Head trauma

Question 1

Epidemiology of TBI

Answer 1

• leading cause of death and disability in <45 yo
• occurs every 15 seconds
• young children, adolescents, young adults, elderly, men >> women
• 35% of TBI = falls

Question 2

Mechanism of injuries (3)

Answer 2

• Blunt:
  
  • high velocity = MVA
  • low velocity = falls, assaults
• Penetrating
  
  • high velocity = bullet
  • low velocity = knife
• Blast
  
  • overpressure waves affecting brain parenchyma and fluid filled vessels/ventricles

** These are the mechanisms that cause primary injury

Question 3

Primary injuries (3)

Answer 3

** Primary = result of mechanical forces at moment of impact

• Focal, multifocal, or diffuse injury
  
  • Vascular
  • Neuronal
  • Axonal
• Contusion
• Laceration

Question 4

Secondary injuries

Answer 4

• Occurs over hours/days in ICUs
• Usually worsens the primary injury
• ICUs aim to avoid these secondary injuries
• Cell and molecular cascades further injuring nervous system
  
  • inflammation, hypercoagulable response, hypotension, hypoxia, ischemia, edema, seizures, hyper/hypo glycemia or metabolism, etc…

Question 5

Blunt TBI

Answer 5

• Contusion (coup or contra-coup)
• extra-axial hematoma
• diffuse axonal injury

Question 6

Contusions (primary injury)

Answer 6

• focal hemorrhagic necrosis
• preference for gyral crests - orbitofrontal, temporal
• often has subarachnoid blood
• dynamic lesions that can expand
• Coup: contusions beneath the site of impact
  
  • moving object hits stationary head
  • contact loading
• Contra-coup: contusions on opposite side of impact
  
  • Head is moving toward stationary object
  • inertial loading

Question 7

Epidural hematoma

Answer 7

• lentiform/convex shape
• middle meningeal artery laceration from skull fracture in that area
• rarely crosses suture lines
• may be associated with “Lucid interval”
  
  • transient consciousness
• can cause sever brain compression but if repaired quickly then brain isn’t severely injured

Question 8

Subdural hematoma

Answer 8

• Crescent shape
• crosses suture lines bc they are below the dura
• rupture of bridging veins –> Venous
• causes severe underlying brain injury
• no “lucid interval”
• can be a chronic hematoma
  
  • –> different densities of blood on CT

Question 9

Subarachnoid hemorrhage

Answer 9

• associated with arterial vasospasm and ischemia
  *

Question 10

Diffuse Axonal Injury

Answer 10

• can be primary and secondary injury
• Clinical presentation:
  
  • patient unconscious since time of trauma (no mass lesion)
• immediate breakdown of microtubules –> interrupted axonal transport –> secondary/delayed axotomy (axon swelling then degeneration/severing)
• preference for junction b/t cortex and white matter, corpus callosum, midline white matter structures
• most often associated with rotational acceleration of head –> shear, tensile and copmressive strain
  
  • Plane of rotation important (axial is more associated w/ loss of consciousness)
• On CT – small bleeds (white marks) in white matter (easier to see on MRI)
• ** important in mild and severe TBI

Question 11

Penetrating TBI (resulting primary injuries)

Answer 11

• Lacerations
• Contusions, extra-axial hematomas

Question 12

Blast TBI (resulting injuries)

Answer 12

• translates mechanical, thermal, electromagnetic energy to the brain
• Fluid containing structures propagate injury by oscillating to the pressure waves
• injury to opthalmic, auditory, vestibular systems
• gray-white matter junction
• Secondary injury:
  
  • dose dependent DAI
  • cerebral edema
  • cell necrosis from vasospasm

Question 13

ICP - Monro-Kellie Hypothesis + normal and under pathologic circumstances

Answer 13

• ICP = P(Parenchyma) + P(CSF) + P(blood)
• ** fixed equation –> values changing will result in compensatory change in other values
• Brain is capable of shunting fluids to make room for extra mass in brain
  
  • ** if mass gets too large, system can no longer compensate so pressure goes up
  • Capacity to accomodate –> Compliance
  • Compliance = high when ICP is low

Question 14

Cerebral Perfusion Pressure

Answer 14

• CPP = MAP - ICP
• mean arterial pressure; intracerebral pressure

Question 15

Cerebral Blood Flow

Answer 15

• Directly related to CPP
• Directly related to radius of blood vessel
  
  • brain can change vessel radius to regulate blood flow
  • ** Auto-regulation
    
    • ​Can be affected by trauma
    • e.g. Vasoparalysis

Question 16

Mild TBI: definition

Answer 16

CDC: 1+ of the following:

• transient confusion, disorientation, impaired consciousness
• dysfunction of memory around time of injury
• loss of consciousness lasting <30min

WHO:

• GCS score 13-15
• exclude intoxication, other injuries

** loss of consciousness not necessary

Question 17

Common lesion location – white or gray matter?

Answer 17

• white matter = weakest link
• high shear stains b/t heterogeneous regions of tissue

Question 18

Treatment and prognosis for mTBI

Answer 18

• Tx = symptom management, recovery counseling/education
• 15% of mTBI pt have persisting symptoms up to 1 yr post-mTBI