How Does Complex Regional Pain Syndrome Occur In People? Introduction Complex regional pain syndrome or CRPS is a chronic neurological pain condition which causes a burning pain or feeling, usually in the arm or leg, but can also occur in other areas of the body. It usually occurs after an injury. According to a leading neurologist in Patna, Bihar who works at a renowned neuro hospital there, CRPS is also called condition reflex sympathetic dystrophy or causalgia. Before we discuss the cause of this condition, we should first discuss symptoms.