L5/S1 disc extrusion

Case contributed by Paul Simkin
Diagnosis certain


New-onset bilateral leg pain and right-sided saddle anesthesia.

Patient Data

Age: 45 years
Gender: Male

The conus terminates at L1, and has a normal appearance. Normal vertebral body marrow signal. No abnormality from T12 to L3.

L4/5: Mild broad-based disc bulge with a moderate left paracentral posterior focal disc protrusion results in stenosis of the subarticular recess and compresses the traversing L5 nerve root. No neural foraminal stenosis and the exiting L4 nerve root is unaffected.

L5/S1: Mild broad-based disc bulge with a large left paracentral disc extrusion extends inferiorly into the sacral vertebral canal. This results in central and left subarticular canal stenosis at the L5/S1 level, compressing the traversing S1 nerve root. Severe narrowing of the upper sacral vertebral canal appears to compress the sacral nerves from S2 onwards, the right more than the left.

Case Discussion

L5/S1 disc extrusion results in compression of the sacral nerves at and below S2, the RIGHT more than the LEFT. There is LEFT L5 and S1 nerve compression from L4/5 and L5/S1 subarticular stenosis.

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