Overview of Traumatic Brain Injury

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Original Editor - Anna Ziemer

Top Contributors - Naomi O'Reilly  

Introduction

Acquired Brain Injury (ABI) or Head Injury are broad terms describing an array of injuries that occur to the scalp, skull, brain, and underlying tissue and blood vessels in the head. Acquired Brain Injuries are broadly classified into:

  • Traumatic Brain Injury derived from an external source 
  • Non Traumatic Injury derived from either an internal or external source

Acquired Brain Injury does not include damage to the brain resulting from neurodegenerative disorders like Multiple Sclerosis or Parkinson’s Disease.

Traumatic Brain Injury Non-Traumatic Brain Injury
Falls Stroke e.g. Haemorrhage, Clot
Assaults Infectious Disease e.g. Meningitis, Encephalitis
Motor Vehicle Accidents Seizure
Sport / Recreation Injury Electric Shock
Abusive Head Trauma e.g Shaken Baby Syndrome Tumours
Gunshot Wounds Toxic Exposure
Workplace Injury Metabolic Disorders
Child Abuse Neurotoxic Poisoning e.g. carbon monoxide, lead exposure
Domestic Violence Lack of Oxygen e.g. drowning, choking, hypoxic & anoxic injury
Military Actions eg. Blast Injury Drug Overdose

Traumatic Brain Injury

Traumatic Brain Injury is “an alteration in brain function, or other evidence of brain pathology, caused by an external force”. [1]

Whole-brain tractography in an aged-matched control and in a case of 26-year-old patient, 15 months post-traumatic brain injury demonstrating loss of connections. [2]

Traumatic brain injury does not always have to be demonstrated by motor impairment but hidden non-motor like symptoms related to cognition and behaviour are altered in all forms of traumatic brain injury. This phenomenon and the nature of the population living with traumatic brain injury not being outspoken either demanding in their rights enforcement as well as the lack of insight into real impact of traumatic brain injury on society earned the traumatic brain injury the “silent epidemic” name. [3]

Traumatic brain injury has been a public health problem for many years, and for years to come will still be a main source of death and severe disability. According to World Health Organisation by 2020 traumatic brain injury will surpass many diseases as the major cause of death and disability.

We are currently observing increasing number of traumatic brain injury due to medical advances in emergency medicine and intensive care but also due to decreasing fatalities as a result of safety and preventative measures such as decreased speed limits, use of helmets or development in army amours.

Traumatic brain injury continues to be critical health and socio-economic problem worldwide across low and high-income countries due its life-long consequences and can affect people at any age. Socioeconomic change of low and middle-income countries drives an increase in traumatic brain injury due to urbanisation and mechanisation.

We are witnessing a change in traumatic brain injury distribution for age groups with childhood and aging being the highest risk population; gender with males being the most at risk between 10 and 20 years old and females between 70 and 80 [3], as well as mechanism contributing to injury with falls increasingly contributing to traumatic brain injury and blast related injury being most popular mechanism of battlefield sustained traumatic brain injury.

The incidence amongst children creates new challenges in the field of traumatic brain injury often overlooked like behavioural change or educational difficulties. Vulnerability to criminalisation amongst adolescents and young people with traumatic brain injury has been becoming another problem. Accessible housing and complex care needs follow the traumatic brain injury increasing incidence amongst elderly (Time for Change).

The access to emergency services as well as neurosurgical services determines mortality and recovery outcomes after traumatic brain injury across the world regions. In lower-income countries the access is scarce and determines higher numbers of severe disability post traumatic brain injury.

Neurorehabilitation is an effective form of post traumatic brain injury treatment following the life-saving and critical care procedures and financially cost-effective approach to reducing the motor and non-motor impairment. Despite the vast supporting evidence, it is not commonly accessible. 

The strict algorithm-based treatment approach to Emergency and Intensive Care Medicine successfully saving lives of people sustaining traumatic brain injury has not been introduced to intermediate either community Neurorehabilitation. The lack of systematic approach to Neurorehabilitation, general underfunding or difficulty accessing the services demonstrate the lack of financial efficiency following ever growing cost of live saving procedures and acute care. This also prevents the people living with traumatic brain injury to capitalise on the most valuable time for rehabilitative treatment and impacts on early achievements. Resultant severely increased care costs, unemployability and loss of income by the traumatic brain injury survivors but also often by family members providing care are other factors contributing to the widely underestimated social cost of traumatic brain injury. 

