What is causing the stenosis or nerve compression in the MRI results?

Common Causes of Stenosis and Nerve Compression on MRI

The most common causes of stenosis and nerve compression visible on MRI are disc herniations, facet joint hypertrophy, ligamentum flavum thickening/ossification, and degenerative spondylosis—with the specific etiology varying by spinal region and patient age. 1

Thoracic Spine Stenosis

In the thoracic spine, spinal stenosis typically results from disc herniations (especially below T7), facet arthropathy, or ligamentum flavum ossification. 1

• Thoracic disc herniations are often calcified (20%-65% of cases) and occasionally intradural (5%-10%), most commonly affecting patients in their third to fifth decades of life 1
• Giant calcified disc herniations represent a specific thoracic pathology that can cause significant cord compression 1
• More than one-third of symptomatic thoracic disc herniations are associated with trauma history 1

Cervical Spine Stenosis

Cervical radiculopathy most commonly results from mechanical nerve root compression due to foraminal narrowing from facet or uncovertebral joint hypertrophy, combined with disc bulging or herniation. 1, 2

• Soft disc herniations and spondylotic changes with foraminal narrowing create the compressive pathology in the cervical region 2
• Degenerative spondylosis without diabetes or red flag symptoms is the predominant mechanism 1

Lumbar Spine Stenosis

In the lumbar spine, disc herniation at L4-L5 and L5-S1 levels is the most common cause of nerve root compression, though ligamentum flavum hypertrophy plays a surprisingly dominant role in load-induced stenosis. 1, 3

Key Lumbar Pathologies:

• Disc herniation: 57% of patients with low back pain and 65% with radiculopathy demonstrate disc herniation on MRI 2
• Ligamentum flavum thickening: Contributes 50-85% of spinal canal narrowing under axial load—more than disc bulging 3
• Facet arthropathy: Common at L4-L5 level and contributes to lateral recess stenosis 4
• Degenerative changes: Include decreased disc height, annular tears, and posterior osteophytes 4

Additional Etiologies Across All Regions

Beyond degenerative causes, inflammatory, infectious, vascular, and neoplastic etiologies must be considered when evaluating stenosis on MRI. 1

• Neoplasm, infection/inflammation, and hemorrhage can cause cauda equina compression in the lumbar region 1
• Dorsal thoracic arachnoid webs or cysts may cause myelopathy 1

Critical Clinical Pitfall

MRI findings of stenosis and nerve compression correlate poorly with symptoms—up to 20-28% of asymptomatic individuals show disc herniation on imaging. 2

• MRI has high rates of both false-positive and false-negative findings for cervical radiculopathy 1, 2
• Clinical correlation is mandatory; imaging abnormalities alone should not drive treatment decisions 2
• The size, type, and location of herniation do not reliably predict patient outcomes 2