The curious case of Sarah Colwill gained global media coverage in 2009.

The 41-year-old awoke one morning to find her Devon drawl replaced by a Chinese accent, after years of severe migraines.

To tabloid editors, such tales of foreign accent syndrome (FAS) provide silly season page fodder, written with a smirk.

For news broadcasters they’re an ‘and finally’ item, with cases reported like dispatches from the Twilight Zone.

“Annie went to sleep speaking like the Queen, and woke up sounding like Rab C. Nesbitt,” wrote the Scotsman in 1997 for example.

As FAS expert Nick Miller can testify, however, the condition is neither as rare or as trivial as the media would have it.

The professor of motor speech disorders at Newcastle University, who has been published extensively on FAS, says: “In a transitory phase after stroke or brain injury it’s actually not uncommon. If you work in neurology, healthcare of the elderly or on a stroke ward, there’s a likelihood that you will come across it.

“However, it is the cases in which people are le with a different accent permanently that are rare.”

In terms of its psychological impact, “most people find it devastating. The way you speak is a really important part of your personality.

“Whatever you put out to other people, whether you’re angry, tired, happy or sad, where you’re from, what your political views are, are all conveyed in your speech. Suddenly that’s all robbed from you and you can’t express how you feel properly.”

FAS describes the phenomena in which a neurological incident such as stroke, brain injury or degenerative condition, causes an apparent change in accent.

Around a third of strokes will result in speech problems – a proportion of these will just happen to culminate in giving the auditory illusion of an accent.

“It’s partly in the mouth of the speaker and the power of movement they have over their lips, tongue and vocal cords,” says Miller.

“But it’s also in the ear of the listener who associates  the changes with foreignness rather than just disordered speech. It’s a bit like when you look at a cloud and you see a giant fluffy rabbit instead of water vapour.”

There are also purely psychological cases of FAS. In the same way a tick, limp or apparent deafness or blindness might occur in someone with nothing physically wrong with them, individuals may suddenly adopt a new accent.

It is generally accepted that between 10 and 30 per cent of any cases arriving in neurology departments are ultimately found to be functional, rather than caused by stroke, injury or disease.

A foreign accent is just one of a myriad of issues that can present in this situation – alongside paralysed arms and legs, blackouts, memory loss and many more symptoms.

One such case was documented in the book Foreign Accent Syndromes, the stories people have to tell, by Miller and Jack Ryalls.

Mrs Y was strongly religious but had committed a grievous sin. Discussions revealed how she had adopted a new accent as part of a whole new persona that distanced herself from her sinful past.

Miller says: “They might have a social anxiety problem and developing a foreign accent might be a protective strategy to distance themselves from a social situation. Their accent may deflect criticism from their true self.”

In FAS with a neurological origin, ‘t’ sounds might be pronounced with a ‘d’. In normal speakers, vocal chords will begin to vibrate around 100 milliseconds earlier for ‘d’ than a ‘t’ – which involves a miniscule release of air into the mouth before being released. “A neurological problem alters the timing of the actions taking place.

It affects the underlying coordination of movement,” says Miller. “Also, lip weakness or difficulty coordinating the two lips together can result in a ‘w’ sound becoming ‘v’. So ‘a glass of vater’ may sound like a German or Russian speaker. Sometimes patients can’t say ‘r’ words so ‘writing’ may start with a ‘g’ and become very eastern European.”

Stress and intonation also characterise an accent. “Welsh and Swedish people tend to have a sing- song style to their speech. If you have a head injury, for example, you might not be able to control when your speech goes up and down and your new intonation pattern might also make you sound Welsh or Swedish.”

In whatever form the condition takes, its fallout can be severe.

A 2011 study lead by Miller and fellow speech and language experts into ‘insider perspectives’ of FAS concluded that: “Without exception, participants confirmed that FAS exercised a life-changing influence on themselves, but potentially on their family, friends and associates too.”

It also found that feeling like a “stranger within  a community with a different accent” was a common experience.

Miller says: “FAS causes a lot of stress and strain on families. With a stroke or a head injury a person may have a distorted face, weak arm or problems walking. But nobody would associate them with talking in a foreign accent.

“There is a tendency for family members to think ‘you’re having us on, when are you going to come to your senses and talk properly again?’ They often can’t.”

Miller and his collaborators questioned 13 people with neurogenic FAS on their experiences of the condition.

Many of their answers were loaded with frustration and despair. One respondent lamented: “I went through this door and when I came through it the next morning it was not me… Where did I go? I was somebody else.”

Another said: “I find it embarrassing, shameful and insulting to my intelligence, lose my self- respect and hate being this way…It causes me great distress because this isn’t the way I used to be and hurts me immensely – more than I can ever express.”

The study also uncovered many of day-to-day irritations of life with FAS. It caused once- loving pets to shun their strange-speaking owners. Sufferers avoided shopping for fear of embarrassment. Another cancelled an evening out for a pizza in case her new Italian accent o ended the waiters.

One interviewee said her friends began calling her ‘poshy’ before gradually drifting out of her life. Another said they’d lost their Britishness.

A respondent with a newly acquired eastern European accent said they almost ‘felt at home’ on a trip to Croatia, such was the feeling of isolation in their native UK.

Not every FAS experience is a negative one, however, as one person questioned put it: “Because I express myself differently, I think it has opened me up as a different person and given me a different experience of life.”

Miller says: “Sometimes, even when the power and range of movement has returned to the vocal chords, lips and tongue, the individual will still speak with the foreign accent.

“Usually this is because there has been some gain from the new accent, perhaps people attended to them more, or were more interested in what they were saying.

“It could also be because they lack the confidence to try to return to their original accent; just as someone whose power returns to their leg after a stroke may still revert to a limp as they are unsure about using it fully.”

FAS cases will often receive cognitive behavioural therapy or counselling. The functional version of the condition can be a manifestation of a range of mental health issues, including depression, anxiety, schizophrenia and conversion disorder, and will be managed accordingly. Neurogenic cases usually undergo speech therapy.

“The speech therapist will identify the changes  in speech that have made the person sound foreign. Is the intonation and stress on the wrong part of the word? Is the voice rising when it should be falling? Are there other differences in particular sounds?

“They then target those in therapy, improving the range, power and speed of movement to the lips and tongue. It can be a lengthy process of several months.”

Overcoming FAS can be incredibly challenging for the individual – given that they are usually also coming to terms with a life-changing event such as stroke or head injury.

They may already be battling with a new sense of identity, even without the accent change.

Understanding of FAS and the development of faster treatments is clouded, by its origins in both the neurological and psychological realms.

It is further complicated by the hugely complex relationships humans have with accent. Accents are deeply embedded in our psyche and we have the ability to alter them on a daily basis, depending on the social situation we’re in.

All of which highlight the need for more research into FAS in the future.