What is a myelogram?
A myelogram, also known as myelography, is a diagnostic imaging procedure performed by a radiologist. It combines the use of a contrast substance with x-rays or computed tomography (CT) to evaluate abnormalities of the spinal canal, including the spinal cord, nerve roots, and other tissues.
The contrast "dye" is injected into the spinal column before the procedure. This substance, or dye, causes the tissue under study to be visible.
After the contrast dye is injected it appears on an x-ray screen allowing the radiologist to view the spinal cord, subarachnoid space, and other surrounding structures more clearly than with standard x-rays of the spine.
The radiologist may also use a CT scan when performing a myelogram. A CT or CAT scan is a diagnostic imaging procedure using a combination of x-rays and computer technology to produce cross-sectional images both horizontally and vertically across the body. These images, called slices, show detailed images of the spinal canal. CT scans provide more detail than standard x-rays.
Anatomy of the spine:
The spinal column is made up of 33 vertebrae that are separated by spongy disks and classified into distinct areas.
The cervical area consists of seven vertebrae in the neck.
The thoracic area consists of 12 vertebrae in the chest area.
The lumbar area consists of five vertebrae in the lower back area.
The sacrum has five, small fused vertebrae.
The four coccygeal vertebrae fuse to form one bone, called the coccyx or tailbone.
The spinal cord, a major part of the central nervous system, is located in the vertebral canal and reaches from the base of the skull to the upper part of the lower back. The bones of the spine and a sac containing cerebrospinal fluid surround it. The spinal cord carries sense and movement signals to and from the brain and controls many reflexes.
Reasons for the Procedure
A myelogram may be performed to assess the spinal cord, subarachnoid space, or other structures for abnormalities, particularly when another type of examination, such as a standard x-ray, is inconclusive. Myelograms may be used to evaluate many diseases, including, but not limited to, the following:
spinal cord or brain tumors
ankylosing spondylitis - a disease that affects the spine, causing the bones to grow together
cysts - benign capsules that may be filled with fluid or solid matter
tearing away or injury of spinal nerve roots
arachnoiditis - inflammation of a delicate membrane covering the brain
There may be other reasons for your physician to recommend a myelogram.
Risks of the Procedure
You may want to ask your physician about the amount of radiation used during the procedure and the risks related to your particular situation. It is a good idea to keep a record of your past history of radiation exposure, such as previous scans and other types of x-rays, so that you can inform your physician. Risks associated with radiation exposure may be related to the cumulative number of x-ray examinations and/or treatments over a long period of time.
If you are pregnant or suspect that you may be pregnant, you should notify your physician. Radiation exposure to the fetus may cause birth defects.
Because a contrast dye is used during the procedure, there is risk of allergic reaction to the substance. Studies show that eighty-five percent of the population will not experience an adverse reaction from iodinated contrast; however, you will need to let your physician know if you have ever had a reaction to any contrast dye, and/or any kidney problems. A reported seafood allergy is not considered to be a contraindication for iodinated contrast.
Because the contrast is injected into the cerebrospinal fluid which also surrounds the brain, there is a small risk of seizure after the injection. Some medications may place you at greater risk for seizure and you may be asked to stop taking a medication for 48 hours before and after the study.