May 5, 2011 -- Karen Butler is from Oregon, not England. When asked where she got her accent, she says from her dental surgeon.

In 2009 Butler, a 56-year-old tax consultant in Toledo, Ore., awoke from denture implant surgery with an accent that's a bit British with a Transylvanian twang, and it just sort of stuck.

"I had just had surgery, so at first we assumed it was because of all of the swelling," said Butler. "But within a week the swelling went down and the accent stayed."

Butler has foreign accent syndrome -- a condition so rare that only about 60 cases have been documented worldwide. Often preceded by a small stroke, the new drawl is thought to stem from a minor injury to a tiny area of the brain responsible for language pattern and tone.

"This is a very small part of the brain that controls the articulation and the intonation of speech that's affected, and that's why it's so rare," said Dr. Ted Lowenkopf, a neurologist and medical director of Providence Stroke Center in Portland, Ore., in an interview with ABC News affiliate KATU. "The chances to hit such a small area are more than a million to one in a stroke."

Because certain blood vessels in the brain are more prone to blockages, a stroke often damages parts of the brain responsible for language production and comprehension.

"Stroke happens in very predictable ways," said Dr. Julius Fridriksson, an associate professor of neuroscience at the University of South Carolina, who has seen many stroke patients but only a couple with foreign accent syndrome. "This type of damage is out of the ordinary."

Butler said she was never tested for a stroke because she felt fine.

"I appear to be completely normal otherwise," Butler said, adding that she never felt any pain or had neurological symptoms other than the change in her speech. "And I'm quite OK with [the accent]."

Nevertheless, Butler endures her fair share of teasing -- mostly from her family. She struggles with the letter "W," which she pronounces like a "V." So her daughter once asked her to say, "I vant to suck you blood" and recorded it with her cell phone as a ring tone.

But Butler brushes it all off.

"With a sense of humor, you can face anything," she said.

Not everyone with foreign accent syndrome is so lighthearted.

"It's very much related to a person's coping ability," said Fridriksson. "Some people become isolated because they're so self-conscious about it."

Although Butler's accent sounds vaguely British -- Welsh, even -- it's purely coincidental.

"Although we think it sounds like a British accent, if you had a language expert listening to her, they would say that's not an English accent," Lowenkopf told KATU. "It's sort of an amalgam of different-sounding speech that sounds like a foreign accent. But it's not truly typical of any one foreign accent."

Because her accent flipped between tax seasons, Butler was forced to start many phone conversations explaining to her clients that she was indeed still Karen Butler, their tax consultant from Oregon. Her husband Glen does his share of explaining too.

"[People] have wanted to know where I met her," he told KATU with a smile.

The accidental accent is usually fleeting and goes away within weeks or months, Lowenkopf said. But the longer it lasts, the more likely it is to stick for good.

Butler kept her voicemail greeting from before the surgery to remind her and others of her once-Oregonian sound. And although speech therapy could help her get it back, she said she's used to her new "foreign" accent.

"I used to be painfully shy, and now there's always something to talk about," she said.