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Fernando Alonso of Spain and McLaren Honda poses for a portrait during day three of Formula One Winter Testing at Circuit de Catalunya on February 21, 2015 in Montmelo, Spain.
On February 22, Formula 1 racer Fernando Alonso's McLaren slammed into a wall at approximately 93 mph while coming out of the third turn at the Montmeló circuit track in Barcelona.
At some point he apparently lost consciousness and showed signs of confusion, so he was airlifted to a hospital in a medical helicopter.
It was an odd crash on a pre-season test run for one of the greatest drivers in the world, but even stranger and scarier was his response when doctors asked him "who are you?" and "what do you do?" - standard questions for someone who suffers a head injury and likely has a concussion.
"My name is Fernando, I race karts and I want to be a Formula 1 driver," was his response, according to the Spanish newspaper El País.
He remembered his 13-year-old self, who wanted to become an F1 racer when he grew up, but nothing beyond that.
He had forgotten the past 20 years of his life, the fact that he was a two-time world champion in his sport, and the four Real Madrid Champion's League wins that had happened in the past 20 years.
A week later his memory had come back, but that leaves us with the question of what happened.
How does someone lose 20 years?
Alonso received a variety of tests including an MRI and CT scan, which ruled out pre-existing abnormalities like epilepsy or an electric shock, and also shows that he didn't suffer lasting damage.
And so in the opinion of neurologist Dr. Rafael Blesa, director of the neurology department at Sant Pau Hospital in Barcelona, this is just normal memory loss that can occur after a concussion.
As Blesa tells El País, "A concussion like that one happens because the brain suffers a blow that affects the neural synapses... When that happens, biochemical substances do not work [normally], meaning that the brain tries to find a memory but fails. Depending on each case, the recovery time can vary. You have to take into account the fact that, within the brain, the circuits that are most sensitive to an impact like his are connected to the memory."
In other words, the brain disruption caused by a concussion temporarily damaged Alonso's brain circuits related to memory. Fortunately in this case, he seems to have recovered fully.
This temporary memory loss is called retrograde amnesia, where someone forgets memories they'd acquired before the injury - it can cover a short period of time or a time period of years or decades, and can be the result of a concussion or other brain damage. (That's distinct from anterograde amnesia, where someone becomes unable to form new memories.)
Alonso seems to have recovered from his concussion completely, even though he was kept in the hospital three days, a length of time that indicates his concussion was quite severe. Amnesia associated with concussions is usually mild.
Multiple concussions can lead to brain damage over time, and getting two concussions in a short period of time can be extremely dangerous and cause serious trauma, which is probably why McLaren is keeping Alonso out of the Formula 1 season opener on March 15 in Australia.
A final impact test will be administered before Alonso is allowed to race again, but provided his amnesia was caused by a concussion that he seems to have recovered from, as his doctors and McLaren team officials say, he should be fine. He released a YouTube video on February 27 telling fans that he is completely okay and excited to race again.