A Patient's Guide to Myelograms of the Spine
What it is: A myelogram is an older test that is used to examine the
spinal canal and spinal cord. Before the CAT scan and then the MRI scan, the
myelogram was the best test to determine whether there was pressure on the spinal
nerves from various causes. During this test, a special X-ray dye is placed
into the spinal sac. Today, the myelogram is still used for very special purposes,
but it is not normally the first test that is used if your doctor suspects you
may have a herniated disc.
What the test shows: The special myelogram dye shows up on X-rays. Multiple
X-rays are taken during the myelogram. The dye outlines the spinal cord and
nerve roots. Anything that is pushing into the nerves shows up as an indentation
pushing into the spinal sac. This indentation could be from a herniated or bulging
disc, lesions, tumors, or injury to the spinal nerve roots. The myelogram is
often combined with a CAT scan to get a better view of the spine in cross section.
What the test does not show: The test uses X-rays and dye. It does not
show the soft tissues directly (unlike the MRI scan). It shows only the bones
and the spinal fluid where the dye has mixed with the fluid. The test is good
when there have been metal plates and screws inserted around the spine that
may make the CAT scan and the MRI scan hard to obtain.
How the test is done: To conduct the test, the doctor must perform a
spinal tap and inject dye into the spinal sac. The dye mixes with the spinal
fluid so that the spinal fluid will show up on X-rays. The patient lies on a
tilting table, and as the table tilts, the movement of the dye shows the outline
of your spinal sac. X-rays are taken as the patient is titled to show the flow
of the dye through the spinal region, and the dye helps doctors determine if
there is any unusual indentation or an abnormal shape.
What risks the test has: A myelogram requires a spinal tap. This test
has more risks associated with it than most other tests. This is one of the
reasons that doctors prefer to use the "non-invasive" tests, such as the MRI
and CAT scans, first. The risks associated with a spinal tap include: infection
of the spinal fluid (meningitis), developing a spinal headache, and having an
allergic reaction to the dye. Myelograms are done using X-rays. X-rays use radiation,
which in large doses can increase the risks of cancer. The vast majority of
patients who get X-rays will never get enough radiation to worry about cancer.
Only patients who must have multiple X-rays (hundreds) over many years need
worry about this risk.
What the test costs: A myelogram of the spine usually has several costs
associated with the test. The first cost is the fee for actually doing the test.
This is called the "technical fee". The second cost is the fee of having a specialist,
such as a radiologist, read and interpret the test. This is called the "professional
fee". There may also be laboratory tests done on the fluid removed during the
spinal tap. You may get several bills for this test, including: one from the
hospital or clinic where you had the myelogram done, one from the specialist
who read the test, and possibly one for the lab tests.
Copyright © 2003 DePuy Acromed.
« Back to Patient Guides