Comedy icon David Letterman explained the scary real-life scenario where he suffered a concussion after falling over. The TV star was visiting colleges with his son as he decided which university he wanted to study at as he opened a new chapter in his life. However, during one of their visits on the father-son road trips, David Letterman fell over and was knocked out, being told he had a concussion from the scary incident. A crowd surrounded him as they called an ambulance, and he was taken to the emergency room. TV star was enjoying road trip with his sonThe star paired up with Barbara Gaines…