Here's a fun fact: Did you know that you can get tapeworms in your brain? You know that you can get a tapeworm from eating infected meat. But when people have tapeworms in their guts, they secrete tens of thousands of eggs a day. And those eggs can end up on food, or other things that people put into their mouths. For some reason—nobody is really sure why—tapeworm eggs that are ingested by humans never mature into adults. Instead, they remain in a larval stage and hang out in a host's bloodstream. Sometimes, they make it to the brain. And, apparently, this happens often enough that it has an actual medical name: Neurocysticercosis.

The good news is that these things are mostly harmless. They don't seem to hurt your brain at all while they're alive. The bad news: As soon as the larvae die, your body's immune system seems to suddenly realize they exist and it goes into overdrive—triggering seizures, loss of feeling in the body, and sometimes leading to death.

Scientific American blogs has the story of one woman in California who had this happen to her. To save her life, surgeons had to remove a calcified tapeworm larva from her brain.

Sara Alvarez was afraid.

It was December 20, 2010, in Sunnyvale, Calif., a town that lives up to its name. The West Coast winter, not as long or as harsh as seasons in the East, gave her the opportunity to take her youngest child out for an afternoon stroll.

In the fading light of dusk, Alvarez, too, began to fade. She lost the feeling in her right leg. Her right foot followed suit. She couldn’t lift or move her right hand. She was weak, and her body was numb.

The National Institutes of Health classifies neurocysticercosis as the leading cause of epilepsy worldwide, and the World Health Organization (WHO) estimates that tapeworms infect 50 million people globally. The CDC says an estimated 1,900 people are diagnosed with neurocysticercosis within the United States yearly.

Read the rest of the story at Scientific American blogs. (WARNING: Surgery images!)