Myelography
Myelography is an x-ray examination of the spinal canal. A contrast agent is injected
through a needle into the space around the spinal cord to display the spinal cord, spinal
canal, and nerve roots on an x ray.
General information about Myelography
Myelographys can be performed in a hospital x-ray department or in an outpatient
radiology facility. The patient lies on the x-ray table on his or her stomach. The
radiologist first looks at the spine under fluoroscopy, where the images appear on a
monitor screen. This is done to find the best location to position the needle. The skin is
cleaned, then numbed with local anesthetic. The needle is inserted. Occasionally, a small
amount of cerebrospinal fluid, the clear fluid which surrounds the spinal cord and brain,
may be withdrawn through the needle and sent for laboratory studies. Then contrast
material is injected. The contrast material (dye) is a liquid that shows up on x rays.
The x-ray table is tilted slowly. This allows the contrast material to reach different
levels in the spinal canal. The flow is observed under fluoroscopy, then x rays are taken
with the table tilted at various angles. A footrest and shoulder straps or supports will
keep the patient from sliding.
In many instances, a CT scan of the spine will be performed immediately after a
Myelography, while the contrast material is still in the spinal canal. This helps outline
internal structures most clearly.
A Myelography takes approximately 30-60 minutes. A CT scan adds about another hour to
the examination. If the procedure is done as an outpatient exam, some facilities prefer
the patient to stay in a recovery area for up to four hours.
Reasons for having a Myelography
The purpose of a Myelography is to evaluate the spinal cord and/or nerve roots for
suspected compression. Pressure on these delicate structures causes pain or other
symptoms. A Myelography is performed when precise detail about the spinal cord is needed
to make a definitive diagnosis. In most cases, Myelography is used after other studies,
such as magnetic resonance imaging (MRI) or a computed tomography scan (CT scan), have not
yielded enough information to be sure of the disease process. Sometimes Myelography
followed by CT scan is an alternative for patients who cannot have an MRI scan, because
they have a pacemaker or other implanted metallic device.
A herniated or ruptured intervertebral disc, popularly known as a slipped disc, is one
of the most common causes for pressure on the spinal cord or nerve roots. Discs are pads
of fiber and cartilage that contain rubbery tissue. They lie between the vertebrae, or
individual bones, which make up the spine. Discs act as cushions, accommodating strains,
shocks, and position changes. A disc may rupture suddenly, due to injury, or a sudden
straining with the spine in an unnatural position. In other cases, the problem may come on
gradually as a result of progressive deterioration of the discs with aging. The lower back
is the most common area for this problem, but it sometimes occurs in the neck, and rarely
in the upper back. A Myelography can help accurately locate the disc or discs involved.
Myelography may be used when a tumor is suspected. Tumors can originate in the spinal
cord, or in tissues surrounding the cord. Cancers that have started in other parts of the
body may spread or metastasize in the spine. It is important to precisely locate the mass
causing pressure, so effective treatment can be undertaken. Patients with known cancer who
develop back pain may require a Myelography for evaluation.
Other conditions that may be diagnosed using Myelography include arthritic bony
growths, known as spurs, narrowing of the spinal canal, called spinal stenosis, or
malformations of the spine. |
