Week 3 - F - Neuropathology 1 - Glial cells, CNS injury, stroke Flashcards
What are the types of CNS glial cell?
Astrocyte Microglia Oligodendrocytes Ependymal
What is the function of the glial cells?
Astrocyte - important in maintaining the BBB and involved in electrolyte balance Microglia - main immune surveillance cell of the brain - phagocytic and engulf bacteria Oligodendrocytes - produce myelin in the CNS to wrap around axons Ependymal cells - lines the choroid plexus of the ventricles in the brain
Nervous system injury can arise from a variety of places Hypoxia is an important causative factor of nerve cell injury and can be caused by different conditions Damage to nerve cells and/or their processes can lead to: Rapid necrosis with sudden acute functional failure - when is this seen? Slow atrophy with gradually increasing dysfunction - when is this seen?
Rapid necrosis with sudden acute functional failure is seen in events such as a stroke where there is no blood supply leading to cell death Slow atrophy with gradually increasing dysfunction is seen in normal age related cerebral atrophy
The neuron is the main communicating cell of the CNS consisting of the axon, covered by myelin sheath What are the gaps in the myelin sheath that help speed up the rate of conduction? What is this type of conduction known as?
The gaps are known as the nodes of ranvier - the help speed up the rates of conduction Known as saltatory conduction
Acute neuronal injury occurs in the context of hypoxia or ischaemia (ie cerebral infarct) How is the neuron described here? it is essentially a term for what a dying neuron looks like
The neuron is described as a red neuron here - it become shrunken
On histology , why is this neuron the colour red? in acute neuronal injury
It is red as the proteins that are left stain red - eosinophilic
Other neuronal responses to neuron injury can occur that dont involve the acute neuronal injury response to hypoxia One of these is Wallerian degenration, what does this term mean?
This is where degeneration of the axon and myelin sheath occur distal to the site of injury
What is the star shaped glial cell with multipolar cytoplasmic processees? What is its function?
This is the astrocyte Important in maintaining homesostasis and the blood brain barrier (BBB)
What neurotransmitter precursor do astrocyte supply?
They supply glutamine - precursor to neurotransmitter glutamate
What is the most important histopathological indicator of CNS injury, regardless of cause?
This is gliosis - Gliosis is a nonspecific reactive change of glial cells in response to damage to the central nervous system (CNS).
What happens in gliosis?
In glisois there is astrocyte hyperplasia and hypertrophy PIc on left shows progression of CNS injury from red neurones forming (hypoxia/infarct related) to eventual gliosis
WHat type of glial cell features in which demylinating disorder?
Oligodendrocytes feature in the demyelinating disorder multiple sclerosis and are sensitive to oxidative damage
Membrane depolarisation jumps from one node to the next through “saltatory conduction” at a much more rapid rate than would occur through depolarisation alone. Myelin insulation also helps to contain depolarisation locally (preventing leakage to adjacent axons) and provides a barrier to injury. If there is axonal damage, what is the type of degeneration known as again?
This anterograde degeneration (wallerian’s degeneration) where axonal and myelin tissue dies distal to the site of injury
The cerebral circulation stems with the circle of willis Which arteries are involved in the ciicle of willis?
Anterior cerebral arteries, anterior communicating artery, middle cerebral artery/internal carotid artery, posterior communicating artery, posterior cerebral arteries
At the circle of willis, which arteries come from the internal carotid artery? Which artery comes off the basilar artery immediately proximal to the posterior cerebral arteries?
Internal carotid artery - gives ophthalmic artery, anterior choroidal, and middle cerebral - opthalmic artery travels beside the sphenoid sinus Proximal to the posterior cerebral is the superior cerebellar artery
WHich arteries come off the basilar artery from posterior cerebral to the vertebral arteries? What are the two inital arteries coming off the vertebral artery?
Basilar - posterior cerebral, superior cerebellar artery, pontine arteries, anterior inferior cerebellar artery Vertebral arteries - posterior inferior cerebellar artery, branch from each vertebral to forma anterior spinal artery
Which artery supplies blood to most midline portions of the frontal lobes and superior medial parietal lobes? Which artery supplies blood to the majoirty of the temporal lobes? What does the posterior cerebral artery mainly supply?
Midline portions of frontal lobes and superior medial parietal lobes - anterior cerebral artery (blue) Majority of temporal lobes - middle cerebral artery (purple) Posterior cerebral artery mainly supplies the occipital lobe (green) - and the inferior temporal gyrus
If there is higher cognitive dysfunction, which artery is likely to be injured? Which lobes are likely to be affected? What type of stroke would present with higher cogntiive dysfunction?
