Brain Injury Classification

There are various ways to classify different brain injuries, including basing the classification on:

Primary or Secondary Injury

According to The American Speech-Language-Hearing Association, one of the ways to classify brain injuries is by whether the injury is a primary or secondary injury. A primary brain injury is one that occurs at the time of initial impact and is caused by mechanical forces, such as acceleration or deceleration or from an object striking the head. Common primary injuries include:

  • Skull fractures
  • Contusions
  • Concussions
  • Diffuse axonal injuries
  • Lacerations
  • Whiplash

A secondary injury occurs as an indirect result of the traumatic event. It is not caused by mechanical force. After traumatic contact to the brain, cellular processes may be initiated and can lead to further dysfunction and death of neurons. These injuries may be delayed from the moment of impact. Common types of secondary brain injuries include:

  • Ischemia
  • Oedema
  • Hypoxia
  • Hypertension
  • Cerebral edema
  • Raised intracranial pressure
  • Hypercapnia
  • Epilepsy
  • Biochemical changes

Mechanism of Injury

Another popular way of classifying head injuries is according to the mechanism of injury. This generally means that the injury is classified as either an open head injury or a closed head injury.

Open Head Injuries

Open head injuries occur when the skin and the outer protection of the brain is penetrated by a foreign object or a bone fragment of the skull. Common causes of these injuries include:

  • Bullet
  • Knife
  • Sharp object
  • Skull fragment

Closed Head Injuries

Closed head injuries involve an outside force without skull penetration. The skin remains intact with these injuries. The severity of these injuries depends on the velocity of impact and the forces applied at the time of impact. These injuries can sometimes result in an increase in intracranial pressure or compression of the brain.

Common causes of closed-head injuries include:

  • Falls of a short distance
  • Accidental hits by a foreign object, such as a ball
  • Tackles while playing football
  • Auto accidents

Morphology of Injury

Another way that brain injuries are classified are by the morphology of the injury. Examples of this include:

  • Fractures – Skull fractures can have various types of characteristics, such as being in the cranial vault or the skull base, being depressed or non-depressed, or being linear or stellate.
  • Focal injuries – Fractures are actually one type of focal injury. Other focal injuries include contrecoup contusions, fracture contusions, coup contusions, and intracranial hemorrhage.
  • Diffuse injuries – Diffuse injuries are usually caused by acceleration or deceleration. They can be difficult to diagnose with commonly available brain scans. These injuries can result in widespread brain damage, coma, or sometimes death. Shaken baby syndrome is one of the more common types of diffuse axonal injuries.

Severity of Injury

The classification type that most lay people hear of is based on the severity of the injury.

  • Mild – A mild traumatic brain injury may affect brain cells temporarily and result in no loss of consciousness or loss of consciousness of under 30 minutes.
  • Moderate – A moderate traumatic brain injury can result in a change to mental status or a loss of consciousness up to six hours.
  • Severe – A severe traumatic brain injury can result in a mental status change or loss of consciousness of more than six hours. Severe traumatic brain injuries can result in long-term complications or death.


The Orange County brain injury lawyers at Aitken * Aitken * Cohn can help explain the classification of brain injuries. Contact us to learn more.