"After winning the title at GLORY 17/LAST MAN STANDING I went straight back into hard training. I was chasing a rematch with Nieky Holzken and wanted that fight to come around soon," says Valtellini.
"We go hard in training and it was no different, I didn't take things any easier coming out of that fight. But this time I started to notice a few things, like sometimes I was sensitive to light or to loud noise, things like that.
"I assumed it was just one of those things that would go away after I took a few days off. But it persisted and so I decided to go and get it checked out. They did some scans and they came back and said that there were some things that didn't look quite right.
"The doctors have diagnosed me with Post-Concussion Syndrome. It was something that occurred from training but I thought it would get better and I didn't take that time to recover, which just made it worse. As a result neither the doctors nor GLORY will clear me to fight until I am symptom-free.
"Unfortunately we don't know when that will be - it could be a week, a month, a year or I could have this forever. Its not fair to the fans, GLORY or the other athletes for me to wait to defend the belt not knowing when I will be better. As such, I have made the difficult decision, in conjunction with GLORY, to vacate the title."
Jon Franklin, GLORY CEO, offered his sympathy to Valtellini and also commended his "selfless" decision to voluntarily vacate the belt in consideration to his fellow welterweight athletes.
"This is of course incredibly sad news and I know I speak for everybody at GLORY when I say that we share Joe's pain in seeing him vacate a championship title which means so much to him. At the same time, I can only salute the selflessness and fortitude he has shown in making what must have been the hardest decision of his professional career," he said.
"The good news is that while the timeline is uncertain, and could be anything from days to weeks to months, Joe is expected to recover to full fitness and at that point he can then make a decision about which course he wants to take. Should he wish to return to competition with the approval of his doctors, he would of course be immediately in the title picture."
Cor Hemmers, matchmaker and Head of Talent Operations, added, "It was very unfortunate to hear about Joe's injury but I think he is being wise to think about his health. It is very sad to see a great talent like Joe not being able to enjoy his belt. Also he is a real fighter and I know that he wanted that rematch with Nieky Holzken really badly.
"If he is not able to come back in the future, at least he was champion for a time and was able to realize his dream and show people who he is. But at the present time I think it is sensible to listen to his doctors and take time off to see how things develop."
Valtellini admits that the decision to vacate the title has been "incredible hard" and that he was "very down" when he settled on his course of action. But the Canadian also says he has much to be positive about, including the potential of his newly-opened gym.
"Because I love the sport so much I am going to remain involved forever. Recently I opened my own facility and we have a lot of fighters coming through, right now I am concentrating on that. Coaching keeps me involved in the sport while I wait for this to get resolved," he says.
"With my background in teaching and my accomplishments in kickboxing I don't think there can be too many guys out there better suited to coaching than I am. And hopefully there will be opportunities in GLORY to take part via commentary and presentation, things like that.
"Recently I was invited to take a role in the remake of the iconic Kickboxer movie and that will be released in theaters soon. It has made me curious about pursuing further work in the film and television industry and already I have some opportunities on the table. There's a lot of things I can do going forward and I am feeling very positive about the future."