Thanks, ladies.
I just wondered if it was anything to do with the tests he had to have because of his allergy to his mother's milk that he had when he was a baby.
In 'Nicolas Cage, The  man behind Captain Corelli' Nic recalls his parents telling him about his health problems as a baby and that he wasn't expected to live.
He says that his mother described him having tests that 'seemed alot more intrusive than your standard allergy test today'

Hmm...I think I read that somewhere too Corelli...which bio do you think you saw it in?