What is the best diagnostic alternative for a patient with back pain and a pacemaker (permanent artificial cardiac pacemaker), who is unable to undergo magnetic resonance imaging (MRI)?

CT Myelography for Back Pain in Pacemaker Patients

Yes, CT myelography is an appropriate and guideline-supported alternative imaging modality for evaluating back pain in patients with pacemakers who cannot undergo MRI. 1

Primary Recommendation

CT myelography is specifically indicated when MRI is contraindicated due to implanted medical devices that are not MRI-safe or MRI-conditional, such as older pacemakers. 1 This technique provides detailed evaluation of the thecal sac, spinal canal patency, subarticular recesses, and neural foramina—all critical structures for diagnosing the cause of back pain. 1, 2

Clinical Decision Algorithm

Step 1: Initial Imaging

• Start with plain radiographs of the symptomatic spinal region as first-line imaging. 1
• Radiographs help evaluate alignment, hardware integrity (if post-surgical), and may identify obvious bony pathology. 1
• However, negative radiographs do not exclude significant pathology and should not stop your workup. 3

Step 2: Advanced Imaging Selection

When radiographs are non-diagnostic or clinical red flags persist:

Choose CT myelography if:

• The pacemaker is not MRI-safe or MRI-conditional 1, 2
• You need to evaluate nerve root compression, especially in the lateral recess (where CT myelography can be more accurate than MRI) 1
• There is concern for spinal stenosis or cauda equina impingement 1
• The patient has had prior lumbar surgery with significant metallic hardware artifact 1

Alternative: Non-contrast CT alone if:

• Primary concern is bony pathology (fractures, spondylolysis, hardware failure) 1
• Evaluating osseous fusion status post-surgery 1
• However, CT without myelography has limited ability to assess neural compression and soft tissue pathology 1

Advantages of CT Myelography

• Safety advantage over MRI in patients with non-MRI-compatible cardiac devices 1, 2
• Superior to standard CT for evaluating neural compression and thecal sac patency 1
• Occasionally more accurate than MRI for diagnosing nerve root compression in the lateral recess 1
• Useful with metallic hardware when MRI would have significant artifact 1, 4
• Dynamic information can be obtained during the myelogram portion of the study 4

Important Caveats and Limitations

Disadvantages to Consider:

• Invasive procedure requiring lumbar puncture and intrathecal contrast injection 1, 2
• Inferior soft tissue resolution compared to MRI for evaluating disc pathology, marrow edema, and paraspinal soft tissues 1, 2
• Radiation exposure from both fluoroscopy and CT components 2
• Cannot directly visualize intrinsic spinal cord pathology as well as MRI 4

Common Pitfalls:

• Do not order CT myelography as a first-line test—always obtain plain radiographs first unless there are urgent neurological deficits. 1
• Do not assume CT myelography will detect all soft tissue pathology; it is primarily excellent for bony and neural compression evaluation but limited for disc signal changes, Modic changes, or early infection. 5
• Ensure the patient does not have contraindications to lumbar puncture (coagulopathy, infection at puncture site, increased intracranial pressure). 2

When CT Myelography May Be Insufficient

If clinical suspicion is high for:

• Intrinsic spinal cord lesions (syrinx, tumor, myelitis) 6, 4
• Early discitis/osteomyelitis (before bony destruction occurs) 1
• Epidural abscess (though CT with IV contrast can help) 1
• Disc herniation with subtle nerve root compression 5

In these scenarios, you may need to coordinate with cardiology to determine if the pacemaker can be made MRI-conditional, or consider alternative diagnostics like bone scan with SPECT for infection/inflammation. 1

Specific Clinical Scenarios

Post-Surgical Back Pain:

CT myelography is particularly useful for evaluating recurrent symptoms after lumbar surgery, as it can distinguish between scar tissue and recurrent disc herniation (though less effectively than MRI with contrast), and assess for hardware complications. 1

Suspected Spinal Stenosis:

CT myelography is highly effective and nearly equivalent to MRI for predicting significant spinal stenosis and excluding cauda equina impingement. 1

Radiculopathy:

CT myelography provides excellent visualization of nerve root compression in the neural foramina and lateral recesses. 1