Traumatic Brain Injury Flashcards
Define traumatic brain injury (TBI)
TBI is an acquired brain injury (AQI). An AQI is a single traumatic event/single event pathology (e.g. subarachnoid haemorrhage or cerebral abscess) but is not applied to progressive conditions such as multiple sclerosis
What are the mechanisms of injury with TBI?
a) Direct high energy blow/impact to the skull
b) Penetrating injury through the skull into brain
c) Collision between the brain and the inside of the skull due to a sudden acceleration/deceleration of the body
Explain why different parts of the brain respond differently to applied force.
As the substance of the brain is composed of cells and axons it does not have a uniform density.
This means that different parts of the brain respond to force in different ways causing it to stretch and shear in a non-uniform manner
How is the severity of brain injury measured?
- Glasgow Coma Scale (level of consciousness)
- Post Traumatic Amnesia (PTA) (time from injury to day to day memory)
- Duration of coma
Name the 2 types of brain injury seen with TBI
Immediate (primary injury) as a direct result of the trauma (e.g. laceration, contusion, haemorrhage) or may occur over time as an indirect result of the injury (secondary brain injury).
How is primary brain injury classified? Describe them
Closed injury - TBI caused without disruption to the skull
Open injury - interruption to the integrity of the skull
What is primary brain injury?
The brain moves relative to the skull especially during acceleration or deceleration. If the acceleration/ deceleration is (abruptly) halted (such as hitting the ground from a height), the soft brain impacts on to the rigid skull. If it is jolted, the brain moves at a different rate to the skull, it wobbles and knocks against sides.
Primary injuries can be classified according to whether the skull remains intact (closed injury) or not (open injury).
In a closed head injury explain what you understand by local impact and polar impact
Local impact damage: contusions (bruising) of the brain tissue directly below the site of impact (can also affect the scalp and meninges)
Polar impact damage: the brain may collide with the opposite side of the skull to the site of primary impact and then oscillate between the two (contra-coup), producing additional shearing damage and contusions at each site.
What is the cause of a closed injury?
A closed injury may cause a local or polar impact on the brain on the inside of the skull. Caused by shearing, laceration, axonal or blood vessel damage
Describe how haemorrhage occurs during a closed injury?
Subdural, epidural or extradural, subarachnoid or intraventricular. Caused by shearing forces on blood vessels and laceration. Subdural haemorrhage occurs with forceful blows to the head and is commonly associated with skull fracture
In closed injuries of TBI where can cortical bruising and laceration occur?
Cortical bruising and laceration occurs mainly at the crests of the gyri, expanding more deeply in a severe injury
What type of injury can occur in the frontal lobes during a closed TBI injury?
Contusions. They occur on the under surface of the frontal lobes and temporal tips as they collide with the bony prominences of the anterior and middle cranial fossae (collision with ridges of the skull)
Contusions may result from what appears to be relatively low velocity impact e.g. a fall or a blow to the head.
Contusion = rupturing of blood vessels in the brain
Describe an open injury
An interruption to the integrity of the skull
A depressed or open fracture can cause compression, contusions or lacerations of the brain tissue under the site of impact and offers a route for infection.
Bone fragments may become imbedded in the brain tissue e.g. due to a gunshot wound.
What is diffuse axonal injury (DAI)?
Is high velocity shearing damage to the long axonal tracts
Occurs in hyperextension/rotational injuries which stretch or sever the axons in their myelin sheaths.
DAI is primarily responsible for the initial loss of consciousness but loss of consciousness does not always occur.
DAI can cause severe brain injury (if widespread) or it can occur in mild and moderate brain injury.
Where is diffuse axonal injury (DAI) most common?
DAI is most common in the parasagittal white matter, corpus callosum and the junction between the midbrain and pons adjacent to the superior cerebellar peduncle.
Identify the type of damage you may see with closed head injury as a result of a collision
Shearing, Laceration (like a cut) -> blood vessel damage
Axonal damage
Haemorrhage -> Contusions (bruising)
What is secondary brain injury? Give an example
Secondary brain injury occurs after the original injury e.g. haematoma, brain swelling, brain shift
Occurs as a consequence of failure of another body system e.g. oedema, massive haemorrhage or injury to the lungs/chest
What can leave the brain vulnerable to secondary injury?
Reduction in blood flow and oxygen delivery to brain tissue
Impairment of cardiovascular autoregulation
What is cytotoxic oedema?
Caused by increased cell membrane permeability and ionic pump failure causing intracellular accumulation of water in neurones, astrocytes (provide structural stability and nutrients to the neurones) and microglia (macrophages of the CNS)
What is vasogenic oedema?
Vasogenic cerebral oedema caused by cellular damage to the blood brain barrier, which allows uncontrolled ion and protein transfer from the intravascular to the extracellular brain compartments leading to water accumulation in the extracellular space
Why might oedema result in neuronal cell death?
- Oedema may lead to a critical reduction in cerebral blood flow as an increase in any one of the fluids (blood, brain tissue or CSF) inside the skull occurs at the expense of the others
- The brain doesn’t store glucose or oxygen
- Cerebral oedema raises intracranial pressure which reduces cerebral blood flow
How does the Glasgow Coma Scale measure brain injury severity?
3 sections each having a summated score of 3 (lowest) to 15 (highest)
3 sections = eye opening, motor response, verbal response
It measures the duration/severity of the coma as 8 or below
Name 3 prolonged disorders of consciousness
Vegetative State
Minimally Conscious State
Locked in Syndrome
Describe locked in syndrome
Associated with brain stem (basilar artery) stroke. Patient is unable to move or communicate, except for eye movement but is fully aware of him/herself i.e. fully orientated in time, place, person and situation, and has an intact and functional memory.
Describe minimally conscious state
A condition of severely altered consciousness in which minimal (often inconsistent) but definite behavioural evidence of self or environmental awareness is demonstrated.
Describe vegetative state
implies the absence of cerebral cortex function (with relative preservation of vegetative/brainstem functions) following severe brain injury.
PVS (persistent VS) = < 1 year
Patients will have no verbal response/ability to communicate, they produce reflexes in response to stimulus, may swallow if food is put in their mouth, may have spontaneous eye movement, they will breathe spontaneously and have a sleep-wake cycle
List the long term consequences of TBI
Bladder and bowel dysfunction
Co-existing injuries
Cognitive and behavioural impairments
Physical problems
What are the acute stages of rehab for TBI?
Respiratory care - ventilator
Neurological status
Stimulate motor activity + function
Prevent contractures
What the phases of subacute rehab for TBI?
Discharge planning, e.g. home or to a rehabilitation unit Family meetings Review of medication Review of nutritional status Initiation of a regular toileting regime Review rehabilitation goals Liaison with outside agencies
Main aim of later stage rehab?
Improve C/V conditioning and community reintegration
