ABI Terminology

Diffuse Axonal Injury

Diffuse axonal injury (DAI) is a type of traumatic brain injury that is caused by inertial forces with shaking or rotation of the head, e.g., Shaken Baby Syndrome, car accident, falls, assaults.^{1 2 3 4 5}  The movement of the skull from external forces injures the unmoving brain by tearing nerve tissues (the rapid stretch of axons; white matter). Can be categorized as multifocal as involvement occurs throughout deep subcortical white matter and midline structures. The brain’s communication and chemical processes (impairment in axon elasticity and transport) are disrupted and may result in coma or death. Additional brain chemicals (including calcium) are released in addition to the injury which causes further damage. Impairments depend on where the shearing occurs in the brain. Imaging appears normal upon radiologic examination, but microscopic examination of brain tissue reveals swelling and disconnected axons.^6 7 5 

Coma is the most common impairment associated with DAI. Increasing evidence suggests that DAI may be associated with progressive neurodegenerative processes that may be associated with Alzheimer’s disease.^8 9  DAI can be graded with the Glasgow Coma Scale for severity.¹⁰  Associated symptoms of DAI include daytime fatigue, disequilibrium, phonophobia (sensitivity to sounds), tinnitus, photophobia (to light), blurry vision, nausea, and headaches. Cognitive impairments include attention, memory, and executive functions. Mood disturbances may be present as well as behavioral dyscontrol. More severe DAI include impaired consciousness and arousal with cranial nerve dysfunction. Motor impairments from tetraparesis to hemiparesis may be present. Motor impairments include spasticity, tremors, dyspraxia. Memory and orientation may be impaired as well as the presence of fronto-limbic issues of agitation, inappropriate behavior, and extreme behavioral dyscontrol.⁷ 

Focal Brain Injury

A type of traumatic brain injury associated with blows to the head that may cause cerebral contusions and hematomas to a localized area.^7 11 12  Focal injuries may cause epidural and subdural hematomas (SDH), subarachnoid, and intracranial hemorrhages (ICH). The severity of the contusion is associated with the amount of energy transferred to the brain. As the frontal and temporal lobes are affected, impairments include attention, memory, motivation, planning, self-control, affect, emotion, and general behavior. Signs and symptoms of epidural hematomas include transient loss of consciousness with rapid deterioration in neurological status. Subdural hematomas may develop over days to weeks or weeks to months and result in increases in intracranial pressure (ICP). Increased ICP may eventually affect vital brain structures such as the brainstem and result in herniation of cerebral contents and severe neurological dysfunction. In general with focal TBIs, it is often difficult to determine if the ICH/SAH came first or the traumatic injury.¹³ 

Secondary Brain Injury

Secondary brain damage is due to the presence of blood causing increased swelling (inflammation) inside the skull. Excess blood may cause cytotoxicity and oxidative stress on the system.¹⁴  May occur minutes after the injury or weeks after. Prevention of secondary brain injury is a medical challenge after the initial brain injury.¹⁵ 

Post-traumatic Amnesia

Post-traumatic amnesia (PTA) may be a useful indicator for the severity of closed head injury.¹⁶  PTA duration has shown correlation with TBI severity.¹⁷  The duration of PTA can range from less than 10 minutes (most common) to more than 4 weeks (less common).¹⁸  Current practice involves the use of the Westmead PTA Scale for PTA. This scale contains seven items that assess orientation and five items that assess memory and is administered on a daily basis.¹⁹ 

Concussion

Concussions are the most common type of TBI and is caused by direct blows to the head or body and may be closed or open. They include violent shaking, whiplash, and violent blows. A concussion occurs when the blood vessels in the brain are stretched and the cranial nerves are damaged. A brief loss of consciousness may or may not occur. Most concussions occur at a microscopic scale and may not show up on diagnostic tests. It is sometimes diagnosed by the exclusion of other diseases. Concussions can cause DAIs and result in temporary or permanent damage. They may take a few months to a few years to heal.⁶  Symptoms of concussion include impairments in verbal memory, reaction time, confusion, amnesia, slowed cognitive processing, altered mood/behavior/personality, headache, nausea, vomiting, balance issues, diplopia, light or noise sensitivity, feeling sluggish, or “feeling down”.²⁰ 

Contusion

A contusion is a bruise in the brain often from direct impact to the head. Large contusions may require surgical removal. A hematoma is heavy bleeding in or around the brain.⁶ 

Coup-Contrecoup

Coup-contrecoup injuries are contusions that occur at the site of impact and also on the opposite side of the brain (additional contusion); “blow” and “counterblow”. They often occur from falls and vehicle accidents with an insult to occipital and temporal regions. Intervention may include surgery with extensive lobectomy or decompressive hemicraniectomy.²¹  Symptoms depend on location of injury, e.g., frontal, parietal, occipital, temporal. Secondary effects include severe headache, seizures, dizziness, emotional challenges, sound and light sensitivity, amnesia, nausea, and slurred speech.²² 

Shaken Baby Syndrome

A violent criminal act that involves the perpetrator aggressively shaking a baby or young child. The forceful motions cause whiplash and Coup-Contrecoup injuries. Blood may accumulate and cause the brain to swell and compress on brain tissue and damage brain cells. Symptoms include irritability, changes in eating patterns, tiredness, dyspnea, dilated pupils, seizures, migraines, vomiting, lifelong disability, coma, and death.⁶ 

Anoxic

Anoxic brain injury occurs when the brain does not receive enough oxygen. Subtypes include “anoxic anoxia” – no oxygen at all, anemic anoxia – not enough blood to carry the oxygen, toxic anoxia – decreased oxygen occurring from toxins or metabolites, and hypoxic anoxia – the brain receives some but not enough oxygen.⁶ 

Skull Fractures

Linear

Most common type which occurs in a break in the bone but no movement of the bone.²³ 

Depressed

Broken pieces of the skull move towards the brain.

Compound

The scalp is cut and the skull is fractured.

Basilar

Skull fracture located at the base and cause damage to the nerves and blood vessels of the spinal cord and brain stem.

Petrous

Fracture located at the ear bone resulting in black and blue areas below the ear, jaw, and neck. Hearing may be affected. Aka ‘Battle’s Sign’.

Anterior Cranial Fossa

Located in the anterior cranial fossa and results in black and blue marks around the eyes. Aka ‘Raccoon Eyes’. Smell eye dysfunction may occur. CSF leak may require serious medical attention.

Diastatic

Results from fractures and separation of cranial sutures in newborns or children prior to them closing.

Cribiform

Results in a fracture in the thin structure located behind the nose. CSF may leak from the brain and out of the nose and if left untreated, may result in death.

Toxic Brain Injury

Also – toxic encephalopathy is the exposure of the brain to toxic substances. May be caused by chemicals commonly used in everyday life. Symptoms include altered mental status, memory loss, and visual problems. Toxic brain injury usually results in permanent damage to the brain.⁶ 

Locked-in Syndrome

A rare condition in which the person can only move their eyes and not any other parts of their body.²⁴ 

Bookmark

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