"I've even seen x-rays of a couple young people who had untreated hydrocelephy (sp - "water on the brain") where the majority of their skull was literally empty - but they both showed no obvious signs of brain damage. It doesn't pay to generalize."

Source?

Ok, Davin, here's a personal one... source: My mother had a benign brain tumor removed in 1983, about the size of a baseball. Two eight hour operations took place and she was in the hospital for three months. Because there was such a large void, the pancreas took over and water was rushed to her brain, she was in intensive care again and now has a permanent catheter attached from her pancreas to her brain. She learned to walk and talk all over again.

She's 93. No walker and no cain.

She was 73 when it happened and I never gave up on her. She has better memory than I have.