In Wisconsin, most (but not all!) injury cases have a three-year statute of limitations. If you received a mild traumatic brain injury from an accident, you are going to be aware of it pretty quickly because the effects on the brain tend to be the worse in the beginning, and then improve. Most people do improve after one of these. If you don’t realize you have a brain injury in the beginning, it is highly unlikely that you will suddenly come to the realization that you had it three years later.