The 19-year-old recently signed a contract extension at the King Power Stadium, but he will now spend the next four weeks at Vale Park.
"We only bring players in who we think are going to add that little bit of quality and something different," Vale's interim manager Rob Page told the club's official website.
"He's a young lad, I spoke to Kevin Phillips about him and whenever he trains with the first team he has got an eye for goal. He's got a great work ethic, he's not a minute's problem so we just think it's an opportunity to bring him in and get him among the squad."
Panayiotou, who has been capped on two occasions by Saint Kitts and Nevis, is eligible to play in tomorrow's League One match against Scunthorpe United.