Closed Head Injury
A closed head injury is a traumatic brain injury that occurs without penetration of the skull, where the brain is subjected to impact and/or inertial forces resulting in potential damage to brain tissue while the skull remains intact.1, 2
Definition and Characteristics
- Closed head injury (CHI) refers specifically to trauma where the skull remains intact (no penetrating injury)
- Ranges from mild to severe, with severity typically classified using the Glasgow Coma Scale (GCS):
- Mild: GCS 13-15
- Moderate: GCS 9-12
- Severe: GCS 3-8 1
- Affects approximately one in five patients who sustain facial fractures 3
- Consequences range from brief loss of consciousness to coma and death 3
Mechanisms of Injury
- Common causes include falls, motor vehicle accidents, and acts of violence 1
- Athletic injuries and blast-related exposures (military personnel) are additional mechanisms 1
- Brain damage occurs through several mechanisms:
Pathophysiology
- The contrecoup-coup phenomenon is a key mechanism:
- Upon skull impact, the brain (less dense than CSF) is initially displaced toward the contrecoup location
- This explains why contrecoup injuries are often more severe than coup injuries 5
- Brain undergoes deformation and distortion depending on:
- Site of impact
- Direction and severity of traumatic force
- Tissue resistance of the brain 4
- Linear translation of acceleration can cause:
- Extra-axial lesions (subdural hematoma, epidural hematoma, subarachnoid hemorrhage)
- Coup and contrecoup contusions 4
- Centroaxial blows (fronto-occipital or occipito-frontal) can produce:
- Damage to deep structures
- Diffuse axonal injury (DAI)
- Brain stem damage 4
Clinical Presentation
- Loss of consciousness (LOC)
- Post-traumatic amnesia (PTA)
- Alteration in mental state (feeling dazed, disoriented, or confused)
- Headache
- Vomiting
- Neurological deficits 1
Diagnostic Evaluation
Clinical Decision Rules
- Clinical decision rules help determine which patients need neuroimaging:
- Canadian CT Head Rule (CCHR)
- New Orleans Criteria (NOC)
- NEXUS Head CT decision instrument 1
Imaging
- CT is the first-line imaging modality for acute head trauma evaluation 1, 4
- Fast, accessible, and can be performed on monitored patients
- Detects scalp injuries, fractures, extra-axial hematomas, and parenchymal injury
- Suitable for following lesion development
- MRI is more sensitive for most post-traumatic lesions except skull fractures and subarachnoid hemorrhage 4
- Indicated when CT findings don't explain clinical state
- Better for follow-up and detecting subtle parenchymal changes
- Should include gradient-recalled-echo sequences to detect hemosiderin and former hematomas
Management
- Management depends on severity and specific findings:
- Mild CHI may require observation
- Severe CHI often requires intensive care management
- Critical care management may include:
- ICP monitoring for GCS ≤8 with abnormal CT findings
- Elevation of head 20-30° to improve venous drainage
- Maintaining euvolemia
- Treating fever and seizures
- Osmotic therapy with mannitol if needed 6
- Surgical intervention may be necessary for:
- Intracranial displacement exceeding 1cm
- Extra-axial collections requiring evacuation
- Hemorrhagic contusions with mass effect 6
Prognosis
- Depends on severity, extent of cerebral damage, timeliness of intervention, age, and comorbidities
- Up to 15% of patients with mild traumatic brain injury may have compromised function 1 year after injury 1
- Mortality is significantly higher in severe closed head injuries 7
Rehabilitation
- Early rehabilitation intervention is recommended as soon as medically stable
- Task-specific, motor training-based interventions can induce neuroplasticity
- Multidisciplinary approach addressing physical, cognitive, and behavioral deficits 6