Across the globe  traumatic brain injury (TBI) is a leading cause of death for persons under age 45.The leading causes of TBI are motor vehicle accidents, falls, and sports injuries. While the brain is by far the most complex object on earth, it is soft and vulnerable with a consistency of firm pudding.  The brain is vulnerable to traumatic damage in two ways. The cerebral cortex can become bruised - contused - when the head strikes a hard object (or a hard objects strikes the head). Or, the deep white matter can suffer diffuse axonal injury when the head is whiplashed without hitting a hard object (or being hit by one).

The brain consists of billions of nerve cells located in the gray matter which communicate with distant nerve cells through long nerve fibers called axons, composing the white matter. Severe sudden twisting or torquing of the brain, as occurs in a sudden acceleration/deceleration - whiplash -- accident, can stretch, twist, and damage these delicate axonal fibers. Under the microscope the axonal damage is called Diffuse Axonal Injury (DAI).

The brain is more susceptible to injury through lack of oxygen (hypoxia) than any other part of the body. Hypoxia can occur in conjunction with other injuries (heart attack) or from any other situation where breathing or oxygen intake is impaired.

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In addition to direct neural damage , injury to the brain can also result as a secondary phenomenon following injury to nonneurologic structures.Edema - is a swelling of the brain. Swelling of the brain becomes dangerous when the swelling causes a rise in intracranial pressure which prevents blood from entering the skull to deliver glucose and oxygen to the brain. Hematoma - is a collection of blood due to tissue injury or the tearing of a blood vessel.Hydrocephalus and Hygroma - are collections of fluid in and around the brain. The brain is hollow; the interior cavities, called ventricles, contain cerebrospinal fluid circulating from the ventricles up over the surface of the brain where the cerebrospinal fluid is absorbed. If blood somehow gets into the cerebrospinal fluid and blocks the spinal fluid absorption sites, spinal fluid will back up into the ventricles, enlarging them - a condition called hydrocephalus.