Pathology Flashcards
Which structures of the brain can suffer traumatic damage? What kind of damage is common?
scalp, skull, meninges and brain/cord
scalp - laceration
skull - fractures
meninges - vascular injury, laceration
brain - contusion, laceration, diffuse axonal injury, diffuse vascular injury
what kind of fractures can occur at the skull
linear fracture
depressed fracture
what is contusion?
bruising and haemorrhagic necrosis of the brain
how can the brain tissue be lacerated?
from a depressed fracture, where bone gets pushed in and tears the tissue
What is a concussion?
a clinical consequence of head injury, involving instantaneous loss of consciousness, temporary resp arrest, and loss of reflexes
What is a concussion caused by?
a sudden change in the momentum of the head and the brain develops areas of undetectable injuries
What does a glasgow coma scale do?
It helps assess severity of brain injury
the lower the score, the higher the chance of severe brain injury
How is the brain and cord protected?
they are enclosed in protective bony cases, and a lot of energy will be needed to breach the bony layer
What is the downside of having bony protection around the brain?
Penetrating injury and closed injury can occur
Penetrating = direct disruption of tissue (depressed fracture) Closed = movement and compression of neurovascularture within confined space
What is secondary traumatic injury?
further damage to the brain following primary injury in certain circumstances
can be delayed or immediate
List 5 possible secondary injuries
ischaemia, hypoxia (generally acute)
raised ICP, infection, epilepsy (delayed)
T/F skull fracture tends to damage only the point of impact
False, skull fractures are able to radiate from primary site of impact
What is the term given to skull fracture with splinter
comminuted fracture
Why is a skull fracture “open”
If the fracture communicates with the surface (bone can be seen superficially)
What can result from a basal fracture?
blood and CSF come out from the nose and/or ear. This is a bad sign
Why is it important to diagnose bone fracture (think how a bone injury occurs) ?
bone fractures are a result of high energy transfer injury and may have severe secondary effects
The tearing of which artery can lead to epi-dural haematoma?
middle meningeal artery
Why is epi-dural haematoma less common for older people
because the dura mater adheres more tightly to the skull with increasing age
What is the cause of subdural haematoma?
tearing of sub-dural vein or sinuses
Why does subdural haematoma happen more frequently in older people?
shrinking of the brain + increased tension on veins
Contusions can occur at two locations upon traumatic injury, what is the name given for the 1) impact site 2) opposite to impact site
1) coup
2) countercoup
When can a contusion occur at the countercoup?
When the brain is not immobilised at the time of injury, so the sudden change of momentum freely moves the brain, causing injury on both sides
Why do contusions occur usually at the base of brain?
because of the irregular lining on the skull floor
what are two stereotypical locations for contusion?
inferior frontal lobe
inferolateral temporal lobe
What is the consequence of injuring the olfactory bulb?
anosmia, loss of smell
If the patient survives traumatic injury, and the contusion heals, why does the injured site look like?
brain has an area of scarring which is yellowish in appearance. The injured area tends to be compressed as well
How does a bullet cause damage to the brain?
direct penetration of the tissue
shockwave effect - damage diameter greater than actual bullet
bullet can break into fragments to cause further injury
How does a diffuse axonal injury present?
brain may appear as normal
How do we visualise axonal damage?
use silver stain, and axons will appear as black lines
on a silver stained image, how does an injured axon appear?
axonal spheroids present - area of axon swelling because the axon cannot function due to injury, but because the soma doesn’t stop producing axonal proteins, the swelling occurs
What are the three presentations of long term brain atrophy
thin corpus callosum, enlarged ventricles, thin white matter
T/F acute compressive injury of the spinal cord only affects the cord at the site of injury
False, because the cord is soft tissue, the injury is not confined. Compression may extend proximally and distally
How much blood and CSF are in the cranium
150 ml of each
what is the initial response of raised ICP
expulsion of as much CSF and venous blood as possible, so the ventricles will decrease in size
Give two severe consequence of raised ICP?
