Mild traumatic brain injury

Background

• Definition: GCS 14-15
• Neurologic dysfunction that varies without gross lesions (ie patients have trouble with memory, attention, and executive functioning
• Occurs after a blunt force or acceleration-deceleration head injury
• Likely secondary to metabolic insult ie low oxygen state, ion changes
• Structural imaging on MRI or CT might not indicate any injury
• Often evidence on microscopic level of injury with histology
• Important to not expose the already injured brain to repeated insults which is why there are usually worsening symptoms after a repeat concussion

Epidemiology

• 2.5 million people sustain a TBI in the United States every year
• 75 to 95 percent, are mild
• Most common causes of TBI are motor vehicle accidents (20 to 45 percent), falls (30 to 38 percent), occupational accidents (10 percent), recreational accidents (10 percent), and assaults (5 to 17 percent)

TBI Pathophysiology

Primary injury

• Contusions
  • Bruises to brain parenchyma
• Hematomas
  • Epidural hematoma
  • Subdural hematoma
  • Intraparenchymal
  • Intraventricular
  • Subarachnoid hemorrhage
• Diffuse axonal injury
• Direct cellular damage
  • Neurons
  • Axons
• Tearing and shearing of tissues

Secondary injury

Brain swelling causes increased ICP which compresses the tissue causing ischemia with direct compression of the vasculature causing brain tissue herniation and brain death

• Leads to expansion of the original injury (predominantly metabolic insult)
  • Calcium and sodium shifts
  • Mitochondrial damage
  • Production of free radicals
• Ultimately leads to damage to axonal integrity and axonal transport
  • Enzyme activity leads to apoptosis
• Microscopic structural injury is often unidentifiable on CT or MRI

Cerebral Blood Flow and Autoregulation

• vasoconstriction
  • HTN, Hypocarbia, alkalosis
• No good way to measure cerebral blood flow
  • Use CPP as surrogate
    • CPP is amount of pressure needed to perfuse the brain
    • CPP=MAP-ICP
      • When ICP elevates, CPP decreases
      • Normal ICP
        • 15 in adults
        • <10 to 15 in children
        • 1.5 to 6.0 in infants
• Autoregulation allows the body to control the cerebral blood flow
  • Autoregulatory mechanism is damaged in most TBI patients

Clinical Features

• Most consistent abnormality is subtle impairments in cognitive function (concussion symptoms)
  • Attention, concentration, amnesia, memory, processing speed, reaction time, calculation, executive function
• Physical signs/symptoms
  • Headache, dizziness, insomnia, fatigue, uneven gait, nausea/vomiting, blurred vision, seizure
  • Postconcussive anosmia (affecting taste as well)
• Behavioral changes
  • Irritability, depression, anxiety, sleep disturbances, problems related to school/work, emotional lability, loss of initiative, loneliness, and helplessness

Differential Diagnosis

Head trauma

• Traumatic brain injury
  • Intracranial hemorrhage
    • Intra-axial
      • Traumatic intracerebral hemorrhage
    • Extra-axial
      • Epidural hemorrhage
      • Subdural hemorrhage
      • Subarachnoid hemorrhage
  • Moderate-to-severe traumatic brain injury
    • Elevated intracranial pressure
  • Mild traumatic brain injury
    • Clinical decision rules for head CT in trauma
    • Post-concussive syndrome
• Orbital trauma
• Maxillofacial trauma
• Scalp laceration
• Skull fracture
  • Basilar skull fracture
  • Skull fracture (peds)
• Pediatric head trauma
  • PECARN head trauma rule

Evaluation

Workup

• Consider head CT (rule out intracranial hemorrhage)
  • Use validated decision rule to determine need
  • Avoid CT in patients with minor head injury who are at low risk based on validated decision rules.
• Consider cervical and/or facial CT

Westmead post-traumatic amnesia scale

Any wrong answer to following questions is considered positive for cognitive impairment after head injury

• What is your name?
• What is the name of this place?
• Why are you here?
• What month are we in?
• What year are we in?
• What town/suburb are you in?
• How old are you?
• What is your date of birth?
• What time of day is it? (morning, afternoon, evening)
• Three pictures are presented for subsequent recall

Diagnosis

• Clinically made, no reliable test that can confirm diagnosis of concussion
• Signs and symptoms may occur immediately or be delayed by days-weeks (see also post-concussive syndrome)

Types

• Simple concussion
  • Gradual resolution of symptoms within 7-10d
• Complex concussion
  • Persisting symptoms or cognitive impairment
  • Symptoms with exertion

Management

Simple

• Limitations on playing and training while symptomatic
• Follow up with primary care provider

Complex

• Refer to sports medicine or concussion specialist

Disposition

Admit

Patient requires inpatient observation if GCS <15, seizure activity present, anticoagulation or bleeding diathesis, or no responsible caregiver to discharge to

Discharge

Patient may be discharged for outpatient observation if (all of the following):