Anterior cerebral artery most likely to be the cause Frontal and parietal lobes would be affected Either a total anterior circulation stroke (TACS) or partial anterior circulation stroke (PACS) would be affected here
Which artery supplies the major bulk of the sensory and motor cortex? Which artery supplies sensory and motor innervation to the trunk and legs? (think of the artery borders and the homunculus)
Middle cerebral artery supplies major bulk of the sensory and motor cortex The anterior cerebral artery supplies the legs and trunk with sensory and motor innnervation - remember anterior cerebral supplies midline portions of frontal lobes and superior midline of parietal
homonymous hemianopia with visual field defect in both eyes on the same side as the lesion (central sparing also) Which artery and where is affected?
Posterior cerebral artery and lesion in the occipital cortex
State which artery supplies each box? What is the anterior choroidal artery a branch of?
Blue box - anterior cerebral artery (legs and trunk) Brown box - middle cerebral artery Pink box - posterior cerebral artery Red box - posterior cerebral artery (deep branches) Anterior choroidal artery is a branch of the internal carotid artery
What is the minimum cerebral perfusion pressure of the brain? Usually the brain receives 15% of cardiac output and uses roughly 20% of the oxygen consumed by body
60mmHg is the minimal cerebral perfusion pressure for the brain
Brain ischaemia and infarction Haemorrhages Vascular malformations Aneurysms These are all part of what broad category? (3rd commonest cause of death)
Cerebrovascular disease
What is usually the main contributing condition to cerebrovascular disease?
Hypertension - can cause aneursyms to burst, haemorrhages, infarcts due to atherosclerotic emboli
What are the areas at the peripheries of the vascular territories supplying the brain that contain neurons particularly sensitive to ischaemia known as?
These are the watershed areas The watershed zones themselves are particularly susceptible to infarction from global ischemia as the distal nature of the vasculature predisposes these areas to be most sensitive to profound hypoperfusion.
What is the definition of a stroke?
Sudden vascular disturbance resulting in focal neurological deficit lasting longer than 24 hours
What is the major cause of stroke?
Atheroembolic stroke accounts for 40% of all stroke cases
What artery to have a clot is the most common cause of cerebral infarction? What is the most common causes of cerbral infarction? Which gender is it more common in?
Middle cerebral artery is more common than anterior and posterior cerebral arteries to have a clot Most common causes of cerebral infarction is thrombus from atherosclerotic segment More common in males to have cerebral infarction
After 12-24 hours of cerebral infarction, what is visible on microscopy?
The neuron death is visible and therefore see red neurones - the shrinking neuron in the cytoplasm has become eosiniophilic
How long does it take for the necrotic area from cerebral infarction to become visible macroscopically?
Takes 48 hours
When are neutrophil the dominant cell type in cerebral infarction and what takes over after 48 hours?
Dominant cell type from 24-48 hours from which the microglia takes over after 48 hours as the predominant cell (macrophagic type cell)
At what stage do the astrocytes increase in cell number and size in cerebral infarction and what is this known as?
Astrocytes increase in number and size is known as gliosis Happens to occur roughly one week after infarct
Localisation of the vascular lesion: - state the artery affected in each * weakness and sensory loss in contralateral leg? * weakness predominantly contralateral face and arm? * vertigo, ataxia, dysarthria, and dysphasia? (what is dysarthria)
weakness and sensory loss in contralateral leg - anterior cerebral artery weakness predominantly contralateral face and arm. - middle cerebral artery vertigo, ataxia, dysarthria, and dysphasia - vertebrobasilar arteries what is dysarthria - difficulty speaking caused by problems controlling the muscles used in speech.
Consequences of hypertension can include Lacunar infarcts - what is the criteria for lacunar infarcts? What is the type of arteries involved in lacunar infarcts known as? What are the potential rupturing aneursysms in lacunar strokes known as?
Lacunar infarct - one of three of Unilateral weakness (and/or) sensory loss in arm, face or leg - Pure sensory stroke - Ataxic hemiparesis Lacunar infarcts involve the perforating arteies of the basal ganglia, thalamus and internal capsule - lenticulostriate arteries Potential rupturing aneursysms are known as Charcot-Bouchard aneurysyms - common cause of intracerebral haemorrhage
Wht is the most common location of intracerebral hameorrhage? What is a common cause of intracerebral haemorrhage?
Most common location is the basal ganglia Then you have the cerebral white matter, cerebellum and thalamus Hypertension is most common cause Charcot Bouchard aneurysms rupturing due to hypertension are a common cause
What is the most common cause of subarachnoid haemorrhage? Where are the location sites for the arterial bleed?
Berry aneurysm ruputre 90% rupture in the internal carotid artery territory 10% rupture in vertebrobasilar circulation These berry aneurysms arise at arterial bifurcations
What are three risk factors for subarachnoid haemorrhage? What are the clinical features?
Smoking, hypertension, kidney disease (ADPKD) CLincial features Sudden headache - feels like someone took a baseball bat to back of the head Vomiting, loss of coonsciousness and seizures can usually follow Neck stiffness
What is another name of berry aneurysms?
Saccular aneurysms
