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Classification of Coma, Concussion and Traumatic Brain Injury

Concussion, Head Injury, Traumatic Brain Injury and Coma Classification Systems

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Various organizations and researchers have proposed classification systems of concussion, brain injury and coma. 

While the Glasgow Coma Scale is in wide use in EMT and ER settings, examination and classification of concussion has been less uniform across medical, research and even sports settings.  Most classifications of traumatic brain injury include considerations of alteration or loss of consciousness, coma level and duration, amnesia, complications such as fracture or intracranial findings.

This page includes a variety of classifications systems for I: Concussion and II: Traumatic Brain Injury


boston bridge structure 2006 Ernest J. Bordini, Ph.D. all rights reserved

Concussions - Diagnostic and Statistical Manual - DSM-IV and DSM-5

The Diagnostic and Statistical Manual - IV had a limited classification system with respect to concussion, including Post-Concussional Disorder in a section of diagnoses requiring further study. No specific definition of mild, moderate, or severe Traumatic Brain Injury (TBI) waswas included though individuals who have suffered significant cognitive, memory and other higher cognitive deficits as a consequence of a brain injury would be diagnosed as Dementia due to Traumatic Brain Injury. Less severely impacted TBI's would be classified as Cognitive Disorder.

The DSM-IV definition of concussion was deemed to require more study is much more conservative than other syndromes which offer a grading of concussions.  Suggested criteria included:

  • unconsciousness lasting more than 5 minutes, and
  • post-traumatic amnesia lasting more than 12 hours subsequent to the closed head injury, and
  • new onset of seizures or marked worsening of pre-existing seizure disorder that occurs within the first six months.

DSM-IV criteria explicitly referred to necessary findings on neuropsychological testing.  Memory and attention difficulties must be present  difficulties in attention and memory must be demonstrated. The definition also includes that three or more of the following symptoms must be present for three months or more:

  • becoming easily fatigued,
  • disordered sleep,
  • headache,
  • vertigo or dizziness,
  • irritability or aggression on little or no provocation,
  • anxiety,
  • depression or affective lability,
  • changes in personality (e.g., social or sexual inappropriateness), apathy or lack of spontaneity.

The most recent version of DSM, the DSM-5 TR.....


 American Academy of Neurology Concussion Severity- March 1997 Practice Parameter:

Grade 1:  
__ Transient Confusion 
                   __ No Loss of Consciousness
                   __ Concussion Symptoms < 15 Minutes

Grade 2:   __ Transient Confusion
                   __ No Loss of Consciousness
                   __ Concussion Symptoms > 15 Minutes


Grade 3:   __ Any Loss of Consciousness, Brief or Prolonged 


AAN Guidelines suggest observation for features of concussion in sports-related concussions:


  • Vacant stare (befuddled facial expression.
  • Delayed verbal and motor responses (slow to answer questions or follow instructions.
  • Confusion and inability to focus attention (easily distracted and unable to follow through with normal activities.
  • Disorientation (walking in the wrong direction, unaware of time, date. and place)/
  • Slurred or incoherent speech (making disjointed or incomprehensible statements).
  • Gross observable incoordination (stumbling, inability to walk tandem/straight line.
  • Emotions out of proportion to circumstances (distraught, crying for no apparent reason)
  • Memory deficits (exhibited by the athlete repeatedly asking the same question that has already been answered or inability to memorize and recall 3 of 3 words or 3 of 3 objects in 5 minutes).
  • Any period of loss of consciousness (paralytic coma, unresponsiveness to arousal


AAN Guidelines Suggest Monitoring for "Early" and "Late" Symptoms of Concussion

  • Early Symptoms:  
  • -Headache
  • -Dizziness or vertigo
  • -Lack of awareness of surroundings
  • -Nausea or vomiting
  • Late Symptoms (days to weeks):
    − Persistent low grade headache
    − Light-headedness
    − Poor attention and concentration
    − Memory dysfunction
    − Easy fatigability
    − Irritability and low frustration tolerance
    − Intolerance of bright lights or difficulty focusing vision
    − Intolerance of loud noises, sometimes ringing in the ears
    − Anxiety and/or depressed mood
    − Sleep disturbance


