Understanding brain injury

The brain weighs approximately three pounds. It has the consistency of blancmange.

It looks like two halves of a walnut and has two hemispheres - left and right.

Your brain is made of approximately 86 billion nerve cells called neurons. Neurons gather and transmit
electrochemical signals – like the gates and wires in a computer.


Structure of the brain

Brain structure Brain structure

An acquired brain injury (ABI) is any brain injury that is not present at birth or degenerative

Acquired brain injury infographic

Causes of acquired brain injury (ABI):

  • traumatic brain injury (TBI)
  • cerebral tumours
  • hypoxia
  • infections
  • neurotoxic disorders
  • stroke.

TBI is an injury to the brain caused by a trauma to the head. 566 for every 100,000 people in the UK had hospital admissions for TBI in 2013/14

Common causes include road accidents (70%), assaults, sporting accidents, industrial accidents
and falls.

Types of TBI:

Open brain injury:

  • skull penetrated, brain exposed.

Closed brain injury:

  • brain not exposed
  • diffuse axonal damage
  • not always easy to see
  • extent of damage.

How damage may occur

Primary injuries (direct effect of the impact):

  • bruising
  • diffuse axonal damage.

Secondary injuries (due to later complications):

  • bleeding
  • brain swelling
  • infections
  • breathing difficulties.

Severity of TBI

Loss of consciousness
Less than 30
30 min to
24 hrs
24 hrs or
Post-traumatic amnesia
Up to 24 hours 1-7 days More than seven days
Glasgow Coma Scale score
13-15 9-12 3-8


Cerebral tumours

Abnormal growth of cells within the brain:

  • malignant - fast growing, invasive
  • benign - slower growing, non-invasive
  • primary - starts in/on the brain
  • secondary - cancer cells transported in the bloodstream from another organ


Hypoxia - low levels of oxygen in the blood.
Anoxia - no oxygen in the blood.

This can leads to death of brain cells. Causes include:

  • carbon monoxide poisoning

  • cardiac arrest

  • drowning

  • respiratory disorders

  • sleep apnoea.

Neurotoxic disorders

Damage to the neurons in your brain. Caused by harmful chemicals including:

  • carbon monoxide

  • pesticides

  • solvents

  • drugs.


Occurs when the blood supply is restricted or stopped, causing brain cells to die.

Ischaemic stroke is when the blood supply is stopped due to a blood clot.

Haemorrhagic stroke is when a weakened blood vessel supplying the brain bursts and causes brain damage.

Brain Injury Information