Selective Epidural Injection: Section 1

Precision Injection Techniques for Diagnosis and Treatment of Lumbar Disc Disease: Part 8

Spinal injectionAs is the case with the intervertebral disc, spinal nerves can be injected with contrast, local anesthetic, or other substances. Both the provocative response (pain occurring in response to a mechanical and/or chemical stimulus) and the analgesic response provide clinically useful information.

Nerve root blocks were first developed to diagnose the source of radicular pain when imaging studies suggested possible compression of several roots.

Derby, et al. Precision percutaneous blocking procedures for localizing spinal pain. Part 2: The lumbar neuraxial compartment. Pain Digest 1993;3:175-88. Ref’s 17-24.

Early studies on selective nerve root injections described an extraforaminal approach, in which a needle is advanced at right angles to the spinal nerve outside the neural foramen. Localization of the needle adjacent to the nerve relies on leg pain provocation, presumably resulting from penetration of the nerve by the needle.

Derby, et al. Precision percutaneous blocking procedures for localizing spinal pain. Part 2: The lumbar neuraxial compartment. Pain Digest 1993;3:175-88. Ref’s 17, 18, 19, 21.

A selective epidural injection is a variation of the selective nerve root injection. As the nerve roots leave the dura to enter the foramen and form the spinal nerve they carry an extension of the dura with them, which become the epineurium of the spinal nerve. The epineurium is in turn enveloped by an epiradicular membrane, which is an extension of the anterior and posterior epidural membranes.

Derby, et al. Precision percutaneous blocking procedures for localizing spinal pain. Part 2: The lumbar neuraxial compartment. Pain Digest 1993;3:175-88.

Injection of contrast into the epiradicular membrane will outline the nerve root, dorsal root ganglion, spinal nerve, and ventral ramus. Proximally, contrast will flow around the dural sac at the takeoff of the nerve root. If injected outside the epiradicular membrane contrast will spread diffusely in the epidural fat, and therefore be of limited diagnostic value.

Derby, et al. Precision percutaneous blocking procedures for localizing spinal pain. Part 2: The lumbar neuraxial compartment. Pain Digest 1993;3:175-88.

A selective epidural injection differs from a selective nerve root injection in that the goal is to inject into the epiradicular tissues. The spread of injected solutions will depend on the anatomy of the epiradicular membrane, which is an extension of the epidural space, leading to the term selective epidural injection.

Updated on: 01/28/16
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Selective Epidural Injection: Section 2
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