Doctors suspected man had brain cancer. He actually had worms. - Ars Technica

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A  60-year-old man in Spain went to the doctor complaining of a headache that he couldn’t shake. It had started two weeks prior and was only getting worse. He also said he had noticed subtle changes in his behavior.

In a neurological exam, doctors found he had a mild delay in his movements, but no other deficits. His blood work was generally normal except for elevated IgE, a signal of immune responses linked to allergies, autoimmune disease, and parasitic infections. The doctors did a computed tomography (CT) scan of his head and saw much more obvious evidence of a problem: There were multiple lesions distributed throughout his brain accompanied by swelling.

In a case report in Emerging Infectious Diseases, the doctors reported working through the possible conditions that could explain all the findings. They noted that the man was not immunocompromised and had never traveled internationally. Their top suspicion was metastatic cancer.

For his headache, the doctors put him on an anti-inflammatory corticosteroid, and he finally got some relief. They then began an extensive series of tests to look for the cancer they thought had spread to his brain. This included a whole-body, contrast-enhanced CT scan, a colonoscopy, and a hybrid positron emission tomography/CT scan often used to map cancer. But the tests didn’t reveal any malignancies.

The doctors did another brain scan, this time with a magnetic resonance imaging (MRI) scan to get a better look at the lesions. With the more detailed imaging, they saw clearly that the lesions weren’t tumors; they were encapsulated tapeworm larvae. On the MRI, the doctors could see the worms’ heads, called scolexes.

The finding surprised the doctors since tapeworms aren’t endemic to Spain and he said he hadn’t traveled. However, the man may have been exposed during his work. Until 10-years prior, when he retired, he had worked in construction, often working alongside people who had migrated from regions where pork tapeworms (Taenia solium) are endemic. The parasitic worms can spread through the fecal-oral route. His doctors speculated his infection might have been a rare case of cryptic transmission from sharing meals and bathrooms with his coworkers, one of whom apparently had a tapeworm infection.

Sneaky worms

Taenia solium can infect people in two ways: by eating cysts in undercooked meat or ingesting eggs through fecal contamination. The parasite infects pigs, and when they ingest eggs from feces, the worms hatch in the pigs’ guts, bore through the intestines, get into the bloodstream, and migrate into a variety of tissues and muscles. There, they form into encapsulated larvae called cysticerci. If a person eats undercooked meat containing cysticerci, the larvae will develop into adult tapeworms in the person’s intestinal tract and live there, possibly for years. Meanwhile, those infected people will be shedding eggs in their feces.

If those eggs get spread around from poor hygiene and sanitation—into water, food, etc.—and make it into a person’s mouth, they do what they do in pigs. The eggs hatch, burrow into the bloodstream, and then go wandering around, embedding in various tissues, muscles, and organs, including the brain.

When cysticerci enter a person’s central nervous system, it’s a disease called neurocysticercosis (NCC), which is the diagnosis the doctors in Spain gave the man. Testing after his MRI revealed his immune system had made antibodies against Taenia solium, confirming the infection.

NCC can be serious, causing seizures, significant neurological deficits, cognitive decline, stroke, and other problems. But it can also be asymptomatic. The severity depends on where in the brain the worms settle. Luckily for the man, the effects were relatively mild. Doctors prescribed him two anti-parasitic drugs, and he recovered.

“Our case emphasizes that the absence of travel history should not preclude NCC from the differential diagnosis of multiple ring-enhancing brain lesions, even in regions where metastatic cancer is statistically much more likely,” they concluded. If they had caught onto the worms sooner, it would have prevented “unnecessary invasive oncologic procedures and lead to prompt, targeted antiparasitic therapy.”

Beth Mole

Senior Health Reporter

Beth Mole

Senior Health Reporter

Beth is Ars Technica’s Senior Health Reporter. Beth has a Ph.D. in microbiology from the University of North Carolina at Chapel Hill and attended...