Objective: To report the first known finding of a variation in the medial attachments of the piriformis muscle that affects its relationship to autonomic grey rami communicantes. Method: Cadaveric dissection for continuing general educational development. Results: An incidental finding was a single case of anomolous attachment of the medial fibres of the piriformis muscle bilaterally such that the fibres arose medial to the ventral sacral foramina. This resulted in the muscle being pierced by sacral sympathetic gray rami that contribute to the autonomic nervous system within the pelvis. Conclusion: Anomalous attachment of the medial fibres of the piriformis can occur with the anatomical result being the piercing of skeletal muscle by branches within the autonomic nervous system. A speculative question is whether this anatomical finding may allow for an autonomic piriformis syndrome analogous to the musculoskeletal pirifomis syndrome.