I know that here, irrespective of the age of the child, a doctor can override parents wishes if a court agrees that it is in the child's interest. That includes allowing a child to die with dignity rather than prolonging hopeless treatment. It's a difficult area, but I think the principle that the long term interest of the child should come first, irrespective of what the parents, or indeed the child, wants. And sadly, every case is different, so any legal guidance will be tricky. In the case of the OP, the child's neurological differences will be bound to be a factor, so this cannot really set a precedent for future cases.