Clinical History
38-year-old male patient who complained of progressive low back pain radiating to the right lower limb with weakness, for a duration of 3 months. On physical examination, right-sided straight leg raising (SLR) test was positive and right extensor hallucis longus weakness was elicited.
Imaging Findings
After 4 weeks of medical management with physiotherapy, the patient did not have any significant symptomatic relief.
MR imaging showed a significant disc bulge at L45 level with root impingement. No abnormal cord/paraspinal soft tissue signals.
The patient underwent a foraminal block at right L4-5 level targeting the exiting L4 root. He had symptomatic relief with a visual analogue pain scale drop of 5 points (from 8 to 3) within 2 hours of the procedure.
On 4 month follow up, he had no pain with normal SLR.
Discussion
A. Background
CT-guided foraminal block (CTGFB) is an image-guided intervention that is useful for immediate pain relief and short-term pain relief. It is a valuable procedure that is a potential alternative to foraminotomy/discectomy. [1]
Technique: Pre-procedural history, consent and visual analogue scale (VAS) pain scale score are taken. Patients are placed in prone position within the CT gantry. Under sterile precautions, the predetermined tract of puncture is anaesthetised and a 21-gauge spinal needle (black-coloured hub) is used, and under CT imaging guidance the tip of the needle is placed within the inferior aspect of the foramen, immediately lateral to the exiting root. 2 ml of iodinated contrast (0.5 ml of 300 mg iodine/dL in 2 cc of distilled water or saline) is injected and check CT is done to look for epidural spill and peri-nerve root tracking of the contrast medium.
Finally, a mixture of 1 cc of bupivacaine and 1 cc of triamcinalone acetate (40 mg) is injected into the needle hub. The needle is then withdrawn and the puncture site is sealed off with a bandage.
The patient is asked to remain immobile for half an hour, and can be discharged from the day care unit after 2 hours of observation. Patients will usually have a VAS pain scale score drop of at least 3 points within 2 hours of the injection.
B. Clinical Perspective
Patients with LBP due to disc disease, who have had a failed trial of medical management/physiotherapy for 4 weeks. CTGFB is useful in this subset of patients.
C. Imaging Perspective
MR imaging is useful in finding out the level of disc disease. In many cases, the level of disc disease may not correspond to the pain dermatome, in which case clinical discretion is needed to determine level/side of intervention.
CT dosimetry is invaluable in reducing patient exposure, where up to 90% dose reduction can be achieved according to published reports. [1]
D. Outcome
CTGFB is a safe technique that can be done using safe approaches like Kambin’s technique that targets the inferior aspect of the foramen, and also by using non-particulate steroids, like dexamethasone. Aspiration prior to injection is an essential step in ensuring procedure safety. [1]
E. Teaching Point
CTGFB is a technically simple and safe procedure that provides effective immediate and short-term pain relief in patients with LBP due to disc disease not responding to conservative medical management.
Differential Diagnosis List
Short-term pain relief from lumbago using CT-guided foraminal block
Spondylodiscitis
Trauma
Final Diagnosis
Short-term pain relief from lumbago using CT-guided foraminal block
