The unnamed 61-year-old, from NY, is said to have "lost touch with reality" before being brought to hospital in 2015.
Only once his brain scan results and other tests were out the experts found out that he may have had a variant of Creutzfeldt-Jakob disease (vCJD). vCJD is a type of a rare neurodegenerative ailment that can be fatal.
The fatal brain condition is usually tied to the mad cow disease, and only a few hundred cases of the have ever been reported, according to Live Science. Chen said it also wasn't clear if the man ate the brains themselves or meat that was contaminated with brain matter, according to the site.
The New York Post reports the man had been known by his family to "eat squirrel brains".
The authors of the report, led by medical resident Tara Chen, incidentally came across the case, not having treated the man himself.
Creutzfeldt-Jakob disease (CJD) is a progressive neurological disorder that affects only about 1 in a million people each year worldwide, according to the National Institutes of Health (NIH).
Theresa May says Brexit transition extension would last ‘matter of months’
The US administration has notified Congress that it will seek trade pacts with the EU, Japan and Britain. Britain says it has not asked for an extension - but didn't rule it out Wednesday.
There are three forms of CJD: one that is inherited, one that comes from exposure to infected tissue from the brain or nervous system, and one that is "sporadic" and does not appear to have a genetic or environmental cause.
It might be shocking for many but, indeed, there was an American who ate squirrel brains. Initial signs and symptoms typically include personality changes, anxiety, depression, memory loss, impaired thinking, blurred vision or blindness, insomnia, difficulty in speaking, difficulty in swallowing and, sudden, jerky movements or seizures.
Most people who contract it only live around a year.
There is no treatment or cure for CJD.
First described in 1996 in the United Kingdom, this beef is already infected with a disease that is similar called bovine spongiform encephalopathy, or "mad cow disease".
The high number caused doctors to review all suspected cases at the hospital between 2013 and 2018. Although the patient passed away after his diagnosis, Chen and colleagues are working to obtain access to his medical records to see if CJD was confirmed at autopsy. More important, four out of the five "mad cow disease" cases occurred across the USA.
The team is now working to obtain the patient's medical records to see if a coroner confirmed CJD upon his death.