Horrible horrible disease and feel sorry for Bruce or anyone else that has to suffer with it or watch a loved one go through it.
I've always said us human beings should be able to sign upfront a criteria by which we allow euthanasia, no set sweeping rules but custom tests/checks which we can define and if we fail then so be it.
For some it may be something simple like not being able to remember your name, and for others it could be massively more complicated, i.e. if I still recognise a family member at least once every six months even for just a few moments then keep me going.
Like a Will is should be your own wishes and others (family/friends) have to respect it. Would save a massive amount of heartache, and cost, for loved ones not to mention huge savings to the NHS.