You fall over a Segway perhaps and you lose the ability to speak your native language?
A CZECH speedway driver knocked unconscious in a crash stunned ambulance drivers when he woke up speaking perfect English.
18-year-old Matej Kus was out cold for 45 minutes after the crash, but when he woke up he conversed fluidly in English with paramedics, even speaking in an English accent.
The teenager had just begun to study the language and his skills were described by friends and team-mates as “basic at best”.
[snip]
"Matej didn't have a clue who or where he was when he came round. He didn't even know he was Czech.
"It was unbelievable to hear him talk in unbroken English."
Unfortunately, the speedway driver's new found skills didn’t last and he remembers nothing of the accident or the following two days. He is now keen pursue studies in English.
He told the Daily Mail, through an interpreter: "It's unbelievable that I was speaking English like that, especially without an accent.
"Hopefully I can pick English up over the winter for the start of next season so I'll be able to speak it without someone having to hit me over the head first.
"There must be plenty of the English language in my subconscious so hopefully I'll be able to pick it up quickly next time."
I mean... It would explain a lot....
Update 9/22: It happened again, although this time it was just the accent:
A 10-year-old boy has woken up with a posh English accent after undergoing life-saving brain surgery.
William McCartney-Moore's usual northern England accent was replaced with a much more refined tones complete with elongated vowels after he had an operation to remove fluid on his brain.
William, who is from York, needed the surgery after falling ill with a rare strain of meningitis last March.
"He survived the operation and the most amazing thing is that he came out of surgery with a completely different accent,'' his mother Ruth McCartney-Moore told the York Press newspaper.
"He went in with a York accent and he came out all posh.
"He no longer had short 'a' and 'u' vowel sounds. They were all long.''
Mrs McCartney-Moore said doctors initially thought her son was going to die.
He lost everything, she said, including his ability to read, write and recognise different objects.
But William began to recover after the operation and was out of hospital in about a month.
"We went on a family holiday to Northumberland and he was playing on the beach and he said,
'Look, I've made a sand castle' but really stretched the vowels, which made him sound really posh,'' Mrs McCartney-Moore said.