I've done the Neuro Psych Test a couple of times too. But I can't remember how they scored it. I do remember part of the Test was similar to an IQ Test. Then there was another part, when I was on a computer asking multiple choice questions. They were basically asking what I would do in in certain situations in life , if I was in that situation.

For example . The question might ask , " what would you do if you ran arch rival ( someone you may have conflicts with when you see him/her ) ? Then it would give you choices that would fit your actions.

Well the testing is to see if you are mentally prepared for the surgery. Because you could end up where I currently am right now. I've got a nasty case of depression caused by the surgery, which was something that was sure to happen anyway.
As long as your score is good before and after surgery, as in the same range or better, then there shouldn't be a problem. Basically, it's for comparison. Before op and after op checks. You'll have to undergo another test afterwards.

As for being diagnosed with something else, well I suffer from anxiety, just nothing major, and I have depression which has been caused by the Epilepsy also. The medication helps at times, but only if consistently taken.