Neurotrauma, brain damage or brain injury (BI) is the destruction or degeneration of brain cells. Brain injuries occur due to a wide range of internal and external factors. In general, brain damage refers to significant, undiscriminating trauma-induced damage, while neurotoxicity typically refers to selective, chemically induced neuron damage.

A common category with the greatest number of injuries is traumatic brain injury (TBI) following physical trauma or head injury from an outside source, and the term acquired brain injury (ABI) is used in appropriate circles to differentiate brain injuries occurring after birth from injury, from a genetic disorder, or from a congenital disorder. Primary and secondary brain injuries identify the processes involved, while focal and diffuse brain injury describe the severity and localization.

Recent research has demonstrated that neuroplasticity, which allows the brain to reorganize itself by forming new neural connections throughout life, provides for rearrangement of its workings. This allows the brain to compensate for injury and disease.

Causes
Brain injuries can result from a number of conditions including:

A Coup injury occurs under the site of impact with an object, and a contrecoup injury occurs on the side opposite the area that was hit.
trauma; multiple traumatic injuries can lead to chronic traumatic encephalopathy. 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 displace rapidly into the opposite side of the skull, causing an additional contusion.
open head injury
closed head injury
penetrating: when a sharp object enters the brain, causing a large damage area. Penetrating injuries caused by bullets have a 91 percent mortality rate
deceleration injuries
poisoning; for example, from heavy metals including mercury and compounds of lead
hypoxia, including birth hypoxia,
tumors
infections
stroke leading to infarct, which may follow thrombosis, embolisms, angiomas, aneurysms, and cerebral arteriosclerosis.
neurological illness or disorders
surgery
drug abuse
neurotoxins- pollution exposure or biological exposure (Annonaceae, rotenone, Aspergillus spores, West Nile Disease, Viral meningitis).
Chemotherapy
Chemotherapy can cause brain damage to the neural stem cells and oligodendrocyte cells that produce myelin. Radiation and chemotherapy can lead to brain tissue damage by disrupting or stopping blood flow to the affected areas of the brain. This damage can cause long term effects such as but not limited to; memory loss, confusion, and loss of cognitive function. The brain damage caused by radiation depends on where the brain tumor is located, the amount of radiation used, and the duration of the treatment. Radiosurgery can also lead to tissue damage that results in about 1 in 20 patients requiring a second operation to remove the damaged tissue.

Wernicke-Korsakoff syndrome
Wernicke-Korsakoff syndrome can cause brain damage and results from a Vitamin B deficiency. This syndrome presents with two conditions, Wernicke’s encephalopathy and Korsakoff psychosis. Typically Wernicke’s encephalopathy precedes symptoms of Korsakoff psychosis. Wernicke’s encephalopathy causes bleeding in the thalamus or hypothalamus, which controls the nervous and endocrine system. Due to the bleeding, brain damage occurs causing problems with vision, coordination, and balance. Korsakoff psychosis typically follows after the symptoms of Wernicke’s decrease and result from chronic brain damage. Korsakoff psychosis affect memory. Wernicke-Korsakoff syndrome is typically caused by chronic alcohol abuse or by conditions that affect nutritional absorption, including colon cancer, eating disorders and gastric bypass.

Iatrogenic
Brain lesions are sometimes intentionally inflicted during neurosurgery, such as the carefully placed brain lesion used to treat epilepsy and other brain disorders. These lesions are induced by excision or by electric shocks (electrolytic lesions) to the exposed brain or commonly by infusion of excitotoxins to specific areas.

Diffuse axonal
Diffuse axonal injury is caused by shearing forces on the brain leading to lesions in the white matter tracts of the brain. These shearing forces are seen in cases where the brain had a sharp rotational acceleration, and is caused by the difference in density between white matter and grey matter.

Diagnosis
Glasgow Coma Scale (GCS) is the most widely used scoring system used to assess the level of severity of a brain injury. This method is based on the objective observations of specific traits to determine the severity of a brain injury. It is based on three traits: eye opening, verbal response, and motor response, gauged as described below. Based on the Glasgow Coma Scale severity is classified as follows, severe brain injuries score 3–8, moderate brain injuries score 9–12 and mild score 13–15.

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