Diagnostic dilemma: After surgery, a 17-year-old could speak only a foreign language

The patient: A 17-year-old boy in the Netherlands

The symptoms: The teenager was admitted to a hospital in the Netherlands for knee surgery after getting injured while playing soccer. The surgery was successful, but when the patient woke up from the anesthesia, he spoke exclusively in English and insisted "repeatedly" that he was in the U.S. Prior to this incident, he spoke the language only during English class in school.

He did not recognize his parents and could not speak or understand spoken Dutch, his native language. According to a report doctors wrote about his case, the patient had no history of psychiatric symptoms and no relevant medical family history, apart from some instances of depression on his mother's side of the family.

What happened next: The nurse who initially noticed the patient speaking English was not immediately worried by it, thinking the teen was experiencing emergence delirium — a state of confusion that can occur during recovery from anesthesia. However, when medical staff still could not get the patient to speak a single word of Dutch a few hours later, they called for a psychiatric consultation.

Related: Can you forget your native language?

The psychiatric team found the patient relaxed and attentive. He was able to answer questions, albeit in English spoken with a Dutch accent. Later on, he started to give short answers in Dutch but found it difficult to do so.

The diagnosis: The 17-year-old was diagnosed with foreign language syndrome (FLS), which happens when patients suddenly and involuntarily switch to using a second language instead of their native language for a period of time.

The treatment: A neurologist found no abnormalities during a full neurological examination of the patient. Then, 18 hours after his surgery, the teen was able to understand Dutch but still couldn't speak it. Some of the teen's friends came to visit him the day after his surgery, and suddenly, he was able to understand and speak Dutch again.

Because the teen spontaneously started speaking in his native language again, doctors saw no need to run any neuropsychological tests, electroencephalograms (EEG) or other types of brain scans on him. He was discharged three days post-surgery.

What makes the case unique: FLS is rare, with only about nine cases described in medical literature. In most of these cases, the patient was a white male who switched from their native language to another one they had learned later in life; the patients weren't typically bilingual growing up. The race of the patients in two cases was not documented.

The authors of the case report said FLS is rarely seen in children, and they suspected that they were the first to formally document a case of FLS in an adolescent. In total, they found eight reported cases of FLS that were similar to that of their patient, in which the person affected switched to a completely different language rather than speaking in a way that could be perceived as a foreign accent.

This is what happens in a related condition — called foreign accent syndrome — in which people adopt a speech pattern that makes it sound like they're speaking with an accent. The rare condition has often, but not always, been seen in the context of brain injuries.

Exactly why FLS happens is unknown, although there have been other cases in which the syndrome emerges after anesthesia. The case report authors noted that an anesthetic's effects on cognition, as well as the clearance of anesthetic drugs from the central nervous system, can lead to emergence delirium. For that reason, they're not sure if FLS can be classified as a distinct condition or merely a variation of emergence delirium.