During the study, a needle is placed in the disc and dye is injected into the disc. The study is done under real-time fluoroscopy. Normal discs are not painful. Abnormal discs may or may not be painful. Tears in the outer layers of the disc and whether the disc actually leaks contents can be determined with a Discogram. Any disc in the spine can be examined in this way but it is most useful in the lumbar region.
When Discograms are Useful
Discograms are not common tests. They are used when other tests are inconclusive and surgery is being considered. MRI scans can give a physician a wealth of information about the structural integrity of a disc, but it cannot determine if it is causing pain. It can show a herniated disc that is pressing on a spinal nerve root and from that it may be inferred whether it is causing damage. Combining the information from a MRI scan with other studies, like an EMG that can determine whether a specific nerve is damaged, can limit the need for a Discogram.
Today, discograms are used mostly to identify abnormal and painful discs in the lumbar region prior to surgery when other studies are not providing adequate information, and conservative care has failed. Performing discograms in the thoracic region and cervical region is often considered very questionable, since the disc structure is different and the information provided may not be accurate. The most useful information provided from a Discogram is that only a single abnormal disc is present and that it is causing symptoms perceived by the patient. When multiple abnormal discs are present, surgery is usually a poor option since pain is likely to be generated from multiple sources and will not be improved with intervention.
The Future of Discograms
In the future, abnormal discs that have cracks and bulges, but are not herniated and causing pressure, may be able to be treated without surgery. The center of the discs contain acid, when cracks develop as they age and are stressed, the acid can leak out and cause a chemical irritation to nerves. At this time, researchers are developing compounds known as bio-sealants to seal cracks and prevent this leaks that are causing pain. Discograms will be useful in the future if these materials being studied actually work.
An experienced interventionalist – either a radiologist or pain physician, should perform a Discogram. Discograms are very painful studies for most patients, and sedation can be used to control the pain. They do have risks, especially for serious infection if not performed properly.