Lisa Alamia had the jaw surgery in December. She underwent the procedure to correct a serious overbite, and it was a success, according to Houston Methodist Sugar Land Hospital. The 33-year-old woke up and had minimal swelling.

But then she began to talk. And she sounded … different. Very different.

The voice coming out of Alamia’s mouth didn’t sound like it belonged to a Houston-area native. It sound very British.

“My daughter laughs at the way I say ‘tamales.’ I used to be able to say it like a real Hispanic girl,” Alamia told KHOU. “Now, I cannot.”

Alamia said her surgeon thought the voice change was “just a psychical result of the surgery and that it would go away as I healed,” according to the hospital. But months later, she still speaks as if she’s from across the pond.

Eventually, she saw neurologist Toby Yaltho at Houston Methodist Sugar Land Neurology Associates, who diagnosed her with a very rare condition: foreign accent syndrome, or FAS.

“This is a fascinating and very rare case,” Yaltho said in a release. “Most neurologists work their entire careers and never come across FAS.”

The rare speech disorder was first described in 1907 by French neurologist Pierre Marie, and since then, there have been only about 100 documented cases. A person with FAS has an accent considered by the patient, others and doctors to sound “foreign” and unlike the patient’s previous dialect. Previous exposure to such an accent isn’t necessary.

FAS usually follows stroke, while it’s also been diagnosed following traumatic brain injury, cerebral hemorrhage and multiple sclerosis. Only a few cases seem to have psychological origins.

In the case of Alamia, Yaltho conducted MRI scans to see if she had suffered a stroke, seizure or another injury that led to FAS. The neurological exam also included an electroencephalogram to detect abnormal brain waves.

The cause of Alamia’s FAS remains a mystery.

“Everything came back normal,” Yaltho said in a release. “There was no evidence of stroke or other abnormalities.”

Meanwhile, Alamia was still in Texas, walking around with a voice that sounded like that of a stranger.

“Mom” comes out as “mum.” And “kidding” sounds like “kitten,” she told KHOU.

The rarity of the condition makes some reluctant to share their diagnoses.

“I didn’t know the reaction I was going to get from people,” Alamia told KHOU. “So I didn’t know if they’re going to judge me. Are they going to think I’m lying or even understand how I’m speaking?”

An Indiana woman named Ellen Spencer, who began speaking with a French-sounding accent following a stroke-like episode, recounted the reactions she would get from people following her FAS diagnosis.

“Peoples would say, you’re making it up; it’s fake; she sounds stupid,” she said on the NPR’s Snap Judgment. “But there’s no question – something happened in my brain.”

In one case, reported in 2011 in BMJ Case Reports, a 55-year-old Texas man spoke with what “multiple medical personnel noted” as what sounded like a Cockney accent. After suffering a seizure, though, the accent seemed “to have reverted to his Texas accent.”

The new accent in people with FAS may persist for only months, or years. The condition could also be permanent. Treatment includes speech therapy, which Alamia is undertaking.

But there is no known cure for FAS.

“The human brain is a complex organ, and we don’t know if we will ever be able to completely understand what causes FAS,” Yaltho said.