Head Injury: Traumatic Brain Injury Definition and Anatomy

Head Injury

• Traumatic brain injury is an insult to the brain caused by an external physical force, resulting in a diminished or altered state of consciousness and impairment of cognitive abilities or physical functioning.

Anatomy

• Scalp
• Skull
• Brain

Epidemiology

• Transportation accounts for 44% of traumatic brain injuries
• Falls account for 26% of traumatic brain injuries
• Other causes include: • Firearms (8%) • Non-firearm assaults (9%) • Annual mortality of children from road traffic accidents is 3.89 per 100,000

Pathophysiology

• Primary vs secondary brain injury
• Monro-Kellie doctrine: the concept of a fixed volume of the cranial vault, where an increase in one component (blood, CSF, or brain tissue) leads to a decrease in another

Concepts

• Autoregulation
• Volume-pressure curve: • 60-55 mmHg: herniation • 50-40 mmHg: point of decompensation • 30-20 mmHg: compensation • 15-10 mmHg: volume of mass

Classification of Head Injury

• Glasgow Coma Scale (GCS): • Eye opening: 1-4 points • Verbal response: 1-5 points • Motor response: 1-6 points • Total GCS: 3-15 points
• Clinical scenario: a 20-year-old male in a motor vehicle accident, intubated, with a GCS score of 8

Approach to Head Injury

• History: • Mechanism of injury • Loss of consciousness • Vomiting • Seizures • Intoxicants • Post-traumatic amnesia
• Clinical examination: • Dilated non-reactive pupils • Hemiplegia/hemiparesis • Aphasia/dysphasia • Facial weakness • Cranial nerve palsy • Papilloedema
• Signs of skull base fracture: • Raccoon eyes • Battle sign

Investigations

• Skull X-ray: useful only for detecting skull fractures, but may waste time in the trauma setting
• CT scan: • Indications:
  • GCS ≤ 14
  • Focal neurological deficits
  • Deteriorating GCS
  • Penetrating head injuries
  • Post-traumatic seizures
  • Loss of consciousness and amnesia
  • Multiple trauma
  • Skull fracture
  • Patients who are intoxicated
  • Patients on anti-coagulant therapy
  • Mechanism of injury • Indications for observation at home:
  • Normal CT
  • GCS 15
  • No focal deficits
  • Easy access to ER
  • Responsible adult to observe at home
  • No complicating circumstances • Indications for re-admission:
  • Drowsiness
  • CSF leak
  • Seizures
  • New focal deficit
  • Fever

Pathology

• Primary injury: • Acute extradural hematoma • Acute subdural hematoma • Contusion/intracerebral hematoma • Diffuse cerebral injury • Skull fracture • Gunshot injuries • Penetrating stab injuries • Concussion in sports • Non-accidental injury
• Secondary brain injury: • Prevention: maintain Po2 > 60 mmHg, systolic BP > 90 mmHg, glucose control, and appropriate IV fluids • Conservative management:
  • GCS 13-15
  • No focal deficits
  • Neurological observations: ICU/high care (hourly) • Surgical management:
  • ICU management:
    • General measures:
      • Head elevation 30 degrees
      • Neck neutral position
      • Urinary catheter
      • Analgesia
      • Gastro-protective agents
      • Anti-seizure prophylaxis
      • DVT prophylaxis
      • Nutrition
      • Fluids
    • Medical management:
      • Ventilation: PCo2 30-35 mmHg
      • Sedation
      • Mannitol
      • Hypertonic saline
    • General monitoring:
      • ECG
      • Saturations: 100%
      • Systolic BP: > 90 mmHg
      • Pulse
      • Temperature: maintain euthermia or mild hypothermia
      • CVP: 8-14 mmHg
      • Glucose: normoglycemic
    • ICP monitoring:
      • Indications:
        • GCS ≤ 8
        • Polytrauma
        • Prolonged ventilation
        • Hypotension
        • Posturing
      • ICP > 20 mmHg: abnormal
    • Brain tissue oxygen tension (PbtO2) monitoring:
      • Normal values: 20-35 mmHg
    • Cerebral perfusion pressure (CPP):
      • CPP = MAP – ICP
      • Targeted value: 60 mmHg
      • Values < 50 mmHg: cerebral ischemia and hypo-perfusion
      • Values > 70 mmHg: cardiorespiratory failure, ARDS

Prognostic Factors

• Age: younger patients have a greater potential for survival and recovery
• Mechanism of injury: e.g., motorbike crashes
• GCS < 8
• ICP > 45
• Hypotension: > 50% increase in mortality with a single episode of hypotension
• Hypoxia: PO2 < 60 mmHg, Sats < 90%

Glasgow Outcome Scale

• 1: Dead
• 2: Vegetative state
• 3: Severe disability
• 4: Moderate disability
• 5: Mild disability

Late Complications

• Post-traumatic seizures
• Hydrocephalus
• Infections
• Post-concussive syndrome: • Somatic: headaches, dizziness, anosmia, hearing difficulties, balance difficulties • Cognitive: difficulty concentrating, dementia, impaired judgment • Psychosocial: emotional problems, personality changes, loss of libido, tiredness, difficulty sleeping

Multidisciplinary Team

• Physiotherapists
• Occupational therapists
• Psychologists
• Social workers
• Nurses
• Doctors