the injured brain Flashcards
what is a coup/countercoup injury?`
damage to brain resulting from
—> initial, sudden high velocity head movement i.e. coup
followed by
—> additional injury occurring in rebound movement i.e. countercoup
what are the different modes of axon damage?
what are two ways in which axons respond to damage?
MODES OF DAMAGE: • stretched axon • sheared axon • compressed axon • twisted axon
RESPONSE TO DAMAGE:
• disturbed ion balance = increased flow of fluid and ions = axon swelling = loss of conduction = loss of function
• Wallenium degeneration = axon separates = distal end of axon degrades
diffuse axonal injury:
- –> primary cause?
- –> secondary injury?
- –> biological changes?
primary cause:
• rapid tensile stretch of axons
secondary injury:
• damage to axonal cytoskeleton
• loss of elasticity
• axonal misallignment
biological changes:
• mechanical damage to sodium channels = massive sodium influx
—-> axonal swelling
—-> triggers calcium influx
—-> calcium activates proteolysis = further damage
what physical affects does DAI have on the brain?
- can cause haemorrhage due to axonal shearing
- can cause a midline shift due to axonal swelling
these affects reduce the network activity
epidural haemorrhage
- arterial injury to the middle meningeal artery
- normally associated with temporal bone or other skull fractures
- has a lenticular shape
- contained within dural sutures
- surgical emergency
subdural haemorrhage
- veinous injury to bridging veins
- typically caused by cortical injury —> skull fracture may not be present
- crescentic shape
- not contained by dural sutures but does not cross falx cerebri or tentorium cerebelli
• often seen in elderly individuals, trauma patients, and child abuse victims
—–> brain atrophy = tension on bridging veins and increased likelihood of rupture
subarachnoid haemorrhage
- blood in arachnoid spaces / hyperdensity in CSF
- caused by aneurysm rupture or post-traumatic superficial cortical contusions
- vasospasm several days after may cause secondary injruy
cerebral parenchymal haemorrhage
haemorrhage of small arterioles/capillaries in brain parenchyma
brain perfusion pressure (BPP) formula
brain perfusion pressure = mean arterial pressure - intracranial pressure
BPP = MAP - ICP
how is water homeostasis achieved in the brain
aquaporin-4 is main water channel in brain and is heavily involved in water homeostasis
AQP-4 facilitates drainage of CSF from arachnoid granulations to sinus spaces
on ventricle sides, AQP-4 used to pump water into CNS
what is a cytotoxic oedema?
swelling due to increased water intake
use an agonist of aquaporin 4 to pump out water and reduce swelling
what is a vasogenic oedema?
disruption of blood brain barrier causes water to leak into the brain
what is the glasgow coma scale and how does it work?
glasgow coma scale rates the:
1) eye opening
2) best verbal response
3) best motor response
a total GCS score is accumulated from these three categories and used to determine the severity of the injury
13-15 = mild TBI 9-12 = moderate TBI <9 = severe TBI
the lowest GCS score is observed in the first 48 hours of the injruy
what are the consequences of a CNS injury to motor and sensory tracts
when an injury happens to sensory/motor tracts, the area not connected to the cell body can not self sustain and degrades
motor: region below lesion cannot self sustain and dies
sensory: region above lesion cannot self sustain and dies
what are the management and repair strategies for CNS injury?
MANAGEMENT:
main goal is to preserve tissue
• preservation of neural tissue (close to site of impact)
• preservation of white matter (descending/ascending pathways)
REPAIR:
• replacement of lost cells
• regrow damaged pathways
• rewire circuitry appropriately
