Hull City midfielder Ryan Mason has announced his retirement after fracturing his skull in January 2017.
The 26-year-old collided heads with Chelsea defender Gary Cahill in a game at Stamford Bridge and has not played since.
"I can confirm that following specialist medical advice I am having to retire from playing professional football," Mason said in a statement released on Tuesday. "I have worked tirelessly in order to be able to return to the pitch.
"Unfortunately, having taken expert medical advice I now have no option but to retire due to the risks involved given the nature of my injury. I am and always will be eternally grateful for the incredible network of people around me who have helped me to recover from what was a life-threatening injury in January 2017."
Mason joined Tottenham Hotspur as a trainee and made his Spurs debut against Dutch club NEC Nijmegen in a UEFA Cup tie in November 2008.
"There are too many names to mention when it comes to talking about Tottenham Hotspur but I would like to say a special thank you to John McDermott (head of coaching and playing development), the gaffer (Mauricio Pochettino) and everybody at Spurs for helping me to achieve my dreams.
"I am so proud to have come through the ranks to play for my club, the club I love. To have had the honour of captaining the team fills me with immense pride."
Mason had loan spells at Yeovil Town, Doncaster, Millwall, Leyton Orient and Swindon Town before returning to Spurs, with whom he made 70 appearances and scored four goals.
Always #OneOfOurOwn, @RyanMason. pic.twitter.com/r9kBYiWGVo
— Tottenham Hotspur (@SpursOfficial) February 13, 2018
He was called into the England squad and earned his only cap in a 1-1 draw with Italy in Turin in March 2015, when he set up Andros Townsend's late equaliser.
Mason said: "Representing my country is an honour that nobody can ever take away from me and something that I am so proud to have achieved.''
Mason joined Hull in August 2016 for a fee believed to be around £13 million and made 20 appearances and scored twice for the club.
"Ryan has sought the guidance of numerous world renowned neurologists and neurosurgeons who have all advised that a return to competitive football is not advised," the Championship club said in a statement.
"Ryan would like to put on record his thanks to all at the club who have aided his recovery to this point and he his is indebted to them for their support and compassion over the past 12 months."
Mason, in his statement, thanked the Hull medical team for helping him recover from the injury, which he told talkSPORT in October required 14 metal plates and 42 stitches in his skull.
"I would like to thank everyone at Hull City, especially the doc, Mark Waller, and all of the medical team for helping me to recover," Mason said.
"I'm retiring from the game with my head held high having done everything in my power over these past 13 months to have given myself every opportunity to return to the pitch."
Hull manager Nigel Adkins also expressed his gratitude to Mason on the team's official website: "I'm really disappointed for him,'' Hull manager Nigel Adkins told the official club website.
"The injury was before my time here but Ryan's worked extremely hard and he's given everything he can to continue playing.
"He's taken a lot of advice and unfortunately it's not nice when you see somebody retire.
"But the consequences of the injury were so significant that he's fortunate to be where we are at this moment in time.
"We wish him well and he's always going to be welcome here at Hull City.''
Cahill, who was involved in the clash that led to the injury, posted a message from his Twitter account that read: "Devastated to hear today's news from Ryan. Competing for a corner is something we've done thousands of times and to see those consequences for a top professional like Ryan is heartbreaking.
"Sending all my love to him and his family, and wishing him the best for the future."
Arsenal goalkeeper Petr Cech, who sustained a fractured skull during a Premier League game in 2006, sent a similar message.
It read: "Yesterday was a sad day for one incredible young man .@RyanMason . Although his story didn't finish with ultimate happy ending , his determination , attitude and bravery he's shown during his recovery is something to be admired and an inspiration for others ! All the best Ryan."
Headway, the brain injury association, offered its continued support, with chief executive Peter McCabe saying: "At Headway we understand the long-term impact a brain injury can have and although this difficult decision must be heart-breaking for Ryan, it is a sensible one.''
Hull are currently 21st in the Championship following their relegation from the Premier League last season.