Hi Lynn-
wlecome to this forum, you've gotten some great advice here. Of course, talk with your parenst...I too went to my dad before talking to my mother about something serious, and it just geared me in the right direction. Educate yourself, too, so you know what questions to ask. Your mom will appreciate your willingness to understand this disease. Once you get over your own shock about her deterioration, remember this is still your mum...same mum you grew up with.
It would probably help you to maybe get with a caregiver's group n your area, perhaps find out how they all dealt with things initially; you don't have to go through this alone.
Good luck and God bless-
Steph