Computed tomography of the sacral plexus and sciatic nerve in the greater sciatic foramen.

The sacral plexus forms the sciatic nerve, which leaves the pelvis through the greater sciatic foramen. The anatomic boundaries of the greater sciatic foramen and the relation of the sacral plexus and sciatic nerve to the structures within are identified and described on axial computed tomography (CT). The piriform muscle, which passes through the center of the greater sciatic foramen, is a recognizable landmark that is extremely helpful in locating the sacral plexus and sciatic nerve on CT. The pelvic CT images of 25 patients studied for unrelated reasons and two patients studied for complaints related to the greater sciatic foramen were reviewed. CT was very useful in demonstrating the anatomy of this region and for the investigation of sciatic pain due to lesions outside the neural canal.