A 60-year-old man in Spain spent weeks being worked up for metastatic brain cancer. The multiple lesions scattered across his brain turned out to be encapsulated tapeworm larvae, and on the MRI his doctors could see the worms' heads.
It began with a headache he couldn't shake for two weeks, along with subtle changes in his behavior. A neurological exam found only a mild delay in his movements. His blood work was normal except for elevated IgE, an immune signal tied to allergies, autoimmune disease, and parasitic infections. Then a CT scan showed something harder to explain away: multiple lesions throughout his brain, with swelling.
The doctors' leading suspicion was cancer that had spread there. He wasn't immunocompromised and had never traveled internationally, so they went looking for the primary tumor with a whole-body contrast CT, a colonoscopy, and a PET/CT scan used to map cancer. Every test came back clean. No malignancy anywhere.
So they took a sharper look with an MRI, and the lesions resolved into something no tumor does: encapsulated larvae of the pork tapeworm, Taenia solium, complete with visible scolexes, the worms' heads. Antibody testing confirmed it. The diagnosis was neurocysticercosis.
What's true, and what the viral version skips
The version racing around social media (worms "burrowed their way into his brain") is, unusually, basically accurate. [1] The only correction worth making is that "brain cancer" was never a diagnosis, just the doctors' working theory before the imaging improved. And the larvae don't drill in from outside. Taenia solium eggs get swallowed through fecal contamination, hatch in the gut, slip into the bloodstream, and ride it into tissues including the brain, where they wall themselves off. When they settle in the central nervous system, that's neurocysticercosis.
How a non-traveler got it
The parasite isn't endemic to Spain, and the man hadn't been abroad. Until he retired a decade earlier, he worked in construction alongside coworkers who had migrated from regions where the pork tapeworm is common, one of whom apparently had an infection. His doctors speculate a rare case of cryptic, fecal-oral transmission from shared meals and bathrooms. That part is informed speculation, labeled as such in the report.
One widely shared post summed up the collective reaction in two characters: "Yay? 😬" [2]
He got lucky on location: the worms settled where they did relatively little harm, though neurocysticercosis can cause seizures, stroke, and cognitive decline. Two anti-parasitic drugs later, he recovered.
Sources
Primary source: Doctors suspected man had brain cancer. He actually had worms.
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