6.01 Spinal cord injury Flashcards
Two types of neural cells
Glia and neurones
Displaced skull fracture
When bone is displaced into the cranial cavity by a distance greater than the thickness of the bone
Frontal impact commonly results from …
A fall following loss of conscious (i.e. you tend to fall forward if you lose consciousness)
3 types of focal brain injury
Contusion
Haematoma
Laceration
Contusion
A direct parenchymal injury of the brain (“bruising”). Causes bleeding from damaged blood vessels.
Coup contusion
Bruising is beneath the site of impact. Occurs most commonly when the head is immobile at the time of injury.
Contre-coup contusion
Bruising is opposite the impact site. Can occur when the head is mobile –> when the brain strikes the opposite inner surface after a sudden deceleration
What does contusion look like?
Small areas of blood on the brain. Old lesions are depressed, retracted, yellowish brown patches (you can’t see the gyri in these places)
Diffuse axonal injury
When the white matter is affected in trauma
Macroscopic findings of diffuse axonal injury
Widespread asymmetry
Axonal swellings
Increased microglia in areas
Causes of DAI
“Traumatic shearing forces” –> severe acceleration/deceleration forces, even in the absence of impact
Grades of DAI
1 - Nothing
2 - Haemmorhage in corpus callosum
3 - Haemorrhage in lateral brainstem
DAI is a common cause of …
coma after trauma in the absence of a focal lesion
“Shearing injury”
Damage inflicted as tissues slide over other tissues. Axons that traverse junctions between areas of different density are stretched (particularly between junctions of white and grey matter)
What causes the axons to tear in DAI?
Axons are not torn upon impact due to mechanical forces; they are stretched. They are torn by biochemical cascades in response to primary injury. Stretching opens Na channels, Ca flows into cells, microtubules are damaged and axonal transport is affected.
Detecting DAI
Unlikely to detect on CT/MRI
Diffusion tenor imaging (advanced imaging is needed)
Why does coma happen after a focal brain injury?
Secondary effects e.g. brain sweling
Why does brain swelling occur?
Vasogenic oedema
Cytotoxic oedema
Increased blood volume
Vasogenic oedema
Breakdown of tight endothelial junctions that make up the BB. Plasma constituents enter the parenchymal space –> oedema spreads quickly
Cytotoxic oedema
The BBB is intact, but the problem is inadequate function of the Na/K pump in the glial cell membrane –> retention of Na and water –> swollen astrocytes
Trauma to nervous tissue releases
Glutamate. It acts on NMDA receptors to let Ca into cell (excitotoxicity). Excess Ca damages a cell.
Other damage after traumatic brain injury
Hypoxia
