Bronwyn Fox, a multiple sclerosis sufferer from the southern New Zealand city of Invercargill, told the Southland Times she woke one morning to find her voice had changed, and an MRI scan showed two lesions on the back of her brain.
Her doctor believed the change in her speech was related to the lesions but had not been able to offer much further help.
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Fox is a third-generation New Zealander who has never visited the United Kingdom and when she first talked to friends on the phone with her new voice they thought it was a hoax call and hung up.
"People say 'where do you come from?' And I say 'Winton' and they say "no, no but where are you from originally?'," she said in her new accent.
"It's very hard for people to realise it's come from my head."
Her husband Rex was unconcerned.
"It's quite entertaining. It brightens up a boring day sometimes," he said.
Only a few dozen people worldwide have been officially documented as suffering from the syndrome since it was first recorded in 1907.
It is linked to damage to the part of the brain that controls speech.
Other known cases of the disorder include an English woman speaking with a French accent after having a stroke and a Norwegian woman who spoke with a German accent after being hit by shrapnel in 1941.
Earlier this year a woman in England began speaking with a Chinese accent after suffering a migraine.
"I've never been to China. I just want my own voice back but I don't know if I ever will. I moved to Plymouth when I was 18 months old so I've always spoken like a local," Sarah Colwill told the Daily Mail.
