Thank you to all for your replies! I understand it a little better!
But what is cognitive testing?? Never heard of it?

My sister was diagnosed with PPMS 4 years ago, ans she also progressed very quickly
She used to be a very bright person but now is like a child of 10,
She was married for 4 months but after she became ill and bound to a wheelchair her 'husband' left her! A week ago she watched a program called 'doctor Oz' and after the program she told me the doctor said she must go on a diet, after an hour of trying to figure out what doctor told her that, I realised she was talking about doctor Oz, how do we handle these situations? And yesterday she asked me to kill her... Seems like we have to ask the neuro to give her stronger anti depressants.

Once again thank you all for your replies, and my heart goes out to you all! Your stories have touched my heart deeply!