In the US, roughly 16 million people will suffer some form of head injury every year, and about 1 out of every six head injuries will experience long-lasting persistent symptoms. Concussions are one of the most common traumatic brain injuries. Your concussion symptoms are tied to the function of the injured part of your brain.
Your brain sits suspended in fluid inside your skull. When you hit your head, if the forces are powerful enough, your brain can bounce back and forth inside the skull – a coup-contrecoup injury. Your brain, brainstem, and spinal cord are all connected. When you whip your brain around inside the skull it can be similar to someone pulling a vegetable out of the ground. When you pull a vegetable out of the ground, typically, it will tear at the root. In this case, instead of a root, we’re talking about the brainstem and the deep midline structures in the brain called the diencephalon. These areas can experience the shearing forces and stretch beyond what they can handle. This is what we call a diffuse axonal injury.