During a Discogram, a small diameter needle is placed into the center of a vertebral disc and a small amount of fluid is injected, which can be seen on the X-ray fluoroscope. This places controlled pressure on the disc. A normal disc is unaffected but a disc which has been causing pain will start to reproduce the patient’s same pattern of pain. At least several adjacent discs are injected, giving the physician a better idea of which are responsible for the current symptoms.
The procedure is done with intravenous pain and sedative medication to keep the pain from becoming severe. Other causes of nerve irritation, such as a bone spur, do not respond to disc injection thus helping decide if the pain is arising from an abnormal disc or other cause. Discography can also detect pain arising from small tears in the annular ligament holding the disc in place. These can allow irritating fluid from the disc to leak along the nerve root and can be hard to visualize on MRI or CT scans.
What to Expect