Not everybody is eligible for DBS.
There are a few factors that may render someone an unsuitable candidate.
The psychological state of mind of the candidate has a lot to do with it.
Besides the more obvious reasons, such as readiness, age and progression of the disease, there are others such as compulsiveness, (I'm getting to that), physotic behaviour, and memory loss, which may preclude someone from having the surgery.
Therefore all candidates for DBS must undergo a neuropsychological assessment.
So off I went to Cabrini, for 3 hours of testing by a neuropsychologist.
Memory tests were a big feature. Not only did I have to repeat long lists of things, name as many things that start with A, and count backwards by 7, I also had to redraw complicated diagrams, and copy numerous picture of those difficult puzzle blocks. (see above). After one and a half hours, I was considered sane and fit for DBS, and could leave early.
It's amazing how far $550 will get you... cash please, no credit cards accepted....