Give it some time. Brain surgery is a major event and the brain takes some time to recover. Remember, the surgeon went in and and poked around with a mixmaster on the brain. The swelling and shock will take a while to recover from.
However there is a chance the brain may not recover from it. Or it may take quite a bit if time.
I had brain surgery two years ago. I have recovered well, but still have a few lingering issues. One of them is my eyes. My vision is fine but my brain interprets things a little different. It has taken a bit to adjust to, but then the brain is an amazing organ and will adjust to almost anything.