Depends on the age of the skeleton and the environment doesn’t it? The brain cavity isn’t 100% sealed. There’s openings for optic nerves, blood vessels, spinal cord, etc.

There’s a guy named Bill Bass that you might enjoy reading about. He has some books about the ‘body farm’ in Tennessee, where they study body decomposition in different situations.

I googled it for us, guys:

This was reported because it violates the rule that the entire shower thought must be in the title. It’s always worth a quick scan of a community’s rules before posting.

Also didn’t they pull brains out the nose for mummification?

You can, without much work actually, remove the brain through the cervical hole (the hole the spine is “connected” to)