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Similar to an SNRB and facet joint
block, a discogram is a test to determine the anatomical source of low
back pain for the patient. This procedure is most frequently used to
determine if degenerative disc disease is the cause of a patient’s pain
(discogenic low back pain). Discograms are also performed to assist in
preoperative planning for candidates for a lumbar spinal fusion.
In this procedure, the discographer inserts a needle in the patient’s back
into the center of the disc. Radiographic dye is then injected into the
disc, and if injecting the dye recreates the patient’s normal pain
(concordant), it is then inferred that the specific disc is the source of
pain for the patient. If the pain is unlike their normal pain (discordant)
it can be inferred that even though the disc may look degenerated on an
MRI scan, it is in fact not the source of the patient’s pain. The test
itself is painful, but the patient needs to be awake and aware in order to
tell the discographer what kind of pain is generated by the injection (see
Figure 1).
As the discogram injection is not for treatment of pain, a steroid
(anti-inflammatory medication) is not injected. However, sometimes a
discographer will inject lidocaine (a numbing agent) into the disc to
decrease the pain of the procedure. Often, after the discogram is
completed, a CT scan is performed to check the morphology (anatomy) of the
disc.
There are a limited number of risks involved with a discogram. Disc space
infection is a serious but rare (<0.1%) potential complication. Because
the needle passes close to the nerve, there is also slight risk of nerve
root damage with the test.
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