Hi there.
My neighbor had signifigant nerve damage in her left leg... she now has a spinal cord stimulator. She mentioned that for her to get a SCS she had to have a psych evaluation. She said that they basically had to make sure she could mentally cope with the surgery and then the ongoing surgeries to replace batteries (though at this point in time I know that they have rechargable ones, that weren't available approx. 10 years ago). She said that she had to answer lots of questions- some quite dumb ones too- and afterwards the psychologist felt that she was a good canidate for the SCS, she had her head screwed on right and she could get the SCS.
I don't know if I have helped any, but if you have any more questions, please ask- because I can ask my neighbor more about it!
Hope your evening is going well!