boy, you aren't going to be happy with any neuro imho, it sounds like you don't trust conventional medicine. there's no way an 80 year old would qualify for a DBS because of their age AND a DBS is only recommended if you respond to sinemet.
The I.V. glutathione treatment was tested by HAUSER at the university of s. florida and found to be totally ineffective. but people are still making a fortune selling it. I've tried everything, I.V. GLUTATHIONE, CHELATION, every supplement mentioned on this board, saw naturpaths that were totally confident they could help me and zippo. think about it, if there was a non-pharmaceutical treatment that was effective, in the age of the internet, wouldn't everyone with pd be using it cuz bottom line, we are all looking for something better than sinemet, were're not sheep.

Diagnosing someone with PD like symptoms in their 80's can be tricky especially when a patient/caregiver isn't letting a neuro do their job. Just my 2 cents.
i totally agree a 2nd opinion is important but keep in mind most neuros are way overworked. have a cookbook approach - try A, B, C, D - and it's up to the caregiver to keep the ball rolling to go down the list of things to try. and these treatments sometimes start off having side affects that go away.

you might want to order a used copy of "THE PARKINSON'S DISEASE TREATMENT BOOK" by AHLSKOG from amazon as a reference. You might check with your mother's insurance company, they might recommend someone or even have a nurse you can talk to.