Mild traumatic brain injury

Background

Mild TBI.JPG
  • 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

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
    • 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

Evaluation

Workup

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 [2]
  • Discharge patient to care of responsible individual
  • Patients might not understand discharge instructions so repeat them to the individual taking care of the patient
  • Recommend strict rest for 1-2 days with gradual introduction back to regular activity[3]
  • 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%)[4]
    • 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

See Also

References

  1. Choosing wisely ACEP
  2. Ronsford J, et al. Impact of early intervention on outcome after mild traumatic head in adults. 2002
  3. Thomas DG, Apps JN, Hoffmann RG, et al. Benefits of strict rest after acute concussion: a randomized controlled trial. Pediatrics. 2015; 2(135):213-223.
  4. Grool AM et al. Association Between Early Participation in Physical Activity Following Acute Concussion and Persistent Postconcussive Symptoms in Children and Adolescents. JAMA. 2016;316(23):2504-2514.