Ch 2 - TBI: Pathophysiology

Question 1

What is the MCC of head injury in adolescents and adults?

Answer 1

Motor vehicle accidents (~50% of cases)

Question 2

What is the single MCC of death and injury in automobile accidents?

Answer 2

Ejection of occupant from the vehicle

Question 3

What is the married status of patients with TBI?

Answer 3

Single (47%) > married (32%) > divorced (16%) > widowed/separated (5%)

Question 4

What % of TBI etiology involve alcohol?

Answer 4

> 50%

Question 5

What is Primary Injury in TBI?

Answer 5

Direct disruption of brain parenchyma from shear forces of the impact occurring immediately and not amenable to medical intervention

Question 6

What are types of Primary Injury in TBI?

Answer 6

Contusion
Diffuse axonal injury (DAI)
Impact depolarization

Question 7

What is brain contusion?

Answer 7

Bruising of the cortical tissue

Question 8

What is Diffuse axonal injury (DAI)?

Answer 8

Immediate disruption of the axons due to acceleration–deceleration and rotational forces that cause shearing upon impact

Question 9

What is secondary axotomy in DAI due to?

Answer 9

Increased axolemma permeability, calcium influx, and cytoskeletal ABN that propagate after the injury

Question 10

What is the characteristic of DAI on imaging?

Answer 10

White matter petechial hemorrhages

Question 11

What is impact depolarization?

Answer 11

Massive surge in extracellular K+ and glutamate release (excitatory) occurs after severe head injury and leads to excitotoxicity (secondary injury)

Question 12

What are types of secondary injury in TBI?

Answer 12

Ischemia, excitotoxicity, energy failure, and resultant apoptosis
Brain swelling/edema
Axonal injury
Inflammation and regeneration

Question 13

What is excitoxicity?

Answer 13

NT (glutamate) causes calcium influx, oxygen-free radical release, lipid peroxidation, mitochondrial failure, and DNA damage > nerve cell death

Question 14

When does brain swelling occur after TBI?

Answer 14

w/in 24 hours due to an increase in cerebral blood volume (intravascular blood).

Question 15

How is brain swelling identified on CT?

Answer 15

Collapse of ventricular system and loss of CSF cisterns around the midbrain

Question 16

When does brain edema occur after TBI?

Answer 16

Later than brain swelling due to an inc in brain volume 2/2 inc brain water content > extravascular fluid

Question 17

What is the pathophysiology of vasogenic brain edema?

Answer 17

Outpouring of protein rich fluid through damaged vessels

Question 18

What pathology is vasogenic brain edema related to?

Answer 18

Extracellular edema

Cerebral contusion

Question 19

What is the pathophysiology of cryptogenic brain edema?

Answer 19

Failing of the cells’ energy supply system > inc cell-wall pumping system> intracellular edema in the dying cells

Question 20

What pathology is cryptogenic brain edema related to?

Answer 20

Hypoxic and ischemic brain damage

Question 21

What is focal injury in TBI?

Answer 21

Localized injury in the brain occurring immediately after the injury and easily visualized by CT or MRI

Question 22

What are types of focal injury in TBI?

Answer 22

Cerebral contusions
Focal ischemia
Focal hemorrhages

Question 23

How do cerebral contusions occur?

Answer 23

Brain hits the inner table of the skull

Question 24

Where do cerebral contusions typically occur?

Answer 24

Inferior frontal lobe and anterior portion of the temporal lobe

Question 25

How does focal ischemia occur (pathophysiology)?

Answer 25

2/2 vasospasms after a traumatic SAH or from physical compression of the arteries

Question 26

What are types of focal hemorrhages?

Answer 26

Epidural Subdural Subarchnoid

Question 27

How do epidural hemorrhages occur?

Answer 27

90% temporal bone fx over the middle meningeal artery or veins

Question 28

What is the clinical presentation of epidural hemorrhages?

Answer 28

Lucid interval (50%) prior to rapid deterioration

Question 29

What is seen on CT in epidural hemorrhages?

Answer 29

Biconvex acute hemorrhagic mass

Question 30

What limits hematoma expansion in epidural hemorrhages?

Answer 30

Tight adherence of the dura to the skull

Question 31

How do subdural hematomas occur?

Answer 31

Shearing of the bridging veins between the pia-arachnoid and the dura

Question 32

Why are subdural hematomas typically larger in elderly patients?

Answer 32

Due to generalized loss of brain parenchyma

Question 33

What is seen on CT in subdural hematomas?

Answer 33

High density, crescentic, extracerebral masses

Question 34

When is the presentation of symptoms in subdural hematomas?

Answer 34

Acute SDH: Immediate sx Subacute SDH: 3 days-3 wks Chronic SDH: > 3 weeks

Question 35

How do subarchnoid hemorrhages occur?

Answer 35

Ruptured cerebral aneurysms and AVMs Leakage from an intraparenchymal hemorrhage Trauma

Question 36

What is seen on CT in subarchnoid hemorrhages?

Answer 36

Blood w/in the cisterns and subarachnoid space ~ 24 hr

Question 37

When does CT sensitivity decrease in subarchnoid hemorrhages?

Answer 37

Dec to 30% 2 weeks after the initial bleed

Question 38

What is a grade I DAI?

Answer 38

Widespread white matter/axonal damage but no focal abnormalities on imaging

Question 39

What is a grade II DAI?

Answer 39

Widespread white matter/axonal damage, and focal findings (MC in the corpus callosum)

Question 40

What is a grade III DAI?

Answer 40

Damage involving the brainstem

Question 41

When is DAI initiated?

Answer 41

Time of the injury by axonal shearing from acceleration–deceleration rotational forces

Question 42

What is the MCC of unconsciousness during first 24 hours after DAI?

Answer 42

Axonal injury

Question 43

Which types of TBI have a higher risk of posttraumtic epilepsy?

Answer 43

Penetrating head injuries

Question 44

What is brain plasticity?

Answer 44

Capability of the damaged brain to “repair” itself by means of morphologic and physiologic responses

Question 45

What is brain plasticity influenced by?

Answer 45

Environment Complexity of stimulation Repetition of tasks Motivation

Question 46

What are the two mechanisms of brain plasticity?

Answer 46

- Neuronal regeneration/neuronal (collateral) sprouting | - Functional reorganization/unmasking neural reorganization

Question 47

What is Diaschisis?

Answer 47

Damage to one region of the CNS alter function of uninjured area fiber tracts causing loss of function at both sites

Question 48

How does functional/behavioral substitution help recovery in TBI?

Answer 48

New strategies are learned to compensate for deficits and to achieve a particular task

Question 49

How does redundancy help recovery in TBI?

Answer 49

Uninjured brain areas normally contribute same function of injured brain

Question 50

How does vicariation help recovery in TBI?

Answer 50

Brain areas alter their properties in order to subserve that function