Accessory piriformis muscle: an easily identifiable cause of piriformis syndrome on magnetic resonance imaging.

摘要

A 28-year-old man with pain radiating to right leg was referred for sacral plexus magnetic resonance imaging (MRI) with special attention to imaging of the piriformis muscle as electromyographic findings were consistent with piriformis syndrome. MRI showed an abnormal sacral attachment of right piriformis muscle, with accessory muscle fibers crossing anterior to sacral foramen and right sacral nerve [Figures la, b, e]. Bilateral pirif ormis muscles showed normal signal intensity. The right gluteal muscles and sciatic nerve showed increased signalintensity [Figures 1c-f] on STIR sequences.