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Myelography

What is myelography?

A myelogram or myelography is a radiologic procedure to take pictures of spinal cord and bony spinal canal. After numbing the back, a thin needle is inserted into the lower back. Radiologic contrast material is then injected and X-rays pictures and/or CT scans are taken.

Other names for myelography

Doctors sometimes call a myelogram a CT myelogram - or CTM - because the patient usually has a computed tomography exam (CT) as well as a regular X-rays.

Why a patient might need a myelogram

Doctors can use myelography to help diagnose diseases that affect the spinal cord (myelopathy) and/or the nerve roots (radiculopathy). Myelography can determine if the spinal cord or nerve roots are compressed, show the location of a spinal tumor, or look for a collection of abnormal blood vessels (a vascular malformation).

Doctors may use an MRI (magnetic resonance imaging) of the spine as a screening study because an MRI is 'noninvasive': It may not require an injection nor involve penetrating the skin. However, a patient who cannot have an MRI (because of a pacemaker, for example) may need to have a myelogram instead.

A doctor also may request a myelogram if the MRI findings do not explain the patient's symptoms, are abnormal but do not show enough anatomic detail, or are confusing. In some cases, a myelogram may show better detail of the bones, ligaments, and discs, as well as the relationships of these structures to the nerve roots and spinal cord.

Who performs a myelogram

A neuroradiologist, a doctor who specializes in the radiology of the nervous system, usually performs the myelogram. A specialist such as a neurologist or neurosurgeon may order a myelogram and refer the patient to a neuroradiologist.

Who should not have myelograms

Pregnant women should not have myelograms because of the use of radiation and contrast material.

How to prepare for a myelogram

The patient should not eat solid foods within 8 hours of the myelogram. Patients can drink clear liquids until 3 hours before a myelogram; a patient should not ingest anything less than 3 hours before the myelogram.

How a myelogram is performed

The patient is usually awake for the procedure (no sedation). He or she may be prepped for an IV (intravenous treatment) in case additional medication or fluids are needed.

The patient lies on his or her stomach on an X-ray table. The lower part of the patient's back is exposed and cleaned with an iodine soap solution. The neuroradiologist injects a local anesthetic into the lower back, where a spinal needle will be inserted. Using X-ray guidance, the neuroradiologist carefully inserts the spinal needle into the spinal canal.

Once the needle is in place, the neuroradiologist may draw a small amount of spinal fluid for analysis, if the referring doctor has requested this. The neuroradiologist then injects a small amount of contrast material through the spinal needle into fluid surrounding the spinal cord.

The X-ray table can be tilted up or down so that the patient's head is either higher or lower than the rest of the body. Gravity then helps the contrast material flow into a specific part of the spine (cervical, thoracic, or lumbar). The contrast material will show up on X-rays, allowing doctors to find any areas that look abnormal.

The patient turns to the right and left for more X-rays. At the end of the procedure, the neuroradiologist removes the needle and places a small bandage over the puncture site.

The patient may then transfer to another room for the CT exam. During the CT scan the patient may be lying on his or her stomach or back, depending on what part of the spine needs scanning. After the CT scan the patient recuperates in an observation area.

How a myelogram feels

Patients usually do not find myelograms painful. However, lying on one's stomach on the hard X-ray table may cause back, leg, or arm pain to become uncomfortable during the exam. The local anesthetic stings a bit as it goes in. Sometimes the patient feels some pressure in his or her lower back as the neuroradiologist inserts the spinal needle. Rarely the patient feels a sharp pain when the needle enters the spinal canal. Patients cannot feel the injection of contrast material.

How long the procedure takes

The myelogram itself takes 20-30 minutes. The CT adds another 10-15 minutes. There usually is some waiting time between the myelogram and CT, so the entire procedure may takes an hour or more.

After the procedure

The patient stays under observation in an outpatient holding area for about two hours. The head of the hospital bed is elevated, and the nursing staff will encourage the patient to drink plenty of fluids. Patients should not drive after the procedure. A responsible adult should accompany the outpatient for at least 12 hours after discharge.

Myelography poses few risks

A myelogram is safer than some other invasive procedures, such as conventional angiography, but riskier than noninvasive procedures such as an MRI. The risks from the spinal puncture include headache, infection, bleeding, or paralysis. Risks from the contrast media include allergic reaction, confusion, nausea, vomiting, and seizures.

However, most side effects are extremely rare. The most common side effect patients experience is headache; about 20 percent of patients will develop a headache after a myelogram.

How and when results are available

The neuroradiologist who performs the myelogram interprets the study and generates a report. A patient usually gets results from his or her own doctor within one day of the exam, although this varies depending on the practice.

What results mean

After an abnormal result, a specialist may recommend follow-up care such as surgery, a directed injection for pain, or radiation therapy. A normal result may mean that the patient needs additional tests to look for other causes for the symptoms.

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