Myelography Procedure: Contrast & Safety for Rad Techs

What Is Myelography?

Myelography (often called a myelogram) is a fluoroscopy-guided examination in which iodinated contrast is injected into the subarachnoid space around the spinal cord and nerve roots. It lets the radiologist see the spinal canal, the meninges, and the nerve roots that plain X-rays cannot show. Today MRI is usually the first choice for the spine, but myelography — especially CT myelography — remains essential when a patient cannot undergo MRI or when spinal hardware distorts the MR image.

As a radiologic technologist, you may assist with myelography in the fluoroscopy suite or CT scanner, and the procedure appears on the ARRT exam. This guide covers indications, contrast media, the step-by-step technique, safety, and high-yield registry points.

Why Order a Myelogram? (Indications)

Magnetic resonance imaging is usually the first imaging test for the spinal cord and nerve roots. However, a myelogram is ordered when:

• MRI is not possible — for example, a cardiac pacemaker, certain metallic implants, or severe claustrophobia unresponsive to sedation.
• Spinal instrumentation (screws, plates, rods) — MRI artifacts from hardware can obscure the neural structures, and CT myelography often visualizes the thecal sac and nerve roots adjacent to hardware more clearly.
• Compression is unclear on MRI or CT — a spine surgeon or neurologist may order a myelogram when they suspect cord or nerve-root compression that is not confidently seen on cross-sectional imaging.
• Disc herniation — to show whether a herniated intervertebral disc is compressing a nerve root or the spinal cord.
• Spinal stenosis — narrowing of the spinal canal from bony spurs (osteophytes) and thickened ligaments.
• Post-surgical evaluation — to investigate residual or new pain after spine surgery.
• Tumor or infection involving the bony spine, meninges, nerve roots, or cord.
• CSF leak evaluation — to localize the site of a dural tear (for example, in spontaneous intracranial hypotension).
• Surgical planning.

Myelography vs. MRI vs. CT Myelography

Contrast Media in Myelography

The classic exam question: what contrast is used for a myelogram? The answer is a nonionic, water-soluble iodinated contrast agent such as iohexol or iopamidol, injected intrathecally (into the subarachnoid space) — never barium, which is reserved for the gastrointestinal tract.

Why nonionic and water-soluble? Older myelography used oil-based agents (for example, iophendylate, "Pantopaque") and hyperosmolar ionic agents that carried high rates of seizures and arachnoiditis (inflammation of the arachnoid membrane). Modern nonionic, low-osmolality water-soluble agents mix readily with CSF, are absorbed and cleared from the subarachnoid space, and make seizures very rare. That evolution is a frequent ARRT talking point.

See Contrast Media in Radiology: Types, Administration, Adverse Reactions for the full breakdown of iodinated agents, osmolality, and reaction management.

Patient Preparation

Your myelogram prep checklist:

• Blood thinners first. Anticoagulants (and certain antipsychotics/antidepressants) are usually stopped several days before — the physician weighs bleeding risk against the reason for anticoagulation. This is one of the most important prep steps.
• Allergy history. Disclose any allergy to iodinated contrast and any history of asthma — these patients are watched more carefully for a reaction.
• Hydration. Patients are advised to increase fluid intake the day before; it is important to be well hydrated.
• Food. Solid food is usually avoided for several hours before, but fluids may continue.
• Do not run the exam at an infected puncture site — myelography should not be performed through infected skin; a different site (or MRI) is chosen.
• Pregnancy — tell the technologist; myelography is generally avoided during pregnancy because of radiation.
• Consent and safety screen — confirm patient, indication, and prior imaging; review medications and coagulation status.

The Myelogram Procedure — Step by Step

This sequence is performed by or under the direction of a qualified physician; the radiologic technologist assists with positioning, fluoro technique, and image acquisition.

Step 1: Positioning

The patient lies face-down (prone) — or on their side — so the fluoroscope can localize the puncture site. Contrast is usually injected into the lower lumbar spinal canal because it is considered easier and safer.

Step 2: Sterile Preparation and Local Anesthesia

The skin is cleaned and numbed with local anesthetic. The patient may feel a brief sting.

