There was very sad case of an abused girl named "Genie" who was never spoken to by her parents - kept in a locked room as a toddler and she was rescued at age 13 and made a ward of the state but never learned the ability to speak despite best efforts of linguists and therapy.

It is if the basics of language and fine motor control required of the vocal cords/tongue/mouth in her brain was not primed and that ability was forever gone.