Traumatic brain injury in sport has become a burning problem with clearly emerging long-term consequences. Many professionals have become involved in developing the evidence about complexity of symptoms, impact of its repetitive nature on brain health and long-term prognosis of sport related concussion. The evidence of its assessment and treatment as well as role in brain degenerative diseases is emerging and enhancing safety of those participating in sports like rugby, football, boxing, horse riding and racing, American football or ice hockey.

Global conflicts like the Global War on Terror had expose the military population to new pathomechanisms, but also enhance the development of subacute care and life-saving and neurosurgical procedures. [4] With the speed of global information share being faster than ever, the civil services benefit from military good practice dissemination.


Classification

There are various classification determinants utilized to classify traumatic brain injury. The clinical presentation and prognosis depend on the individual nature of the injury with often coexisting types of TBI. The classification is important for acute management, treatment and prognosis as well as neurorehabilitation requirements. 

Primary v Secondary Injuries

Depending on the timing and impact nature (Mechanical, Non-Mechanical) and accompanying pathophysiological processes. 

Primary Injury

Occurs at the time of injury and is induced by mechanical forces. Two main mechanisms that cause primary injury are:

  • Contact (i.e.: an object striking the head or the brain striking the inside of the skull) 
  • Acceleration - Deceleration. 

Primary injury due to acceleration-deceleration results from unrestricted movement of the head and leads to shear, tensile, and compressive strains. These forces can cause intracranial hematoma, diffuse vascular injury, and injury to cranial nerves and the pituitary stalk. (Silver at al. 2005)

Secondary Injury

Is not mechanically induced; it may be delayed from the moment of impact, and it may superimpose injury on a brain already affected by a mechanical injury (Silver at al.2005) The secondary damage is caused by cascade of processes impacting “cerebral blood flow (hyper or hypoperfusion), impaired cerebrovascular autoregulation,  cerebral metabolic disfunction and impaired cerebral oxygenation.”( Werner & Engelhard 2007). The ischemia and oedema are secondary injury types. [hyper link to pathophysiology to be added later]

The outcome form head injury is determined by above types with primary injury extend being only sensitive to preventative measures and secondary injury extend being susceptible to neuroprotective therapeutic interventions.

Focal v Diffuse Injuries

Focal Injury

Usually due to contact and causing scalp injury, might present as skull fracture, contusions and/or intracranial haemorrhage. Those injuries are detectable by CT, MRI or PET scans.

Contusions are the bleeding on the brain and include fracture contusion, coup contusion (at the site of the impact) and contrecoup contusion(directly opposite to the impact site). This mechanism is related to moving of intracranial content in the skull and impinging on internal surface of the skull. 

Commonly observed injury is coup-contrecoup injury presenting with contusion on opposite sides of the brain.

Diffuse Injury

Usually due to acceleration/deceleration injury and concussion resulting in diffuse axonal injury (DAI) and brain swelling. DAI is difficult to diagnose with commonly available CT or MRI scans, and is demonstrated by histological white matter injury of the cerebral hemispheres, the corpus callosum, the brain stem and, less commonly, the cerebellum. DAI might be accompanied by some focal lesions, but again only diagnosable microscopically.  

The tearing of the nerve tissue disrupts the brain’s regular communication metabolic processes. This disturbance in the brain can produce temporary or permanent widespread brain damage, coma, or death. The shaken baby syndrome is a type of diffuse axonal injury.

These injuries are commonly found together.

Opened v Closed Injuries

Open / Penetrating Injury 

Open/ Penetrating Injury occurs from the impact of a bullet, knife, or other sharp object that forces hair, skin, bone, and fragments from the object into the brain and dura mater is breached.  The area of damage is determined by the trajectory of the object and possible ricocheting when travelling through different density tissues (skulls, brain).

A "through-and-through" injury occurs when an object enters the skull, goes through the brain, and exits the skull and has got complex impact on the brain tissue with penetration injuries, additional shearing, stretching, and rupture of brain tissue.

Closed / Non-Penetrating Injury

A closed injury is an injury to the brain caused by an outside force without any penetration of the skull. The most serious complication is the brain oedema within constrained space of the skull and resultant increase in the intracranial pressure and compression of brain structures and cranial nerves.

Degree of Severity

Mild, Moderate, or Severe Traumatic Brain Injury depending on degrees of severity. Mild traumatic brain injury may affect the brain cells temporarily, but more serious injuries can result in long-term complications or death.

