Risks of discography include discitis, neurologic and visceral injury, dye
reactions, spinal headache and others. Spinal cord injury, vascular injury,
pre-vertebral abscess, and subdural empyema have all been reported post-discography
(9). An article in 1993 mentioned an overall complication rate of 13% with cervical
discography, including the subsequent development of an acute epidural abscess
that led to myelopathy and eventual quadriplegia (10). The same article stated
that information gained from cervical discography was not worth its potential
risks (10). Another publication in 1981 mentioned one patient in whom cervical
spondylodiscitis developed 48 hours after discography, lasting 15 months, and
a second patient developed quadriplegia within seconds after injection of the
contrast material into the intervertebral space (11). In 1995 it was recognized
that the incidence of complications with discography were 0.15% per patient
and .08% per disc (6). Although the complications associated with discography
may indeed be serious, the majority of serious and high complication rates were
reported before 1970, and have decreased enormously since that time due to improvement
in injection techniques, imaging, contrast materials, and physician training.
The procedure performed in the new millennium is very different from that which
was performed years ago (6). In addition, as with most procedures, there is
an inverse relationship between complication rate and physician experience.
The possibility that discography may cause persistent back pain is another
question that has been raised. This has been difficult to ascertain since discography
is generally performed in subjects with pre-existing back pain. A correlation
between ongoing back pain for greater than one year after discography in patients
with significant emotional, psychological and chronic pain problems has been
identified (15). Also of note is that subjects with disability claims account
for more than 80% of those with persistent pain after experimental discography,
and subjects with normal psychometric test results had no reports of significant
long-term back pain after discography (15). Discographic pain reports are not
only related to anatomic abnormalities, but are influenced by personality as
assessed by the Minnesota Multiphasic Personality Inventory. It was found that
patients with high scores on the hypochondriasis, hysteria and depression scales
may tend to overreport pain during discographic injection (28).
Another ongoing debate involves a comparison between magnetic resonance imaging
of the spine, and the information obtained by discogram. MRI is an excellent
diagnostic tool that can differentiate between annulus fibrosis and nucleus
pulposus, as can a discogram. MRI can also be used to define details of the
normal aging process of the disk. The major advantage of discogram is that it
can confirm that a patient's symptoms are discogenic, whereas MRI cannot (4).
Discogram is far more than an imaging study, and the most valuable information
from the test is gained from symptom reproduction. A correlation has been found
between pain drawings and discographic pain responses (16). Another recent significant
finding on discography was that painless, disrupted discs were found in elderly
patients. Particularly In this patient population, discography was felt to be
helpful in differentiating clinically significant abnormalities from those associated
with the aging process (18).
Bernard looked at the value of lumbar discography followed by computed tomography
in detail. He studied 250 patients with low-back pain and found that in 93%
the combination of lumbar discography followed by computed tomography provided
additional useful diagnostic information that affected patient management and
the selection of treatment alternatives. Lumbar discography followed by CT proved
valuable in determining the significance of equivocal or multiple level abnormalities,
determining the type of disc herniation, defining surgical options, and evaluating
the previously operated spine. He also noted that computed tomography-discography
may be more sensitive than magnetic resonance imaging in the early stages of
disc degeneration because 18 of 177 discs with a normal T2-weighted image were
discographically abnormal and the CT-discogram revealed annular tears or fissuring
(23).
With regards to the patient with an iodine contrast allergy, gadolinium may
be used with magnetic resonance imaging subsequent to injection instead of computed
tomography.
False positive findings on discography have also been investigated recently.
The ability of a patient to separate spinal from non-spinal sources of pain
on discography was questioned after a publication by Carragee found that patients
with no history of back pain who had undergone posterior iliac bone graft harvesting
for non-lumbar procedures often experienced a concordant painful sensation on
lumbar discography with their usual gluteal area pain (20). Another study concluded
that the side of an annular tear does not correlate with the side of a patient's
back pain, and that the pain symptoms provoked during discography may not originate
from a lumbar disc (25). One must be proficient and cautious when interpreting
discography results.
Discogram has helped to prove that normal discs on MRI may still be responsible
for producing a patient's pain (12,13). In addition, disks with abnormal morphology
on MRI have been shown to be painless on discogram. Reproduction of pain of
significance and familiarity to the patient, degenerative morphology, and accurate
needle position constitute the criteria that define a positive discogram result.
It is important that all three factors above are met in order for discography
to maintain a high level of specificity as a diagnostic tool. It is felt at
this time that MRI can neither replace, nor predict discography (12,13).
Cervical analgesic discography has also been studied (22), and may also be
used in some cases to treat discogenic pain symptoms if other treatments fail.
