Epidural Corticosteroid Injections: Technical Considerations - Part C

Technical Considerations Continued ...

Transforaminal injections (Fig 5), preferred in many centers as the most specific and effective route for epidurals, are administered laterally through the selected neuroforamen under fluoroscopy, thus explaining the descriptive label "selective transforaminal epidural injection."(5, 20) This technique allows for smaller volumes of injectate since the medicine is placed closer to the site of pathology at the interface of the nerve root, the disc, and the ventral dura. Injectate tends to flow more ventrally or preferentially to the symptomatic side and along the involved nerve root. A smaller gauge needle is generally used with less risk of needle-related trauma including bleeding and a larger hole for leak if there is intrathecal puncture. The injection can provide additional physiologic information not uncovered from spinal imaging, electrodiagnostics, or from the physical examination of a patient. Pain reduction obtained from transforaminal epidural steroid injections can be helpful in identifying a pathologic segment or nerve root level causing pain extending into the extremities or even into the thoracic spine, flank, or abdomen when thoracic selective ESIs are performed (5).

Figure 5a

Figure 5b

Figures 5 (a-b). Figures a and b demonstrate the desired needle position for selective epidural blocks in the lumbar region. The injection can be performed with either a single-needle technique, often using a slight bend on the end of the needle, or a two-needle technique as shown above. In this case, a 18-gauge introducer needle was first advanced to contact the L5 transverse process. At this point, the needle was then directed slightly caudally but not advanced. Through the introducer needle, a 22-gauge needle with a slight distal curve was slowly advanced through the intertransverse membrane to lie at the 6 o’clock position of the pedicle. As shown in figures 5a and 5b, the needle is at the lower aspect of the pedicle, and this position will be just under the exiting L5 dorsal root ganglion. If the pedicle is viewed as a clock, the 6 o’clock position is directly under the pedicle. Contrast was then injected.

Figure 5c

Figure 5 (c). Injection of contrast outlines the dorsal root proximally within the epidural space. The dorsal root ganglion is contained within the foramen and usually bounded by the distal ventral ramus. In this case, a negative outline is seen with contrast surrounding the root. Typically, for a diagnostic block, 0.5 cc to 1 cc of local anesthetic such as 2% Xylocaine or 0.5% Sensorcaine is injected. For a therapeutic block, 2 cc is usually injected, consisting of an equal volume of Xylocaine and Celestone. Depo-Medrol should probably not be used proximal neural structures. Prophyline glycol is harmful to neural tissue. Celestone, however, has been shown in animal studies to be relatively innocuous if injected subarachnoid, as long as the total volume is less than approximately 2 cc or 12 mg.

Therapeutically, the selective administration of epidural corticosteroid at the presumed most symptomatic level can provide pain relief from neural irritation and inflammation which can allow a patient to progress in their conservative rehabilitation plan. This may include advancement in a progressive physical activity protocol as well as in spinal stabilization and strengthening exercises. Frequently, an irritative nerve injury cannot be visualized on imaging studies and may not be detectable with electrodiagnostics but may be identified with a positive response to a diagnostic selective nerve block / transforaminal epidural injection. The information obtained can be used for therapeutic non-operative or surgical intervention.