Fig. 1

Axial spin-echo T1- and T2-weighted magnetic resonance imaging （MRI） revealed left extraforaminal disc herniation at L5/S1 level before initial surgery （A and B; arrows）. Frontal view of MRI revealed the left sciatic nerve （C; arrows）, and axial view of MRI revealed piriformis muscle （D; arrows）. Dotted lines indicated bifurcation of the sciatic nerve （C）. The piriformis muscle on the left side was thicker than that on the right side R: right side, L: left side.