Accessory piriformis muscle

Case contributed by Ali Alsmair
Diagnosis certain


The patient presented with intermittent right sciatica, with suspicion of right piriformis syndrome.

Patient Data

Age: 45 years
Gender: Female

Evidence of a right accessory piriformis muscle which crosses over the right sacral foramen.

The right S2 nerve passes between this accessory muscle and the proper right piriformis muscle, without significant compression or nerve or muscle edematous changes.

Annotated image

Selected images show the accessory right piriformis muscle (arrows), with a S2 nerve passing beneath it, without significant compression.

Case Discussion

Accessory piriformis muscle is a recognized cause of piriformis syndrome , but in this case there was no significant nerve root compression or signs of denervation.

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