I assume you are represented by counsel in your medical malpractice lawsuit. If a hospital maintains the medical records you suspect were altered, you may want to ask your lawyer to request the "audit trail." The audit trail contains electronic information about your chart, including who accessed your chart, when they accessed it, and whether any changes were made.
Audit chains are helpful if the records are electronic. However, many private practitioners have old fashioned paper files. A doctor or employee could easily modify the records without any trail. In that case, all you can do is ask prying questions at deposition or trial to get them to admit it or to make it seem like they are lying.
The alteration of medical records in a case like yours can be problematic. It is very difficult to collect personal assets from a medical provider. It is not nearly so difficult to collect the liability coverage of the provider. The problem is that when a provider changes his records it can be said that the rights of the insurance carrier are prejudiced and the coverage is then voided. I sure hope that this is not the case for you. Talk with your lawyer.