The pain of sciatica is agonising, and may be described as tingling or numbness which radiates through the buttock, sometimes following the course of the sciatic nerve, down the back of the thigh and front of lower leg, and sometimes as far as the foot. Sciatica is the result of inflammation along the sciatic nerve, which is the longest nerve in the body and runs from the buttocks all way to the feet. Usually caused by pressure on the nerve at the lower spine.