One of the more bizarre neurological conditions has to be chronic deja vu:

Imagine suffering from chronic deja vu. You don't even go to the doctor because you feel like you've already been there.

"We had a peculiar referral from a man who said there was no point visiting the clinic because he'd already been there, although this would have been impossible," said psychologist Chris Moulin, who runs a memory clinic at the University of Leeds in the UK.