That would be a possibility and something that can be dealt with easily. It will also show if there is kidney failure (that is what it showed with my cat). I am not sure if your vet really is not interested in the neurological problems, or if the kidney problem is the most important problem. I lost my cat to kidney failure, so that would be the primary issue that you have to deal with....besides that there is little that could be done to help with neurological problems. Kidney disease can be managed.
As to the hearing, or any other issues, kidney failure causes a lot of toxins to accumulate in the blood. This can lead to all sorts of problems, although I have never heard of hearing problems from it. My cat did go blind, but did really well getting around. The sooner you deal with this, the better.
And if the worst happens and it is kidney failure, it helped me deal with it to know that it is not painful for the cat. My vet and my MD both said that the toxins in the body cause a state of euphoria but no pain.