Traumatic brain injury

Diagnosis

Definition (as per CDC 2015 report to congress): disruption of normal brain function caused by a bump, blow, or jolt (such as with acceleration/deceleration movement) to the head or a penetrating head injury. Explosive blasts can also cause TBI. “Alteration of brain function” can include any one of the following:

1. Any period of loss or decreased consciousness
2. Any loss of memory for events immediately before (retrograde amnesia) or after the injury (post-traumatic amnesia)
3. Neurologic deficits such as muscle weakness, loss of balance and coordination, disruption of vision, change in speech and language, or sensory loss
4. Any alteration in mental state at the time of injury, such as confusion, disorientation, slowed thinking, or difficulty with concentration

Criteria for severity levels according to CDC report to congress:

Mild TBI

• Structural imaging is normal
• Loss of consciousness, if any, is less than 30 minutes
• Post-traumatic amnesia, if any, may occur in the day following head injury
• Best GCS within 24 hours is 13-15

Moderate TBI

• Structural imaging may be normal or abnormal
• Loss of consciousness is more than 30 minutes but less than a day
• Post-traumatic amnesia is typically greater than a day but less than a week
• Best GCS within 24 hours is 9-12

Severe TBI

• Structural imaging may be normal or abnormal
• Loss of consciousness is greater than a day
• Post traumatic amnesia is greater than a week
• Best GCS within 24 hours is 3-8

Glasgow coma scale

The GCS was first introduced by Teasdale and Jennett in an attempt to predict outcomes after severe head injury; it scores between 3-15 (Jennett et al, 1976)

Eye opening

1. no response
2. to pain
3. to speech
4. spontaneous

Verbal response

1. no response
2. incomprehensible sounds
3. inappropriate words
4. confused (sentences)
5. oriented

Motor response

1. no response
2. extension to pain
3. abnormal flexion to pain
4. flexion / withdrawal to pain
5. localizes pain
6. obeys commands

• Frontotemporal lobes of the brain are particularly susceptible to impact upon bony protuberances within the skull

Factors that influence outcomes

Factors that influence outcomes according to CDC report to congress

• Individual characteristics
  • Age (children < 7 years old who suffer moderate-severe TBI have substantially worse short- and long-term outcomes; older adults have lower survival rates compared to young and middle-aged adults)
  • Pre-injury functioning (higher pre-injury functioning tends to preserve more functional capacity)
• Social-environmental factors
  • Socioeconomic status
  • Caregiver and family functioning
  • Social support
    • Returning to participation in pre-injury social roles is an important aspect of functioning
    • Factors such as living independently, maintaining employment, or be involved in meaningful interpersonal relationships can influence outcomes
• Access to care after hospitalization
  • Discharge home (intensity of rehab not well defined) vs outpatient rehab vs inpatient rehab (most intense)
  • Insurance

Additional modifiable risk factors associated with cognitive symptoms (Roberts, et al, 2021)

• High pain interference in daily life
• High anxiety symptoms
• High depressive symptoms
• Physical impairment
• Low physical activity
• Current smoking
• Short sleep duration
• Sleep apnea history
• Stroke, diabetes, hypertension, or cardiovascular history

Postconcussion syndrome

Postconcussion syndrome is discussed on a separate page.

Chronic traumatic encephalopathy

Chronic traumatic encephalopathy is discussed on a separate page.

Second impact syndrome

Second impact syndrome is discussed on a separate page.

References

Center for Disease Control and Prevention. Report to Congress on Traumatic Brain Injury in the United States: Epidemiology and Rehabilitation. (2015). https://pubmed.ncbi.nlm.nih.gov/26184889/

Jennett B, et al. Predicting outcome in individual patients after severe head injury. The Lancet 1031–1034 (1976). https://pubmed.ncbi.nlm.nih.gov/57446/

Roberts AL, et al. Modifiable risk factors for poor cognitive function in former American-style football players: findings from the Harvard football players health study. 2021. Journal of Neurotrauma 38:189-195. https://pubmed.ncbi.nlm.nih.gov/32640866/