What is a Traumatic Brain Injury (TBI)?

A traumatic brain injury (TBI) is an injury to the brain that occurs as a result of a blow or jolt to the head, neck, or body. TBIs can range in severity from mild, to moderate or severe. Each year, it is estimated that around 200,000 Australians suffer a TBI. Mild TBI (also known as concussion) is the most common form of TBI, with around 170,000 cases occurring in Australia annually.

What is a TBI?

A traumatic brain injury (TBI) is an injury to the brain that occurs as a result of a blow or jolt to the head, neck, or body. A TBI can involve an object penetrating the skull (penetrating TBI: e.g. bullet or a shattered piece of skull), or the skull may remain intact (non-penetrative TBI: e.g. being struck in the head by an object).

What is the difference between a TBI and an Acquired Brain Injury (ABI)?

ABI is a term used to refer to any type of brain damage occurring after birth. An ABI can result from a number of different circumstances or health-related events – it is not just one type of disease or condition.

TBI is just one type of ABI. Other causes of ABI include:

  • Stroke
  • Seizures
  • Brain tumours (cancer)
  • Infections (e.g. meningitis, encephalitis)
  • Degenerative brain conditions such as Parkinson’s and Alzheimer’s disease.
  • Drugs or alcohol
  • Poisoning events
  • Not getting enough oxygen to the brain (e.g. from a near-drowning event or cardiac arrest)

What causes a TBI?

TBI can occur under a range of circumstances. The most common causes of TBI include:

  • Falls
  • Sports
  • Motor vehicle crashes
  • Workplace accidents
  • Assault (including domestic and family violence)

Who is at risk of TBI?

TBI can happen to anyone. However, research has indicated that individuals most at risk of experiencing a TBI include infants and young children, young adults aged between 15 – 24 years, males of any age range, and adults over the age of 65.

Spectrum of severity

TBIs can range in severity from mild, to moderate or severe. The severity of a TBI is often clinically assessed using the Glasgow Coma Scale (GCS). This tool assesses a person’s motor, verbal, and eye responses to determine the severity of their injury. A person’s GCS score can range from 3-15 points, with 3 indicating very severe TBI and 15 indicating a person is fully awake, responsive and has no problems with their memory or thinking ability. A mild TBI is typically defined as a GCS score of 13-15.

Generally, the more severe the injury, the more significant the symptoms and loss of function will be. A number of factors can also influence the severity of a TBI. These factors may include: a prior history of TBI, the time before receiving medical treatment, the way the TBI is managed and/or treated, whether the TBI was penetrating, if and for how long consciousness was lost, and the area(s) of the brain that were impacted.

What are the signs and symptoms of TBI?

TBI can result in a range of signs (things we can see) and symptoms (things people tell us they are experiencing). Each TBI is unique, and signs and symptoms of TBI can vary from person to person. TBI signs and symptoms may present immediately after the injury has occurred, or they may develop over the hours or days that follow.

Signs and symptoms of a TBI include:

Infants and young children who have suffered a TBI may not yet have the communication skills needed to be able to explain how they are feeling. As such they may show signs including being inconsolable, crying non-stop and may refuse to eat, drink, or breastfeed. To learn more about TBI in children, click here.

What are the consequences of TBI?

TBI can have wide-ranging physical and psychological effects. Some of these are apparent immediately after a TBI has occurred, while others may develop over time. The specific complications that arise following TBI depend on the brain areas that are affected and to what degree. Some complications are irreversible, while others may be treated or managed with the help of medical specialists and allied health professionals. You can read more about them here.

Altered state of consciousness

Moderate to severe TBI can result in a range of prolonged or permanent changes in a person’s state of consciousness, awareness, or responsiveness. These include:


Coma occurs as a result of widespread damage to the brain. A person who is in a coma is unconscious, unaware of anything and unable to respond to any stimulus. That is, they are both unaware and unawake. After a few days to weeks, a person may emerge from a coma or enter a vegetative state.

Vegetative state

When a person is in a vegetative state, they are awake but still unaware of their surroundings. A person in a vegetative state may be able to open and close their eyes, make sounds, respond to basic reflexes, or move (e.g. withdraw their hand when it’s squeezed hard). They are also able to regulate their breathing and heart rate without assistance. A vegetative state can become permanent, or individuals may progress to a minimally conscious state.

Minimally conscious state

A minimally conscious state is a severe but not complete impairment of awareness. A person in a minimally conscious state will show some signs of self-awareness or awareness of their environment (e.g. make eye contact, follow objects with their eyes, reach for objects, respond to questions with limited ability, react to commands in a usual by inappropriate way such as blinking). A minimally conscious state may result directly from a TBI (or other form of ABI), or it can be a transitional state when people are emerging from a coma or vegetative state.

Brain death

Brain death occurs when there is no measurable activity in the brain and brain stem. A person with brain death requires artificial life support as the damage to their brain is so severe that they are no longer able to carry out basic functions such as breathing on their own. Brain death is considered irreversible.


Physical complications

TBI can a result in a range of conditions that affect the brain and body function, including:

  • Seizures. Some people may develop seizures following TBI. Seizures may occur only in the early stages of injury, or years after it has occurred. People who experience recurrent seizures may be diagnosed with post-traumatic epilepsy.
  • Fluid build-up in the brain (hydrocephalus). Following TBI, cerebrospinal fluid may build up within spaces of the brain called cerebral ventricles in some people. This can result in increased pressure and swelling in the brain.
  • Skull fractures or penetrating wounds can tear the layers of the protective tissues (meninges) that surround the brain. This can result in infections if bacteria enter the brain. If not treated, an infection of the meninges (meningitis) can spread to the rest of the nervous system.
  • Blood vessel damage. TBI resulting in damage to several small or large blood vessels in the brain can lead to complications such as stroke and blood clots.
  • Headaches/Migraines. It is common for people to experience frequent headaches/migraines after a TBI.
  • Vertigo/Dizziness and Balance Problems. Many people experience dizziness, balance problems and/or difficulties with coordination following TBI.
  • Cranial nerve damage. Nerve damage to the nerves that emerge directly from the brain which can result in complications including paralysis of face muscles or losing sensation in the fact, altered sense of taste or smell, changes in vision, swallowing problems, dizziness, tinnitus (ringing in the ears), and hearing loss.
  • Lack of ability to control one’s bladder (urinary incontinence) or bowel (faecal incontinence).
  • Impaired movement or motor speed deficits (dyspraxia/apraxia).
  • Reduced muscle strength (paresis/paralysis).
  • Difficulty feeding and swallowing.


Following a TBI a person may experience changes in their cognitive (thinking) ability and skills, behaviour, and emotions, as well as problems with communication and sensation/perception. The consequences of TBI can be a source of frustration, conflict and misunderstanding for the person with TBI as well as their family members, friends, support workers and healthcare providers. Adjusting to new challenges that arise following TBI can take time, patience and understanding.


This article includes information adapted from the Mayo Clinic ,  Cleveland Clinic and American Speech-Language-Hearing Association websites.


Connectivity does not offer medical advice for individuals. If you have suffered a traumatic brain injury, please seek medical advice.


What is a TBI? References.
  1. Thomas, E., Fitzgerald, M. & Cowen, G. Post-concussion states: How do we improve our patients’ outcomes? An Australian perspective. J Concussion 4, 205970022096031 (2020).


Updated July 2023