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Spine imaging: disc, infection, fracture and tumours

Uncomplicated back pain without red flags is not imaged; with a red flag — MRI. On MRI the disc is described with uniform nomenclature, infection (the disc and both adjacent endplates) is separated from metastasis (vertebral body and pedicle), and an osteoporotic fracture from a pathological one.

לקריאה בעברית

Why it matters in the exam

ACR: low back pain without red flags for less than 6 weeks — no imaging. Red flags (fever, weight loss, known malignancy, progressive neurological deficit, cauda equina syndrome, immunosuppression, significant trauma) — MRI. Disc nomenclature: bulge — beyond the margins over more than 25% of the circumference; herniation — less than 25%: protrusion when the base is wider than the tip, extrusion when the tip is wider than the base or there is migration, sequestration when there is a free fragment. A paracentral herniation at L4–L5 compresses the traversing L5 root; a foraminal herniation at the same level compresses the exiting L4 root. Modic changes: type 1 oedema (dark on T1, bright on T2), type 2 fat (bright on T1), type 3 sclerosis (dark on both).

Spondylodiscitis: high disc signal on T2, destruction of both endplates on either side of the disc, enhancement, and sometimes a paraspinal or epidural abscess — MRI with gadolinium is the test. In tuberculosis the disc is relatively spared, there is spread beneath the anterior ligament over several levels, a large calcified psoas abscess and angular deformity (gibbus). Osteoporotic versus malignant fracture: a convex posterior border, pedicle involvement, an epidural mass, diffuse marrow replacement and restricted diffusion — point to malignancy; a retropulsed posterior corner fragment, a horizontal band of oedema, a "fluid sign" and normal marrow in the rest of the vertebra — to osteoporosis.

Tumours by compartment: intramedullary — ependymoma in an adult (central, haemorrhage at the poles, syrinx) and astrocytoma in a child (eccentric); intradural extramedullary — meningioma (thoracic, woman, dural tail, calcification) and schwannoma ("dumbbell" through the foramen); extradural — metastases. After back surgery, early complications: haematoma, infection, CSF leak and a retained disc fragment; later — separating fibrosis (enhances uniformly) from a recurrent disc (enhances only at the rim). Cervical myelopathy: high cord signal on T2 at the level of stenosis. Vertebra plana in a child — eosinophilic granuloma. Baastrup disease — "kissing" spinous processes with bursitis between them.

Key points

• No red flags — no imaging.
• Protrusion — wide base; extrusion — wide tip.
• Spondylodiscitis — disc and both endplates.
• Malignant fracture — pedicle, convex border.
• Ependymoma in adults, astrocytoma in children.

Summary table

In the full version for subscribers

• A simple algorithm
• Memory aid
• Exam traps
• 5 review cards
• Enough for IMLE

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Sources

• NASS/ASSR/ASNR Lumbar Disc Nomenclature: Version 2.0, 2014 — Definitions of bulge, protrusion, extrusion and sequestration
• ACR Appropriateness Criteria: Low Back Pain, 2021 — Red flags and initial imaging
• WHO Classification of Tumours of the Central Nervous System, 5th edition (2021) — Spinal ependymoma

Sources are given for further reading; the text is written afresh and not copied from them.

Reviewed by the Examqo AI Professor · 2026-11-06. The text may contain errors; when in doubt, check the source.