Arizona native Michelle Myers woke up two years ago sounding like she'd just come back from a very long vacation.

The 45-year old has never been to London, but after falling asleep with a headache, she awoke with what sounded like a British accent, according to ABC news affiliate KNXV.

What Myers experienced may be a case of a rare illness called Foreign Accent Syndrome, or FAS. It's less implausible than it sounds – the disorder typically materialises after a neurological trauma, such as a brain injury.

According to the University of Texas at Dallas, FAS has been documented in hundreds of cases globally, including accent changes from Japanese to Korean, British English to French, American English to British, and Spanish to Hungarian.

FAS is easier to understand when you think about the minute changes that characterise what we perceive to be an accent.

Silence a few hard "r"s, curl the tongue on the occasional vowel, seal the lips, or swallow a consonant, and you're suddenly speaking as someone might sound on a different continent.

Making all these changes consistently – every time they utter a certain vowel, letter, or consonant – is what distinguishes people with the syndrome from someone attempting an accent.

The Norwegian who sounded like a German at the height of WWII

On an unlucky day in 1941, at the height of World War II, a piece of shrapnel pierced the brain of a Norwegian woman known as Astrid L. The injury occurred during a raid in her German-occupied country, and when she regained consciousness, she spoke with the accent of the enemy.

"She complained bitterly of constantly being taken for a German in the shops, where consequently the assistants would sell her nothing," neurologist Georg Herman Monrad-Krohn wrote in the first detailed case report on Foreign Accent Syndrome.

Since then, researchers have published more than 100 case studies of FAS. Usually, the condition arises in a person whose first language is somewhat similar to the language that their new accent suddenly appears to mimic.

In Myers' case, she woke up sounding like she spoke British English, as opposed to the American English she has spoken all her life.

An American with a British accent

When Myers speaks, "everybody only sees or hears Mary Poppins," she told ABC news affiliate KNXV.

It's unclear precisely what triggered Myers' symptoms – or if she actually has FAS or something else entirely.

The syndrome typically surfaces after brain damage. In most cases, the precursor is either a stroke or a traumatic brain injury, when the brain regions linked with speech are harmed.

In other cases, the syndrome may be exacerbated by an underlying psychiatric disease such as schizophrenia, but it is unclear if that illness on its own would be enough to trigger FAS.

"In the cases of psychosis, the new accent persists throughout the entire episode and may disappear after the psychotic episode subsides," the authors of a 2015 case report identifying a 34-year-old woman who had symptoms of FAS and schizophrenia wrote.

Myers told KNXV that this wasn't the first time she'd awoken with a different accent; throughout her life, she's temporarily spoken with Australian and Irish lilts for as long as two weeks.

In this current episode, however, the British accent has persisted for about two years, she said.

This article was originally published by Business Insider.

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