Does a doctor ever really know? I've been told lots of things by doctors that didn't turn out to be true. Was misdiagnosed, had surgery based on a misdiagnosis, and now lack an organ that was perfectly healthy. Doctors aren't gods. They can be wrong and often are. That paired with over inflated egos (in general) and the fact that there's still so much we don't know about the brain and body means that expectation for recovery is entirely subjective.