What Is The Treatment For Cerebral Palsy?

Hi my 26 nyear old son suffers from Cerebral Palsy. He has always had normal bowel movements and opened his bowels every day. However the past 4 weeks he has become constipated and in alot of stomach pain. The GP gave him laxatives which completely cleared him out but after this he is constipated again. This has happened several times. He is either constipated or takes laxatives and has diarrea. We do not think it is his diet because he does not eat or drink, he is fed via a tube directly into his stomach with a special liquid diet. Can you possily give us any advice please.