Taylor Twellman, the United States international whose career was cut short by concussions, has demanded change to the way football deals with head injuries after labelling Tottenham's handling of Jan Vertonghen "disgusting" and "pathetic".

The 39-year-old former New England Revolution striker founded ThinkTaylor – a foundation that is driven and dedicated to changing the culture in the world of concussions – in 2011 after his playing career was brought to a premature end.

Twellman was incensed on Tuesday by Spurs' medical staff allowing Vertonghen to return to the field in the Champions League semi-final against Ajax following a head injury that eventually led to the groggy-looking defender being taken off.

Twellman wrote on Twitter: "Vertonghen under NO CIRCUMSTANCES should have been allowed to come back onto the field.....DISGUSTING PATHETIC demonstration from @SpursOfficial medical staff!"

A Tottenham official told Press Association Sport after the match that Vertonghen was fine and had passed all concussion tests, but the American was unmoved by that as the defender continues to be assessed.

"Protocol is just a bunch of words on paper," Twellman told Press Association Sport. "It's the actions of going through it and when I watched it, and I watched that play thoroughly, I saw a lot of the protocol time that these doctors are saying they spent... I saw a lot of that time dealing with some blood coming out of the nose.

"If you're going to say to me you followed the protocol, well, hold on here, how much of that protocol was spent fixing the blood and trying to get the nose to stop bleeding? I mean, he almost passed out."

Head coach Mauricio Pochettino, who helped prop up Vertonghen when he eventually came off, said in his post-match interview that Spurs' medical staff followed concussion protocols.

"The interesting thing on these head injuries now is that by the time coaches and players publicly make a comment after a game, they've actually already seen the backlash," Twellman said.

"Does that make any sense? So, I am always a little wary of reading into that. My question to Pochettino would be very simple: if it is the doctor's decision then what was he watching?

"Because for a player to have the reaction that Vertonghen had that quickly...Take the blood out of the equation because naturally everyone is going to look at the blood. I don't care if there is blood involved or not.

"For the reaction that Vertonghen had coming back on the field that quickly, then I'd have a serious question about what that doctor saw and what he assessed."

Twellman says that three neurologists messaged him during the game to say that "they would have heavily endorsed" Vertonghen coming off given what they saw following the collision with Toby Alderweireld.

The fact that the Spurs defender was allowed back on is part of a wider problem that the former striker believes "no one wants to have a real conversation" about.

Twellman, like brain injury charity Headway, believes neutral doctors and head injury substitutions would help, while he also backed medical professionals using TV replays and punishment for clubs that do not adhere to concussion regulations.

"It bothers me that even in 2019 we're still having the conversation," he said. "(I feel) disappointed. I think off the top of my head, I've probably had thousands of conversations with important people within all of these football associations, confederations, FIFA and medical professionals.

"All these people and it has been going on since 2013 and I am still having it. I feel like I am in a hamster wheel going around in a circle.

"You know, awareness is one thing, right? Education and awareness are one thing. What you do with that education and awareness is another (thing)."