Hi,
While it doesn't affect the brain directly as in a brain disease or damage, it does compromise the brain's ability to interpret corrupted signal it receives through the compromised nerves. Respectively it in turn sends out signals through compromised nerves to the appropriate muscles to do their thing. Sadly with the nerves being the "glue" that ties it all together can't make head nor tail of the instruction and we get corrupted signals to the muscles, either freezing, jittering or confusion, worst case we actually do something right!
For me when I strike a problem trying to step it is as though the brain sends out the usual signal to make tracks, it then figures I sent that signal so we are now stepping and I should follow up with the other foot stepping. Sadly the first step never got accomplished as the signal was corrupted and nothing happened other than I got down to kiss the wonderful ground beneath me, I stumble or fall. In the rear occasion neither leg gets the signals and I'm glued to the ground for a few minutes until the eyes get in on the act and say hay you didn't move, lets try that again. Now with this happening often the brain has learnt to catch me because the eyes see the earth hasn't moved beneath me, so get another signal out quick smart to catch myself before that beloved Papal kiss!
It amazes me how well the brain can re-educate itself to correct some of the deficiencies that are developing. Sadly it can't re educate the corrupted nerves to get it right. I always figured I could do anything, it just takes me time to figure out how to accomplish it.
I can't say the fight goes on, because frankly the ANS hasn't decided to let me join the fight, it insists on playing it's own silly game to which I'm the bystander.
Cheers