     Concussion Severity: R.C. Cantu, 1991     Cantu's system is often used in reasearch involving sports concussion

    Cantu Concussion Severity Grades  (1991)

    Grade 1:   No Loss of Consciousness AND Post Traumatic Amnesia < 30 Minutes
    Grade 2:   Loss of Consciousness < 5 Minutes OR Post Traumatic Amnesia of 30 Minutes to 24 Hours
    Grade 3:   Loss of Consciousness > 5 Minutes OR Post Traumatic Amnesia > 24 Hours

  • In 2001 Cantu's system was updated and included additional symptoms:

    Grade 1: No Loss of Consciousness and Post-Traumatic Amnesia < 30 minutes, and post-concussion symptoms 15-30 min. 
    Grade 2: Loss of Consciousness < 1 minute or post-traumatic amnesia 30 min.- 24 hrs
    Grade 3: Loss of Consciousness > 1 minute, Post-traumatic amnesia > 24hrs, or signs and symptoms < 1 week.

    Ruff Concussion Grades:

    Type I :
    __ altered mental state or transient loss of consciousness (LOC)
    __ 1-60 seconds of post-traumatic amnesia (PTA)
    __ one or more neurological symptoms

    Type II:
    __ definite LOC with time unknown or < 5 minutes
    __ 60 seconds to 12 hours of post-traumatic amnesia (PTA)
    __ one or more neurological symptoms

    Type III:
    __ 5 - 30 minutes of LOC
    __ more than 12 hours of PTA
    __ one or more neurological symptoms


Traumatic Brain Injury (TBI) can be defined as damage to brain tissue caused by an external mechanical force as evidenced by 1. Loss of consciousness due to brain trauma, 2. post-traumatic amnesia (PTA), 3. skull fracture, or 5. objective neurological findings attributed to TBI on physical examination or mental status examination (1999 - Traumatic Brain Injury Model Systems National Data Center)


The Glasgow Coma scale is frequently employed at time of injury by Emergency Medical Technicians and during acute admission for brain injury. It consists of a 1-5 rating of three areas: best occular response, speech, and movement/response to pain resulting in a best possible score of 15.

Glasgow Coma Scale:   13-15 mild; 8-12 moderate; < 7 = severe head trauma, (poor prognosis)
(Teasdale & Jennett, 1974).  

Eye opening    Spontaneous = 4 ; To speech = 3; To painful stimulation = 2; No response = 1

Motor response  Follows commands = 6; Makes localizing movements to pain = 5; Makes withdrawal movements to pain = 4;
                              Flexor (decorticate) posturing to pain = 3; Extensor (decerebrate) posturing to pain = 2; No response = 1

Verbal response  Oriented to person, place, and date = 5; Converses but is disoriented = 4; Says inappropriate words = 3
                                    Says incomprehensible sounds = 2; No response =

Definition of Severe Traumatic Brain (TBI) involves a GCS score below 9 within 48 hours of the injury.  National Institute of Health (NIH) sponsored Traumatic Coma Data Bank (TCDB).

 Foulkes MA, Eisenberg HM, Jane JA, et al. The Traumatic Coma Data Bank: design, methods, and baseline characteristics. J Neurosurg. 1991;75. 

Other classification using GCS

"complicated mild" or "moderate" when the GCS exceeds 12 but accompanied by intracranial lesion on neuroimaging (skull fractures do not necessarily meet this criterion) - Williams, Levin, & Eisenberg, 1990

"Very Severe" GCS = 3-5 "Severe" GCS = 6–8 (Zhang, Jiang, Zhong, Yu, & Zhu (2001, Chinese J. of Traumatology).

Severity of Injury Based on Post-Traumatic Amnesia (PTA) Duration (Bigler, as cited in Lezak, 1995).

Post-traumatic amnesia, or the period of time until continuous memory is established is another simple method of classifying severity of head injury.

