Cerebrovascular Disease Flashcards
rapid necrosis of nerve cells and/or their processes most commonly leads to what clinical picture?
sudden acute functional (stroke)
slow atrophy of nerve cells and/or their processes most commonly leads to what clinical picture?
gradually increasing dysfunction (age related cerebral atrophy)
how does acute neuronal injury appear microscopically?
shrunken and angulated nuclei
loss of nucleolus
intensely red cytoplasm - “red neurone”
at what stage are red neurones normally seen microscopically?
after hypoxia / ischaemia
typically visible 12-24 hrs after irreversible insult (stroke)
shows neuronal cell death
if an axon is severed, what occurs in either side of damage?
cell body swelling, enlarged nucleolus
degeneration of axon and myelin sheath distal to injury
what are the main functions of astrocytes?
maintain the BBB
involved in repair and scar formation (due to lack of fibroblasts)
how do astrocytes usually respond to CNS injury?
gliosis = astrocyte hyperplasia and hypertrophy
this is indicator of CNS injury, regardless of cause
how does old gliosis appear histologically?
nuclei become small and dark
they lie in a dense net of processes (glial fibrils)
what type of damage are oligodendrocytes particularly susceptible to?
oxidative damage
how do ependymal cells (which line ventricles) respond to CNS injury?
limited reaction to injury
disruption causes local proliferation of these cells - small irregularities on the ventricular surfaces “ependymal granulations”
how do the microglia (macrophage like cells) respond to CNS injury?
proliferate
recruited through inflammatory mediators
aggregate around necrotic and damaged tissues
M2 more acute, M1 - chronic
why does the brain deteriorate so quickly once hypoxia and ischaemia occur?
no O2 to create more ATP
mitochondria inhibit ATP synthesis so reserve is consumed within few mins
why can excito-toxicity cause oxidative stress in neurones?
excitatory signal depolarises neurone and releases glutamate
lack of energy means astrocytes don’t reuptake glutamate
loss of glutamate in synapse causes lots Ca2+ entry into post-synaptic terminal = mitochondrial dysfunction and oxidative stress
what are the 4 main types of oedema in the brain?
cytotoxic oedema
ionic/osmotic oedema
vasogenic oedema
haemorrhagic conversion
what causes cytotoxic oedema?
Na+/K+ channel dysfunction -> cells retain Na+ and water
what causes ionic/osmotic oedema?
water and Na+ from capillaries move into brain parenchymal extracellular space
what causes vasogenic oedema?
BBB disrupted -> leaking fluid from capillaries affect white matter
what causes haemorrhagic conversion?
when RBCs cross BBB
what is meant by cerebrovascular disease?
an abnormality of brain caused by pathological process in blood vessels
what are the 4 main components of cerebrovascular disease?
brain ischaemia and infarction
haemorrhages
vascular malformations
aneurysms
what would cause a global hypoxia and ischaemic damage to the brain as opposed to focal area of ischaemia?
cardiac arrest and severe hypotension (trauma with hypovolaemic shock)
focal = vascular obstruction
what is the definition of a stroke?
sudden disturbance of cerebral function of vascular origin that causes death or lasts over 24 hours
what gender and age are most common for stroke to occur?
peak incidence is >70yrs
men > women
strokes caused by atherosclerotic thrombus are most common in which artery of cerebrum?
middle cerebral artery or its branches
where do embolic strokes usually originate from?
atheroma in internal carotid or aortic arch
emboli from heart due to AF
what are risk factors for cerebral infarction?
hypertension serum lipids, obesity, diet diabetes mellitus heart disease drugs smoking
what symptoms do patients often experience if they have a stroke due to carotid artery disease?
contra-lateral weakness / sensory loss
if dominant hemisphere, may be aphasia or apraxia
what symptoms would usually indicate a middle cerebral artery stroke?
weakness in contralateral face and arm
what symptoms would usually indicate an anterior cerebral artery stroke?
weakness and sensory loss in contralateral leg
strokes in vertebro-basilar arteries can cause what symptoms?
vertigo
ataxia
dysarthria
dysphasia
what is meant by vascular remodelling and how can this perpetuate a stroke?
accelerated atherosclerosis
arteriolosclerosis (thick, stiff vessel walls prone to rupture)
eventual fibrinoid necrosis of vessel walls
where do micro aneurysms most commonly occur in the brain circulation?
branches of middle cerebral artery near the basal ganglia
what is a lacunar infarct?
small “lake” like infarcts up to 15mm diameter
due to damage of lenticulostriate arteries in basal ganglia
when can lacunar infarcts cause most damage?
if extends into internal capsule - can cause extensive motor weakness in face and limbs
what are the hallmarks of hypertensive encephalopathy?
global cerebral oedema
tentorial and tonsillar herniation (due to raised ICP)
petechiae
anteriolar fibrinoid necrosis - high BP
what are the clinical findings of hypertensive encephalopathy?
severe hypertension and symptoms of raised ICP
where do most intracerebral haemorrhages occur?
most common - basal ganglia
thalamus, cerebral white matter and cerebellum
how do intracerebral haemorrhages appear macroscopically?
asymmetrical shifts and herniations of brain well demarcated softening of adjacent tissue surrounding oedema
what vascular malformations can predispose to cerebrovascular disease?
arteriovenous malformations
cavernous / venous angiomas
why do vascular malformations predispose to haemorrhage?
shunting from artery to vein = vein undergoes smooth muscle hypertrophy, vein is not compliant and ruptures easily
can also form aneurysms which rupture
what normally causes a subarachnoid haemorrhage?
rupture of a saccular aneurysm (berry aneurysms)
where do berry aneurysms normally occur?
internal carotid artery
vertebro-basilar circulation
*usually at arterial bifurcations
what can be seen macroscopically around a berry aneurysm?
intracerebral haematomas next to aneurysms
infarcts of brain parenchyma - due to arterial spasm
haematoma may compress structures and cause features of raised ICP
what are the risk factors for berry aneurysms?
smoking
hypertension
kidney disease
what symptoms are usually experiences upon rupture of berry aneurysm?
severe headache
vomiting
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