Our current MSc students Charlie Guy, Alice Roberts, Sophie Mok and their supervisor Abduelmenem Alashkham have presented a rare case with combined variation of the sciatic nerve and piriformis at the British Association of Clinical Anatomists conference. Image Sciatica is a common clinical problem due to sciatic nerve (SCN) irritation or compression. Approximately 6-8% of cases are attributable to piriformis syndrome (PS) which can be caused by variation of the SCN or the piriformis muscle: this manifests as acute buttock tenderness, and sciatic pain, tingling and numbness in the posterior thigh, calf or foot. In classical presentation, the SCN exits the pelvis undivided from the greater sciatic foramen, passing inferior to the piriformis, before bifurcating proximal to the popliteal fossa into a common fibular nerve (CFN) and a tibial nerve (TN). During routine dissection at Edinburgh University, variations of the right-sided piriformis, and the SCN were observed in an 83-year-old, Genelyn embalmed male cadaver. Piriformis was split into two – superior and inferior – bellies. The SCN was divided into TN and CFN prior exiting the pelvis. The TN passed below the piriformis inferior belly. The CFN has three roots, two of which ran between the two piriformis bellies, and the third passed below the piriformis inferior belly: the three roots merged forming the CFN. This variation could be a cause of PS. Therefore, knowledge of such variation is important for effective diagnostic assessment and surgical intervention of sciatica. Publication date 18 Dec, 2019
