Indications
- MRI contraindicated (non-MRI-compatible pacemaker, cochlear implant, cerebral aneurysm clip)
- Post-surgical spine with metallic hardware obscuring MRI
- CSF leak localization (intracranial hypotension — myelography with positional imaging or digital subtraction myelography)
- Radiculopathy or myelopathy requiring higher resolution than MRI
- Arachnoiditis evaluation
- Nerve root avulsion (pre-operative assessment)
- Post-myelography CT for precise anatomic localization before surgery
Contraindications
| Contraindication | Notes |
|---|---|
| Active infection at puncture site | Absolute — risk of meningitis |
| Coagulopathy (INR >1.5, platelets <50,000) | Absolute — hemorrhagic complication risk; correct before procedure |
| Papilledema / increased intracranial pressure | Absolute — tonsillar herniation risk; LP contraindicated |
| Allergy to iodinated contrast | Absolute — Omnipaque is intrathecal; premedicate if mild allergy, consult if severe |
| Seizure disorder (cervical myelogram) | Relative — high cervical Omnipaque increases seizure risk; discuss with neurology |
| NSAIDs / anticoagulants | Hold per protocol: NSAIDs 5 days, warfarin 5 days (INR <1.5 confirmed), heparin 4–6 hours, LMWH 12–24 hours |
Equipment and Patient Preparation
Contrast: Omnipaque 300 (iohexol 300 mg/mL) — the only FDA-approved intrathecal contrast agent. Gastrografin and Visipaque are NOT approved for intrathecal use. Dose: 8–12 mL for lumbar, 6–8 mL for thoracic or cervical via lumbar route.
Needles: 22-gauge Quincke or Sprotte spinal needle; 25-gauge Whitacre (pencil-point) reduces PDPH rate.
Patient preparation:
- NPO 4 hours before procedure
- Hold medications per protocol (see above)
- IV access established
- Informed consent with specific discussion of PDPH (10–30% with standard needle; <5% with pencil-point needle)
- Pre-procedure neurological exam documented
Step-by-Step Protocol — Lumbar Myelogram
| Step | Action | Key Points |
|---|---|---|
| 1 | Scout AP and lateral fluoroscopy of lumbar spine | Identify interspaces; note scoliosis, prior surgery, spondylolisthesis |
| 2 | Position prone on fluoroscopic table; pillow under abdomen to reduce lordosis | Lateral decubitus acceptable for patients unable to lie prone |
| 3 | Sterile prep and drape | Full sterile technique — meningitis risk from skin flora |
| 4 | Identify entry level: L2-3 or L3-4 preferred | Avoid L4-5 in severe degenerative disease (narrow interspace); avoid L1-2 (conus at risk in shorter patients) |
| 5 | Anesthetize skin and subcutaneous tissue with 1% lidocaine (3–5 mL) | Do NOT inject lidocaine intrathecally — neurotoxic |
| 6 | Advance spinal needle under lateral fluoroscopy, midline approach | Needle tip directed slightly cephalad; "give" felt as dura is punctured |
| 7 | Remove stylet: confirm CSF flow | Free CSF drip = intrathecal; no flow = reposition. Bloody CSF: replace stylet, wait, check for clearing |
| 8 | Collect CSF if clinically indicated (2–5 mL) | Cell count, protein, glucose, culture, cytology as ordered |
| 9 | Attach contrast syringe; inject Omnipaque 300 slowly (8–12 mL lumbar) | Inject slowly over 1–2 minutes; watch under fluoroscopy as contrast enters thecal sac |
| 10 | Confirm intrathecal distribution under fluoroscopy | Contrast should mix with CSF immediately and flow freely; nerve root sleeves become visible within contrast column |
| 11 | Remove needle; apply pressure/bandage | |
| 12 | Tilt table to distribute contrast: Trendelenburg for thoracic, steep Trendelenburg for cervical | Keep chin flexed to prevent contrast from entering cranial CSF (can cause seizures) |
| 13 | Fluoroscopic spot images: AP and obliques at each level of interest | Oblique views demonstrate nerve root sleeve filling; lateral view for AP cord compression |
| 14 | Transfer to CT immediately for CT myelogram | Axial 1–2 mm slices; sagittal and coronal reconstructions |
| 15 | Post-procedure: 30° head elevation for 4–6 hours | Reduces PDPH; reduce contrast flow to cranial CSF |
Epidural injection versus intrathecal: Intrathecal contrast distributes freely in CSF and outlines individual nerve roots within the thecal sac. Epidural contrast coats the outside of the dural sac in a "paint-brush" pattern — if this pattern is seen, the needle is NOT intrathecal; reposition before injecting the full dose.
