Diagnostic dilemma: A man's preference for 'soft' bacon may have given him brain worms

The patient: A 52-year-old man in the United States

The symptoms: The patient reported to an outpatient clinic after noticing a change in his typical migraine symptoms. Over the previous four months, medications were no longer effective in treating his migraines, and they started occurring more frequently than usual — about once a week — while also becoming more severe. He also reported worsening pain across the back of his skull.

What happened next: Doctors took the man's vital signs, which were not out of the ordinary. They also took a CT scan of his brain, which revealed numerous cyst-like lesions scattered throughout both hemispheres. Specifically, these growths appeared in the organ's white matter, the insulated wiring that extends off brain cells.

The patient was immediately admitted to the hospital for a neurosurgical consultation. An MRI backed up what was seen on the CT scan, but it also revealed a buildup of fluid around the cysts in the man's brain.

The diagnosis: Suspecting a possible parasitic infection, the neurosurgery department sent the patient to infectious disease specialists, who ran a number of tests. One test showed that the man's blood carried antibodies against Taenia solium, a tapeworm typically found in pigs — lodging in their intestines and muscles and passing in their feces. In the man's case, the worm's larvae had invaded his brain and were embedded within cysts inside the tissue. When T. solium infects the nervous system in this way, the condition is known as neurocysticercosis.

The treatment: The patient received antiparasitic and anti-inflammatory drugs while being monitored in the intensive care unit for several weeks, after which he was seen at an infectious disease outpatient clinic. "The patient was successfully treated, with regression of lesions and improvement of headaches," his doctors wrote in a report of the case.

What makes the case unique: Humans can be infected by T. solium when they inadvertently consume the worm's larvae or eggs. People can end up being exposed if they eat undercooked pork, for instance, or if they drink water contaminated with the feces of infected pigs or touch their faces or food after touching pig poop.

Consuming undercooked pork containing the larvae can cause an intestinal infection called taeniasis, while consuming feces containing the eggs triggers infections in other tissues, including the brain. The eggs initially travel into the brain's blood vessels and compartments for cerebrospinal fluid, the clear fluid that bathes the brain, and they then trigger inflammatory immune responses that break down the brain's protective barrier.

T. solium is endemic to many regions of the world, including various parts of Central and South America, Africa and Asia, which means the parasitic infection regularly spreads in those locations. In fact, in these endemic areas, neurocysticercosis is a common cause of epilepsy, according to the World Health Organization. While the infection is not endemic to the United States, about 2,000 or so cases are reported in the country each year, and they are often related to travel to and from places where T. solium is endemic.

But in the man's case, he "denied recent travel to high-risk areas, with his only notable travel history being attendance on a cruise to the Bahamas 2 years prior," the report noted. (There is minimal data on whether T. solium is present in the Bahamas.)

Upon further questioning, the man "admitted to a habit of eating lightly cooked, non-crispy bacon for most of his life," the report said. The Food and Drug Administration recommends cooking pork to at least 145 degrees Fahrenheit (about 63 degrees Celsius), though it can be difficult to check the temperature of bacon, given it's a thin cut of meat. However, if cooked until crisp, it should have reached a safe temperature, according to the U.S. Department of Agriculture.

Based on the man's eating habits, his doctors concluded that his "lifelong preference for soft bacon" may have led him to eat undercooked bacon occasionally, leading to taeniasis, the intestinal form of the tapeworm infection. From there, he may have accidentally given himself cysticercosis via improper handwashing, the doctors speculated. In other words, he may have inadvertently been exposed to the worm's eggs in his own feces.

"Undercooked pork consumption is a theoretical risk factor for neurocysticercosis via autoinoculation, as we suspected in this case," the medical team concluded. "It is historically very unusual to encounter infected pork in the United States, and our case may have public health implications."