This is usually helped by repentance and deliverance from spirits of swearing, hate, obscenities, etc. It is strange that some people seem to be needing operations on a fairly routine basis. There have been a number of times we have found Mutilation to be the ruler. He often has a partner named Accident Prone, they seem to work together to bring a person accidents and operations. I had many operations until it was cast out.
Traumatic shocks open the way for many demon to enter.
Some of the natural ones are paranoid fear, depression, despair, discouragement, suicides, paralysis, demons of affliction, death and fear of death, etc. I was prayed for many times in an attempt to overcome demons who had come in at our son's death. These demons strengthened those already in my mind and body. Every Sunday for almost two years I was prayed for and the demons would be quiet for a week or less. I became convinced that my problems were to much for God, I had not repented enough or God hated me.