The condition, called "foreign accent syndrome", affects only a tiny number of patients.
It can mean that a native English speaker can end up sounding more like Spanish or French.
It can follow a stroke - or another kind of head injury, and while the problem often clears up on its own, it can be another highly upsetting blow for patients often struggling with other disabilities.
To add insult to injury, some doctors dismissed the problem as more likely to be psychiatric in origin than physical.
Now researchers at
A small number of them all had tiny areas of damage in various parts of the brain.
This might explain the combination of subtle changes to vocal features such as lengthening of syllables, altered pitch or mispronounced sounds which make a patient's pronunciation sound similar to a foreign accent.
Dr Jennfier Gurd, who led the research with phonetician Dr John Coleman, said: "The way we speak is an important part of our personality and influences the way people interact with us.
"It is understandably quite traumatic for patients to find that their accent has changed.
"Patients derive some comfort from knowing more about the causes of their rare condition and many are happy to help scientists to understand better the nature of the brain and its role in human accents."
Dr Coleman told BBC News Online: "There is a good likelihood in time you are going to improve and become more like you used to be."
Read article here: http://news.bbc.co.uk/2/hi/health/2300395.stm