Traumatic brain injury (TBI) is defined by the Centers for Disease Control and Prevention as a disruption of normal brain function that can be caused by an external force, such as a bump, blow, or jolt to the head, or a penetrating head injury. Although different medical specialties or organizations will use different language, the defining characteristics for a TBI are:
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Acquired external force (nondegenerative, noncongenital, not related to birth trauma)
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Resulting in alteration in physiological brain function (temporary or permanent)
One of the most critical aspects in the evaluation and treatment of TBI is the assignment of injury severity. Unfortunately, however, no single classification system of TBI exists that encompasses all the clinical, pathological, and cellular/molecular features of this complex process. In this chapter, we review the most commonly used definitions and classification schema for TBI.
Definitions
Mild traumatic brain injury
The American Congress of Rehabilitation Medicine (ACRM) provided the first diagnostic criteria for mild TBI in 1993. This foundational definition is “a traumatically induced physiological disruption of brain function” with the criteria in the list that follows but excluding any Glasgow Coma Scale (GCS) score less than 13 after 30 minutes. The subsequent diagnostic criteria for moderate and severe TBI have been rooted in this original definition.
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Any loss of consciousness (LOC) (not to exceed 30 minutes)
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Any loss of memory immediately before or after injury event (not to exceed 24 hours)
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Any alteration of metal status (dazed, disoriented, confused, etc.)
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Any focal neurological deficits that may or may not be transient
Complicated mild traumatic brain injury
Inconsistencies with inclusion criteria for studies concerning mild traumatic brain injuries resulted in the introduction of the term complicated mild TBI (mTBI) in 1990. At the time of publication, a complicated mTBI was defined as a closed head injury with GCS 13 to 15 but differentiated from an “uncomplicated” mTBI by the presence of a depressed skull fracture and/or any injury-related intracranial abnormalities (e.g. hemorrhage, contusion, edema). Over time, the term has been simplified to include any mTBI with radiographic intracranial abnormalities. This term has largely been used for outcome-related research studies. ,
Common classification systems
Glasgow Coma Scale
The most common classification system for assigning TBI severity remains the GCS, first published by Jennet and Teasdale in 1974 ( Table 3.1 ). High-yield information with regard to GCS, however, includes:
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Use best available score within first 24 hours to diagnose severity
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With LOC, GCS is serially measured until consciousness is regained.
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Best motor response provides the greatest prognostic factor for recovery.
| Mild | Moderate | Severe | |
|---|---|---|---|
| GCS | 13–15 | 9–12 | 3–8 |
| Structural Imaging | Normal | Normal or abnormal | Normal or abnormal |
| LOC | 0–30 min | >30 min, <24 h | >24 h |
| AOC | Up to 24 h | >24 h | >24 h |
| PTA | 0–1 day | >1 day, <7 days | >7 days |
Loss of consciousness
Duration for LOC after TBI has also been used to measure severity of TBI. According to Greenwald et al., mild TBI is defined as alteration or LOC less than 30 minutes, moderate TBI is defined as greater than 30 but less than 6 hours, with severe TBI including LOC greater than 6 hours. In contrast, Department of Defense (DoD) and Department of Veterans Affairs (VA) Clinical Practice Guidelines (CPG) uses 24 hours of LOC to differentiate between moderate and severe TBI (see Table 3.1 ).
Posttraumatic amnesia
The time between injury event and ability to demonstrated continuous memory has been well documented as early as 1932 and has been labeled as posttraumatic amnesia (PTA). Duration of PTA has been largely used for outcome studies but can also be used to assign TBI severity when accurately measured.
Department of Defense/Department of Veterans Affairs Clinical Practice Guidelines
The DoD, VA, and Defense and Veterans Brain Injury Center (DVBIC) have collaborated with other federal and civilian medical professionals to develop the most up-to-date evidence-based clinical guidelines and definitions. The VA/DoD CPG is intended for use not only by the VA and Armed Forces but also by the general public. The VA/DoD CPG publication provides a classification table for diagnosis of TBI severity using the variables discussed earlier (see Table 3.1 ).
Less common classification systems
Abbreviated Injury Scale
The Association for the Advancement of Automotive Medicine developed an anatomical-based coding system called the Abbreviated Injury Scale (AIS) in 1969 with the goal of describing and classifying severity of traumatic injuries. With regards to TBI, the AIS has been used in epidemiological studies but has not gained widespread use for clinical purposes:
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Mild TBI: AIS 1 to 2
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Moderate TBI: AIS 3 to 4
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Severe TBI: AIS greater than 5
Simplified Motor Score
Despite the widespread use of the GCS, it has been widely criticized for poor interrater reliability and complexity. The three-point Simplified Motor Score (SMS) was created to simplify the diagnosis for severity of TBI. Retrospective studies comparing SMS to GCS reveal that the SMS performs as well as the GCS for classifying severity and predicting outcome. The SMS has largely been used for outcomes-based research and has not gained clinical popularity as a classification system. ,
Review questions
- 1.
A 34-year-old male presents to your outpatient clinic with a self-reported history of recent head trauma from a fall while inebriated. The event was unwitnessed, and the details are unclear. The patient reports persistent cognitive symptoms, headaches, and balance deficits. Which of these options has the best diagnostic value?
- a.
Thorough physical examination including Montreal Cognitive Assessment.
- b.
Neuropsychological testing
- c.
Computed tomography (CT) of brain
- d.
Magnetic resonance imaging (MRI) of brain
- a.
- 2.
A patient with a history of mild TBI (mTBI) 4 days ago presents to the emergency room (ER) with seizure activity. Electroencephalogram (EEG) demonstrates a seizure locus in the left frontotemporal lobe and head CT demonstrates subdural hematoma (SDH). What is the most likely assumption about the initial diagnosis?
- a.
The patient is suffering a late onset seizure
- b.
The patient likely has a history of undiagnosed epilepsy
- c.
The initial assessment incorrectly identified the severity of injury
- d.
The patient was not properly medicated for seizure prophylaxis after a concussion
- a.
- 3.
A 67-year-old male patient is brought into the ER after involvement in a motorcycle accident. The patient’s initial Glasgow Coma Scale (GCS) score was 8 and has improved to an 11 in the ER. Which of these is the best predictor of outcome?
- a.
Best motor response of 5
- b.
Verbal response of 4
- c.
Eye opening and verbal response score total greater than 8
- d.
None of the above
- a.
Answers on page 385.
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- 4.
A 25-year-old woman presents to your clinic with complaints of headaches and irritability after running into a signpost while jogging. She reports “blacking out” briefly and felt disoriented and dizzy after she “came to.” Her symptoms resolved after 15 minutes. Which of these is most accurate?
- a.
The woman’s injury is head trauma and not a TBI
- b.
The woman experienced loss of consciousness (LOC)
- c.
The woman likely sustained a mild traumatic brain injury, although LOC versus posttraumatic amnesia (PTA) is difficult to distinguish from the history given
- d.
The woman’s symptoms are suspicious for a moderate injury
- a.
- 5.
A 33-year-old veteran comes into clinic for a TBI screening. Which of these questions will best elucidate a history of TBI?
- a.
Did your injury result in a scalp laceration?
- b.
Did you experience headaches immediately after your injury?
- c.
Do you remember today’s date and the name of the current president?
- d.
Do you have a history of posttraumatic stress disorder (PTSD)?
- a.
References
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