Transforaminal Epidural Block and Selective Nerve Root Block

Published on 10/03/2015 by admin

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Last modified 10/03/2015

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Chapter 6 Transforaminal Epidural Block and Selective Nerve Root Block

Transforaminal epidural block (TFEB) is defined as spread of an injectate through the epidural space as well as along the spinal nerve. It is used therapeutically because the injectate spreads into the anterior epidural space, which is the perceived target site of the disease. Local anesthetics with or without steroid can be used. TFEB injections can control inflammation and can stabilize sensitized nociceptive neural activity due to the many different pain sources originating in the spine.

TFEB requires a lower volume (1-3 mL) of injectate than conventional epidural block achieved by direct injection to the anterior epidural space. This smaller volume can decrease the toxicity from the injectate. No further injection is recommended if the first TFEB was not effective. If the initial response to TFEB is favorable but short-lived, a series of injections (3-6 times per year) or pulsed radiofrequency lesioning of the corresponding dorsal root ganglion (DRG) is recommended (see Chapter 7). The interval for sequential block varies from days to weeks for a series of injections.

Selective nerve root block (SNRB) is defined as spread of injectate not into the epidural space but along the spinal nerve. It is used for diagnostic purposes. SNRB can be used to define the source of pain and is especially useful when clinical findings and results of electrodiagnostic and imaging studies are equivocal. In addition, SNRB may be particularly useful in identifying the symptomatic level in patients with multilevel pathology.

Real-time fluoroscopic guidance during the injection of contrast material is essential. Provocation of paresthesia is not mandatory for SNRB. SNRB under fluoroscopic guidance or with use of a nerve stimulator guarantees a safe and precise block. Frequent checks of anteroposterior (AP) and lateral images with the fluoroscope are highly recommended to avoid direct trauma to spinal nerves.

Anatomy and procedures

Cervical Region

Anatomy

There are seven cervical vertebrae but eight cervical nerve roots. The first cervical nerve root is located between the occiput and the atlas, and each subsequent nerve root is located above its corresponding vertebra. If symptoms correlate with the seventh cervical nerve root, the C6-C7 foramen is the target for the block. The cervical neural foramen is a bony canal 4 to 5 mm long through which the cervical nerve roots pass anterolaterally (at about a 45-degree angle with respect to the coronal plane) and downward (at about a 10-degree angle with respect to the axial plane) (Figs. 6-1 to 6-4). Cervical spinal nerves from C3 to C7 exit the intervertebral foramen in the direction of the posterior, lower half of the foramen (Figs. 6-2 to 6-4). The cervical nerve roots occupy about one quarter to one third of the volume of the foramen and is accompanied by radicular arteries and veins (Figs. 6-1 and 6-2).

The vertebral artery at the caudal portion of the foramen is immediately anterior and medial to the ganglion (Figs. 6-1

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