Traumatic Brain Injury

Traumatic Brain Injury

Traumatic brain injury, also called acquired brain injury or simply head injury, is a result of a sudden blow to the head when an external force is applied causing a disruption of the physiological stability of the brain locally. It can also occur when an object pierces the skull and enters the brain tissue and when elevation in the intracranial pressure occurs and potentially dramatic changes in the blood flow within and to the brain. These changes may produce a diminished or altered state of consciousness. Traumatic brain injury is a nondegenerative, noncongential defect in which there may be permanent or temporary impairments to cognition, physical, and psychosocial functions.

Various terms are used to describe the brain injuries that occur when a mechanical force is applied either directly or indirectly to the brain. A force produced by a blow to the head is a direct injury, whereas a force applied to another body part with a rebound effect to the brain is an indirect injury. (Workman, 2006) Brain injuries can manifest itself as clinically from concussion to coma and death.

Primary brain damage results from the physical stress within the brain and is caused by open or closed trauma. An open head injury occurs when there is a skull fracture or when the skull is pierced. There is an exposure to the outside environment. A closed head injury is the result of blunt trauma, where the integrity of the skull is not damaged, and is the most serious, and depends on the degree and mechanism of injury.

Fractures associated with open head injuries are linear, depressed, open and comminuted. A unique fracture is the basilar skull fracture, which occurs at the base of the skull and usually extends into the anterior, middle or posterior fossa. Leakage of cerebral spinal fluid can occur from the nose or ear. This type of fracture is of significance because it can potentiate into a hemorrhage caused by damage to the internal carotid artery, damage to cranial nerves and infection. The most penetrating injuries to the skull are gun shot wounds and knife injuries (Workman, 2006). Depending on the velocity, mass, shape, and direction of the impact determines the degree of injury. The higher the velocity the more the damage to the brain tissue. As with any open area to the body, the patient is at high risk for infection related to an object piercing the skull and from environmental contamination.

Closed head injuries are caused by blunt trauma in which a concussion, contusion, and laceration to the brain may result. The most severe of the closed head injuries is anoxal injury (diffuse type). Diffuse anoxal injury is used related to high speed acceleration/deceleration as with automobile accidents. (Workman, 2006). With this type of injury there is significant damage to the axons in the white matter. Lesions may be found in the corpus callosum, midbrain, cerebellum and upper brainstem. Depending on the severity, small areas of hemorrhage followed by possible enlargement of the lateral ventricles may be detected on CT scan. For severe cases, the majority present in a coma. Survivors usually require long term care.

There are other factors that must be considered in the dynamics of head injuries: acceleration and deceleration. An acceleration injury is caused by an external force placing the head in motion. A deceleration injury occurs when the moving head suddenly is stopped or hits an object. These forces can result in shearing, straining, and distortion of brain tissue, particularly of the axons in the brainstem and cerebellum. (Workman, 2006).

Secondary brain injuries include any neurological damage that occurs after the initial injury. They increase the morbidity and mortality after head trauma. The most common is increased cranial pressure. Hypoxemia, increased carbon dioxide, or systemic hypotension may precipitate increased ICP. Damage to the brain tissue occurs primarily because the delivery of oxygen and glucose is interrupted.

Brain injuries are described as mild, moderate, or severe. The Glasgow Coma Scale (GCS) is used to determine the severity of a brain injury, within the first 48 hours. The GCS determines eye opening, verbal response, and motor response. The highest score that can be obtained is 15. As follows, is the range for which each are classified:

* Mild traumatic brain injury: 13-15 and a loss of consciousness

* Moderate traumatic brain injury: 9-12 with a period of loss of consciousness for up to six hours and may be accompanied by other systemic injuries

* Severe traumatic brain injury: 3-8 and a loss of consciousness for more than six hours

Another tool that is used is the Ranchos Los Amigos scale of cognitive functioning and measures the severity of cognitive function. As follows, is the levels in which each is classified:

* Level