Components of the Circle of Willis in the Brain

Description

Arising from the sacral plexus on the anterior surface of the piriformis, the sciatic nerve courses laterally to medially across the deep gluteal region, then exits the pelvis through the greater sciatic foramen inferior to the piriformis to enter the posterior thigh. Superior and lateral to this relationship sit the gluteus medius and minimus, while the gluteus maximus overlies the field superficially. Nearby run the superior and inferior gluteal vessels, and the internal pudendal vessels with the pudendal nerve may be inferred as they wrap around the ischial spine toward the lesser sciatic foramen. A tight space. That infrapiriform corridor is a frequent pain generator. Hypertrophy, spasm, or an anatomic variant in which the sciatic nerve splits and one division pierces the piriformis can mimic L5 to S1 radiculopathy, producing buttock pain with radiation along the posterior thigh and, at times, distal paresthesia. This relationship also matters for posterior hip approaches and for safe intramuscular injection technique, where the superolateral quadrant of the buttock is chosen to reduce risk of sciatic nerve injury. Use this artwork in gross anatomy teaching of the gluteal region, musculoskeletal and pain medicine modules discussing piriformis syndrome, and surgical or sports medicine publications addressing deep gluteal space entrapment. It also supports patient-facing education on sciatica differentials when paired with lumbar spine diagrams. Anatomical accuracy verified by SciePro's Medical Advisory Board.