Spine MRI — Degenerative Disease, Red Flags & When to Scan

Spine MRI

The best test for the cord, nerve roots and marrow — and, paradoxically, a test that finds “abnormalities” in almost everyone, so it must be used for the right reasons.

What it shows

MRI images discs, the spinal cord, nerve roots, marrow and soft tissues directly. It is the modality of choice for radiculopathy, myelopathy, suspected infection or malignancy, and cauda equina.

Signal is not symptom: disc degeneration, bulges and facet change are near-universal with age and are found in large numbers of pain-free people. Findings must match the clinical picture.

Red flags — when MRI is urgent

Cauda equina syndrome: bilateral sciatica, saddle anaesthesia, bladder/bowel dysfunction — emergency MRI.

Cord compression / myelopathy: progressive weakness, sensory level, gait/hand dysfunction — urgent.

Infection or malignancy: fever, IVDU, immunosuppression, known cancer, weight loss, night pain — image promptly (discitis/osteomyelitis, metastatic disease).

When NOT to rush to scan

For non-specific low back pain without red flags, guidelines discourage early routine MRI: it rarely changes management, drives incidental findings, and can worsen outcomes through over-medicalisation. Image when the result would change treatment — planning surgery/injection, or excluding serious pathology.

Reference: Brinjikji W et al. Systematic literature review of imaging features of spinal degeneration in asymptomatic populations. AJNR 2015;36:811–16.

Educational summary for clinicians; imaging decisions follow local pathways. Not medical advice.