CNS Trauma: Imaging Flashcards
Outcome of occipital impact?
- scalp haematoma (potentially w/ underlying fracture)
- bleeding beneath skull (epidural/extradral or subdural haematoma
- haemorrhagic contusion (bleeding withing brain)
CT scan: “concave shape” and prognosis?
Extra-dural -> kills you through coning (herniation of brain through tentorium + foramen magnum)->
[pressure on the brainstem -> death through stopping breathing or CVS (BP regulation) problems]
CT scan: “irregular margin”
Subdural]- fresh blood is what is visible usually
Note that old blood looks similar to brain on CT- can be hard to identify large subdurals
How to treat extra-dural or subdural haematoma?
Release pressure: Craniectomy or burr-hole to relieve pressure (depending on size etc)
If image is unclear but brain appears swollen and pt is unconscious
You want to know pressure: put pressure probe (ICP pressure monitor) into brain
NB: NO LP AS YOU ARE WORRIED ABOUT CONING, and you don’t know if you need to relieve pressure or not
Common sites of TBI (e.g. haemorrhagic contusions)
Orbito-frontal cortex and temporal poles
NB: because brain is knocked forward and collides against sharp point within skull
Why we see discrepancies between what is seen on scans and the symptoms of TBI pts?
Diffuse axonal injury
Describe mechanism of diffuse axonal injury (DAI)
Lots of force applied to brain damages long distance axons (particularly vulnerable)
You have essentially disconnected massive parts of brain
(might not be visible on CT)
Alternative ways of using imaging on diffuse axonal injury?
Diffusion tensor imaging (from MRI scanner): you can view structure of white matter
[also good for MS and stroke]
How does diffuse axonal injury affect the functions of the brain?
[early TBI white matter damage]:
Disconnection and damage to wiring; inflammation and damage to protein transport along axons
Network disruption between diff, parts of the brain (default mode network)
Standard way of imaging for diffuse axonal injury
Susceptibilty weighted imaging (from MRI)
How susceptibilty weighted imaging works?
Blood contains haemosiderin, making it (para-)magnetic
Haemorrhages leave iron in the brain, which can be seen on this scan
[good to see microbleeds + linear vascular injury]
Most common distribution of injury location in susceptibility weighted imaging?
Parafalcine distribution (on one side of falx- where forces are highest)
Relationship between TBI and dementia?
Repeated head traumas can cause increased tau and amyloid (just like dementia)]- but the locations of these differ between the two
