Can a computed tomography (CT) scan detect disc herniation?

Can CT Scan Detect Disc Herniation?

Yes, CT can detect disc herniation, but it is significantly less sensitive than MRI, particularly for soft tissue pathology and nerve root compression. 1

CT Capabilities and Limitations

What CT Can Detect

• CT offers superior visualization of bony structures including osteophytes, uncovertebral joints, and facet joints that may contribute to nerve impingement 1
• Modern multidetector CT (MDCT) demonstrates high diagnostic accuracy for lumbar disc herniation, with sensitivity of 98.8% and specificity of 96.5% at the disc level when compared to MRI 2
• CT can visualize disc margin abnormalities and free disc fragments irrespective of dural sac deformity, making it potentially more effective than myelography for lateral disc herniations 3
• CT excels at detecting lateral disc herniations within or lateral to the intervertebral foramen, which may be missed on myelography 3

Critical Limitations

• CT is less sensitive for evaluating nerve root compression, especially from herniated discs, compared to MRI 1
• CT is significantly inferior to MRI for identifying soft-tissue pathologies including spinal cord contusion, epidural hematoma, and nerve root avulsions 1
• CT cannot adequately assess the discoligamentous complex, which is crucial for determining spinal stability 1

When to Use CT vs MRI

MRI is Preferred When:

• Evaluating suspected disc herniation with radiculopathy - MRI is the most sensitive imaging modality for soft tissue abnormalities and correctly predicts 88% of cervical disc lesions compared to only 50% for CT alone 4
• Assessing nerve root compression or spinal cord involvement - MRI provides superior visualization of neural structures 1, 4
• Clinical examination suggests neurological deficits - MRI is the gold standard when there is a positive neurological examination referable to the spinal cord 1

CT is Appropriate When:

• MRI is contraindicated (pacemakers, certain implants, severe claustrophobia) 1
• Evaluating bony pathology including fractures, osseous stenosis, or hardware integrity 1
• Assessing spinal fusion status postoperatively - CT is the gold standard for evaluating bony fusion 1, 5
• Time-sensitive trauma evaluation where CT offers logistical advantages 1

Algorithmic Approach

For suspected disc herniation with radiculopathy:

1. Order MRI cervical or lumbar spine without contrast as first-line imaging 4
2. Reserve CT for patients with MRI contraindications 1
3. Consider CT myelography if MRI is nondiagnostic due to hardware artifact or when MRI is contraindicated 1, 4

For postoperative patients:

1. Use CT without contrast to assess hardware integrity and fusion status 1, 5
2. Use MRI without and with contrast to evaluate recurrent disc herniation vs scar tissue 6

Common Pitfalls

• Do not rely on CT alone when clinical examination suggests nerve root or spinal cord involvement - this requires MRI for adequate soft tissue assessment 1
• Avoid ordering CT with contrast for routine disc herniation evaluation - contrast adds no diagnostic value in the absence of "red flag" symptoms 1
• Remember that newer MDCT with iterative reconstruction improves diagnostic accuracy approaching MRI performance for disc herniation detection, but soft tissue evaluation remains inferior 2
• Be aware that purely ligamentous cervical spine injuries are exceptionally rare (0.1-0.7% of blunt trauma) and CT can miss these 1