Hard tongue

My mom has had a hard time chewing and swallowing her food because she says she has a hard tongue. She is getting an MRI soon but what they are looking for is rare. She wears a mouthguard at night and that’s the only thing I know that she might do differently than other people. Any idea or thoughts on what it could be?

Hard to say based on this alone and without examining the tongue. There are a variety of infiltrative disorders that can involve the tongue, which is why I suspect the MRI is being performed.