WASHINGTON - Scientists are raising the first hope of recovery from an autism-like disease that leaves thousands of girls unable to talk or walk - with an experiment that erased symptoms of the disorder in genetically engineered mice.

Thursday's report challenges the long-held belief that the brain damage from Rett syndrome is permanent, but it comes with a big warning: Researchers don't know how to even try such treatment in people yet, making the discovery one of both optimism and continued frustration.

"The thing that keeps your feet on the ground with this study is it shows the principle of reversibility, but doesn't give you any clue about how to accomplish that," cautioned lead researcher Dr. Adrian Bird, a geneticist at Scotland's Edinburgh University.

Still, parents rejoiced at the research, saying it gave them hope that even if finding actual therapies takes another decade, their severely disabled daughters still may have a chance to improve.

"To think even 10 or 20 years down the road ... she could learn to talk and walk," said Jennifer Endres of her daughter Jillian, 4, who smiles delightedly as she watches other children play but can't even hold a toy in her own hands. "If it can happen in Jillian's lifetime, that means the world to us."

And the work, published Thursday by the journal Science, could affect more than Rett syndrome, because the same genetic culprit plays a role in certain forms of autism and other brain diseases, too.