Cavitation is the formation of microscopic bubbles within brain tissue as it is pulled away from the skull when the head suddenly stops or accelerates. Cavitation occurs when an object moves rapidly through a liquid, such as when the brain moves through cerebral spinal fluid. The formation and collapse of these bubbles causes disruption of brain tissue. Cavitation injuries occur on the opposite side of the brain from the point of impact. They are sometimes referred to as contrecoup 

The brain is composed of billions of nerve cells called neurons. A neuron is a specialized cell which conducts electrochemical impulses. A neuron consists of a cell body and cell extensions called processes. There are two types of processes: long single processes known as axons and short, branching processes known as dendrites. An axon can be up to three feet in length. When the head stops suddenly, the brain rotates on the brain stem, where the stem exits the skull in a forward and downward motion. The layers of the brain farthest from the brain stem move faster and farther than the layers which are closest. As the brain moves, the layers stretch and pull at different rates.

Diffuse axonal injury occurs when the layers of the brain move at different rates, causing the axons to be stretched, torn, and twisted. Nerve impulses are transmitted from one nerve cell to another by electrochemical transmissions across synapses at the end of the axons. If the myelin is sufficiently damaged, the nerve impulse is not transmitted to the adjacent neuron. This causes a loss of brain function. It is important to note that when the body of a neuron is sufficiently damaged, the cell will die. Unlike many types of cells within the body, neurons do not regenerate. Brain damage resulting from the destruction of large numbers of neurons is permanent. It is now thought that most of the loss of brain function following acceleration or deceleration trauma is the result of diffuse axonal injury.