Actually, it's pretty well established that morphing does NOT heal brain injuries. Rachel's amnesia in MM#1, or Loren's in #49, were both caused by injuries, and neither was healed when they morphed.
When you think about it, it makes sense that the morphing technology would have been specifically programmed to leave the brain alone. Memories are stored by the specific pattern of links that form between neurons, correct? Which means, if the brain was 'reset' to the genetic blueprints every time you morphed, there'd go all your memories!