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Traumatic Brain Injury (TBI)

Basics

  • Definition: Alteration in brain function caused by external mechanical force
  • Systems affected: neurologic, psychiatric, cardiovascular, endocrine/metabolic, gastrointestinal, pulmonary
  • Synonyms: head injury, concussion

Epidemiology

  • 801,700 ED visits and 326,600 hospitalizations annually in US
  • 61,000 deaths/year (~30% of all injury-related deaths)

Etiology and Pathophysiology

  • Most common mechanisms (male vs female %):
  • Falls (35.6 vs 23.9)
  • Motor vehicle crashes (22.5 vs 10.8)
  • Struck by/against object (2.3 vs 0.9)
  • Intentional self-harm (0.8 vs 0.3)
  • Assault (7.5 vs 1.7)
  • In children (0-17 years): falls (7.7%), motor vehicle crashes (6.8%), contact sports (45% of TBI ER visits related to sports)
  • Pathophysiology: mechanical injury triggers cellular and molecular cascades → cerebral edema, ischemia, apoptosis

Risk Factors

  • Alcohol/drug use
  • Prior/recurrent head injury
  • Contact sports
  • Seizure disorder
  • ADHD
  • Male sex

Geriatric considerations

  • Subdural hematomas common after falls; symptoms may be subtle or delayed

Prevention

  • Safety education and fall prevention
  • Use of seat belts, helmets (bicycle, motorcycle)
  • Protective headgear for contact sports

Pediatric considerations

  • Suspect child abuse if fall <4 feet or suspicious history/injury, retinal hemorrhages present

Diagnosis

History

  • LOC, headache, vomiting, amnesia, confusion, dizziness, photophobia
  • Epidural hemorrhage may have "lucid interval" (initial LOC → recovery → recurrent LOC)

Physical Exam

  • Serial neurologic and cognitive testing (frequency based on GCS and stability)
  • Signs of increased ICP: hypertension, bradycardia, irregular respiration (Cushing triad)
  • Signs of basilar skull fracture: raccoon eyes, Battle sign, hemotympanum, CSF rhinorrhea/otorrhea

Differential Diagnosis

  • Other causes of altered mental status: toxicologic, infectious, metabolic, vascular

Diagnostic Tests

  • Screen for coagulopathy, alcohol/drug use
  • Noncontrast head CT: first-line imaging
  • Pediatric: skull x-rays only if abuse suspected
  • Mild TBI/concussion cognitive screening tests

Treatment

General Measures

  • Most mild TBI require no intervention
  • Early education and graduated return to activity if no symptoms persist
  • Moderate/severe injury: avoid hypotension/hypoxia
  • Maintain cerebral perfusion pressure 60-70 mm Hg
  • Head elevation 30° reduces ICP
  • Hyperventilation (temporary for impending herniation)
  • Mannitol or 3% hypertonic saline to reduce ICP
  • Seizure prophylaxis (phenytoin or levetiracetam) for 1 week or longer in select patients

Medications

  • Hypertonic saline preferred for ICP
  • Mannitol dosing: 0.25-2.0 g/kg IV over 30-60 minutes (adjust in children)
  • Sedation: propofol preferred; midazolam alternative
  • Phenytoin for seizure prophylaxis (monitor QT interval)
  • Avoid corticosteroids (increase mortality, late seizures risk)

Issues for Referral

  • Neurosurgery consult for penetrating trauma, abnormal CT meeting BIG-3 criteria

Surgery and Procedures

  • Early hematoma evacuation improves mortality, esp. GCS <6
  • CSF drainage reduces ICP but unclear long-term benefit
  • Surgical repair if CSF leak persists >24 hours

Admission Criteria (Brain Injury Guidelines - BIG)

  • BIG-1: Normal neuro exam, minor CT findings, no anticoagulation → observe 6 hrs, discharge if stable
  • BIG-2: Normal neuro exam, moderate CT findings, no anticoagulation → admit, repeat neuro checks

  • BIG-3: Abnormal neuro exam or severe CT findings or anticoagulation → admit ICU, neurosurgery consult

  • C-spine immobilization for all head trauma

Ongoing Care and Follow-Up

  • Follow-up within 1 week to assess return to activities
  • Rehabilitation for significant injury
  • Assess risks and benefits of restarting anticoagulation post-injury
  • Screen for depression and PTSD

Patient Education

  • Discharge to competent adult supervision
  • Clear instructions on signs of deterioration (worsening headache, focal deficits, altered mental status)
  • Patients need NOT be awakened during sleep unless instructed

Prognosis

  • Gradual improvement may continue for years
  • Mortality ~30 per 100,000 annually in US
  • Poor prognosis with low GCS, nonreactive pupils, old age, midline shift, comorbidities
  • 50% mild TBI return to work by 1 month; >80% by 6 months

Complications

  • Chronic subdural hematoma (especially elderly)
  • Late post-TBI seizures (risk increases with severity)

Clinical Pearls

  • TBI involves primary mechanical injury plus secondary cascades leading to cerebral edema and cell death
  • Imaging indicated for skull fracture, altered consciousness, neurologic deficits, persistent vomiting, scalp hematoma, abnormal behavior, coagulopathy, age >65