In an interview with the Times, the 29-year-old Leicester back-rower revealed he had decided to hang-up his boots after being told he would be risking his long-term health after an 11-month concussion battle.
Denton, who won the last of his 42 caps for Scotland in Argentina last summer, told the newspaper: "I have had this thing hanging over me for a long time now.
"Since the injury I have woken up every morning with pressure in my head and visual disturbances and not really knowing what is going on.
"Pretty much for that whole time I've been assuming that next week I will be better.
"Every time I tried to go through the comeback protocol, I'd fail. I've tried everything but nothing's worked."
Denton suffered a blow to the head during Tigers' league clash with Northampton Saints at Twickenham last October.
But his attempts to make a return to the game floundered before he was finally given the news by neurosurgeon Richard Sylvester he should call time on his career for his own good.
Had he been fit, Zimbabwe-born Denton would have been in contention for a place in Gregor Townsend's Scotland squad for the World Cup in Japan.
And the number eight – who qualified for Scots thanks to his Glaswegian mother- admits he will miss most pulling on a dark blue jersey.
"The idea of never being able to run out in front of 70,000 people at Murrayfield again is not enjoyable," he said.
"I so want the boys to do well (in Japan) and would so want to be there but that is not going to happen.
"It is important to me that I don't look back with sadness at what could have been, instead look forward and remain proud of what has been.
"There was a lot more I wanted to achieve. All of a sudden I am not able to do that."