Discography was first described in 1948 as an investigative technique for herniated nucleus pulposus. Since that time, new imaging techniques that are more appropriate for this diagnosis have been developed. Discography is currently used to determine whether the disk is the source of pain in patients with predominantly axial back or neck pain.

During discography, contrast medium is injected into the disk and the patients response to the injection is noted; provocation of pain that is similar to the patients existing back or neck pain suggests that the disk might the source of the pain. Computed tomography (CT) is usually performed after discography to assess anatomical changes in the disk and to demonstrate intradiscal clefts and radial tears.

Early studies suggested that discography had a low specificity, but more recent studies have failed to induce pain in asymptomatic controls, suggesting that discography has utility in identifying patients with discogenic pain. Pain reproduction during discography in symptomatic individuals is variable, with a lower incidence of pain reproduction in patients with disk degeneration than in those with posterior tears of the anulus fibrosus or significant disk bulges.

Controlled clinical trials of discography are lacking, and a standard against which to compare is elusive. When comparing outcomes of fusion procedures, lumbar discography is sensitive but lacks specificity

The cardinal lesion that renders a lumbar disk painful is internal disk disruption. The characteristic feature of internal disk disruption is a radial fissure extending to the innervated outer third of the annulus fibrosus. As radial fissures extend to the outer third of the annulus, nerve endings are exposed to the inflammatory and algogenic chemicals produced by nuclear degradation. As a radial fissure develops, fewer and fewer lamellae remain intact to bear the load. At some stage the threshold for mechanical nociception will be attained, especially if the nerve endings have been chemically sensitized. Disk stimulation reveals this condition by showing a reduced threshold for mechanical stimulation of the disk.

In theory, discography provokes pain by the following mechanisms:

Specific indications for discography include the following:
Complications associated with discography include spinal headache, meningitis, discitis, intrathecal hemorrhage, arachnoiditis, severe reaction to accidental intradural injection, damage to the disk, urticaria, retroperitoneal hemorrhage, nausea (2%), seizures (4%), headache (10%), and increased pain (81%).

Discography has not been found to result in herniation of nucleus material or annular deterioration. Long-term follow-up studies have not demonstrated damage to normal disks after discography.

The incidence of discitis is 2-3% when a single-needle technique is used and 0.7% when a double-needle technique is used. The incidence of discitis might decrease to less than 1% when prophylactic antibiotics are used.

Pro
Discography provides valuable information to the clinician and the patient. CT myelography and MRI are used to detect disk herniations and other space-occupying lesions that may compromise lumbar nerve roots. CT scans and MRI are excellent for investigating radicular pain, but offer little in the investigation of back pain and somatic referred pain.

Opponents of discography refer to studies by Holt. However, the means and methods used by Holt have been scathingly refuted. His studies have been replicated using more stringent conditions, with blinded investigators, independent observers, and manometrically monitored discography. Under these conditions, lumbar disks do not hurt in asymptomatic individuals and disk stimulation is a highly specific diagnostic test. For a disk to be deemed painful, stimulation must reproduce the patients accustomed pain, provided that stimulation of the disk above or below (preferably both) does not reproduce pain.

Some surgeons have proclaimed that by selecting the correct disk for treatment, discography leads to greater success rates than anterior lumbar fusion. Disks selected for treatment are those that are symptomatic on stimulation and that express loss of signal intensity on MRI. Failing to find a painful disk on discography should preclude surgery; so too should finding multiple painful disks or obtaining indeterminate results. Discography is only a diagnostic tool to test whether a disk is painful. Unjustified surgery can be prevented by heeding indeterminate or negative results.

Con
Some authors believe that the test has no proven efficacy in improving patient outcomes, and that it leads to inappropriate surgery. These authors also believe that discography was popularized and adapted before validity and utility were determined. Disagreement on discography involves 3 major areas.

The first area of disagreement on discography is the concept of internal disk disruption as a symptom-producing complex. Proponents of discography theorize that the cardinal lesion that renders a lumbar disk painful is internal disk disruption. However, authors that oppose discography believe that the concept is a combination of a variety of anatomic and physiologic facts garnered from disparate sources and cobbled together to provide a theory to support the concept of internal disk disruption.

The second area of disagreement is the contention that discography is important as an informational tool in internal disk disruption to help us understand what is or is not wrong. What is the point of an informational tool for the purpose of establishing a diagnosis for which no proven therapy exists?

The third area of disagreement is that discography leads to inappropriate surgery. Nachemson stated that the origin of back pain remains unknown in a majority of patients. The benefit of surgery for low back pain and sciatica at the present time is proven in scientific matter only for disk herniation giving nerve root pain.

Interpretation :