Principles and Cerebrovascular Disease Flashcards
What is the dura?
the tough fibrous outer layer which bridges crevices and is attached to the skull
What is the arachnoid?
delicate sealed bag for CSF - bridges crevices - impermeable to salt and water
What ropes across the subarachnoid space?
arachnoid trabeculae
Where is the cerebral artery branch?
embedded in the pia - susceptible to tearing and damage
What is the pia mater?
delicate - next to brain and dips into crevices
What are the main cellular components of the CNS?
nerve cells glial cells blood vessels microglia connective tissue - meninges
What are the glial cells?
astrocytes, oligodendrocytes, ependyma
What can damage the cells of the CNS?
hypoxia trauma toxic insult metabolic abnormalities nutritional deficiencies infections ageing genetic abnormalities
What are the neuronal responses to injury?
acute neuronal injury
simple neuronal atrophy
sub-cellular alterations
axonal reactions
Why are neurons particularly susceptible to hypoxic damage?
due to activation of glutamate receptors -> Ca overload
can’t use anaerobic glycolysis
Why would you be better drowning in cold water?
slows metabolic processes and cell death down
What is the axonal reaction?
the reaction within the cell body that is associated with injury to the axon
What is the responses to axonal injury?
- increased RNA and protein synthesis
- swelling of the cell body
- peripheral displacement of the nucleus
- enlargement of the nucleolus
- anterograde degeneration of the axon - distal to site of injury
- breakdown of myelin sheat
How do astrocytes react to injury?
proliferation (gliosis)
reactions leading to cell death or degeneration
What is the process gliosis?
where astrocytes undergo hyperplasia and hypertrophy
nucleus is enlarged, becoming vesicular and the nucleolus is prominent
cytoplamsic expansion with extension of ramifying processes
What can be seen on old lesions of gliosis?
nuclei become small and dark and lie in a dense net of processes - fibrils
comparable to scar formation
What is injury to oligodendrocytes a feature of?
demyelinating diseases
How do oligodendrocytes react to injury?
very limited response
where are ependymal cells found?
lining the ventricular system
What is disruption of ependymal cells associated with?
local proliferation of sub-ependymal astrocytes producing small irregularities on the ventricular surfaces - ependymal granulations
What can produce changes in ependymal cells?
infectious agents i.e. viruses
How do microglia respond to injury?
- proliferate
- develop elongated nuclei
- forming aggregates about small foci of tissue necrosis
- congregate around portions of dying neurons
How long does brain need to lose blood supply before there is irreversible damage?
4 minutes
How much CO and O2 does the brain receive?
15% of CO and 20% of O2
How is blood flow maintained in the brain?
autoregulatory mechanisms
Where does the blood supply in the brain come from?
internal carotid arteries and vertebral arteries
Why is the circle of willis protective?
occlusion of any one pathway does not stop flow to one area unlike when blood flow is deeper into the brain
Where is the circle of willis?
base of the brain
What does occlusion to the anterior cerebral artery lead to?
contralateral sensory loss in foot and leg
paresis of arm and foot, relative sparing of thigh and face
Where does the anterior cerebral artery lead?
frontal lobe
What happens with occlusion to the middle cerebral artery?
hemiparesis
hemisensory loss
aphasia/dysphasia - loss of language or vocal chord function
apraxia
what does the brain stem consist of?
mid-brain, pons, medulla
What does the brain stem control?
cardio-respiratory centres
what do bleeds on the occipital lobe cause?
homonymous hemianopia because of the cross over of optic nerve
What does a stroke in the cerebellum cause?
ataxia
nystagmous - eye twitch in extreme visual fields
intention tremor
pendular reflexes - acts like a pendulum when it shouldnt
what is the mortality of Cerebrovascular disease?
20% in the first month
What are the potential causes of cerebrovascular disease?
brain ischemia and infarctions
haemorrhages
vascular malformations and developmental abnormalities
What may cause hypoxic ischemic damage?
respiratory obstruction, lung and heart disease, epilepsy, cardiac arrest
Which groups of neurons are more vulnerable to hypoxic/ischemic damage?
pyramidal cells of hippocampus
purkinje cells of cerebellum
What are watershed areas?
junctions of arteries which are the first areas to be deprived
When may hypoxic ischemic encephalopathy occur?
in any circumstance that results in global decrease in HbO2 available to the brain
What is a stroke?
a sudden disturbance of cerebral function of vascular origin that causes death or lasts over 24 hours
What are the types of stroke and their commonality?
infarction (84%) or haemorrhage (16%)
What is a cerebral infarction?
caused by local interuption of cerebral blood flow due to thrombosis or emboli
What is an embolis?
a clot that has broken off
What are risk factors for stroke?
atheroma, HBP, serum lipids, obesity, diet, T2DM, heart disease, smoking
What is the morphology of a cerebral infarct 4-12 hours later?
brain may appear normal
What is the morphology of a cerebral infarct 15-20 hours later?
ischemic neuronal changes develop
What is the morphology of a cerebral infarct 24-36 hours later?
inflammatory reaction, extravasion of RBCs and activation of astrocytes and microglia
What is the morphology of a cerebral infarct 36-48 hours later?
necrotic area visible macroscopically, becomes swollen and softer than surrounding tissue
What is the morphology of a cerebral infarct 3 days later?
macrophages are in the area
What is the morphology of a cerebral infarct 1-2 weeks later?
liquification of tissue and gliosis
What is the morphology of a cerebral infarct months later?
cavitation and completion of glial scar
What is the most common cause of haemorrhage?
spontaneous
What is a spontaneous haemorrhage??
rupture of a saccular aneurysm
Where do most aneurysms occur?
arise at arterial bifurcation in territory or internal carotid (90%)
What are the potential morphologies of aneurysms?
- rupture of berry aneurysm - bleeds into subarachnoid space
- intracerebral haematomas adjacent to aneurysm
- infarcts of brain parenchymal due to arterial spasms (40%)
What are the clinical features of haemorrhages?
-abrupt onset (headache, vomiting, loss of conciousness)
What are the signs of a haemorrhage?
bloody CSF, meningeal signs incl. neck stiffness
What are the complications of a haemorrhage?
cerebral infarcts, acute hydrocephalus, herniation
Why may chronic hydrocephalus develop in patients surviving the initial haemorrhage?
due to organisation of blood in the leptomeninges and or arachnoid granulations with resultant obstruction of CSF flow
What does hypertension cause in the brain?
increased atheroma
hyaline arteriosclerosis
microaneurysms
shift in autoregulatory curve to the right
What is the pathology of hypertension in the brain?
- lacunar infarcts
- intracerebral haemorrhage
- multi-infarct dementia
- hypertensive encephalopathy
