Pyriformis syndrome MRI

A 50 yo male with left side radiating pain, sciatica like symptoms, with possible post ganglionic compression by neurological examination.
MRI lumbar spine performed first, showed a left ward disc bulge at L5-S1 with possible compression of nerve root on left side but clinically imaging findings were not corresponding to neurological findings.

So screening extended further along the course of sciatic nerve at the greater sciatic notch shows:

There is an asymmetry in size of pyriform muscles, left side muscle is bulky than right due to accessory fibers of muscle. Signals are normal.

Accessory fibers of muscle extending medial to left side S2 neural foramen, crossing over the left S2 nerve with possible encroachment.

PYRIFORMIS SYNDROME

Pyriformis syndrome, a rare cause of lower back pain and sciatica secondary to sciatic nerve entrapment at the greater sciatic notch caused by an abnormal condition of the piriformis muscle such as hypertrophy, inflammation or anatomic variations.
Frequently misdiagnosed or the correct diagnosis is delayed because of its rarity, nonspecific clinical symptoms, and absence of definite diagnostic tests. Familiarity with this syndrome is important for making the correct diagnosis.