I prefer my brain worms figurative to literal, but since RFK, Jr. has brought us to this, a primer on how tapeworms can get into your brain and what happens when they do. (Spoiler: it's not good!)
Hidden Epidemic: 
Tapeworms Living Inside People's Brains
Parasitic worms leave millions of victims paralyzed, epileptic, or worse. So why isn’t anyone mobilizing to eradicate them?
discovermagazine.com