herniation of brain tissue through dural openings
hypoxia because the ICP opposes arterial pressure
What are the two main sub-types of cerebral oedema and what are the individual causes?
vasogenic - BBB disruption and increased permeability
cytotoxic - cell membrane damage and increase of intracellular fluid
Which sub-type of cerebral oedema can be treated? What are the three treatments?
vasogenic
Steroids, isotonic pressure manipulation, hypocarbia inducing therapy
Which cerebral oedema is primarily a result of a stroke?
cytotoxic oedema
What are the two ways of causing hydrocephalus?
obstruction along the draining pathway
absorptive problem, only in normal pressure hydrocephalus
What is medial herniation?
when the medial temporal lobe herniates through the tentorial opening (also called transtentorial herniation)
What is duret brainstem haemorrhage?
When there is herniation of the brainstem, the brain tissue can move, but the vessels are fixed, so there can be tearing of small blood vessels, causing haemorrhage
This is a secondary effect of ICP
Most cases of meningitis occur in _______, but there is higher ______ in older individual. The case fatality is 47%, and those who survive are likely to have _________
younger children
mortality
neurological sequelae
T/F bacterial meningitis is most serious
True, viral causes are generally self-limiting
What is aseptic meningitis
might be bacterial cause, but you can’t culture the bacteria
What are some non-infectious causes of meningitis
malignancy, drugs, inflammatory conditions
What is the most common cause of meningitis?
viral, usually caused by entero-virus, which is generally self-limiting
What are the three common bacterial causative agents of meningitis?
Strep pneumonia
Type A Neisseria
Haemophilus influenzae
Why are the three bacteria common in meningitis?
they are encapsulated, so are able to evade compliment fixation and avoid phagocytosis
They are also commensals of the nasalpharynx
Which three other bacteria also cause meningitis in children under 3 months?
E Coli
Group B strep
Listeria
Describe the pathogenesis of bacterial meningitis
normal flora enters the bloodstream, and if not killed, they can enter the BBB to increase permeability of BBB and increase ICP. The resulting inflammation damages the meninges
What are the specific clinical features of meningitis?
stiff neck, altered mental state, photophobia, seizures
What is the definitive diagnosis of meningitus?
composition of CSF, or PCR in the 16s region
T/F the abnormal composition of CSF can tell you whether the cause of meningitus is bacterial or viral
False, the CSF composition can fall into the reference range, but there are always exceptions
What are the normal values of CSF?
Pressure < 150mmHg
Clear appearance
protein < 0.4g/L
Glucose > 60% in blood
What is the change of CSF composition in bacterial meningitis?
raised pressure, cloudy appearance with neutrophils, raised proteins, decreased glucose, positive gram stain
What is the change of CSF composition in TB meningitis?
ZN positive with lymphocytes
raised pressure, very high protein, very low glucose
basically an extreme version of bacterial meningitis
T/F you can determine the appearance of CSF macroscopically
False, you need a lot of cells to make the appearance cloudy
need microscope
T/F CSF result is inaccurate if the analysis is not done immediately
True, white cells drop by 20% over 4 hours, so it requires immediate analysis
What is the change of CSF composition in viral meningitis?
clear appearance, normal pressure, reduced protein, increased glucose
What is the sequence of treatment for meningitis?
life support
fluid/antibiotics/steroids
IV cephalosporin (add penicillin and gentamicin in infants under three months)
What is the most common sequelae of meningitis?
hearing loss
What is the most important cause of encephalitis?
HSV
What’s the differential clinical sign of encephalitis?
altered consciousness
What is the drug of choice for meningoencephalitis
add in acyclovir for suspicion of encephalitis
Define “stroke”
stroke is the neurological deficit following a vascular event
What is a TIA?
a stroke-like episode that resolved completely
What are the three main processes of stroke?
