Agree with Tony.
Any time the tumor gets large it can impact the 4th ventricle. Not sure if I was clear in my first statement, but it is the blockage of the 4th ventricle that causes the hydrocephalus, from whatever source. That is why I said that it could be the AN, and also other sources.
If I could charge for cousults, I wouldn't be worried about employment after my surgery like others. Unfortunately, nurses cannot charge "fee for service". And, on this site especially, I wouldn't dare to keep from "kin" whatever little knowledge I have.