A concussion is a “whiplash of the brain”. We all know that whiplash forces can cause serious injuries to the neck (cervical spine). The head (brain) is farther out on the whip so it stands to reason, applying basic physics, that the brain would be subject to even greater forces than the neck.
The neck is protected from whiplash forces by strong ligaments. The brain is not so protected and more susceptible to whiplash forces. The human brain is a jelly-like substance contained within a hard structure, the skull. The acceleration/deceleration forces of whiplash cause the brain to be “whipped” backwards and forward, subjecting the brain to linear acceleration and deceleration forces, as well as rotational forces causing brain injury. See the section on ????? for more information about the effects of rotational forces on the brain.
These forces can disrupt neurons, axons, neural and meningeal structures, and blood vessels, causing both focal and diffuse brain injuries. (Focal brain injuries are those to a specific area of the brain. Diffuse brain injuries are spread diffusely throughout the brain.
Whiplash of the cervical spine (neck) is easy to understand-and well accepted in the medical literature. Remember: The “head-bone is connected to the neck bone”. The same forces that cause a whiplash of the neck cause even greater forces to the brain. It is a matter of simple physics that the forces are greater the farther out on the whip (the farther away from the fulcrum).
Whiplash injuries to the brain occur most frequently in motor vehicle collisions (car accidents). The most common is the “rear-ender” where the victim’s vehicle is struck from behind. The forces of collision cause an “acceleration/deceleration” biomechanical model (whiplash) which biomechanical experts recognize as “biphasic” (two phases). In the acceleration phase, the vehicle is violently pushed forward with the seat pushing the trunk forward while restrained by the shoulder and lap belt. The neck and head is not so restrained except by the head rest which is often improperly adjusted and the head actually goes backward above the head rest. The seat back can act as a spring which magnifies the forward thrust of the trunk while the head stays back.
Then comes the second phase where the head rebounds forward with a “whiplash” snap. As it does so, another force (rotational) comes into play which contributes to the concussion injury. The “three point” restraint system in most automobiles restrains only one of the two human shoulders, either the left shoulder of the driver or the right shoulder of the passenger. This causing a dramatic “rotation” of the upper torso-and of the head. It is well known that the brain is more susceptible to rotational forces which cause greater injury. It is quite common for the driver to have more damage to the left side of the neck and the passenger to the right side of the neck. In many cases, the driver’s head and neck is turned, looking at the rear view mirror or watching for traffic, causing additional rotation force. Experts have called this phenomenon the “complex interplay of seat design, occupant mass, occupation position, and vehicle dynamics” which produces whiplash injuries to both the neck and the brain.