When Angie Yen woke up on April 28, it felt like just another morning.

But when the 27-year-old dentist got in the shower and started singing — something she always did — she was shocked by the sound she heard.

Instead of her normal Aussie accent, Yen was stunned to hear a "foreign accent" that "sounds very Irish".

"When I started singing I was singing in a different sound and also talking words in a funny accent," the Brisbane woman told news.com.au.

Panicked, she phoned one of her friends who was in equal disbelief at her sudden accent change.

"He was the one who actually told me and sent me links later about foreign accent syndrome (FAS), he had watched some videos on YouTube years ago," she said.

Fearing she had — or was about to — have a stroke (a possible cause of FAS), Yen went to hospital that day.

But because she was showing no other signs of illness she was discharged and told to go home and rest.

"They couldn't do anything, I was normal. I just sounded different and (they said), 'you're still healing from your surgery so maybe your vocal cords are damaged'," she said.

On April 19 Yen had gotten her tonsils removed – a simple procedure that had taken just half an hour.

Her ear, nose and throat specialist also suggested Yen wait to see if her voice change disappeared on its own.

But as the days wore on, Yen said her new accent didn't go away, leaving her friends and family in disbelief.

"Most of them just laugh, my friends (at first) just are like, 'oh my goodness it's not real, you're faking it'," she said.

"But after a while they realise I'm not joking because there's no way you pretend in an accent for two or three days, even in a normal conversation."

Two days after waking up with the foreign accent, Yen decided to make a TikTok account and go public with her journey.

Yen said she was motivated to share her experience after seeing how people with FAS get treated like a "joke".

"I can 100 per cent connect with them and know what they are feeling because I feel so lost because it's so rare," she said.

"But I hope by using this platform to spread awareness that hopefully one day people know if you wake up with a foreign accent or a weird-sounding accent that you go straight to a hospital, there's something wrong in your brain that needs to be looked at and it's not just something funny that you laugh about."

It's now been 12 days since Yen woke to a "foreign accent" which hasn't gone away, leading her to believe she does in fact have FAS.

She is getting an MRI and blood test this afternoon and is booked in to see a neurologist on the advice of her ear, nose and throat specialist.

Yen said she still struggles to accept her new accent but is thankful for the support of her loved ones.

"I'm very lucky to have very supportive friends and family so whether there's anything wrong in my head I don't know, if they find something hopefully there is a cure or treatment for it," she said.

What is foreign accent syndrome?

"Foreign accent syndrome is when someone suddenly develops what is perceived to be a foreign accent," Professor Lyndsey Nickels, a speech therapist and language impairment specialist at Sydney's Macquarie University, told news.com.au.

"This is despite the person having never necessarily having spoken that particular foreign language, never necessarily having spent time abroad, nor having mixed with people with that foreign accent."

Nickels, who is not treating Ms Yen, said she had never heard of an instance where tonsil surgery caused FAS.

"Foreign accent syndrome is usually thought to be caused by brain damage (eg from stroke or brain injury following a bump to the head) which causes difficulty with moving or co-ordinating the muscles that we use to produce speech (lips, tongue, voice box, breath)," she said.

"In turn this means that the speech sounds change."

Cases of FAS are considered to be rare due to the fact that not every case will be documented, and it is also uncommon for speech muscle problems to manifest as a particular accent.

"When the new speech sounds are similar to those of an existing accent, the speaker can be perceived to be speaking with a foreign accent," Nickels said.

"People with foreign accent syndrome don't speak with all the features of a foreign accent, but there are enough things about the way they speak to make it seem as though they have a different accent."

Treatment for FAS is available from speech therapists and pathologists.

"They have expertise in this area and will work on improving speech movement and co-ordination to regain accuracy of speech sounds," Nickels said.

"Many people will also get some spontaneous improvement soon after the injury too."