Ischaemic cause, to infarction
Haemorrhage
Subarachnoid haemorrhage
How can an infarction occur in the brain?
usually occlusion, but can also be caused by severe global hypoperfusion
T/F only occlusions in the arteries can lead to brain infarction
False, a blockage in venous sinuses can lead to increased ICP, and eventually oppose the arterial pressure supplying the brain
Large artery occlusions are usually a result of _______, while Small vessel occlusion is more likely caused by _______. Venous occlusion, on the other hand, can only be caused by _______.
embolus
thrombosis
thrombosis
Can you ever get a brain infarct from deep vein thrombosis?
Yes, but not very common. 1/3 of the population has probe-patent interatrial septum, such that a thromboembolus can cross from right atrium directly into left atrium, if the pressure in RA is high enough. The embolus can enter the brain
What are the four common sites of atherosclerosis in the brain arteries
bifurcation of common carotid
MCA
Vertebral artery
Basilar artery
What is endarterectomy
strip the artery’s media and intima in order to prevent flow problem and embolus from occluding vessels downstream
T/F Infarction is immediately visible macroscopically
False, you don’t see infarction immediately, hence CT and MRI are not very sensitive at this stage
What does the brain look like after several hours of infarction?
cell membrane breaks down, tissue filled with fluid, vasogenic oedema, swelling
increased ICP can then cause herniation
What does a dying neuron look like microscopically
The neuron will initially swell up, but gradually become hyper-eosinophilic and shrink down. The nucleus will shrink, and eventually disappear
What does a brain look like weeks after an infarction
liquefactive necrosis - tissue breaks down, macrophages enter to clean up
There is sharp demarcation between healthy and necrotic tissues
What is the end result of an infarction?
a cystic space filled with CSF. Functionally, the neurological impairment will depend on the location of the infarct
What’s a secondary haemorrhagic infarct in the brain caused by?
First a primary occlusion causing ischaemia of distal vessels. The thromboemoli can resolve independently leading to reperfusion. However, the vessel can no longer sustain arterial pressure, there lead to haemorrhagic infarct
What is the most common small vessel disease?
small vessel hyaline arteriolosclerosis
How does small vessel hyaline arteriolosclerosis lead to haemorrahagic infarct
The vessel wall thick, but weak, so it can balloon out and cause local berry aneurysm that can rupture
What is lacunar infarction caused by?
small vessel occlusion and small infarction
T/F lacunar infarct can cause significant neurological deficit
True, if the infarct is at crucial areas like the internal capsule
T/F cerebral infarction is commonly the cause of death
False, patients more commonly die from complications of the infarction or from the existing risk factors (CV disease)
What structures are commonly involved in cerebral haemorrhages due to hypertension?
hypertension commonly leads to arteriolosclerosis, and affects generally small vessels and deep structures
basal ganglia, thalamus, lobar white matter, pons, cerebellum
Why is cerebellum haemorrhage a surgical emergency?
there may be acute obstruction of the 4th ventricle, so CSF needs to be drained immediately to prevent raised ICP
What is a slit haemorrhage?
a small haemorrhage not large enough to cause significant tissue destruction, which resolves slowly and form a slit-like scar
What is the protein deposited in amyloid angiopathy? What is the significance of that?
a-beta-amyloid
It’s the same protein associated with Alzeimers
T/F amyloid angiopathy typically cause occlusion
False, amyloid deposits in smaller vessels, so it is more likely to rupture and cause haemorrhagic infarct
What is arteriovenous malformation caused by? What is the pathology involved?
congenital abnormality
artery and veins are connected without capillary bed so high pressure blood enters veins to cause rupture
What pathology can lead to non-traumatic subarachnoid haemorrhage?
berry aneurysms in large vessels, particularly in the anterior vessel bifurcation
What is the consequence of subarachnoid haemorrhage?
blood products can cause vasospasm
cerebral oedema, raised ICP
ventricular obstruction
What is the treatment of large aneurysms?
clip the neck of aneurysm to prevent more blood from leaking and prevent vaso-spasm
