The Discography Controversy

Introduction
Discography (also called provocative disk injection (1)) has been used as a diagnostic modality for spine pain since the middle of the 20th century. Lindblom from Sweden introduced discography as a concept in the early 1940's (6). Some have said that Smith introduced cervical discography in 1952 (1), others have said that Cloward first introduced it in 1958 (2). Schmorl is credited with being the first to inject a lumbar disc for radiographic visualization (23). Nonetheless, since the dawn of discography, there has been controversy surrounding its use. Today, it is used as a diagnostic tool in the work-up of back pain at all vertebral levels. Discography has been felt to be especially beneficial in the work-up of suspected disc-originating or "discogenic" pain. There have been numerous publications both in favor of and against its use. This report is an attempt to summarize the vast array of beliefs regarding discography and it's use in both the lumbar and cervical areas.

Discussion
Discography is an intricate procedure in which many factors play into the production of consistent, reliable, beneficial data in assisting the clinician to identify both the source of a patient's pain, and the best possible treatment algorithm. It is a far more complex procedure than obtaining a complete blood count to identify a patient with anemia for example. It is an operator-dependent procedure in which interventionalists must use their clinical judgment to ascertain whether or not the patient is a good candidate for discography, what useful information may be obtained, and which of the three techniques to perform the procedure are best in the particular patient presentation. Discography is not simply an attempt to visualize the disc, but an attempt to identify problematic, injured intervertebral discs by reproduction of the patient's usual pain complaint during the procedure. It has been identified that the outer 1/3 of the annulus fibrosis is the source of pain during discography (24). There are few tools that allow direct investigation of clinical pain. However, discographic injection is such a tool (16). Herein lies the true value of Discography. Three criteria generally are used to determine whether a particular disc is responsible for a patient's pain symptoms. First, the injection of that disc must cause significant pain. Second, the pain quality must be concordant with that of the patient's usual pain. Third, a control disk must have a negative injection (21).

Pre-operative discography has been shown to correlate well with favorable post-operative results in both the lumbar and cervical areas (3,4,5,29,30,31). In the surgical treatment of patients, discography can help with selection of the right patient, selection of the right level or levels involved, and selection of the right operative treatment (3). In one study regarding treatment for low back pain, pre-operative positive discogram findings correlated with an 89% sustained clinical benefit from operative intervention, whereas negative discogram findings correlated with only 52% clinical success post-operatively (4). In general, it has been noted that surgeons who reported less favorable outcomes had not performed pre-operative discography to determine the surgical levels (1). Another study showed that 70% of patients that underwent surgical intervention after discography had a good or excellent result. The author concluded that with proper utilization, cervical discography is a valid diagnostic tool (29). A study published in 2000 revealed that after having had discography followed by discectomy and anterior fusion, 78.6% of patients continued with good to excellent results. It was felt that in a "select group" of patients with chronic intractable neck pain but negative or indeterminate imaging findings who are being considered for surgical intervention, cervical discography can help localize the symptomatic level and potentially benefit the patients prior to surgical intervention (30). Garvey, Schofferman and Palit have all published papers recently that have reported favorable results after cervical fusion for cervical discogenic pain, and stressed the importance of properly selecting patients for these procedures (32,33,1). Grubb published an article in 2000 examining a series of 173 cervical discograms performed over 12 years. He concluded that cervical discography was a safe and valuable diagnostic procedure (34). It was felt by the authors of another study that discography should be applied as a diagnostic tool when neurological compression and significant disc herniation have been ruled out by myelography, CT scan, or MRI (31). By selecting the correct disc for treatment, discography leads to greater success rates with anterior lumbar fusion (4). This is especially true if the discs treated are symptomatic on stimulation and express loss of signal intensity on MRI (26).

Regardless of potential benefit, the question is often raised whether the information gained from discography is worth the potential risks of the procedure. Information obtained during discography must be interpreted correctly and be deemed useful in planning treatment. Some have felt that cervical discography is a painful and expensive procedure without diagnostic value (7,8,14,27). Much of the criticism is based on a study by Holt, who reported that in an asymptomatic prison population, extravasation of contrast was seen in 93% of discs and great pain was provoked in 100% of the disc injections. Holt's study was performed in the 1960's and current methods were not employed (7,8). A similar study to Holt's was published in 1996 that concluded that discography has a low false positive rate (17).