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Brain Injury Diagnosis

Brain Injury Severity

Brain injury severity is the primary factor in predicting the injury’s impact on an individual. A brain injury can be classified as mild, moderate or severe.

How is brain injury severity measured?

Mild, moderate, and severe brain injuries all have symptoms that indicate their severity. The following table shows the symptoms of each categorization.


Mild Brain Injury Moderate Brain Injury Severe Brain Injury
  • Brief, if any, loss of consciousness
  • Vomiting and Dizziness
  • Lethargy
  • Memory Loss
  • Unconsciousness up to 24 hours
  • Signs of brain trauma
  • Contusions or bleeding
  • Signs of injury on neuroimaging
  • Unconsciousness exceeding 24 hours (coma)
  • No sleep/wake cycle during loss of consciousness (LOC)
  • Signs of injury appear on neuroimaging tests

Depending on the brain injury’s severity, a person may enter into an unconscious state, where one appears to be in a deep sleep and cannot be aroused or respond purposefully. Assessments typically reveal that the individual has no sleep and wake cycles. This loss of consciousness (LOC) is referred to as a coma. Depending on varying factors and the severity of the injury, the individual may remain in a coma, emerge from a coma, or experience an increased level of consciousness.

Someone who is truly in a coma will not be considered for any type of brain injury rehabilitation program. People can, however, experience different states of consciousness after brain injury. Understanding these disorders of consciousness can be important when discussing treatment and possible rehabilitation options.

Types of disorders of consciousness

  • Vegetative State – An individual is unaware, but begins to have sleep and wake cycles; normal digestion, breathing, and heart rates; and may open his or her eyes. The individual may occasionally respond to stimuli.
  • Persistent Vegetative State – Doctors consider a person to be in a persistent vegetative state one year after traumatic brain injury or three to six months after a hypoxic or anoxic brain injury. However, in certain rare cases, individuals with traumatic brain injury have emerged from a vegetative state after more than one year, and individuals with hypoxic or anoxic brain injury have done the same after more than three months. Research continues to study the recovery process of people who are considered to be in this state.
  • Minimally Conscious State – An individual shows slight but definite self-awareness or awareness of their environment. They may inconsistently speak short phrases or words, respond to simple commands, may make “yes or no” gestures or verbalizations (sometimes incorrectly), follow people with their eyes, grasp or hold objects, and show appropriate emotional responses, such as smiling or crying. One person may only demonstrate a few of these behaviors, while others exhibit all of them. An individual is considered out of a minimally conscious state if he or she can communicate consistently (at least “yes” and “no”) or can use common objects, such as a glass or brush.
  • Locked-in Syndrome – An individual can only move his or her eyes, not any other part of their body, and is conscious and able to think. The person may use vertical eye movements and eye blinking codes to communicate and operate environmental controls. Locked-in syndrome is rare.
  • Brain Death – A person with brain death is not alive because all the brain functions, including the brain stem, no longer work. Physicians refer to the Uniform Determination of Death Act (UDDA) to make the determination of brain death based on several specific medical criteria. Brain death is not reversible.

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