• No head CT required per above criteria OR head CT performed and not requiring neurosurgical intervention
• Patient GCS 15 on discharge
• No seizures
• No anticoagulation or bleeding diathesis
• Responsible caregiver at home to discharge to

Discharge instructions

• Given good follow up instructions detailing a graded return-to-activity program and symptoms to anticipate during recovery
• Encourage cognitive rest and avoidance of repetitive head injuries
• Discharge patient to care of responsible individual
• Patients might not understand discharge instructions so repeat them to the individual taking care of the patient
• In one study of adolescents, strict rest immediately after mild TBI offered no benefit.
• Physical activity at any level (light aerobic, moderate, full) within first 7 days compared with no activity associated with lower rates of persistent symptoms at 28 days (29% vs. 40%)
  • Multicohort study - 2400 children, aged 5-18, in the emergency department
  • Still recommend strict rest for first 24-48 hours
• Follow up for full examination, gait and cognition testing
  • Mini-Mental State Exam
  • Standardized Assessment for Concussion
    • Takes 10-15 mins to administer, often not performed in ED

Prognosis

See also post-concussive syndrome

• At 3 mo after injury 20-40% are symptomatic
  • With treatment for the most common symptoms of headache, difficulty concentrating, and short-term memory difficulties being rest and (in some circumstances) NSAIDS.
• At 1 yr after injury 15% are symptomatic

Calculators

PECARN Pediatric Head Injury

PECARN — Pediatric Head CT Decision Rule

Age Group	Select One
Patient Age	1 <2 years    ≥2 years

Age <2 Years — Risk Factors

Criteria	No	Yes
GCS <15 (altered mental status)	1
Palpable skull fracture	1
Occipital/parietal/temporal scalp hematoma	1
Loss of consciousness ≥5 seconds	1
Not acting normally per parent	1
Severe mechanism of injury (MVC with ejection/rollover/fatality, pedestrian/cyclist without helmet struck by motorized vehicle, fall >3 feet, head struck by high-impact object)	1
Risk Factors (<2y)	/ 6

Age ≥2 Years — Risk Factors

Criteria	No	Yes
GCS <15 (altered mental status)	1
Signs of basilar skull fracture (hemotympanum, raccoon eyes, Battle sign, CSF otorrhea/rhinorrhea)	1
Vomiting	1
Loss of consciousness	1
Severe headache	1
Severe mechanism of injury (MVC with ejection/rollover/fatality, pedestrian/cyclist without helmet struck by motorized vehicle, fall >5 feet, head struck by high-impact object)	1
Risk Factors (≥2y)	/ 6

Interpretation (for selected age group)
0	Very low risk — ciTBI risk <0.02% (<2y) or <0.05% (≥2y). CT not recommended.
1 (intermediate*)	Low risk — ciTBI risk ~0.9% (<2y) or ~0.8% (≥2y). Observation vs. CT. *Only if GCS=15 and no skull fracture/AMS. Consider observation for 4-6 hours.
GCS<15 or skull fx	High risk — ciTBI risk 4.4% (<2y) or 4.3% (≥2y). CT recommended.

References
Kuppermann N, Holmes JF, Dayan PS, et al. Identification of children at very low risk of clinically-important brain injuries after head trauma: a prospective cohort study. Lancet. 2009;374:1160-1170. PMID 19758692.

Canadian CT Head Rule

Canadian CT Head Rule

High Risk (for neurosurgical intervention)
Criteria	No	Yes
GCS <15 at 2 hours after injury	1
Suspected open or depressed skull fracture	1
Any sign of basal skull fracture (hemotympanum, raccoon eyes, CSF otorrhea/rhinorrhea, Battle sign)	1
Vomiting ≥2 episodes	1
Age ≥65 years	1
Medium Risk (for brain injury on CT)
Amnesia before impact >30 min	1
Dangerous mechanism (pedestrian struck, occupant ejected, fall from ≥3 feet or ≥5 stairs)	1
High Risk Criteria	/ 5
Medium Risk Criteria	/ 2

Interpretation
All No	CT NOT required — Low risk for clinically important brain injury. Safe for discharge with head injury instructions.
Medium risk ≥1	CT recommended — Risk of brain injury on CT. Imaging indicated.
High risk ≥1	CT required — High risk for neurosurgical intervention. Urgent CT head.

References

Stiell IG, Wells GA, Vandemheen K, et al. The Canadian CT Head Rule for patients with minor head injury. Lancet. 2001;357(9266):1391-1396. PMID 11356436. Stiell IG, Clement CM, Rowe BH, et al. Comparison of the Canadian CT Head Rule and the New Orleans Criteria in patients with minor head injury. JAMA. 2005;294(12):1511-1518. PMID 16189364. Inclusion criteria: GCS 13-15, age ≥16, injury within 24 hours, witnessed LOC/amnesia/disorientation.

See Also

• Head Trauma (Main)
• Severe traumatic brain injury