Stephen Curry and NBA officials were most emphatic. The NBA’s MVP suffered a contusion, not a concussion, in a frightening fall during Game 4 of the Western Conference finals.

The distinction is a byproduct of enlightenment about the short- and long-term dangers of head injuries, even though they’re far more rare in the NBA than the NFL. His appearances in the immediate aftermath of the tumble aside, Curry said he was fine and that he passed all the necessary tests.

“There’s a concussion protocol that all the team doctors and athletic trainers follow that I’ve been through before, I think two times in my career,” Curry said. “I felt a lot better than I did those last couple times. That was good news on my end. Rode the bike for a little bit, got my heart rate up and made sure that it didn’t get worse. Ran up and down the hallway, and all the balance tests and stuff like that.”

Curry tumbled hard, flipping over Trevor Ariza and bracing some of the impact of the fall to the Toyota Center floor with his hand and arm. Curry called it the scariest fall he’d ever had, saying he got a “bad feeling” about being unable to control his body. He lay motionless for a few moments, but did not pass out, he said.

“I felt like I was in the air for a long time,” he said. “Once I hit the ground, you kind of hear voices from trainers and people just telling me to take my time and not rush yourself getting up. And want to make sure that you pass all the tests that they needed to do so that I could get back on the floor. So that’s what happened.”

Under the NBA’s concussion protocol, players undergo “a baseline brain function test each year, via a neurological and cognitive assessment.” From the league’s official policy summary:

If a player is suspected of having a concussion, or exhibits the signs or symptoms of concussion, they will be removed from participation and undergo evaluation by the medical staff in a quiet, distraction-free environment conducive to conducting a neurological evaluation.
If a player is diagnosed with concussion, he will not return to participation on that same day.
A player that is diagnosed with concussion should have their physical and cognitive exertion limited as much as possible while they are still experiencing symptoms of concussion.

Curry was back on the floor by the third quarter, but his game was off. He missed seven of 11 shots, but finished with 23 points and four assists.

“I was out for, what, probably an hour from the time I hit the ground to the time I got back in the game?” he said. “You don’t go through your regular routine, and it’s a different kind of situation. It took me a couple minutes just to get back in the rhythm of the game. I was in the back watching the team make a comeback, in the locker room, so I kind of understood what we were doing differently to get back in the game. So I tried to follow that game plan, but just personally wanted to break a sweat and get back into the rhythm of the game.”

The official line was that Curry had suffered a contusion. “He wouldn’t play, he wouldn’t be cleared with a concussion. … That’s pretty hardline,” Golden State General Manager Bob Myers said.

And the difference between a contusion and a concussion?

“A contusion means that just the soft tissue has been injured – it doesn’t involve any of the brain matter, so the brain itself was not injured.” James Gilbert, a physician with the the Centers for Advanced Orthopaedics, told the Washington Post in an e-mail. “A concussion is a mild traumatic brain injury, where the brain matter itself has been injured.”

Curry was able to speak with reporters, unbothered by bright lights, after the game. Concussion symptoms sometimes may not become evident immediately and the Warriors are faced with playing again Wednesday night. Unlike the NFL, games are tightly spaced, which makes monitoring Curry even more important, Gilbert writes.

“The possibility of a delayed onset of concussion is the big issue here. The Center for Disease Control breaks concussion symptoms down into four groups – physical, cognitive, emotional and sleep-related. You might not see these symptoms on the initial concussion survey. There is a very, very defined concussion protocol in the NBA and all pro sports leagues, so it’s relevant that the team physicians labeled Curry’s injury a contusion and not concussion. The team physicians will do an initial assessment for concussion, a Sideline Concussion Assessment Tool (SCAT), and if the symptoms are high enough, he won’t be allowed back in the game and it will trigger treatment protocol. It takes about a week to 10 days to go through that protocol of rest and assessment.
So, Curry’s SCAT was  not significant and he was allowed to go back and play. But, you still need to be vigilant about a delayed onset of concussion. He might not have demonstrated symptoms initially, but 24-72 hours later, he may manifest symptoms of concussion. That’s because if the brain matter and neurons are injured, they undergo chemical changes to create a lower electro-chemical threshold for exercise or cognitive challenges to create symptoms of concussions. So because that threshold has been lowered due to the brain trauma, you may see the concussion symptoms come down at a later date on a delayed basis due to cognitive or physical challenges. The key thing is even though he’s not diagnosed with a concussion now, the team physicians and trainers need to be very vigilant and keep a close eye on hoe he’s doing physically or cognitively. If he were to start demonstrating any of the red flags, they might have to re-assess the injury and re-label it as a concussion.”