+1... My grandfather fell off a ladder once. After several days of headaches, his wife (not my grandmother) took him into the hospital. Turned out he had a subdural hematoma. Several hours of surgery later, and a long time in the hospital, he recovered enough to carry on for another 11 years.

One of my high school classmates took a fall out of the back of a (moving) pickup, felt fine for a while, then began feeling quite ill. Three hours later he died. Subdural hematoma's are nothing to mess with.