A Brazilian man has stunned the world after performing a rendition of 'Yesterday' by The Beatles during open brain surgery.

Anthony Kulkamp Dias, 33, was wide awake throughout his surgery and serenaded doctors while they removed a tumour from his brain.

Doctors told G1 Brasil that they asked Dias to sing so that they can monitor his cerebral activity and avoid damaging areas of the brain which control sense, movement and speech - this is also known as "cerebral monitoring".

The 33-year-old bank worker strummed his guitar while singing along to 'Yesterday' by The Beatles, 'Emanuel' - a song he'd composed following the birth of his son - and a number of other Brazilian country songs.

Meanwhile, behind a surgical sheet, doctors operated on his brain.

Kulkamp Dias, who was a professional musician for 20 years, discovered the tumour a fortnight after his son was born. He told G1 Brasil: "I played six songs at determined moments.

"My right hand was a bit weaker because that was the side that they were operating on. So I stopped and rested. "I was interspersing songs and talking with them."

A spokesperson for Nossa Senhora da Conceição hospital, where the surgery was performed, added that Kulkamp Dias' serenade "surprised everyone".