Does shaking your head cause brain damge?this could be as far as nodding to violently shaking it. a brief explanation why would be greatly appreciated

Depends: In an infant, shaking the head can be catastrophic. In adults the mere act of shaking your own head willfully is not likely to cause harm. Now if someone else physically ; aggressively shakes your head, this may cause injury to neck and brain, particularly in elderly individuals. A case in point is the brain trauma that occurs in sports with repetitive sudden jars to the head (soccer, football).