A 60-year-old man walked into a hospital in Castellón, Spain in 2025 with two weeks of worsening headaches and changes in his behavior that no one could quite name. Something was off – his moods, his thinking, a vague wrongness that he couldn’t describe and his doctors couldn’t immediately explain. What followed was one of the stranger diagnostic journeys in recent medical memory: first, the near-certainty of a brain cancer diagnosis, and then, on closer imaging, something nobody expected to find at all.
Multiple brain lesions appeared on the scans, and they initially looked exactly like metastases – the kind of spreading tumor shadows that tell a doctor cancer has arrived from somewhere else in the body. The man had no relevant travel history. He was a lifelong resident of his region. CT scans showed multiple abnormal spots consistent with tumors that had spread from cancer elsewhere in the body, leading doctors to suspect advanced brain cancer – and yet whole-body scans, a colonoscopy, and specialized imaging failed to identify cancer anywhere in his body.
So if it wasn’t cancer, what was it? The answer was a brain tapeworm infection, and the case has since been published in a journal most people only encounter when something genuinely unusual has happened.
The Parasite Nobody Was Looking For
The case report, titled “Autochthonous Neurocysticercosis Brain Lesions Mimicking Metastatic Disease,” was published in the CDC’s Emerging Infectious Diseases journal. It describes a condition called neurocysticercosis (NCC) – the medical term for what happens when larvae of the pork tapeworm Taenia solium make their way into the brain and set up residence there.
Neurocysticercosis occurs when larvae of the pork tapeworm invade the central nervous system. Rather than remaining in the intestines as adult worms, the parasite’s larvae migrate through the bloodstream and become trapped in tissues, including the brain, where they form fluid-filled cysts. These cysts may remain unnoticed for years before triggering symptoms.
That last part is what makes this condition so medically treacherous. A brain tapeworm infection can persist for years – sometimes the better part of a decade – without any obvious sign: no fever, no rash, no red flag. When symptoms do appear, they vary depending on the number and location of cysts, and they overlap almost perfectly with brain tumors, strokes, and other neurological disorders. Headaches, behavioral changes, and neurological effects are common across all of those conditions, which makes diagnosis genuinely difficult.
In this man’s case, the overlap was complete enough that the initial working diagnosis was metastatic cancer. It took a higher-resolution MRI to change everything. Unlike the earlier CT images, the MRI clearly showed tiny encapsulated larvae with visible tapeworm heads inside the brain lesions. The moment that imaging came back, the entire clinical picture shifted.
How Someone Gets Tapeworm Larvae in the Brain
Most people, when they hear “tapeworm,” picture something acquired from eating undercooked pork – and that association isn’t wrong, exactly, but it’s incomplete in ways that matter. Eating undercooked infected pork usually leads to an intestinal tapeworm. But accidentally swallowing the parasite’s eggs – typically through food or water contaminated with feces – can send the larvae into the bloodstream, where they may form cysts in the brain and other organs. Those are two distinct routes with two very different outcomes.
What causes brain cysts is swallowing the eggs, which enter the body through contaminated food, water, or surfaces touched by someone who carries the adult tapeworm in their gut and hasn’t washed their hands properly. The eggs hatch in the intestine, the larvae punch through the intestinal wall, enter the bloodstream, and from there they can reach the brain, the muscles, the eyes, or the skin. The brain is where the consequences tend to be most severe.
For the Spanish man, the transmission route was unusual enough to make the case worth publishing. He and his close contacts had no recent travel to areas where the pork tapeworm is endemic. He had spent much of his adult life working on construction sites, though, where he often shared meals and bathroom facilities with migrant workers from these areas – a phenomenon the researchers identified as autochthonous transmission, meaning locally acquired infection in a region where the parasite is not normally found.
In Europe and the United States, neurocysticercosis is a disease seen predominantly in migrants and returning travelers. Autochthonous transmission is exceptionally rare. This case matters to the medical community not just as a remarkable individual story, but as evidence that the parasite can pass between people in daily contact, without any international travel involved.
The Diagnostic Challenge That Nearly Sent Him to Oncology
WHO classifies Spain as suspected endemic for Taenia solium, and autochthonous cases have been documented there, but the disease is rare enough that doctors do not routinely screen for tapeworm larvae in the brain, which made the diagnosis especially unexpected and explains why cancer was the first hypothesis. The diagnostic journey in this case is a useful illustration of how completely a parasitic infection can masquerade as something else when clinicians have no particular reason to suspect it.
The man was on dexamethasone, a corticosteroid prescribed to reduce brain inflammation while doctors worked through the cancer hypothesis. As it turned out, dexamethasone is also used to manage the inflammation that neurocysticercosis can cause – particularly the inflammation that arises when cysts are treated with antiparasitic drugs. The medication given for what doctors thought was one problem happened to be treating the actual problem at the same time.
What spared him from a brain biopsy – a procedure that carries real risks and would have been the likely next step to confirm or rule out cancer – was the decision to upgrade the imaging. Doctors also evaluated serum antibodies against T. solium using enzyme-linked immunoelectrotransfer blot at the Spanish National Centre for Microbiology, the national reference laboratory. The official report confirmed a positive diagnostic result, and after noting fulfillment of two major diagnostic criteria, they established a definitive diagnosis of neurocysticercosis.
