 cases of severe neurological damage and permanent paralysis are reported subsequent to transforaminal epidural steroid injection3 as compared with only 3 cases of paraplegia after interlaminar epidural steroid injection.4 Two of 3 patients reported with previous interlaminar epidural steroid injection, had prior spine surgery at the level of the interlaminar injection,4,5 and in one of the cases, a 21-gauge IM needle was used.4 Postsurgical changes in the epidural space and arterial spinal vasculature4,5 and the use of IM needle might have contributed to this complication.4 Also, the overall rate of intravascular injection with lumbosacral transforaminal epidural steroid injection is reported to be 11.2%6 as compared with 1.9% after interlaminar epidural steroid injection.7 We clearly mentioned in the introduction of our article that “there are concerns regarding the safety of the transforaminal route, and there is a search for a technically better route with fewer complications for drug delivery into the ventral epidural space.”2
January 2014 • Volume 118 • Number 1
Safety of Interlaminar and Transforaminal Epidural Steroid Injections To the Editor
B
ased on the results of their study comparing the efficacy of lumbar epidural steroid injection via a parasagittal interlaminar approach with that following a midline interlaminar approach, Ghai et al.1 concluded that a lumbar transforaminal epidural steroid injection (TFESI) targeting the “safe triangle” does not guarantee safety due to potential radiculomedullary artery (Adamkiewicz artery) injury. While we agree with this conclusion, we respectfully disagree with the authors’ implied opinion that the parasagittal interlaminar approach may be safer than the approach following traditional TFESIs. At least 3 cases of lumbar paraplegia have been reported after interlaminar lumbar epidural steroid injections.2 The proposed mechanism is similar to that for paraplegia from a lumbar TFESI in which the epidural needle injured or penetrated the radiculomedullary artery and particulate corticosteroid was injected into the spinal canal with resultant spinal cord embolism and subsequent paraplegia. In fact, anatomic studies have demonstrated that after the radiculomedullary arteries enter the neuroforamina near the anterior aspect of the dorsal root ganglion and exiting nerve root,3,4 they often travel a distance superiorly and laterally in the lateral epidural space joining the anterior spinal artery which ultimately supplies the anterior 2/3 of the spinal cord. In addition, in about 63% of cadavers studied, there is a posterior branch of the radiculomedullary artery which supplies the dorsal aspect of the cauda equina.5 It is conceivable that the epidural needle might encounter the radiculomedullary artery in the lateral or in the midline posterior epidural space. In light of the radiculomedullary artery anatomical positions inside the spinal canal as described above, neither midline nor parasagittal interlaminar lumbar epidural steroid injections are completely risk-free with respect to potential needle vascular injury and paraplegia, particularly if particulate corticosteroids are used, as has been determined for TFESIs. Furthermore, Kambin’s triangle approach for TFESIs might be the safest of all approaches.6–8 Boqing Chen, MD, PhD Todd P. Stitik, MD Patrick M. Foye, MD Physical Medicine and Rehabilitation New Jersey Medical School Metuchen, New Jersey [email protected] REFERENCES 1. Ghai B, Vadaje KS, Wig J, Dhillon MS. Lateral parasagittal versus midline interlaminar lumbar epidural steroid injection for management of low back pain with lumbosacral radicular pain: a double-blind, randomized study. Anesth Analg 2013;117:219–27
236 www.anesthesia-analgesia.org
2. Thefenne L, Dubecq C, Zing E, Rogez D, Soula M, Escobar E, Defuentes G, Lapeyre E, Berets O. A rare case of paraplegia complicating a lumbar epidural infiltration. Ann Phys Rehabil Med 2010;53:575–83 3. Kroszczynski AC, Kohan K, Kurowski M, Olson TR, Downie SA. Intraforaminal location of thoracolumbar anterior medullary arteries. Pain Med 2013;14:808–12 4. Murthy NS, Maus TP, Behrns CL. Intraforaminal location of the great anterior radiculomedullary artery (artery of Adamkiewicz): a retrospective review. Pain Med 2010;11:1756–64 5. Rodriguez-Baeza A, Muset-Lara A, Rodriguez-Pazos M, Domenech-Mateu JM. The arterial supply of the human spinal cord: a new approach to the arteria radicularis magna of Adamkiewicz. Acta Neurochir (Wien) 1991;109:57–62 6. Park JW, Nam HS, Cho SK, Jung HJ, Lee BJ, Park Y. Kambin’s Triangle Approach of Lumbar Transforaminal Epidural Injection with Spinal Stenosis. Ann Rehabil Med 2011;35:833–43 7. Glaser SE, Shah RV. Root cause analysis of paraplegia following transforaminal epidural steroid injections: the ‘unsafe’ triangle. Pain Physician 2010;13:237–44 8. Zhu J, Falco FJ, Formoso F, Onyewu O, Irwin FL. Alternative approach for lumbar transforaminal epidural steroid injections. Pain Physician 2011;14:331–41 DOI: 10.1213/ANE.0000000000000009
In Response
W
e agree with Chen et al.1 that neither midline interlaminar nor parasaggital interlaminar approaches of epidural steroid injection are completely risk free with respect to potential needle-related vascular injury because of wide variation of spinal vascular anatomy. While we did conclude that the administration of epidural steroid injection was without complication with both parasaggital interlaminar and midline interlaminar approaches in our study subjects,2 this does not imply that complications cannot occur with these procedures. Our study was not powered to detect vascular complications with these procedures. What we implied in our article was that transforaminal epidural steroid injection is associated with higher incidence of catastrophic complication, and this is supported by literature. At least 18 cases of severe neurological damage and permanent paralysis are reported subsequent to transforaminal epidural steroid injection3 as compared with only 3 cases of paraplegia after interlaminar epidural steroid injection.4 Two of 3 patients reported with previous interlaminar epidural steroid injection, had prior spine surgery at the level of the interlaminar injection,4,5 and in one of the cases, a 21-gauge IM needle was used.4 Postsurgical changes in the epidural space and arterial spinal vasculature4,5 and the use of IM needle might have contributed to this complication.4 Also, the overall rate of intravascular injection with lumbosacral transforaminal epidural steroid injection is reported to be 11.2%6 as compared with 1.9% after interlaminar epidural steroid injection.7 We clearly mentioned in the introduction of our article that “there are concerns regarding the safety of the transforaminal route, and there is a search for a technically better route with fewer complications for drug delivery into the ventral epidural space.”2
January 2014 • Volume 118 • Number 1
