The 22-year-old, who was recalled from a previous loan spell at Norwich City, has joined Boro for the rest of the season.
On bringing in the wingman, head coach Jonathan Woodgate said: “It is great Patrick has signed up for the club.
“He is an exciting player, he wants to play games, and he has the bit between his teeth.
“He fits the mould of what we are looking at. He is young and hungry, and wants to do well.”
Meanwhile, Boro number one Darren Randolph is being strongly linked with a return to former club West Ham.