When the pork tapeworm infects your muscles, there are usually no symptoms, save for the occasional lump under your skin. If they make it to your eye, it will affect your vision and require surgery to remove. And if they make it to your brain ...
Turns out your fear of holes is completely justified.
They can cause headaches, seizures, and death -- often the result of the worm dying in your head, causing your brain to swell. So in a godawful twist of fate, this is the one case where you desperately want the worm to stay alive and please continue feasting on your brain.
The pork tapeworm lives in areas where pigs are allowed to eat human feces, which means that the parasite is found pretty much anywhere there is an abundance of pigs and a lack of modern plumbing. For this reason, Muslim-majority countries are almost devoid of the tapeworms, since they refuse to eat filthy, filthy pigs. And hey, turns out they had a good reason. Chalk one up in the plus category for Islam, for those keeping track.