Complex sentence: Piriformis syndrome is a neuromuscular disorder that occurs when the sciatic nerve is compressed or otherwise irritated by the piriformis muscle causing pain, tingling and numbness in the buttocks and along the sciatic nerve.
Split into simpler sentences: Piriformis syndrome is a neuromuscular disorder that occurs when the sciatic nerve is compressed or otherwise irritated by the piriformis muscle. This causes pain, tingling and numbness in the buttocks and along the course of the sciatic nerve.