PTA Duration............Severity of Injury

  • < 5 minutes..............Very mild
  • 5 - 60 minutes...........Mild
  • 1 - 24 hours.............Moderate
  • 1 - 7 days...............Severe
  • 1 - 4 weeks..............Very severe
  • > 4 weeks................Extremely severe

Mayo Head Injury Classification System (2007)

A. Classify as Moderate-Severe (Definite) TBI if one or more of the following criteria apply:
1. Death due to this TBI
2. Loss of consciousness of 30 minutes or more
3. Post-traumatic anterograde amnesia of 24 hours or more
4. Worst Glasgow Coma Scale full score in first 24 hours < 13 (unless invalidated upon review, e.g., attributable to intoxication, sedation, systemic shock)
5. One or more of the following present: • Intracerebral hematoma, •Subdural hematoma, Epidural hematoma, Cerebral contusion, Hemorrhagic contusion, Penetrating TBI (dura penetrated), Subarachnoid haemorrhage, Brain Stem Injury

If none of Criteria A apply, classify as Mild (Probable) TBI if one or more of the following criteria apply:
1. Loss of consciousness of momentary to less than 30 minutes
2. Post-traumatic anterograde amnesia of momentary to less than 24 hours
3. Depressed, basilar or linear skull fracture (dura intact)

If none of Criteria A or B apply, classify as Symptomatic (Possible) TBI if one or more of the following symptoms are present:
Blurred vision; Confusion (mental state changes); Dazed; Dizziness; Focal neurologic symptoms; Headache; Nausea

Reference:  James F. Malec, Allen W. Brown, Cynthia L. Leibson, Julie Testa Flaada, Jayawant N. Mandrekar, Nancy N. Diehl, Patricia K. Perkins. Journal of Neurotrauma. September 2007, 24(9): 1417-1424. doi:10.1089/neu.2006 .0245.

Head Injury Interdisciplinary Special Interest Group of the American Congress of Rehabilitation Medicine (1993):

Traumatic Brain Injury (TBI) Mild head injury is defined as "a traumatically induced physiologic disruption of brain function, as manifested by one of the following:

  • Any period of loss of consciousness (LOC)
  • Any loss of memory for events immediately before or after the accident
  • Any alteration in mental state at the time of the accident
  • Focal neurologic deficits, which may or may not be transient.

The other criteria for defining mild traumatic brain injury (TBI) include the following:

  • Glasgow Coma Scale (GCS) score greater than 12
  • No abnormalities on CT scan
  • No operative lesions
  • Length of hospital stay less than 48 hours

The following criteria define moderate traumatic brain injury (TBI):

  • Length of stay of at least 48 hours
  • GCS score of 9-12 or higher
  • Operative intracranial lesion
  •  CT abnormality

Defense and Veterans Brain Injury Center Working Group on the Acute Management of Mild Traumatic Brain Injury in Military Operational Settings.  Dec. 2006   

Traumatic Brain Injury Definition

The Department of Defense and the Department of Veterans Affairs (May 2007), by consensus, have defined traumatic brain injury (TBI) as any traumatically induced structural injury and/or physiological disruption of brain function as a result of an external force that is indicated by new onset or worsening of at least one of the following clinical signs, immediately following the event:

1. Any period of loss of or a decreased level of consciousness.

2. Any loss of memory for events immediately before or after the injury;

3. Any alteration in mental state at the time of the injury
(e.g., confusion, disorientation, slowed thinking);

4. Neurological deficits (e.g., weakness, balance disturbance, praxis, paresis/plegia, change in vision, other sensory alterations, aphasia.) that may or may not be transient.

5. Intracranial lesion.

External forces - Forces causing brain injury include the head being struck by an object, the head striking an object, the brain undergoing an acceleration/ deceleration movement without direct external trauma to the head, a foreign body penetrating the brain, forces generated from events such as a blast or explosion, or other force yet to be defined. 


Open Versus Closed TBI. A TBI resulting from something passing through the skull into brain, such as a bullet or fragments from an explosion, is called a penetrating or open head injury. A TBI that results from either an object hitting the head or from the head hitting something forcefully, such as the dashboard of a car, is referred to as a nonpenetrating or closed head injury.

The above criteria define the historical event of a TBI. If a person meets these criteria, they should be diagnosed as having sustained a TBI.



Merck Manual Traumatic Brain Injury



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