RFK Jr. says doctors found a dead worm in his brain. Here's how it happens and why it's rare in the U.S.

Natalie Rahhal
Experts say Robert F. Kennedy Jr. was most likely describing neurocysticercosis, a tapeworm brain infection that can cause seizures.
Experts say Robert F. Kennedy Jr. was most likely describing neurocysticercosis, a tapeworm brain infection that can cause seizures. (Mario Tama/Getty Images) (Mario Tama via Getty Images)

Independent presidential candidate Robert F. Kennedy Jr. says he is living with a dead worm in his brain, according to court documents obtained by the New York Times. Kennedy, 70, said the remains of the parasite were discovered in 2010 after he saw a neurologist for memory loss and brain fog, amid fears he could have brain cancer like his late uncle, Sen. Edward M. Kennedy. He claimed in a 2012 deposition that what at first appeared to be a tumor “was caused by a worm that got into my brain and ate a portion of it and then died.” Kennedy suspects he picked up the parasite during a trip to South Asia. Speaking to the N.Y. Times, he said he no longer experiences memory loss or fogginess related to the health incident, which, he noted, did not require treatment. Kennedy later tweeted on May 8, "I offer to eat 5 more brain worms and still beat President Trump and President Biden in a debate." He added, "I feel confident of the result even with a six-worm handicap."

How can something like this happen? Here’s what to know about the condition, known as neurocysticercosis.

Kennedy’s condition can develop if you accidentally eat or drink the larvae of parasites but, the vast majority of the time, it’s caused by a certain kind of tapeworm, known by the scientific name Taenia solium, Dr. Michael Wilson, a neurologist specializing in infectious diseases at the University of California, San Francisco, tells Yahoo Life.

“Here’s how that can happen: A person becomes infected with a tapeworm by eating contaminated meat like pork,” explains William Sullivan, a professor of pharmacology, toxicology, microbiology and immunology at the Indiana University School of Medicine, tells Yahoo Life. “In their intestine, the tapeworm produces tens of thousands of eggs that are then shed in feces. Now, if they’re not careful about washing their hands after going to the bathroom, [a person] can infect themselves with the tapeworm eggs.”

Or, the infected person’s dirty hands can contaminate food or water with tapeworm eggs. “Either way, the baby tapeworms (larvae) that come out of the eggs are tiny enough to break through the intestinal wall and form cysts in other organs, including the brain,” says Sullivan.

“Once the tapeworm gets to the brain, it will form a cyst” — or fluid-filled sac — ”in the brain tissue and just sit there,” Wilson says. “It can sit there not causing any clinical symptoms for many years, and we don’t really understand why.” But eventually, “the immune system will say, ‘Hey, wait a minute’ and attack it,” he explains.

The brain inflammation caused by the immune system’s attacks leads to symptoms — by far the most common of which is a seizure — and not caused by the worm itself, says Wilson. Worm larvae “reside in the brain, but it’s not like they’re chewing through it,” he adds.

A seizure is almost always the symptom that leads to the discovery of an active neurocysticercosis infection, but other effects, such as speech or cognitive impairment, are possible depending on the location and number of larval cysts. If a patient was struggling with memory loss, however, Wilson says he would probably look for another explanation.

In the U.S., neurocysticercosis is rare. The Centers for Disease Control and Prevention (CDC) estimates there are about 1,000 new hospitalizations for the infection each year. But, globally, it’s a major problem. The World Health Organization (WHO) estimates that tapeworms are responsible for about 30% of epilepsy cases in “endemic areas where people and roaming pigs live in close proximity.” People living in poorer countries with less access to clean running water are at greater risk. If pork is kept at safe temperatures and thoroughly cooked, and good hand hygiene is practiced, the infection becomes very rare.

Neurocysticercosis is not a common traveler’s disease, says Wilson. “Given the amount of Americans who travel to these parts of the world, it’s very rare that people come home and are at risk for this type of infection because they usually have access to clean water while abroad,” he notes.

Treatment depends on when the infection is discovered and where the cysts are in the brain. In extremely rare cases, Wilson says a worm’s cyst can block the flow of cerebrospinal fluid, causing life-threatening brain swelling. When this happens, the worm has to be surgically removed.

If the worm is in its “active phase,” meaning the inflammation from the immune system’s attacks haven’t killed it, it’s treated with antiparasitic medication, according to the CDC. But often — and as Kennedy’s description suggests was the case for him — the worm isn’t discovered until the calcification stage. “Once the immune system has destroyed it, it just leaves this calcification, this little scar” in the brain, Wilson says. Typically, it may be a few weeks or months between when someone has a seizure until the worm is killed and calcified. At that point, there shouldn’t be any further complications and there’s nothing left for doctors to do.

This article was originally published on May 8, 2024 and has been updated.

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