Complex Regional Pain Syndrome is a primary pain disorder, defying clear explanation for its cause. It is an infrequent, but not rare disorder, that often causes severe pain problems in affected limbs or even in the torso or head. In this condition patients tend to experience pain to light touch, color changes in the skin, swelling, excessive perspiration, temperature changes and motor loss to the affected area. Pain is often much greater than would be expected from the initial injury.