What MRI protocol is recommended for diagnosing disc (intervertebral disc) herniation?

MRI Protocol for Diagnosing Disc Herniation

MRI lumbar spine without IV contrast is the most appropriate imaging study for diagnosing intervertebral disc herniation due to its superior ability to accurately depict soft-tissue pathology, assess vertebral marrow, and evaluate spinal canal patency. 1

Recommended MRI Protocol

• MRI without IV contrast is the preferred initial study for diagnosing disc herniation, with superior diagnostic accuracy (96%) compared to other imaging modalities 2
• Essential sequences include:
  • Sagittal T2-weighted images (for anatomical delineation and rapid localization) 3
  • Axial T2-weighted images (for detailed evaluation of disc herniation and nerve root compression) 3, 4
• T2-weighted imaging is particularly valuable as it can differentiate between normal nucleus pulposus and degenerated/herniated discs based on signal intensity differences 3

Advantages of MRI for Disc Herniation

• Superior soft-tissue contrast allows excellent visualization of disc material, nerve roots, and spinal cord 1
• Multiplanar capabilities provide comprehensive evaluation of disc pathology from different angles 2
• Non-invasive nature compared to myelography or CT myelography 2
• No ionizing radiation exposure to patients 2
• High sensitivity (91.7%) and specificity (100%) for detecting lumbar disc herniation 5

Special Considerations

• For cervical disc herniation, MRI cervical spine without IV contrast should be performed, as it best displays compression of the cord by disc herniation, bone fragments, and hematomas 1
• For patients with suspected cauda equina syndrome due to disc herniation, urgent MRI assessment is recommended 1
• For post-operative patients with suspected recurrent disc herniation, MRI without and with IV contrast may be helpful to distinguish recurrent/residual disc from post-operative scarring 1

Alternative Imaging Options (When MRI is Contraindicated)

• CT myelography can be performed to assess for spinal canal narrowing due to disc herniation, but is inferior to MRI in assessing soft tissue pathology 1
• CT without IV contrast can answer whether cauda equina compression is present, with 50% thecal sac effacement on CT predicting significant spinal stenosis 1

Clinical Correlation

• MRI findings should be correlated with clinical symptoms, as disc abnormalities are common in asymptomatic patients 1
• MRI can help identify the specific characteristics of disc herniation including:
  • Pathological type of herniation
  • Herniated position
  • Degree of herniation
  • Presence of nerve root or dural sac compression 6

Common Pitfalls to Avoid

• Overreliance on limited protocol MRI - While sagittal T2-weighted imaging alone may be accurate for detecting disc herniation, it is less accurate for evaluating nerve root compression (sensitivity only 54.84% compared to 80.65% for full protocol) 4
• Failure to correlate with clinical findings - MRI has high sensitivity but modest specificity for identifying clinically significant soft tissue injuries 1
• Inadequate assessment of facet joints - Facet joint asymmetry is closely related to lateral lumbar disc herniation and should be evaluated on MRI 6