Step 3: Lumbar Puncture

Under fluoroscopic guidance, a spinal needle is advanced into the subarachnoid space — typically at the L3–L4 level (commonly L2–L3 or L3–L4), below the conus medullaris. A free slow flow of CSF confirms correct needle position. If the referring physician requests it, a small sample of CSF is sent for laboratory studies before contrast is injected.

Step 4: Contrast Injection

Nonionic iodinated contrast is injected through the needle, then the needle is removed and the puncture site cleaned. Typical intrathecal volumes are roughly 10–15 mL for lumbar studies and 15–20 mL for cervical/thoracic studies.

Step 5: Flow and Image Acquisition

The radiologist slowly tilts the table so the contrast flows up or down within the subarachnoid space and coats the nerve roots and cord. For a cervical study, the table is tilted head-down (Trendelenburg) to move the contrast cranially. The patient must remain still to avoid blurred images. Spot radiographs document the flow, and side-view (oblique/lateral) images are obtained.

Step 6: CT Myelography

A CT scan frequently follows immediately while contrast is still present, adding cross-sectional detail. The whole myelogram typically takes 30–60 minutes; the CT adds another 15–30 minutes.

Post-Procedure Care and Aftercare

• Observation. The patient is observed in a recovery area for 1–2 hours while vital signs and condition are monitored.
• Head elevation. Many facilities keep patients resting with the head elevated at a 30–45° angle for up to four hours — and encourage continued head elevation/rest for about 24 hours — to keep contrast from pooling toward the intracranial subarachnoid space. This reduces headache and the (already rare) neurotoxic risk.
• Hydration. Fluids are encouraged to help clear the contrast and prevent headache.
• Activity restriction. Refrain from strenuous activity and from bending over for 1–2 days.
• When to call. Report fever above 100.4°F (38°C), excessive nausea or vomiting, severe headache lasting more than 24 hours, neck stiffness, leg numbness, or trouble urinating or moving the bowels.

Complications and Safety

• Post-dural-puncture headache is the most common complication (roughly 10–30%). It is positional — worse when sitting or standing and improved lying flat — and usually begins within 2–3 days. Mild cases respond to rest and fluids; severe, persistent cases may require an epidural blood patch.
• Contrast reactions are infrequent and usually mild (itching, rash, sneezing, nausea, anxiety). Hives or wheezing are rare; severe heart or lung reactions are rare.
• Seizures are very uncommon with modern nonionic agents — historically far more common with older ionic/hyperosmolar and oil-based agents.
• Other rare complications: nerve injury from the needle, bleeding around the nerve roots (epidural hematoma — higher risk with anticoagulation), and inflammation or infection of the meninges.
• Obstruction risk. Introducing a needle below a complete spinal block can change pressure within the canal and be dangerous — which is why a suspected high-grade block or cord compression is assessed carefully before lumbar puncture.
• Radiation. Use pulsed fluoroscopy, low frame rates, tight collimation, and last-image-hold per ALARA. See Fluoroscopy Procedures and Safety: A Complete Guide for Rad Techs for dose-management fundamentals.

Normal vs. Abnormal Myelogram Findings

• Normal — the contrast column outlines the thecal sac and nerve root sleeves; nerve roots appear as slender filling defects within the contrast.
• Disc herniation — an extradural filling defect indenting the contrast column at the disc level.
• Spinal stenosis — narrowing or a complete block of the contrast column, sometimes described as an "hourglass" configuration.
• Intradural tumor — an intradural filling defect (for example, schwannoma or meningioma) that expands the thecal sac, often with a curved "meniscus" margin.
• CSF leak — an extrathecal collection of contrast at the site of the dural defect.

Related Contrast Procedures

Myelography is one member of a family of image-guided contrast procedures you may assist with:

• Arthrography Procedures: Shoulder & Knee Contrast Studies for Rad Techs — contrast inside joints
• IVP and IVU Procedures: Excretory Urography for Rad Techs — contrast studies of the urinary tract
• Barium Studies: UGI, Small Bowel Follow-Through, and Barium Enema — GI fluoroscopy with barium
• Hysterosalpingography (HSG): Procedure Guide — contrast evaluation of the uterus and fallopian tubes