My goodness - YOU ALL MUST CONSIDER ME IGNORANT - but I cant help but think that if someone has parasites in their head....then they are in serious trouble!!!
It is not necessarily dangerous, it depends on the load.
Many people don't want to consider the idea that every humans and animals are infected by one or several kinds of helminths so they prefer to describe their annoying symptoms by a specific word depending on the "disease". (i am aware that some "diseases" can be caused by others things than helminths, but some can)