How are thoracic epidural nerve blocks administered for pain management?

Updated: Jun 19, 2018
  • Author: Anthony H Wheeler, MD; Chief Editor: Meda Raghavendra (Raghu), MD  more...
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Answer

Answer

Transforaminal thoracic corticosteroid epidural injections are performed using the prone paravertebral. Although some experienced pain practitioners perform this technique described above using fluoroscopic guidance to aid in accurate needle placement and to reduce the risk of injury due to needle placement. It is also requisite for documenting the validity of therapeutic or diagnostic injections. With the patient in the prone position on the fluoroscopy table, the end plates of the affected vertebra are aligned or squared up on fluoroscopy. The fluoroscopy beam is rotated to a more ipsilateral oblique position to bring the images of the spinous process and head of the ribs medially.

A "magic box" consisting of the superior end plate, the inferior end plate, the lamina or lateral pedicle lines, and the rib head are visualized. This "magic box" represents the target for needle placement. A skin wheal of local anesthetic, antiseptically prepared, is placed at a point overlying the above mentioned box that corresponds to the inferior aspect of the foramen. A 25-gauge or 22-gauge, 3.5-inch spinal needle is placed through the previously anesthetized area and advanced until the tip is near the level of the posterior elements.

Care is taken to ensure that the needle tip does not stray laterally (pleura) or medially (spinal cord). Lateral fluoroscopy is used to view and advance the needle tip into the foramen. AP fluoroscopy is used for guidance of the needle tip to pass just medial to the lateral laminar border. Insertion of the needle past the foramen produces entry into the intervertebral disc.

After satisfactory needle position is confirmed, 0.2-0.4 mL of contrast medium suitable for subarachnoid use is gently injected under active fluoroscopy. The contrast may be seen to flow into the epidural space, with some flow distal along the nerve root sheath. On the lateral view, the foramen can be seen to be filled with contrast and a cross section of the nerve root is identified. The injection of contrast should be immediately stopped if the patient complains of significant pain upon injection.

After a satisfactory pattern is observed, and no evidence of subdural, subarachnoid, or intravascular spread of contrast is observed, 3-6 mg of betamethasone solution or 20-40 mg of methylprednisolone or triamcinolone 20-40mg suspension with 0.5-1.5 mL of 2-4%, preservative-free lidocaine is slowly injected. Injection of the local anesthetic and/or steroid should be discontinued if the patient complains of any significant pain on injection, although transient pressure paresthesia is often appreciated.

After satisfactory injection of the local anesthetic and/or steroid, the needle is removed and pressure is placed on the injection site. This technique may be repeated at additional levels as a diagnostic and/or therapeutic maneuver.


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