Patients with Spinal Stenosis Can Benefit from Nerve BlocksDespite our many advances in medicine and especially all the improved technology, we still don't know what causes back pain for many people. And without an understanding of the cause, it is difficult to find an effective way to treat it. We do know now that some patients have back pain coming from the facet (spinal) joint(s). Using an injected anesthetic to the facet joint's nerve has confirmed that this area can be a pain generator. Once the nerve can no longer send signals to the spinal cord, then the pain stops. Destroying that nerve with heat using radiofrequency denervation relieves the pain permanently.
In this study, X-rays and MRIs were reviewed after patients who had both a nerve block and radiofrequency ablation (destruction) of the nerve. The authors were looking for any clue from the anatomy that might help point to those patients who will have a good response from nerve blocks and ablation. Radiologists who didn't know what treatment was done or what the results were (who got better, who didn't) looked at each of these areas: disc height, disc condition, vertebral alignment, facet joint space, and joint condition.
In particular, they were interested in knowing if the presence of decreased disc height might be a predictor of treatment success or failure. Secondly, they looked at stenosis (narrowing) of the spinal canal or of the intraforaminal spaces as a possible spinal pathology linked with joint pain. The intraforaminal space is a hole where spinal nerve roots pass through going from the spinal cord down to the leg. Sometimes disc degeneration leads to increased load on the joints, which, in turn, cause joint pathology. Arthritis, bone spurs, and thickening of the joint could also be the origin of nerve irritation leading to back pain.
What they found was that people with spinal stenosis did benefit from radiofrequency ablation (RFA) of the nerve to the affected facet joints. Identifying patients with stenosis might help guide treatment to include RFA when it might not have been considered otherwise. It was observed that patients with spinal stenosis did tend to have facet joint hypertrophy.
Joint hypertrophy refers to an enlargement of the joint due to arthritic changes. There are some experts who think that it's these changes in the joint that put more strain on the joint making them more likely to develop pain. It wasn't clear if the joint hypertrophy led to the stenosis or the other way around. So for now, they can't use joint hypertrophy as a way to predict treatment results.
As for whether or not a decrease in disc height made a difference -- they found that patients with decreased disc height were more likely to get pain relief from the nerve block but not from the nerve ablation. Just what the relationship between disc height and disc condition is with facet joint pain remains unclear. It makes sense that a thinner disc would bring the facet joint surfaces closer together creating increased load and subsequent arthritic changes. But this particular study wasn't able to offer any additional information to further understand that relationship.
The statistical analysis did not support spinal stenosis as a strong predictor of treatment success. There just weren't enough patients who had a positive response to the nerve block and then to the radiofrequency treatment. The authors suggest a follow-up study should be done with more subjects. This study included 127 patients and may not have been large enough to make firm conclusions.
In general, more studies are needed to help sort out which patients can best benefit from radiofrequency nerve denervation. Whereas patients with stenosis were previously told facet joint treatment wouldn't help them, this study calls that recommendation into question. Older adults are more likely to suffer from stenosis and that was consistent with the fact that older adults got better results from nerve blocks and nerve ablation compared with younger adults with persistent back pain.
Milan P. Stojanovic, MD, et al. MRI Analysis of the Lumbar Spine: Can It Predict Response to Diagnostic and Therapeutic Facet Procedures? In The Clinical Journal of Pain. February 2010. Vol. 26. No. 2. Pp. 110-115.
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