Hi sachah, and thanks for posting on the ANA Forums!
I am not sure what to tell you about your mother-in-law. For me, receiving vestibular therapy helped me greatly, and my vestibular therapist ran various tests which showed my progress from falling five times in my first visit and scoring a 34 on balance testing to eventually scoring an 89 (which is better than most non-AN patients my age).
So, my questions would be: what did her vestibular therapist say regarding her lack of progress? Did the neurologists and specialists give any reasons why her dizziness was becoming worse and worse (other than age)? It's interesting that her stability has been declining ever since her GK treatment 10 years ago. Typically, the GK treatment would kill the tumor, and while there may be initial balance issues, especially as the acoustic neuroma swells from the radiation, but over time, the patient's balance should improve, not get worse. Of course, everyone's situation is different, but this is a puzzle to me.
Has she had an MRI recently? Was her GK treatment successful? I guess I have a lot more questions than I do solutions.
I wish her the best as she deals with a very disturbing condition. Some of us know how disabling dizziness can be.
Don