Skull growth

I only remember this horrifying fragment: I have a strange growth on the top of my head–it’s almost growing like a helmet of some sort. When I touch it, it feels like it’s bone, but it’s on the outside, growing overtop of my skin and hair. At one point I’m finally able to take the growth off. When I do, there are funguses that have grown on the underside of this bone thing and I have to brush a whole lot of this little green worms off of my scalp.