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Acquired Brain Injury

An acquired brain injury is an injury to the brain that is not hereditary, congenital, degenerative, or induced by birth trauma (BIAA, 2019). An acquired brain injury makes the assumption that there was normal brain development at birth, and that the injury acquired occurred afterwards. There are 2 types of acquired brain injuries, traumatic and non-traumatic. 

A traumatic brain injury (TBI) is an injury that affects how the brain works (CDC, 2021). TBI can further be divided into injuries involving direct impact to the head, caused by an external source, and those injuries that involve inertial forces (BIAA, 2017). 

Traumatic impact injuries can further be divided into 2 subcategories:

  1. Open/ penetrating injury- an open wound to the head by a foreign object. With open injuries, the initial contusion typically occurs right beneath the point of impact (coup) and then occur contralateral to the side of impact (contrecoup). 

  2. Closed/ non-penetrating injury-brain damage due to indirect contact without the entry of any foreign object into the brain (ASHA, 2021). With closed injuries, tearing and shearing of axons, known as diffuse axonal injury (DAI) often occurs. These injuries result in focal injuries such as epidural or subdural hematomas or intracerebral hemorrhage. 


A traumatic inertial injury is a non-impact injury. One of the most common types of inertial injury involves acceleration-deceleration forces where the brain is rapidly accelerated within the skull followed by rapid deceleration. These occurrences can result in coup-contrecoup injuries. 

When the brain accelerates forward, there is an injury to the brain where it contacts the skull (the coup injury). Upon impacting the skull, the brain then rebounds impacting the opposite side of the skull (the contrecoup injury). When rotational forces or angular forces are added to the equation, diffuse axonal injury results. 

A non-traumatic brain injury also causes damage to the brain by internal factors, such as lack of oxygen, or nutrients to the nerve cells of the brain, exposure to toxins, pressure from a tumor or blockage or other neurological disorder (BIAA, 2021). 

Following an initial injury, secondary aspects occur, including:

  • hypoxia

  • anemia

  • metabolic abnormalities

  • hydrocephalus

  • intracranial hypertension

  • hemorrhagic activity

Other delayed effects occur as well as the injury process extends past the time of the initial injury or cell death and further exacerbates the effects of the injury by extending the amount of damage to the brain (BIAA, 2021). 


Causes of Traumatic Brain Injury



Motor Vehicle Accidents

Shaken Baby Syndrome

Abusive Head Trauma

Gunshot Wounds

Workplace Injuries

Child Abuse

Domestic Violence

Military Actions

Causes of Non-Traumatic Brain Injury


Infectious Disease (encephalitis, etc.)

Seizure Disorder

Electric Shock

Neurotoxic Poisoning

Tumors (surgery, radiation, chemo)

Toxic Exposures

Metabolic Disorders

Lack of Oxygen to the brain

Overall, acquired brain injury is the second most prevalent disability in the U.S., estimated at 13.5 million Americans (BIAA, 2021).

TBI (5.3 million)

Stroke (6.2 million)

Epilepsy (2.0 million)

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