Use one nomenclature (bulge, protrusion, extrusion, sequestration), place the herniation in its zone, and name the nerve root it touches — because the root, not the disc, explains the symptoms.
Orient first
- Combined task force nomenclature: a bulge involves more than 25% of the disc circumference; a protrusion has a base wider than its dome; an extrusion has a dome wider than its base or migrates; a sequestration has lost continuity with the parent disc — verify against the current version.
- Zones in the axial plane: central, subarticular (lateral recess), foraminal and extraforaminal — a subarticular L4/5 herniation compresses the traversing L5 root, a foraminal L4/5 herniation the exiting L4 root.
- Degenerative findings are common in people without pain; report the ones that correlate with the stated level and side.
Acquire the study
- Non-contrast MRI lumbar spine: sagittal T1 and T2, axial T2 through each disc level, ± sagittal STIR; contrast only after surgery or for infection or tumour.
The manoeuvre
- Sagittal T2: disc height and signal, alignment (listhesis), the conus level and canal size.
- Axial T2 at every disc: herniation type and zone, and the root it contacts, displaces or compresses.
- Lateral recess and foramen: foraminal stenosis on sagittal T1 (loss of the perineural fat around the exiting root).
- Central canal stenosis: the combined effect of disc, facet hypertrophy and ligamentum flavum thickening, graded at the tightest level.
- Red flags: cauda equina compression, marrow signal change (infection, metastasis), and an unexpected mass.
What confirms it
- A herniation at the clinically relevant level whose zone matches the compressed root.
What licenses you to exclude it
- A normal MRI excludes compressive radiculopathy from disc disease at the imaged levels.
The classic misread
- Naming the disc level but not the root — the clinician needs the root.
- Counting levels wrongly in a transitional lumbosacral segment; state how the levels were numbered.