Types of Brain Injury


  • A concussion is caused when the brain receives trauma from an impact or a sudden momentum or movement change.
  • A concussion is the most common type of traumatic brain injury.
  • A concussion can be caused by direct blows to the head, gunshot wounds, violent shaking of the head, or force from a whiplash type injury.
  • A person may or may not experience a brief loss of consciousness (not exceeding 20 minutes). A person may remain conscious, but feel “dazed” or “punch drunk”.
  • A concussion may or may not show up on a diagnostic imaging test, such as a CAT Scan.
  • Skull fracture, brain bleeding, or swelling may or may not be present. Therefore, concussion is sometimes defined by exclusion and is considered a complex neurobehavioral syndrome.
  • concussion can cause diffuse axonal type injury resulting in permanent or temporary damage.
  • It may take a few months to a few years for a concussion to heal.


  • A Diffuse Axonal Injury is a “shearing” injury to brain tissues and structures.
  • It can be caused by shaking or strong rotation of the head, as with Shaken Baby Syndrome, or by rotational forces, such as with a car accident.
  • Injury occurs because the unmoving brain lags behind the movement of the skull, causing brain structures to tear.
  • The tearing of the nerve tissue disrupts the brain’s regular communication and chemical processes.
  • This disturbance in the brain can produce temporary or permanent widespread brain damage, coma, or death.
  • A person with a diffuse axonal injury could present a variety of functional impairments depending on where the shearing (tears) occurred in the brain.


  • A contusion can be the result of a direct impact to the head.
  • A contusion is a bruise (bleeding) on the brain.
  • Large contusions may need to be surgically removed.


  • Coup-Contrecoup Injury describes contusions that are both at the site of the impact and on the complete opposite side of the brain.
  • This occurs when the force impacting the head is not only great enough to cause a contusion at the site of impact, but also is able to move the brain and cause it to slam into the opposite side of the skull, which causes the additional contusion.


  • Second Impact Syndrome, also termed “recurrent traumatic brain injury,” can occur when a person sustains a second traumatic brain injury before the symptoms of the first traumatic brain injury have healed. The second injury may occur from days to weeks following the first. Loss of consciousness is not required. The second impact is more likely to cause brain swelling and widespread damage.
  • Because death can occur rapidly, emergency medical treatment is needed as soon as possible.
  • The long-term effects of recurrent brain injury can be muscle spasms, increased muscle tone, rapidly changing emotions, hallucinations, and difficulty thinking and learning.


  • Penetrating injury to the brain 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.
  • Objects traveling at a low rate of speed through the skull and brain can ricochet within the skull, which widens the area of damage.
  • A “through-and-through” injury occurs if an object enters the skull, goes through the brain, and exits the skull. Through-and-through traumatic brain injuries include the effects of penetration injuries, plus additional shearing, stretching and rupture of brain tissue.
  • The devastating traumatic brain injuries caused by bullet wounds result in a 91% firearm-related death rate overall.
  • Firearms are the single largest cause of death from traumatic brain injury.

Sources: Brumback R. Oklahoma Notes: Neurology and Clinical Neuroscience. (2nd ed.). New York: Springer; 2006. and Center for Disease Control and Injury Prevention.


  • Shaken Baby Syndrome is a violent criminal act that causes traumatic brain injury. Shaken Baby Syndrome occurs when the perpetrator aggressively shakes a baby or young child. The forceful whiplash-like motion causes the brain to be injured.
  • Blood vessels between the brain and skull rupture and bleed.
  • The accumulation of blood causes the brain tissue to compress while the injury causes the brain to swell. This damages the brain cells.
  • Shaken Baby Syndrome can cause seizures, lifelong disability, coma, and death.
  • Irritability, changes in eating patterns, tiredness, difficulty breathing, dilated pupils, seizures, and vomiting are signs of Shaken Baby Syndrome. A baby experiencing such symptoms needs immediate emergency medical attention.

Source: National Center on Shaken Baby Syndrome


  • Locked in Syndrome is a rare neurological condition in which a person cannot physically move any part of the body except the eyes.
  • The person is conscious and able to think.
  • Vertical eye movements and eye blinking can be used to communicate with others and operate environmental controls.


  • Anoxic Brain Injury occurs when the brain does not receive oxygen. Cells in the brain need oxygen to survive and function. Types of Anoxic Brain Injury:
    • Anoxic Anoxia – Brain injury from no oxygen supplied to the brain
    • Anemic Anoxia – Brain injury from blood that does not carry enough oxygen
    • Toxic Anoxia – Brain injury from toxins or metabolites that block oxygen in the blood from being used

Source: Zasler, N. Brain Injury Source, Volume 3, Issue 3, Ask the Doctor


  • Hypoxic Brain Injury results when the brain receives some, but not enough, oxygen. A Hypoxic Ischemic Brain Injury, also called Stagnant Hypoxia or Ischemic Insult, occurs because of a critical reduction in blood flow or low blood pressure leading to a lack of blood flow to the brain.

Source: Zasler, N. Brain Injury Source, Volume 3, Issue 3, Ask the Doctor Column


The following are terms used to describe types of skull fractures that can occur with open head injuries:

  • Depressed Skull Fracture – The broken piece of skull bone moves in towards the brain.
  • Compound Skull Fracture – The scalp is cut and the skull is fractured.
  • Basilar Skull Fracture:
    • The skull fracture is located at the base of the skull (neck area) and may include the opening at the base of the skull.
    • Can cause damage to the nerves and blood vessels that pass through the opening at the base of the skull.
  • Battle’s Sign
    • The skull fracture is located at the ear’s petrous bone.
    • This produces large “black and blue mark” looking areas below the ear, on the jaw and neck.
    • It may include damage to the nerve for hearing.
    • Blood or cerebral spinal fluid may leak out of the ear. This is termed “CSF Oterrhea.”
  • Racoon Eyes
    • The skull fracture is located in the anterior cranial fossa.
    • This produces “black and blue” mark looking areas around the eyes.
    • Cerebral spinal fluid may leak into the sinuses. This is termed “CSF Rhinorrhea.”
    • Nerve damage for the sense of smell or eye functions may occur.
  • Diastatic Skull Fracture
    • The skull of infants and children are not completely solid until they grow older.
    • The skull is composed of jigsaw-like segments (cranial fissures) which are connected together by cranial sutures.
    • Skull fractures that separate the cranial sutures in children prior to the closing of the cranial fissures are termed “diastatic skull fractures.”
  • Cribiform Plate Fracture
    • The cribiform plate is a thin structure located behind the nose area.
    • If the cribiform plate is fractured, cerebral spinal fluid can leak from the brain area out the nose


When a person receives an impact to the head from an outside force, but the skull does not fracture or displace this condition is termed a “closed head injury”. Again, separate terminology is added to describe the brain injury. For example, a person may have a closed head injury with a severe traumatic brain injury.

  • With a closed head injury, when the brain swells, the brain has no place to expand. This can cause an increase in intracranial pressure, which is the pressure within the skull.
  • If the brain swells and has no place to expand, this can cause brain tissues to compress, causing further injury.
  • As the brain swells, it may expand through any available opening in the skull, including the eye sockets.When the brain expands through the eye sockets, it can compress and impair the functions of the eye nerves. For instance, if an eye nerve, Cranial Nerve III, is compressed, a person’s pupil (the dark center part of the eye) will appear dilated (big). This is one reason why medical personal may monitor a person’s pupil size and intracranial pressure.