Wow ~ Is he continuing to see the psychiatrist? I doubt he was on the medication LONG enough to even KNOW if they helped or not. Some of these medications can take up to 6 WEEKS to even begin to work! So was he on them that long? I doubt it.
He needs to continue seeing the psychiatrist and get back on the medications. He certainly should NOT have abruptly stopped taking them. That is dangerous to do! Make sure he doesn't do that again! That can cause seizures, and if he had a brain injury to begin with during surgery, it could cause more problems!
I've not heard of this, but it doesn't mean it can't happen. Strange things do happen during/after surgery. I wish you the very best. Will you keep us posted as to your progress? We'd really like to know how things go. God bless and please take care. Hugs, Lee