There are two kinds of discograms (also known as discography). Discography is another term for discogram. The first is the analgesic discogram. The second is a provocative discogram. The patient is awake but lightly sedated for either type.
During the analgesic discogram, the disc is injected with a numbing agent. The idea is to observe the effect of a local anesthetic on pain and function. This helps the doctor see if pressure on the spinal nerve(s) is the source of low back pain. The exact level of the problem can be found.
An analgesic discogram can give useful information for making treatment decisions. Sometimes the patient gets relief from pain just by having the injection. No further treatment is needed. Since this effect doesn't occur in every patient, analgesic discogram isn't done for every patient with disc-related back pain.
Other substances such as a saline solution or contrasting dye can be injected into the disc. When this injection causes pain it's called a provocative discogram. Injecting saline increases pressure in the disc making the pain worse. This method identifies the disc as the source of pain.
Injecting an X-ray dye and doing a CT scan right away lets the doctor see the internal anatomy of the disc. Tears of the outer disc covering (annulus) and/or disc material (nucleus) leaking out can be seen using the contrast dye.