CT Myelography¶

Definition¶

CT myelography combines intrathecal contrast injection with CT scanning to evaluate the spinal canal, thecal sac, and nerve roots. It is the primary alternative to MRI when MRI is contraindicated or unavailable, and remains superior to MRI in certain specific situations.

Technique¶

Procedure¶

1. Lumbar puncture — typically performed at L2–L3 or L3–L4 under fluoroscopic guidance
2. Contrast injection — non-ionic, water-soluble iodinated contrast (e.g., iohexol) is injected into the subarachnoid space, contrast concentration depends on level being visualized, dose depends on contrast type
3. Patient positioning — the patient is tilted to distribute contrast to the region of interest (Trendelenburg for cervical studies)
4. CT acquisition — thin-section CT is performed after contrast has distributed to the target level (typically 1–4 hours after injection)

Key Technical Points¶

• Contrast volume: 10–15 mL for lumbar, 15–20 mL for cervical/thoracic studies; must consider cooncentration
• May need to reposition patient prior to scanning (barrel roll techniques to adequately "coat" the canal)
• Delayed imaging (3–6 hours post-injection) may rarely be needed for complete distribution
• Both bone and soft tissue windows should be reviewed
• Prone and supine imaging can help differentiate ventral from dorsal compression
• Dynamic techniques may be needed in evaluation for CSF leak analysis

Indications¶

• MRI contraindication — cardiac pacemaker/defibrillator, certain metallic implants, severe claustrophobia unresponsive to sedation
• Post-surgical spine with hardware — CT myelography often provides better visualization adjacent to metallic hardware than MRI (less artifact)
• CSF leak evaluation — localizing the site of dural tear in spontaneous intracranial hypotension or post-surgical CSF leak
• Complex spinal stenosis — when MRI findings are equivocal or don't correlate with clinical symptoms
• Dynamic evaluation — upright or flexion-extension CT myelography can demonstrate positional stenosis not seen on supine MRI

Imaging Findings¶

Complications¶

• Post-lumbar puncture headache — the most common complication (~10–30%); positional headache worse when upright
• Infection — meningitis (rare with proper sterile technique)
• Bleeding — epidural hematoma (rare; higher risk with anticoagulation)
• Seizure — very rare with modern non-ionic contrast agents
• Allergic reaction to contrast — rare with intrathecal administration

Key Points¶

• CT myelography is the primary alternative when MRI is contraindicated
• It is often superior to MRI in the post-surgical spine with metallic hardware
• Intrathecal contrast outlines the thecal sac and nerve roots, allowing indirect visualization of compression
• The most common complication is post-lumbar puncture headache
• CT myelography can provide dynamic evaluation (upright, flexion-extension) not possible with standard MRI

References¶

1. Pontes ICM, Edelmuth DGL, Takahara S, Kihara Filho EN, Lucato LT, Helito PVP, Kranz PG. CT Myelography: How to Do It. RadioGraphics. 2024;44(1):e230088.
2. Patel DM, Weinberg BD, Hoch MJ. CT Myelography: Clinical Indications and Imaging Findings. RadioGraphics. 2020;40(2):470-484.
3. Mamlouk MD, Ochi RP, Jun P, Shen PY. Decubitus CT Myelography for CSF-Venous Fistulas: A Procedural Approach. AJNR Am J Neuroradiol. 2021;42(1):32-36.
4. Pomerantz SR. Myelography: modern technique and indications. Handb Clin Neurol. 2016;135:193-208.
5. Rodriguez D, Branstetter BF 4th, Agarwal V, Palfey S, Ching KC, Bump GM, Hughes MA. JOURNAL CLUB: Incidence of Complications Following Fluoroscopically Guided Lumbar Punctures and Myelograms. AJR Am J Roentgenol. 2016;206(1):20-25.
6. Plewa MC, Hall WA, McAllister RK. Postdural Puncture Headache. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2025.
7. CT myelography. Radiopaedia.org. https://radiopaedia.org/articles/ct-myelography

Related Articles¶

• CT of the Spine
• MRI of the Spine
• Thecal Sac and CSF Spaces
• Spinal Canal and Neural Foramina