Brain Injury Flashcards
What are the two main types of traumatic brain injury?
- Open (e.g. shrapnal, knife, bullet)
- Closed (e.g. acceleration and deceleration forced in RTA)
What are the main mechanisms of closed TBI damage?
▪️Contusions
▪️Diffuse axonal injury
▪️Cerebral atrophy
▪️Intracranial bleeding (haematoma)
▪️Chronic traumatic encephalopathy
May be complicated by
▪️Raised intracranial pressure
▪️Anoxia
What are contusions?
Areas of cerebral bruising, particularly in the grey matter, where blood leaks into the extravascular space
Which brain areas are most vulnerable to contusions?
The orbitofrontal lobe and anterior temporal lobe
(social function, decision making and memory)
What brain areas are least vulnerable to contusions?
Primary motor, somatosensory, and visual cortices
What is diffuse axonal injury?
The shearing of the brains long connecting nerve fibres (white matter) as the brain shifts and rotates in the skull
How does diffuse axonal injury occur?
- Damage to the soma
- Ca2+ influx
- Membrane damage
- Disruption of normal transport
- Swelling
- Axon snaps forming retraction balls
When does diffuse axonal injury occur?
Usually 24 hours post injury
How does diffuse axonal injury show on T2 MRI?
High signal patches (light)
What other issues may follow diffuse axonal injury?
Generalised atrophy and ventricular enlargement
What is diffusion tensor imaging fractional anisotropy?
A measure of connectivity in the brain, scored from 0-1, with a lower score representing less restricted movement, indicated disrupted fibre tracts and/or demyelination
What DTI-FA findings have been observed in those with brain injury?
Reduced FA and increased mean diffusivity, particularly in those with mood disorder
Which brain areas show particular disruption connectivity and reduced FA in brain injury?
The corpus callosum and long white matter tracts of the cerebral hemisphere (e.g. frontooccipital fasciculus)
What other populations show reduced FA?
▪️Individuals with lower IQ
▪️Individuals with depression and ADHD
What symptoms might you see in someone with DAI in the brain stem?
Slurred speech and severe ataxia
What are the key neuroimaging markers of DAI?
▪️Shear haemorrhages
▪️Often due to microhaemorrhages at the grey/white matter interface
▪️Often parafalcine (fold of dura mater between hemispheres)
What are the best imaging techniques for detecting DAI haemorrhages and why?
- Susceptibility weighted imaging
- Gradient echo
Haemoglobin turns into haemosiderin which stays in the brain tissue. This contains iron which is magnetic and shows up as dark patches.
When does cerebral atrophy occur in brain injury?
Over the course of weeks/months post-injury, particularly in the white matter if affected by DAI
What are the main neuroimaging signs of cerebral atrophy?
▪️Ventriculomegaly
▪️Thinning of corpus callosum
▪️Whole brain volume decrease
Which type of brain matter is particularly affected by cerebral atrophy and why?
White matter due to diffuse axonal injury
What is important you differentiate cerebral atrophy from and why?
The development of hydrocephalus due to raised CSF pressure. This is much more serious process.
What are the three main causes of raised intracranial pressure?
▪️Extradural haemorrhage
▪️Subdural haemorrhage
▪️Intraparenchymal haemorrhage
What are the two key types of herniation?
▪️Uncal (transtentorial)
▪️Tonsilar (coning)
What happens in uncal herniation?
Rising intracranial pressure causes the uncus to slide down into the posterior fossa, compressing the brainstem and posterior cerebral artery.