Measures of Severity

The main measures of severity used to classify the injury include:

  • Glasgow Coma Scale (GCS): is a point scale used to assess a patient's level of consciousness and neurological functioning after brain injury. The scoring is based on best eye-opening response (1-4 points), best motor response (1-6points) and best verbal response (1-5 points) with cut off point for coma at 8 points. For more in depth information see GCS student’s guide

Duration of Loss of Consciousness

Describing alteration in consciousness duration: 

  • Mild (mental status change or loss of consciousness [LOC] < 30 min), 
  • Moderate (mental status change or LOC 30 min to 6 hr), 
  • Severe (mental status change or LOC > 6 hr)

Posttraumatic Amnesia (PTA)

Posttraumatic Amnesia is described by the time elapsed from injury to the moment when patient presents with continuous memory of what is happening around them.

Overview of Classification Criteria for TBI Severity based on Glasgow Coma Scale, Loss of Consciousness, Posttraumatic Amnesia and structural imaging:

Severity GCS LOC Structural Imaging
Mild 13 - 15 < 20 min to 1 Hour Definition Dependant
Moderate 9 - 12 1 hour to 24 Hours Normal or Abnormal
Severe 3 - 8 > 24 Hours Normal or Abnormal

Symptoms

Traumatic brain injury can have wide-ranging physical, cognitive, psychological and physiological effects occurring immediately or elapsed. The symptoms might differ depending on the severity of TBI, but some are not specific to the type of injury.

Mild TBI

Physical Symptoms Sensory Symptoms Cognitive Symptoms
With or without loss of consciousness. If loss of consciousness: a few seconds to a few minutes Blurred Vision State of being dazed, confused or disoriented
Headache Ringing in the Ears Memory or concentration deficits
Nausea or Vomiting Bad taste in the mouth or changes in the ability to smell Mood changes or mood swings
Fatigue or Drowsiness Sensitivity to light or sound Irritability
Problems with speech Feeling depressed or anxious
Difficulty sleeping or sleeping more than usually Fatiguability
Dizziness or loss of balance

Moderate to Severe TBI

Physical Symptoms Sensory Symptoms Cognitive Symptoms
Loss of consciousness from several minutes to hours or days Blurred vision Coma and other disorders of consciousness 
Persistent headache or headache that worsens Double vision Profound confusion
Repeated vomiting or nausea Ringing in the ears Irritability
Convulsions or seizures Bad taste in the mouth or changes in the ability to smell Agitation, combativeness or other unusual behaviour
Dilation of one or both pupils of the eyes Sensitivity to light or sound Sad or depressed mood
Clear fluid or blood draining from the nose or ears Fatiguability
Sudden swelling or bruises behind the ears or around eyes
Inability to awaken from sleep
Weakness or numbness
Loss of coordination or balance
Irregular breathing
Difficulty speaking

Summary

With the complexity of the traumatic brain injury and its consequences there is no speciality capable to deal with them alone. In traumatic brain injury management the role of Multidisciplinary Team is invaluable with Physiotherapist / Physical Therapist role at its heart form acute to chronic stages. 

The currently growing insight into devastating impact of traumatic brain injury on individual’s, families’ and society’s life initiates widespread change in research and evidence implementation resulting in prevention, services design, legislation and funding. We are seeing developments in neuroprotective and neurorestorative treatments and therapeutic approaches driving the neuroplastic change at cell and network levels. We are accessing more precise diagnostic enabling more effective treatment choices. We are capitalising on gains of more advanced medical and rehabilitation centres with knowledge and evidence being widely shared. We are living in truly exciting times when more than ever can be done for traumatic brain injury survivors. 

References

  1. Menon DK, Schwab K, Wright DW, Maas AI; Demographics and Clinical Assessment Working Group of the International and Interagency Initiative toward Common Data Elements for Research on Traumatic Brain Injury and Psychological Health. Position statement: definition of traumatic brain injury. Archives of Physical Medicine and Rehabilitation. 2010 Nov;91(11):1637-40. doi: 10.1016/j.apmr.2010.05.017.
  2. Cavaliere C, Aiello M, Di Perri C, Fernandez-Espejo D, Adrian M. Owen AM, Soddu A. Diffusion tensor imaging and white matter abnormalities in patients with disorders of consciousness. Frontiers in Human Neuroscience. 2015 Jan;8:1-7. doi.org/10.3389/fnhum.2014.01028
  3. 3.0 3.1 Peeters W, van den Brande R, Polinder S, Brazinova A, Ewout W, Steyerberg EW, Lingsma HF, Maas AI. Epidemiology of traumatic brain injury in Europe. Acta Neurochirurgica. 2015;157:1683–1696. DOI 10.1007/s00701-015-2512-7
  4. Baker MS. Casualties of the Global War on Terror and their future impact on health care and society: a looming public health crisis. Military Medicine. 2014 Apr;179(4):348-55. doi: 10.7205/MILMED-D-13-00471.