Pick up a walnut and shake it. Do you hear the walnut rattling around in there? Now imagine putting a small moist muffin in there and shake that around. Though you may not hear it rattle, when you open it up you will probably see the muffin beginning to crumble. Well, that’s what it’s sort of like with your brain in your skull. There are, of course, a few differences (for most of us, at least). The brain is surrounded by spinal fluid which significantly dampens movement. On the other hand the base of the skull, especially at the front has a lot of sharp, rough edges. So what does this have to do with brain injury and whiplash? First, let’s look at a blow to the head, whether your head hits the ground or a baseball strikes you in the forehead. Your skull goes in one direction while your brain goes in the other, so the skull and brain collide. This, depending on the amount of impact, can cause anything from a bump under the skin to a concussion to bleeding in and around the brain. When there is bleeding in and around the brain and swelling or bruising of the brain, you can see it on an MRI or CAT scan. The brain injury from a concussion is not able to be visualized on a conventional MRI or CAT scan. By the way, loss-of-consciousness, which was for a long time considered the sine qua non of a concussion may not be detectable when experiencing a concussion. With a concussion, the connections between the fine fibers of the nerves gets disrupted and the more extensive the disruption, the worse the symptoms. These symptoms can range from headache to nausea to loss of smell to dizziness to reduced reaction time to memory loss to slowed thought processes to personality changes such as loss of interest and depression.
But you don’t have to hit your head against anything to sustain a concussion, as Mets star baseball player, Jason Bay discovered when he hit the outfield wall without hitting his head. He suffered a whiplash injury in which his head went backwards and forwards rapidly. By doing this, the brain shifted in the skull like the muffin in the walnut shell (there are other complicating factors such as the brain stretching and compressing with forceful, rapid movement and the changes in pressure in the head related to spinal fluid pressure changes and blood flow changes but we will leave these out to keep things relatively simple). When this happens it’s as if the head actually struck the wall. Fibers can get disrupted and symptoms of a concussion can become evident. In Bay’s case, the symptoms have persisted and he has yet to be able to return to baseball.