The thing is that you read case studies with this caveat in mind, recognising that they're statistically flawed. When you don't have better information available, case studies and low n studies give some direction, some previously observed information.
See also knee arthroscopy for patients with osteo arthritis - many of these surgeries were performed before a trial with a control group was possible. That trial found that people who got the sham surgery did as well as the people who got the real surgery. Case studies are lousy, often harmful, medicine.