Head Trauma

Overview

Definition

Head trauma is an injury to the skull, brain, and/or intracranial structures.

Epidemiology

• 2.8 million people suffer head injuries each year in the United States.
• 75% of cases are considered mild.
• The most common injury resulting in death
• Bimodal age distribution, with children, young adults, and the elderly having a higher incidence
• More common in men than women

Etiology

• Falls (most common cause in the elderly)
• Motor vehicle accidents
• Occupational accidents
• Sports 
• Physical assault

Classification of Severity

Glasgow Coma Scale (GCS)

• The GCS exam addresses the level of consciousness after a head injury.
• Patients receive a score for the best response in each area.
• Scores in each area are combined to reach a total score of 3–15.
• ↑ the number → the better the prognosis
• Score ≤ 9:
  • Indicates coma
  • Patient needs endotracheal intubation for airway protection

Traumatic brain injury (TBI) severity scale

• Mild TBI:
  • GCS of 13–15
  • Non-severe mechanism
  • 0–30-minute loss of consciousness
  • Amnesia brief, < 24 hours
• Moderate TBI:
  • GCS of 9–12
  • Loss of consciousness for > 30 minutes and < 24 hours
  • Headache
  • Vomiting
  • Amnesia > 24 hours and < 7 days
  • Alteration in mental status at the time of injury
• Severe TBI:
  • GCS < 9
  • Prolonged loss of consciousness (> 24 hours)
  • Neurologic deficits
  • Amnesia > 7 days 

Pathophysiology

Timing

• Primary:
  • Occurs at the moment of injury
  • Coup (on the side of impact) and contrecoup (on opposite side) injuries
  • Acceleration-deceleration injuries (abrupt brain movement and deformation within cranial cavity; common in motor vehicle collisions)
• Secondary: 
  • Injuries that occur hours/days/weeks after trauma
  • Result from the body’s response to the original trauma
  • Molecular injury mechanisms (inflammation, apoptosis, secondary ischemia)
  • Can result in local or diffuse brain edema, hemorrhage or ↑ intracranial pressure (ICP), electrolyte disturbance
  • May eventually lead to coma and death

Types

• Open (penetrating):
  • Injury that involves penetration of the skull, dura mater, and fracture of the calvarium
  • Brain tissue is directly injured by fragments of bone or other objects such as bullets, knives, etc.
• Closed:
  • More common than open injuries
  • Intact cranium and dura mater
  • Brain is damaged due to acceleration-deceleration.
  • Can be focal or diffuse

Types of Injuries

Skull fractures

• Occur when mechanical force exceeds the integrity of calvarium
• Often associated with intra- and extracranial injuries
• Parietal bone is most commonly fractured.

Linear fractures:

• Most common skull fractures
• Patient presents with swelling overlying the fracture site.
• Neurologic symptoms or intracranial hemorrhage are rare.
• Usually, no intervention is needed.

Comminuted fractures:

• Complex, with multiple bone fragments
• Associated with a significant force of impact
• Often become depressed fractures

Depressed fractures:

• Significant force results in inward displacement of a portion of the skull.
• May be closed or open (with skull laceration)
• May be seen on exam as obvious depressed area
• Can lacerate dura mater, create a point of entry into the cerebrospinal fluid, and introduce infection
• Clinical presentation depends on underlying brain injury.

Elevated fractures:

• Elevation of a bone fragment above calvarium
• Rare, usually involve frontal bones
• Associated with tangential impact
• Usually have significant underlying brain injury

Basilar skull fractures:

• Include fractures of:
  • Cribriform plate of the ethmoid bone
  • Orbital plate of the frontal bone
  • Temporal bone
  • Sphenoid bone
  • Occipital bone
• Most common through a temporal bone
• Epidural hematomas common (injury to middle meningeal artery and vein)
• Presentation depends on the degree of brain, cranial nerves, and vessels injury:
  • Rhinorrhea or otorrhea (cerebrospinal fluid (CSF) leak)
  • Hemotympanum (blood behind tympanic membrane)
  • Raccoon eyes (periorbital ecchymosis)
  • Battle sign (retroauricular or mastoid ecchymosis)
  • Subconjunctival hemorrhage
  • Nausea and vomiting
  • Cranial nerve palsies 

Intracranial bleeding

Focal cerebral contusions:

• Most common hemorrhagic lesions
• Usually in basal frontal and temporal regions
• Disruption of intraparenchymal vessels may lead to larger intracerebral hematomas.

