I briefly went through the google hits for "acquired savant syndrome", and all the stories appear to be just that, nothing published/peer-reviewed. The only scientific-looking review is by Darold A. Treffert, which is published in the author's own journal, from the looks of it.
Edit: oops, not an answer, was intended to be a comment.
Agreed, iirc he's one of the only people "studying" this, meaning he's more able to present shoddy evidence without pushback.
Like at the neurological/genetic level(s). Only debatable examples I can think of are Jason Padgett and a few other "acquired savants".