CAUSES OF PIRIFORMIS SYNDROME

ANATOMICAL VARIANTS OF THE SCIATIC NERVE AND PIRIFORMIS MUSCLE

Different anatomic variations of the sciatic nerve and piriformis muscle.

(A) The commonest variant seen in 80% individuals where the undivided nerve passes below the piriformis muscle

(B) This is seen in about 12% of individuals where the tibial and peroneal divisions of the sciatic nerve pass through the bifid piriformis

(C) Uncommon variant where the nerve divisions encircle around the undivided muscle (3%)

(D) Uncommon variant seen 1-2% are, where the undivided nerve passes through the bifid muscle bellies of the piriformis

 (E, F) are rare variants and include passage of divisions around the upper part of bifid muscle seen in < 1% or passage of the whole nerve superficial to the muscle < 1%