MyelographyMyelography

What is MyelographyWhat is Myelography

An x-ray exam of the spinal cord and the fluid-filled space surrounding it.

X-ray film is taken after injecting a contrast medium through a needle into the subarachnoid space surrounding the cord.

A myelogram may be used to find a variety of different problems.

A Myelogram may find...A Myelogram may find...

Blockages in the spinal canal that may be caused by a tumor or by a ruptured spinal disc

Inflammation of a membrane covering the brain and spinal cord

Difficulties in blood supply to the spinal cordAbnormalities of the spinal cord and the nerves

that branch off from it

MyelographyMyelography

By defining the level and extent of abnormalities, myelography is an important method of diagnosis for physicians, particularly neurosurgeons who need to locate pathologies for surgical treatment.

Most often a myelogram will be performed in conjunction with a computed tomography scan or a magnetic resonance imaging scan to provide the most adequate information possible.

IndicationsIndications

A patient experiencing pain or numbness-may be an indicator of a lesion within the spinal canal or protruding into the spinal canal.

These lesions could be both benign and malignant tumors, cysts, herniated nucleus pulposus, and extradural masses or bone fragments caused by trauma.

Commonly...Commonly...

Most myelograms are performed in the cervical and lumbar regions because the greatest amount of pathology and trauma occur here.

A herniated nucleus pulposus is the most common pathologic finding of myelography.

Symptoms include numbness, pain , or a burning sensation in particular areas of the body, especially in the extremities.

ContraindicationsContraindications

Sensitivity to iodine or contrast media

Arachnoiditis The presence of blood in

the cerebral spinal fluid Abnormal intracranial

pressure A spinal puncture

performed within two weeks of the myelogram

Furthermore, bleeding abnormalities, such as elevated prothrombin and partial thromboplastin times, decreased platelet count, or patients on anticoagulation therapies should also abstain from a myelogram.

Preprocedural CarePreprocedural Care

Thorough explanation of the procedure by the performing physician.

Signed informed consent by the patient. The patient will then be asked to do several

things before the exam…

Patient is asked to…Patient is asked to…

Stop smoking the day before the exam and on the day of the exam.

Drink 4-8 ounces of fluid every hours while awake starting at noon the day before the exam.

Have a clear liquid breakfast two hours before the procedure (tea, apple juice, broth, etc.).

Empty bladder just prior to procedure.

DRUGSDRUGS

Since most patients exhibit apprehension, fear and anxiety of the exam, a sedative or muscle relaxant is prescribed 1 hour prior to starting the procedure.

A common drug and dosage used is 10 mg of diazepam (Valium) given intramuscularly.

EquipmentEquipment

Radiographic-fluoroscopic room

90-degree two-way tilt table with footrest, ankle boots, and shoulder supports

Prep razor Lab requisitions Positioning sponges

Sterile tray includes: contrast medium, anti-septic solution, sterile gloves, basins, three prep-sponges, band-aid, towels, gauze sponges, fenestrated drape, 5 and 20 ml syringe, 18, 22, and 25 g needles, 18 g spinal needle, extension tubing, local anesthetic, and test tubing.

Injection ProcedureInjection Procedure

Most common puncture sites are the lumbar and basal cistern regions. Lumbar is safest.

Radiologist uses fluoro to locate the best placement for the needle.

Puncture site is shaved and cleaned with Betadine and the fenestrated drape is centered on the puncture site.

The skin and underlying tissue are injected with a local anesthetic.

Injection ProcedureInjection Procedure

Patient is positioned lying on one side with knees drawn up and chin tucked into the chest while the spinal needle is inserted.

This position allows the spaces between the vertebrae to open up.

The spinal cord ends at the interspace between L-1 and L-2, so commonly the needle is inserted well above, at L-3, L-4.

Radiologist uses fluoro to guide the needle into the subarachnoid space.

An indication that the needle is in the correct place is a backflow of CSF through the needle.

Injection ProcedureInjection Procedure

Once the needle is in place, CSF will be collected and sent to the lab for analysis.

The physician will then slowly injected the iodinated contrast agent, watching with fluoro for abnormalities within the spinal canal.

After contrast is administered, the needle is removed and the radiographer is ready to position the patient to take images of the contrast filled subarachnoid space.

Contrast MediaContrast Media

An ideal contrast medium:

Mixes well with CSF Is readily absorbed by

the body Is nonreactive with

body substances or to the patient

Provides good radiopacity.

The 3 most common types used in myelography are:

Air or gas Oil-based Water-soluble

Air or gas contrastAir or gas contrast

RareSometimes employed when the patient has

a sensitivity to iodineCauses no known patient reactionsInadequate radiopacity under fluoroscopy Difficult to move in the spinal canal

Oil-based contrastOil-based contrast

Used in mid1940s till early 1980sGood radiopacity but poor visualization of

nerve rootsMajor drawback: the contrast had to be

removed from the spinal canal after the exam because it was not readily absorbed or excreted by the body

Frequently associated with arachnoiditis

Water-soluble contrastWater-soluble contrast

Widely preferred today because: low viscosity, excellent visualization of nerve roots, and it is rapidly absorbed and excreted by the body within 48 hours

Only drawback is that the filming procedures must be performed immediately because the contrast is absorbed so quickly.

Filming and PositioningFilming and Positioning

Under fluoro, the table and patient are tilted from upright to trendelenburg to facilitate flow of contrast to area of interest

In trendelenburg, patient’s chin must remain hyperextended to prevent contrast from entering the head.

Once spot filming is completed, routine radiographs are taken by the radiographer

Positioning is dictated by the area of interest

Radiologist tilts the table to pool the contrast at the appropriate level for routing filming

AP and Lateral view of the AP and Lateral view of the lumbar spinelumbar spine

Post Procedural CarePost Procedural Care

Once the spinal needle is removed, the puncture site should be bandaged

Patient should maintain a semi-erect position of 15-30 degrees for the first 8 hours following the procedure

Fluids and foods are encouraged to help eliminate contrast from the body and prevent headaches

Patient is asked not to engage in strenuous physical activity or bend over for one or two days

ComplicationsComplications Headaches are the most

common complication. They are caused by the passage of air through the subarachnoid space into the ventricles of the brain.

A totally erect position should be avoided during and after the procedure.

Rest and increased fluid intake will usually relieve a mild headache.

Other rare complications may include: nausea, obscured visualization due to the contrast injected into the wrong space, and irritated nerve tissue.

Rare contrast media reactions include: headache, nausea, vomiting, chest pains, abnormal heart rates, changes in blood pressure, seizures, aseptic meningitis, allergic symptoms, and central nervous system abnormalities.

ConclusionConclusion

Myelography may be done in either a hospital x-ray department or an outpatient radiology unit.

For patients who cannot have an MRI, myelography will usually be performed.

A CT scan is almost always performed immediately after the exam while the contrast is still present in the spinal canal. This combination of imaging studies is known as CT myelography.

ConclusionConclusionMyelography usually takes about 30 to 60

minutes to complete and a CT scan can add another 30 to 60 minutes to the total examination time.

Myelography is more expensive than CT and MRI done alone because of the likelihood of the extra expense of the hospital stay for patient observation.

In some cases, myelography will show the cause of pain and other spinal symptoms even when a CT scan and MRI is negative.