"I guess I'll just start out with where this all kind of began," said NASCAR's most popular driver Dale Earnhardt Jr., at the start of the press conference at Charlotte Motor Speedway following the shock announcement that he wouldn't be competing in this weekend's race because he was suffering from concussion.

Earnhardt's current condition stems from being caught up in the last-lap accident last Sunday at accident that swept up 25 cars into one of the biggest wrecks the series has seen in recent times. But he admitted that the problem actually goes back rather further than that.

"We had a test at Kansas about five weeks ago," he said. "We blew a right front tyre going into turn 1, and I remember everything about that accident and everything after that accident, but I knew that I didn't feel ... You know your body, and you know how your mind works, and I knew something was just not quite right."

However, Earnhardt hadn't sought medical advice after the accident because it would have meant the end of his Chase prospects before they'd even got underway.

"I decided to just try to push through and work through it - I'd had concussions before and knew exactly kind of what I was dealing with," he said. And sure enough, he was soon feeling on the mend - although he admitted that he'd participated in several races feeling distinctly underpar.

"I felt pretty good after a week or two and definitely 80, 90 per cent by the time the Chase started, and by the time we got to Talladega I felt 100 per cent - felt really good," he said. "And then the accident at the end of that race ...

"I was hit in the left rear quarterpanel, and it was sort of an odd kind of a collision where the car spun around really quick and just sort of disoriented me, and I knew that I had sort of regressed and had a bit of a setback, and knew," he said.

Earnhardt had appeared to escape relatively lightly from the Talladega wreck, even stopping to pick up his team mate Jimmie Johnson who needed a lift back to pit lane after the #48 was heavily damaged.

"Again, you know how your body is and you know when something is not quite right, and I knew as soon as it happened that I had reinjured myself, for lack of a better way to describe it. It was not even half of the impact that I had at Kansas, but it was enough to cause me some concern.

"I went a couple days wondering how my body would react and sort of waiting for it to process what was happening," he continued. "I started having headaches and stuff immediately after the wreck, and then into the next day and into Tuesday, and I thought, man, this is pretty soon after the other accident in Kansas. I should probably take this really seriously and seek some professional opinions on this ... I contacted my sister, and we talked about seeing a neurosurgeon, and we ended up getting steered toward Dr Petty."

Dr Jerry Petty is a neurosurgeon who works extensively with NASCAR and with the NFL. He ran tests on Earnhardt that included an MRI scan to check for a more serious cerebral haemorrhage a contusion, and everything came back looking clear.

"I was really honest with him about how I felt and honest with him about the whole process from Kansas all the way on," Earnhardt added. "He spent the night thinking about what we discussed and everything that we did on Wednesday and couldn't, in good faith, couldn't clear me to race this weekend.

"I trust his opinion," said Earnhardt of Dr Petty. "That's why I went to see him. He's been a good friend of mine for a long time and has helped me through a lot of injuries before, so I believe when he tells me I don't need to be in the car and I need to take a couple weeks off that that's what I need to do."

Dr Petty was also present, at the press conference at Charlotte on Thursday, and agreed with Earnhardt' account.

"I couldn't give you a better history than he just did," said the neurosurgeon. "He had no amnesia on either side of either of the incidents, which is very important.

"What he has is really called a diffuse axonal injury, and it's something that does not show on scans, and we don't have test that will show that other than symptoms and signs," Dr Petty continued. "Sometimes there will be some residual signs left over, but Dale had none of those. His eyes did what they were supposed to do; his balance tests and so forth are perfect."

However, that didn't mean that Earnhardt's concussion wasn't genuine or potentially serious. "By and large it's the history that the patient gives is the thing that tells you that they've had a concussion. A concussion can be seeing stars; a concussion can be just being addled for a minute. Any time the brain is not doing what it's supposed to be doing after an acceleration or deceleration, that's a concussion.

"The one symptom that is more important than all the tests is headache. As long as there's any headache the brain is not healed, and until that's healed and had some time to rest and then you provoke it again and can't make it happen again - it's then you feel like you're on the road to recovery.

"What we'll do now is we want him to have four or five days after he has no headache, and then we'll give him some sort of test like to get his pulse rate up, see if we can provoke a headache, and then if we can't, we'll let him go out and drive a lap or two and see how that goes, and if that goes well, we'll probably clear him to race."

Dr Petty's approach to Earnhardt's situation has been informed by his work in the NFL, where a concussion automatically means that a player has to sit out a week on the bench.

"We've patterned our rules [here in NASCAR] after the NFL to a degree," he said. "We would do the same procedure about giving them five or six days without a headache and then doing provocative tests. I don't think that, so far as I know, they're not allowed to go back any earlier than some of the NFL guys are allowed to go back."

Earnhardt's car owner Rick Hendrick was fully supportive of the way that Earnhardt had handled the situation this week.

"I think that's one thing everybody admires about Dale is how honest and up front he is," he said. "He cares a lot about the team, his fans, and the sport in general. But when he knew that there was something not right, he went to see Dr Petty here, and I admire him.

"The good news is this is kind of preventative maintenance not to take a chance and there's no damage," Hendrick added. "We were so happy yesterday that the MRI was completely normal, no damage. We don't have a problem there."

Earnhardt added that he was feeling otherwise fine, and would dearly love to race this weekend. He said there was no question that the two-week benching could end up stretching through to the end of the season in November.

"I'd like to get back in the car and compete as soon as I can, as soon as the doctors feel like I'm able to do that," he said. "I would love to race this weekend, and I feel perfectly normal and feel like I could compete if I were allowed to compete this weekend. But I think that the basis of this whole deal is that I've had two concussions in the last four to five weeks, and you can't layer concussions. It gets extremely dangerous."

As for this weekend, Earnhardt said that he had no intention hanging around Charlotte and getting in the way feeling like a spare wheel.

"Yeah, I don't have any plans of being here this weekend," he said. "I think that I'd be more of a distraction to the team and their efforts in the race. I think they've got a good opportunity to have a good run this weekend, and I feel like minimising the distraction would help them out.

"I'm really going to feel pretty odd not being in the car. I'm anxious, real, real anxious just to get back into the car," he admitted, wrapping up with: "I think you learn not to take things for granted, and I just hate that this has caused such a fuss."

Regan Smith will take over Earnhardt's seat for this weekend's race at Charlotte and next weekend's event at Kansas, after which Earnhardt hopes to return to action for the last four races of the 2012 season.