Cervical Diskography: Analysis of Provoked Responses at C2–C3, C3–C4, and C4–C5

As radiologists, we depend heavily on imaging as our primary diagnostic tool. We have thus come to believe that what we see with imaging is objective truth: only what we see is real; what we do not see does not exist. Most radiologists have little direct patient contact, so there is a tendency to discount or ignore the patient's history and physical examination findings. These aspects of diagnosis, which are dependent upon patient responses, are considered to be too subjective.

Is there any facet of radiology that has led to more controversy than diskography, an examination dependent more on a patient's responses than on imaging? Some radiologists feel there is no scientific basis for diskography, because it relies heavily on a patient's subjective responses. Others further complain that not enough reproducible studies have been performed to assure scientific credibility.

Radiologists may find it hard to believe that what we see is not always clinically significant, and what we cannot see may exist nonetheless. MR imaging is one of the most sensitive and specific tools radiologists have, yet studies have shown that many spine abnormalities we see may not be clinically significant (1, 2). Therefore, it would be folly to treat a patient solely on the basis of imaging findings, and without regard to clinical context. Furthermore, there have been studies showing that imaging may fail to reveal the cause of disease, whereas the cause may be revealed by a more subjective test, such as a physical examination or diskography (3).

Schellhas et al attempt to bridge the gap between what radiologists do or do not see with imaging, and what might be a clinically relevant cause for a patient's pain. It is an elegant study. Their science begins to provide us with an objective, valid rationale for the use of upper cervical diskography as an additional diagnostic tool, particularly when imaging fails to correlate with clinical findings. In practical terms, diskography can be a valuable diagnostic tool when MR findings are too numerous to interpret. It provides us with a tool to narrow the diagnosis to what is clinically relevant. Furthermore, in cases where the imaging findings fail to reveal the cause of pain, diskography may enable the radiologist to detect the cause.

Those of us who directly treat patients afflicted with chronic pain soon realize that pain is a complex, multi-faceted phenomenon. Sometimes overwhelming pain masks lesser pains. We see examples of painful vertebral compression fractures where, after successful vertebroplasty, the dominant pain disappears; but then the patient gradually notices the appearance of a different pain (eg, degenerative facet disease, diskogenic pain, or spinal stenosis) that becomes more and more bothersome. We see this as an unmasking of lesser pains that were present, but were overshadowed by a much more intense pain. If we treat only the acute compression fracture that is obvious on image, but ignore all other patient concerns, we fail as physicians.

The study by Schellhas et al is a step toward scientifically validating the use of upper cervical diskography. We hope the authors will continue, as more needs to be done prospectively to verify this technique's clinical significance. If upper cervical diskography proves to be a clinically valid test that helps in the selection of patients for treatment, then it will become an extremely valuable tool for the radiologist, particularly in those cases when imaging does not clearly show the abnormality.

We congratulate the authors for a scientific work that elucidates a most difficult and subjective patient problem, pain, and for tackling an emotional issue, diskography.