What is the average drop of the cerebellum when others are having surgery?

My husbands drop is 5 mm? Or cm? I just knOw it is at a 5.
So we are curious how many people are having their surgeries with less of a dtop?

The dr’s in our area consider all the symptoms and issues related to chiari as chronic headaches.

We are trying to get into a nuerosurgeon in colorado. I guess we will see how much these dr’s are willing to help us!