Understanding Brain Injury Pathology

Brain Injury Pathology – More than Simply Hitting Your Head

By Gordon S. Johnson, Jr.

Brain injury goes beyond just simply hitting you head. Severe brain injuries often do involve a blow to the head, but significant injury can occur from rapid acceleration and deceleration, such as whiplash. Therefore, to comprehend brain injury, we must understand what forces are at work in the skull.

The terms brain injury and traumatic brain injury are synonymous. The terms concussion and mild traumatic brain injury are synonymous. Brain injury is frequently shortened to TBI and mild brain injury to mTBI.

Brain Injury Pathology Biomechanics

The forces inside the skull which cause damage include both impact and/or rotational forces. Impact forces come from the direct force against brain tissue from the collision of the hardness of the skull and the softness of the brain. Shearing is the word often used to describe the outcome of rotational forces. When the layers within the brain move across each other at various speeds, a twisting injury can be the result. The twisting shears the long parts of these cells, like a paper shearer would do to paper. Both impact and rotational damage can happen any time substantial forces are directed against the head.

For instance, when the head hits a windshield, damage occurs to the brain surface from the direct force to the head. However, the rotational forces will also be catastrophic to the internal parts of the brain because of the rapid stopping of the movement of the head and the brain. Rotational forces incorporate arc movements. Rotation in the brain can happen whether the head is the object moving in an arc or whether it is the internal structures of the brain that are moving in an arc.

Impact brain damage will most likely be focal, or concentrated in a specific section of the brain. Shear brain damage is likely to be diffuse, or distributed throughout widespread parts of the brain. The term diffuse axonal injury signifies distributed damage over a large area of the axons, or the long portion of the neuron. The neuron is the main thinking cell in the brain which communicates with other brain cells through its wire-like protrusion the axon. Damaged axons will continue to die as the first days after injury pass. If the axon cannot communicate with other neurons, the neighboring neurons will have difficulty as well.

Primary versus Secondary Brain Injury Pathology

Brain injury incorporates both the instant damage to the brain and the damage that can happen in the following days. In severe brain injury, the secondary damage can cause even more severe problems than primary damage.

The delayed effects of secondary damage, even in a mild injury, can often prove the diagnosis. Therefore, the Emergency Room evaluations often overlook the disabling potential of mTBI.

Moderate brain injury includes loss of consciousness or other important neurological disabilities, but it doesn’t involve extended coma. Moderate brain damage often presents with a combination of pathology somewhere between mild and severe brain injury. Some deficits should be expected after moderate brain damage. However, many people have significant recovery after moderate brain injury. A supposed full recovery does not indicate that frontal lobe issues, difficult to assess in a doctor’s office or through a neuropsychological exam, may not be problems anymore. They may be causing significant day-to-day impairment. Mood and behavioral deficits are the areas that often go under-diagnosed.

Gordon Johnson

Attorney Gordon Johnson is one of the nations leading brain injury advocates. He is Past-Chair of the TBILG, a national group of more than 150 brain injury advocates. He has spoken at numerous brain injury seminars and is the author of some of the most read brain injury web pages on the internet.

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