An Intro to Brain Injury

The Anatomy of a Head Injury

by Eric A. Roy, Ph.D., C.Psych.
Director of the Centre for Habilitation Education and Research

Injuries involving some type of blow to the head are among the most common in our society. Some 700,000 people in North America suffer traumatic head injuries each year, and between 70,000 and 90,000 are left permanently disabled. Head injuries can range from relatively minor damage to the scalp and face such as lacerations, abrasions and bruising to more serious consequences involving damage to the brain. While traumatic brain injury occurs much less frequently, it is important to know how it is identified and what to do for the person.

Loss of consciousness, even for a very brief period, is one of the clearest indications that the brain may have been affected by a blow to the head. A confusional state involving uncertainty about time, date, and location and/or a period of memory loss for the events surrounding the head injury are also indicators of trauma to the brain. Any of these symptoms following a blow to the head should be taken seriously.

With the most severe symptoms, loss of consciousness for more than a few minutes, the person should receive immediate medical attention. With less severe symptoms the person should be watched for a period of several hours after the head trauma. The person's state of consciousness, orientation to time and place and immediate memory function (e.g., remembering a series of four numbers) should be evaluated periodically during this time. Any evidence of deterioration may be a sign of the delayed effects of brain injury due to swelling or internal bleeding and require that the person receive medical attention as soon as possible. Some appreciation for how and why these symptoms arise will provide insight into why even a seemingly mild blow to the head may have very serious and potentially life-threatening consequences.

The effects of a blow to the head on brain function arise from the structural characteristics of the skull and the brain and the direction and size of the forces acting on the head. The brain, a rather soft tissue with the consistency somewhere between egg white and jello, is covered by three membrane layers. The outer-most layer, called the dura mater, is connected to the inside of the skull at various suture points which serve to suspend the brain within the skull. The brain sits atop the brain stem, an extension of the spinal cord which passes out the base of the skull through a hole called the foramen magnum. Brain injuries arise from three characteristics of this brain-skull anatomy: the rigidity and internal contours of the skull, the incompressibility of brain tissue and the susceptibility of the brain to shearing forces.

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