What is a brain injury?

There are two types of brain injuries: (1) traumatic and (2) non-traumatic. A traumatic brain injury may also be called a head injury or if mild, a concussion.

A non-traumatic brain injury is caused by something inside the body, like a stroke, infection, tumor, lack of oxygen, or exposure to a toxin like polychlorinated biphenyls (PCBs).

A traumatic brain injury happens when a sufficient external force outside the body causes damage to the brain tissue or disrupts brain function. The outside force could be the head hitting or being hit by an object, an object penetrating the skull and brain, a force causing the body and head to move suddenly and the brain to move inside the skull, forces from a blast, or other forces like electrical or thermal energy.

There are two stages of a traumatic brain injury known as the Primary Injury and the Secondary Injury. The Primary Injury is the injury that occurs at the time of initial trauma that causes structural or functional disturbance. The Secondary Injury is what happens to the brain after the Primary Injury.

Brain damage from the Primary Injury includes bleeding, bruising, swelling, cuts, tears, or the shearing of nerves. Bleeding can happen in the brain or the layers inside the skull that cover the brain. Sometimes, the bleeding is microscopic and may not show up on brain imaging like a CT scan. Swelling in the brain can happen with or without bleeding. Brain damage can be localized to a specific area or widespread and scattered throughout the brain known as Diffuse Axonal Injury (DAI). DAI is widespread damage to the white matter in the brain. It is not necessarily the whole brain but discrete regions of the brain.

The Secondary Injury exacerbates the initial damage and leads to further damage and dysfunction. Various mechanisms occur in the brain after the Primary Injury, which may include decreased blood or oxygen supply, inflammation, excitotoxicity (excessive concentration of the amino acid glutamate), oxidative stress (imbalance of free radicals), and metabolic dysfunction (brain’s supply and use of energy). These secondary mechanisms lead to harmful events that can change normal brain functions and lead to cellular impairment, degeneration, and death. Secondary Injury occurs over time, from minutes to days, and the inflammatory response is believe to continue for years after injury.

A brain injury is not like a broken bone. While a broken bone can be painful and have its own serious effects, scientists and doctors are still uncovering and learning about the brain and how it responds to trauma. The reasons why brain tissue changes occur after a traumatic brain injury are complex and wide ranging, and can have diverse serious consequences. Understanding these complexities and the latest research in brain injury medicine is important for proper diagnosis, treatment, rehabilitation, and protecting the legal rights of brain injury victims.

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If you found this post helpful, you might also like to explore the other topics listed below and the many other topics in our comprehensive Safety & Prevention Guide, Brain Injury Guide, and Bike Injury Guide.