Could you get the specialist to write you a letter - or at least a copy of the letter to your son's carers. That way you have less of a chance of miscommunication, and you will have some idea of the evidence on which they based their decision.

You might also want to write a letter to the specialist detailing anything you have noticed and any family history - the more information he/she has the better.

And well done for persisting in this very challenging situation.