A poke in the disc! Cervical provocation discography as a method of diagnosis

Provocation discography is the diagnostic evil twin of nerve blocks: while nerve blocks aim to identify the source of pain by eliminating it, discography is intended to identify the source by provoking it, deliberately injecting an irritant into intervertebral discs. Although it sounds like a nasty violation of the oath to “do no harm,” it’s actually a simple and useful idea that has the potential to get desperately needed answers about exactly which part of your neck is giving you so much grief.

Provocative discography

The irritant injected into the disc has high contrast for visibility on X-ray, to confirm the placement of the injection. The pain of the irritant can be quickly relieved with a little anaesthetic.

It’s basically the same as prodding with fingertips to see exactly which bit of anatomy hurts … only the prodding is with a needle deep in the neck. And it’s not as painful as it sounds. It’s only a mild provocation. If the injection causes the same kind of pain that the patient normally suffers from — “is that it?” — that disc is quite likely a factor in your neck pain. On the other hand, if the poked disc does not produce any all-too-familiar discomfort, then the disc probably is not to blame.

It’s basically the same as prodding with fingertips to see exactly which bit of anatomy hurts … only the prodding is with a needle deep in the neck.

Despite the simplicity in principle, it’s certainly not a perfect diagnostic method. It’s no more a sure thing than any other diagnostic method for neck pain, but it certainly has the potential to clarify the situation. Some discography results may be ambiguous or just dead wrong, while other results may be crystal clear. Surgeons have expressed concerns about false positives, lack of standard methods, and numerous potential confounding factors, such as a neck with multiple partially involved joints. Because of such problems and probably others, discography does not have clear scientific support for diagnosing low back pain: The American Pain Society gave a thumbs down to provocative discography in their official guidelines for low back pain.

But the situation is different for neck pain. Discography received strong scientific endorsement in 2009 with the publication of a paper in Pain Physician. Manchikanti et al make the strong and positive statement that, despite the controversies, “cervical discography plays a significant role in selecting surgical candidates and improving outcomes.”

Is discography truly more useful in the neck than it is in the low back? Or is the difference simply due to the complexity of the problem, with different authors finding different answers? It’s impossible to be sure, but probably not necessary either: there’s enough good sense in the method and supporting evidence for it that it’s in the “worth a shot” category. It’s certainly not appropriate for new cases of neck pain, but for patients struggling with long term pain there’s not much to lose and a real hope of a clarified diagnosis. Discuss the possibility with your physician.