Hi ruby.
I am confused....you are a 75yrold lady right,had symptoms for 8yrs+
Not snooping but back in 2006 they thought you had pls(I have pls 15yrs) so I guess you had umn signs on your clinical exam,you do say you had balance issues.
Benign focal amyotrophy does not fit.
I would think you may have pls as origionally thought but have developed disuse atrophy.
I have small amounts of atrophy in my weaker areas.
You should get a second opinion on that,does not sound right.