Thanks everyone for your words of encouragement and support. Sorry I disappeared from the forum shortly after my first post -- I was away on a much needed break while my sister cared for my mom. I have returned home to find the situation as depressing as when I left. It's so sad to see my mom, whose mental faculties are still completely sharp, struggling to cope as her body fails her. While the dizziness (I like the term "brain fog" because it sounds totally like what she describes) has, for the moment, subsided somewhat, in the past 4-6 weeks the hearing in her good ear has become more and more problematic and she continues to feel nauseated. She has seen two doctors plus an emergency room physician recently and none can detect any obvious problem; they say she's simply at a point where her body isn't working well any more. One doctor felt the after-effects of the tumour are significantly contributing to her problems but could not recommend any treatment for someone of her advanced age and overall condition.
So... it's looking like my mom is going to need a change of residence where she can have ongoing nursing care sooner than later. She's definitely not able, at this point, to attempt any exercises that might improve her symptoms or embark on more rounds of testing; she simply can't cope with anything like that. I'm sad about it -- she has always been SO independent -- but I'm heartened to hear the positive stories about nursing care that some of you have shared. I am personally thinking that she would be relieved not to have to keep trying so hard to do the things she feels she must do, and that having ongoing care would reduce her stress levels. Now it's up to one of my family members -- most likely me -- to have the difficult conversation with her as to whether or not she feels ready to take that step. I suspect she is, and that she will feel relieved to discuss it openly; now I just need to overcome my own fear (shared by my sister and brother) of broaching the topic. We don't want her to feel like we have anything but her own best interests at heart and given that she has shared strong opinions in the past about families who "dump" senior family members in institutions, we're understandably nervous as to how she will react. But nervousness aside, I think the time has come to at least talk about it.
My mom's story might come across as very sad, but I recently feel like I've made peace with the situation. My mom has lived a long, full life despite difficult circumstances, and rather than mourn the fact that she's nearing the end of her days, we should celebrate her achievements, especially given the challenges she has overcome.
To be continued...