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Lumbar extrusion - good lumbar numbering example

Case contributed by Frank Gaillard
Diagnosis certain

Presentation

Pain down back of right leg and into bottom of foot.

Patient Data

Age: 30 years
Gender: Male

MRI lumbar spine

mri

The conus terminates at the L1 level. Lumbarized S1. Normal marrow signal.

L1/2: Normal appearance of the intervertebral disc. No canal stenosis.

L2/3: Normal appearance of the intervertebral disc. No canal stenosis.

L3/4: Normal appearance of the intervertebral disc. No canal, subarticular or foraminal stenosis.

L4/5: Normal appearance of the intervertebral disc. No canal, subarticular or foraminal stenosis.

L5/S1: Disc desiccation with central and subarticular right-sided disc extrusion which compresses the descending S1 nerve root, no foraminal compression.

S1/S2: Normal appearance of the intervertebral disc. No canal, subarticular or foraminal stenosis.

Case Discussion

This case illustrates how important it is to correctly identify spinal levels. The symptoms are those of S1 compression, but S1 has L5(ish) morphology and it is easy to mistake it for L5 (which was done when this study was first interpreted).

When numbering consider:

  • symptoms
  • scouts - count from above if possible
  • size of L5 nerve root on sacral ala, it should be much bigger than L4
  • the shape of S1 and L5 on axial imaging
  • iliolumbar ligaments
  • position of conus ribs

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