Once the diagnosis was confirmed, the path forward was relatively clear. The patient was treated with albendazole (400 mg twice daily) and praziquantel (1,200 mg three times daily), alongside a dexamethasone taper, without complications. Two antiparasitic drugs, a careful steroid wean, and the man went home without the brain surgery that a cancer diagnosis would almost certainly have required.
A Disease That Carries a Major Global Burden
According to a 2024 paper in the Neurology journal, the global burden of cysticercosis is estimated at between 3.51 and 6.47 million cases. The infection is a significant cause of long-term disability, conservatively estimated at 1.37 million disability-adjusted life years, mostly taking the form of seizures and epilepsy. The highest disability rates have been recorded in sub-Saharan Africa, followed by Latin American, Caribbean, and Southeast Asian regions.
Neurocysticercosis is the leading cause of acquired seizure disorder worldwide. When someone in an endemic region develops adult-onset epilepsy with no obvious explanation, neurocysticercosis is frequently the underlying cause. Epilepsy attributable to NCC accounts for roughly one-third of all epilepsy cases within these populations.
In the United States, neurocysticercosis accounts for a substantial number of hospitalizations each year, with national hospital discharge data pointing to thousands of cases annually. The vast majority of those cases are in people who were born in or have traveled to endemic regions, but as the Spanish case illustrates, local transmission in non-endemic settings is possible under the right conditions.
For families with members who work in close quarters with people from high-prevalence countries – construction, agriculture, food service – that’s not a theoretical risk to dismiss. A brain tapeworm infection belongs in the differential when headaches and behavioral changes persist together and don’t resolve with expected treatments.
What the Symptoms Actually Look Like
A brain tapeworm infection rarely announces itself with dramatic, unmistakable signs. It tends to arrive through symptoms that seem like other things first.
The Cleveland Clinic notes that neurocysticercosis sufferers may have seizures, headaches, or memory problems, among other serious symptoms. The Spanish man presented with progressive headaches and behavioral changes – which describes a spectrum broad enough to include dozens of other conditions. A doctor who isn’t thinking about parasitic infections has no reason to jump there first, particularly in a country where routine screening for the disease is uncommon.
Beyond headaches and behavioral changes, current research supports viewing neurocysticercosis not purely as a seizure disorder but as a broader syndrome encompassing epilepsy, neuropsychiatric symptoms, ocular effects, motor problems, and cognitive changes. Depending on where the cysts land and how many there are, it can look like a psychiatric condition, a movement disorder, a vision problem, or cognitive decline. The cysts themselves are silent until the immune system reacts to them – either when they die naturally or when they’re disrupted by treatment – and that inflammatory reaction is what generates most of the symptoms.
Symptoms may not appear until months or even years after the initial infection. That delay is exactly why the disease is so often caught late, and why a case like the man in Castellón – who had likely been carrying the infection for years before his headaches began – is more common than most people realize.
What Treatment Looks Like, and What It Doesn’t
Treatment for neurocysticercosis is effective but requires careful management. Killing the larvae quickly isn’t necessarily straightforward – the inflammation that follows cyst death can temporarily worsen symptoms before the patient improves. The combination of antiparasitic drugs and anti-inflammatory steroids is specifically designed to address both the parasite and the body’s response to it dying.
For the Spanish patient, the treatment course was clean. He received his antiparasitic drugs, his steroids were tapered down, and he left without complications. That outcome – someone presenting with what looked like advanced, metastatic brain cancer leaving a hospital having avoided a biopsy and a cancer treatment pathway – was only possible because someone ordered a better scan, thought laterally, and ran a blood test for a parasite most European doctors rarely encounter.
You can read about the long-term risks of the anti-inflammatory drugs often used in these scenarios in this piece on what loading your body with ibuprofen actually does – the same physiology that makes inflammation-fighting drugs useful also explains why they require careful dosing and monitoring.
Read More: What Happens If One Conjoined Twin Dies, But The Other Continues Living?
The Bigger Picture
Neurocysticercosis is almost entirely preventable. The transmission route – microscopic eggs on unwashed hands, on contaminated surfaces, in food or water – is the kind of thing that basic sanitation stops. The disease thrives specifically where sanitation infrastructure is poor and where people can’t consistently access clean water. It is not a random horror but a predictable consequence of inadequate public health infrastructure, and the burden falls most heavily on the populations least equipped to carry it.
In places where the disease isn’t expected – Western Europe, the United States – it gets missed. It gets called something else first. It costs people weeks of anxiety and invasive diagnostic procedures and the wrong medications before someone runs the right test. The Spanish man was lucky: lucky that a higher-resolution scan was ordered, lucky that his doctors thought to test for a parasite they wouldn’t normally suspect, and lucky that the antiparasitic drugs worked as cleanly as they did. Not everyone gets that sequence of decisions in the right order. The archive of cases where they didn’t – where someone got the biopsy, or the cancer treatment, or the delayed diagnosis – is longer than anyone would like it to be.
Disclaimer: The author is not a licensed medical professional. The information provided is for general informational and educational purposes only and is based on research from publicly available, reputable sources. It is not intended to constitute, and should not be relied upon as, medical advice, diagnosis, or treatment. Always consult a licensed physician or other qualified healthcare provider regarding any medical condition, symptoms, or medications. Do not disregard, avoid, or delay seeking professional medical advice or treatment because of information contained herein.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.