Extra-axial hemorrhage:

• Epidural hematoma:
  • Results from rupture of the middle meningeal artery
  • Life-threatening condition 
  • Rapidly expanding blood collection in the potential space between the skull and dura mater 
  • Initial loss of consciousness marked by lucid interval (temporary neurological recovery)
  • Computed tomography (CT) scan shows biconvex, hyperdense blood collection that does not cross the suture lines.
  • Usually requires emergent surgery
• Subdural hematoma:
  • Blood collection between the dura and the arachnoid membrane due to rupture of bridging veins
  • CT scan shows crescent-shaped blood collection that crosses the suture lines.
• Subarachnoid hemorrhage:
  • Results from tear of small pial vessels
  • Usually in sylvian fissures and interpeduncular cisterns
  • Can extend into intraventricular hemorrhage

Diffuse axonal injury (DAI)

• Associated with acceleration-deceleration injury with unrestricted head movement 
• Rotational forces affect the brain areas with different density (gray-white matter junction).
• Symptoms can be mild, but typically are severe. 
• Severe DAI patients have loss of consciousness, which persists to a vegetative state (90% of cases).
• CT scan or magnetic resonance imaging (MRI) shows numerous minute punctate hemorrhages with blurring of grey-white interface.
• Most significant cause of morbidity in patients with TBIs as it results in vegetative state 

Concussion

• Mild TBI
• GCS score 13–15
• Usually no visible abnormalities on CT scan
• Believed to be a functional rather than anatomic disturbance
• Results from mild cortical contusions on coup or contrecoup sides
• Mild axonal injury
• Early symptoms of concussion include:
  • Headache
  • Dizziness 
  • Disorientation
  • Amnesia for the traumatic event
  • Nausea and vomiting
• Post-concussion syndrome:
  • Symptoms persist weeks to months after injury.
  • Headache, dizziness, cognitive impairment, and psychological symptoms
  • May be a result of secondary injury:
    • Release of excitatory neurotransmitters
    • Generation of free radicals

Diagnosis

History and physical exam

• Reported loss of consciousness and for how long
• Mental status (GCS evaluation)
• Scalp lacerations, palpable fractures
• Signs of basilar skull fractures:
  • Oto-/rhinorrhea
  • Ecchymosis (periorbital, periauricular)
  • Conjunctival hemorrhage, blood behind tympanic membranes
• Neurologic exam

Canadian CT Head Rule (CCHR)

The CCHR is used to determine the need for CT in adult emergency department patients with minor head injuries. Its sensitivity is close to 100% for identifying clinically significant brain trauma (i.e., trauma that requires neurosurgical intervention).

Requirements:

• None of the exclusion criteria are met.
• At least 1 of the inclusion criteria is present.

Inclusion criteria:

• Loss of consciousness
• Amnesia to the head injury event
• Witnessed disorientation
• GCS 13–15

Exclusion criteria:

• Age < 16 years
• Blood thinners
• Seizure after injury

High-risk factors:

• GCS < 15 2 hours post-injury
• Suspected open skull fracture
• Sign of base of skull fracture
• Vomiting more than twice
• Age > 65 years

​Medium risk factors:

• Amnesia post-event > 30 minutes
• Dangerous mechanism of injury
• Pedestrian struck by motor vehicle
• Occupant ejected from motor vehicle
• Fall from > 3 feet (1 meter) or down 5 stairs

Interpretation:

• If no risk factors, CT of the head is unnecessary.
• If any of the above risk factors are identified, a CT of the head should be obtained.

Imaging

• CT scan without contrast (1st line):
  • Skull fractures
  • Dura mater injury
  • Midline shift 
  • Bleeding (epidural, subdural, subarachnoid, intracerebral)
  • Diffuse axonal injury (DAI) 
• CT angiography: if vascular injury is suspected
• MRI: 
  • For late diagnosis (> 48 hours after trauma) 
  • Can evaluate for contusion and concussion better than CT 

Management

Initial management

• Airway protection: intubation usually required for GCS < 9
• Fluid resuscitation, oxygenation
• Assessment and management of associated injuries
• Antifibrinolytic therapy:
  • For moderate TBI (GCS 8–13)
  • Within 3 hours of injury
  • Reduces mortality

Concussion (mild TBI)

• No specific treatment
• Observation for 4–6 hours or CT scan without contrast
• Avoid narcotics or anything that could alter the patient’s mental status.
• Control pain with over-the-counter medicines such as acetaminophen or ibuprofen.
• Athletes should abstain from contact sports until cleared by a medical provider.

Moderate or severe TBI

Intensive care management (typically required):

• Maintain euvolemia (isotonic intravenous fluids).
• Maintain cerebral perfusion pressure:
  • Avoid hypotension.
  • Monitor ICP (if GCS < 9 or evidence of hemorrhage).
• Mechanical ventilation
• Correct coagulopathy
• Maintain optimal body temperature and glucose levels
• Seizure prophylaxis

Control of ICP:

• Head elevation
• Hyperventilation
• Sedation and analgesia
• CSF drainage: through ventriculostomy
• Osmotic therapy:
  • Hypertonic saline
  • Mannitol

Surgery:

• Decompressive craniectomy for refractory ICP elevation
• Evacuation of hematoma:
  • Epidural: if > 30 cc of blood
  • Subdural: if > 10 mm or > 5 mm midline shift on CT
  • Intracerebral: if significant mass effect
• Closure of dura, debridement, elevation:
  • For depressed skull fractures
  • For penetrating injuries