Intrathecal Confirmation Signs
| Sign | Description |
|---|---|
| Free CSF flow | CSF drips freely from needle hub without aspiration — primary confirmation |
| Contrast mixes with CSF | Contrast immediately mixes and flows with CSF; nerve roots visible within contrast column |
| Nerve root sleeves visible | Individual root sleeves fill with contrast — definitive intrathecal confirmation |
| Contrast flows with table tilt | Heavier contrast flows dependently when table is tilted — behaves like CSF |
Key Imaging Findings
Lumbar Nerve Root Compression
| Finding | Significance |
|---|---|
| Nerve root sleeve cutoff | Disc herniation or bony foraminal stenosis compresses/effaces the root sleeve — blunted or absent filling on oblique view; document level and side |
| Extradural defect | Indentation on the contrast-filled thecal sac from herniated disc or osteophyte |
| Foraminal stenosis | Narrowing of the nerve root sleeve as it exits the foraminal canal |
| Redundant nerve roots | Bunched or serpiginous nerve roots above a stenotic level from chronic cauda equina compression (neurogenic claudication) |
Arachnoiditis
| Finding | Significance |
|---|---|
| "Empty thecal sac" | Nerve roots clumped peripherally along dural sac wall; no individual roots visible in central contrast column — pathognomonic for arachnoiditis |
| Root clumping | Nerve roots fused together into one or few thick strands |
| Loss of root sleeves | Root sleeves obliterated — absent filling despite adequate contrast |
CSF Leak (Intracranial Hypotension)
| Finding | Significance |
|---|---|
| Extradural contrast extravasation | Contrast exits thecal sac into epidural space at leak site — use positional/dynamic imaging to localize |
| Epidural contrast pooling | Contrast accumulates in epidural space at the level of the fistula |
| Rapid descent of contrast column | Faster-than-expected descent of intrathecal contrast column toward leak site |
CT myelogram adds critical information. Fluoroscopic myelogram identifies the level of compression and general morphology; CT myelogram provides precise axial anatomy for surgical planning. Always perform both in sequence. For CSF leak localization, consider digital subtraction myelography (DSM) or dynamic CT myelogram — these have higher sensitivity for high-flow and slow-flow leaks.
Post-Procedure Care
| Timeframe | Instructions |
|---|---|
| Immediately post-procedure | Maintain 30° head elevation — reduces PDPH |
| 4–6 hours | Remain in head-elevated position; encourage oral fluids |
| 24 hours | Avoid strenuous activity, heavy lifting; no vigorous Valsalva |
| Driving | Do not drive for 24 hours after procedure |
| PDPH management | Positional headache: hydration, caffeine (500 mg IV), analgesics; if >24–48 hours: epidural blood patch |
Reporting Checklist
- Procedure: fluoroscopic lumbar myelogram / CT myelogram
- Intrathecal confirmation: CSF flow / contrast distribution
- Contrast: Omnipaque 300, volume injected (mL)
- CSF collected: yes (volume) / no; sent for: (studies ordered)
- Levels evaluated: lumbar / thoracic / cervical
- Thecal sac: normal caliber / effaced at level (___) — document AP diameter
- Nerve root sleeves: normal / cutoff at level (___) / side
- Extradural defect: absent / present — level, laterality, degree of compression
- Arachnoiditis: absent / present — level, pattern
- CSF leak: absent / present — level (if identified)
- Post-procedure instructions given
Dictation Template
Fluoroscopic lumbar myelogram was performed via [L__-__] intrathecal approach using a [22/25]-gauge [Quincke/Whitacre] spinal needle. Intrathecal needle position was confirmed by free CSF flow. [X] mL of CSF was collected and sent for [studies]. [X] mL of Omnipaque 300 was injected intrathecally under fluoroscopic guidance. Contrast distributed freely within the thecal sac.
Fluoroscopic spot images demonstrate the thecal sac filling from [L__] to [T__]. The nerve root sleeves are normally formed bilaterally at L1-2, L2-3, L3-4, and L4-5. [At L__-__ on the [right/left], there is effacement/cutoff of the [right/left] [L__] nerve root sleeve, consistent with nerve root compression at this level.] [No extradural defect is identified.] [No evidence of arachnoiditis.]
The patient was transferred to CT for CT myelogram.
Common Pitfalls
| Pitfall | How to Avoid |
|---|---|
| Epidural injection mistaken for intrathecal | Always confirm CSF flow before injecting contrast; epidural contrast coats outside of dural sac — do not inject full dose; reposition and confirm |
| PDPH from large-bore needle | Use 22-gauge pencil-point (Whitacre/Sprotte) whenever possible; maintain post-procedure head elevation; pre-counsel patient |
| Contrast entering cranial CSF | Keep chin flexed throughout and after procedure; do not place patient flat; contrast entering cranial cisterns can cause seizures |
| Missing L4-5 root on oblique | Oblique views must be performed at the correct angle (~45°) to profile the root sleeves; if the foramen is not seen in profile, the oblique is incorrect |
| Arachnoiditis mistaken for normal | Look for individual nerve roots within the contrast column; absence of visible root sheaths or peripheral clumping is the key finding — do not assume "normal" just because the thecal sac fills |
| CT delayed beyond 30–60 minutes | CT must be performed immediately after myelogram before contrast is reabsorbed; delayed CT loses intrathecal contrast and degrades image quality |