Dear Doctors: There was a story in the news recently about a man who had a tapeworm living in his brain. Our two teenage boys also saw it and are now obsessed. They’re grossed out and fascinated, and they are asking lots of questions. An explanation would be welcome.
Dear Reader: You’re referring to a case study that, because of the startling details, jumped from the New England Journal of Medicine into the news cycle. It concerns a 38-year-old man in Boston who was rushed to the emergency room after he fell out of bed, then became combative, disoriented and began speaking gibberish.
During his exam in the E.R., which included lab tests that ruled out liver or kidney dysfunction, the man suffered a prolonged seizure. Due to the fact that he had no other health issues, and with the important clue that he had previously lived in a rural part of Central America, the doctors began to suspect they were dealing with a parasitic infection. Detailed brain scans revealed three distinctive lesions, and a diagnosis emerged.
The cause of the man’s seizures, as well as his altered mental state, was neurocysticercosis. That’s the most severe form of a parasitic infection known as cysticercosis, which can occur when someone ingests the eggs of the pork tapeworm. Although rare in the U.S., cysticercosis is found worldwide. It’s most common in rural areas of sub-Saharan Africa, Asia, South America and Central America, where the patient was from.
To understand what happened to the patient, we need to look at the life cycle of the pork tapeworm. It includes a stage of development known as larval cysts, which are fluid-filled sacs that contain the immature stage of the parasite. When tapeworm eggs are ingested, they hatch inside the body. The resulting larval cysts can enter the bloodstream and circulate, becoming lodged in the muscles, eyes and brain. In neurocysticercosis, the prefix “neuro” indicates that tapeworm larvae have reached the tissues of the brain.
Larval cysts can grow to considerable size. In a different case, which also made the news, surgeons were operating on a patient they believed had brain cancer. Instead of a tumor, though, they found a larval cyst the size of a quail’s egg in the patient’s brain. When they cut it open, a small tapeworm was inside.
Larval cysts can be transmitted via the fecal matter of an infected person. This can happen when the carrier fails to wash their hands properly after using the bathroom. They can transfer tapeworm eggs and larvae to any surface they touch, including food. Someone who eats that food or touches those surfaces and then touches their mouth is at risk of infection.
Neurocysticercosis is a serious condition. It can cause the seizures and altered mental state that the patient you heard about was experiencing. It can also lead to death. The patient was fortunate to have a good outcome. Antiparasitic agents and anti-seizure medications were used to prevent a return of the seizures. But because the larval cysts caused structural changes to his brain, he is expected to continue taking anti-seizure medications for the foreseeable future.
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(Send your questions to askthedoctors@mednet.ucla.edu. Owing to the volume of mail, personal replies cannot be provided.)
