The missing element of MRI, for concussion cases, is of the jaw joint where the jawbone meets the skullbase. Players like Mcgahee will display a disloged dime sized cartilage disk in the TMJ. As a natural cushion it works great, when slipped, it creates a "Glass Jaw". It's been found to be the only anatomical marker common in all concussion prone athletes. mahercor laboratories has much more info.