Primary and secondary brain injury

src: i.ytimg.com

Primary and secondary brain injury are ways to classify injury processes that occur in brain injury. In traumatic brain injury (TBI), primary brain injury occurs during initial insult, and results from the displacement of the physical structure of the brain. Secondary brain injury occurs gradually and may involve a series of cellular processes. Secondary injury, which is not caused by mechanical damage, may be caused by a primary injury or not dependent on it. The fact that people sometimes get worse after a brain injury was originally thought to be that a secondary injury is occurring. It is not well understood how much the contribution of primary and secondary injuries each has clinical manifestations of TBI.

Primary and secondary injuries occur in insults other than TBI as well, such as spinal injury and stroke.

Video Primary and secondary brain injury

Primary

In TBI, primary injury occurs immediately from early trauma. Primary injuries occur during trauma and include bruising, vascular damage, and axonal cuts, in which the axons of neurons stretch and tear. Brain blood barrier and meninges may be damaged in primary injury, and neurons may die. The cells are killed in a non-specific manner in the primary injury. The network has a deformation threshold: if they are defective over this threshold, they are hurt. Different areas of the brain may be more sensitive to mechanical loading because of their different properties resulting from differences in their makeup; for example, myelinated tissue may have properties different from other tissues. So some tissues may experience more strength and more hurt in primary injury. Primary injury causes secondary injury.

Maps Primary and secondary brain injury

Secondary

Secondary injury is the indirect result of injury. This is the result of a process initiated by trauma. This occurs within hours and days of primary injury and plays a major role in brain damage and death caused by TBI. Unlike in most forms of trauma, most people who are killed by brain trauma do not die instantly but days to weeks after the event. In addition, rather than improving after being hospitalized because most patients with other types of injuries, about 40% of people with TBI get worse. This is often the result of a secondary injury, which can damage the uninjured neurons in the primary injury. This occurs after various brain injuries including subarachnoid hemorrhage, stroke, and traumatic brain injury and involves a metabolic cascade.

Secondary injury can occur due to injury complications. These include ischemia (insufficient blood flow); cerebral hypoxia (insufficient oxygen in the brain); hypotension (low blood pressure); cerebral edema (brain swelling); changes in blood flow to the brain; and increase intracranial pressure (pressure inside the skull). If the intracranial pressure is too high, it can cause a deadly brain herniation, in which the part of the brain is pressed through the structure of the skull.

Other secondary injuries include hypercapnia (excessive levels of carbon dioxide in the blood), acidosis (too acidic blood), meningitis, and brain abscess. In addition, changes in the release of neurotransmitters (chemicals used by brain cells to communicate) can cause secondary injury. Imbalance in some neurotransmitters can lead to excitotoxicity, damage to brain cells resulting from overactivation of biochemical receptors to excitatory neurotransmitters (those that increase the likelihood that neurons will fire). Excitotoxicity can cause many negative effects, including cell damage by free radicals, potentially causing neurodegeneration. Another factor in secondary injury is the loss of cerebral autoregulation, the ability of the blood vessels of the brain to regulate brain blood flow. Other factors in secondary damage are damage to the blood brain barrier, edema, ischemia and hypoxia. Ischemia is one of the main causes of secondary brain damage after head trauma. A similar mechanism is involved in a secondary injury after ischemia, trauma, and injury that occurs when a person does not get enough oxygen. After a stroke, the ischemic cascade, a set of biochemical cascades occurs.

src: 4.bp.blogspot.com

Prevention

Because the primary injury occurs at the time of trauma and ends so quickly, little can be done to disrupt it in addition to preventing the trauma itself. However, since secondary injury occurs over time, it can be partially prevented by taking steps to prevent complications such as hypoxia (oxygen deprivation). Furthermore, secondary injury provides an opportunity for researchers to find drug therapy to limit or prevent damage. Because various processes occur in secondary injury, any treatment developed to stop or mitigate needs to be addressed by more than one of these mechanisms.

Thus efforts to reduce the disability and death of TBI are considered to be best aimed at secondary injury, since primary injury is considered irreversible.

src: images.slideplayer.com

See also

• Wallerian degeneration

src: www.frontiersin.org

References

Source of the article : Wikipedia