Brain injury

A brain injury is any injury occurring in the brain of a living organism. Brain injuries can be classified along several dimensions. Primary and secondary brain injury are ways to classify the injury processes that occur in brain injury, while focal and diffuse brain injury are ways to classify the extent or location of injury in the brain.

A traumatic brain injury ("TBI") is an alteration in brain on a structural, physiologic, chemical and/or neurotransmitter pathway as well as other evidence of brain pathology, caused by an external force. (“About Brain Injury”). A post-traumatic brain injury is the alteration of the neurologic function by the TBI event. Multiple TBI events can lead to chronic traumatic encephalopathy.

A concussion is the most common type of traumatic brain injury. It can be caused by direct damage to the head, gunshot wounds, violent shaking of the head (very common in children), or force from a whiplash type injury. A concussion is caused when the brain receives trauma from an impact or a sudden momentum or movement change. The blood vessels in the brain may stretch, and cranial nerves may be damaged.

A contusion could be caused by direct damage to the head, where a bruise is bleeding on the brain.

A coup-contrecoup injury occurs when the force impacting the head is not only strong enough to cause a contusion at the site of impact, but also able to move the brain and cause it to slam into the opposite side of the skull, which causes the additional contusion.

A diffuse axonal injury can be caused by strong shake on the head, as in "shaken baby syndrome", or by rotational forces, such as a car accident. Injury occurs when the unmoving brain lags behind the movement of the skull and causes the brain structures to tear. The tearing of the nerve tissue disrupts the brain communication and chemical processes. This disturbance in the brain would cause brain damage or death. There are specific areas that will shear connections within the brain substance that are indicative of a diffuse axonal injury.

Locked in syndrome is a rare neurological condition wherein the patient is unable to physically move any part of the body except the eyes. The patient is still conscious and able to think.

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