Variations of the sciatic nerve in relation to the piriformis muscle

The sciatic nerve arises from the sacral plexus and exits the pelvis through the greater sciatic foramen below the piriformis muscle as a common trunk. Sometimes this nerve can emerge divided into two components: the common fibular nerve and tibial nerve, finding variations that could give rise to a condition of nerve compression. In this paper we describe two variations of the sciatic nerve in the same individual, where in the first common fibular nerve passes through the piriformis and then descends along the tibial nerve and the second, where the common fibular nerve is formed from a higher branch that pierce to piriform muscle and a lower branch passing under him, then join at the inferior margin of this muscle and form the common fibular nerve, which descends with the tibial nerve. Variations of the sciatic nerve in relation to the piriformis muscle could explain the piriformis syndrome.