Pathophysiology of Stroke Flashcards
What are the 4 main features of a stroke?
- Rapid onset of symptoms
- Signs of focal disturbance of cerebral function
- Symptoms last 24 hours or longer
- No apparent cause other than vascular
What is a stroke in evolution?
A stroke that is actively progressing, with symptoms worsening
Which type of stroke is more likely to effect a specific region, leading to stereotyped deficits?
Ischaemic
Why do haemorrhagic strokes produce less predictable symptoms?
Because of possible secondary mechanisms such as raised intracranial pressure, cerebral oedema, or compression
What might more diffuse, global cerebral dysfunction indicate?
Cerebrovascular disorder (not “stroke”)
Which brain areas are supplied by the anterior (carotid) circulation?
Most of the cerebral cortex, subcortical white matter, basal ganglia, internal capsule
Lesions in the anterior circulation are more likely to lead to what kind of dysfunction?
Hemispheric, such as aphasia, apraxia, agnosia
Which brain areas are supplied by the posterior (vertebrobasilar) circulation?
The brainstem, cerebellum, thalamus, and parts of the occipital and temporal lives
Lesions in which part of the circulation are more likely to cause signs of brainstem dysfunction?
The posterior (vertebrobasilar) circulation
Name some of the main signs of posterior lesions and brainstem dysfunction?
Coma, drop attacks, nausea, ataxia, sensorimotor deficits
What is a TIA?
Transient ischaemia attack - when the deficits resolve quickly, typically within an hour
What type of emboli causes TIAs with different presentations?
Cardiac emboli
What type of stroke causes recurrent TIAs with identical presentations?
Thrombosis / cerebral embolism
What is a minor stroke?
An event with deficits that last longer than TIAs but resolve completely within a few days
What is the most common cause of stroke?
Ischaemia (90% of strokes)
What are the two main arteries supplying blood to the brain?
The common carotid artery and the vertebral artery
What is the ring of vessels that connects the anterior and posterior circulations of the brain?
The circle of Willis
What are the 4 main arteries of the internal carotid circulation?
- Anterior choroidal
- Anterior cerebral
- Middle cerebral
- Lenticulostriate
What are the 6 main arteries of the vertebrobasilar circulation?
- Vertebral/basilar
- Posterior inferior cerebellar
- Anterior inferior cerebellar
- Superior cerebellar
- Posterior cerebral
- Thalamic
Which artery connects the anterior circulation of the right and left hemispheres?
The anterior communicating artery
What is the role of the posterior communicating arteries?
To provide an alternative pathway if there is a blockage in the internal carotid or vertebral arteries
What is ischaemia?
The interruption of blood flow to the brain, depriving cells of glucose and oxygen
What is an infarction?
Tissue death due to inadequate blood supply, typically within the ischaemic core when flow is less than 20% of its normal amount
What is selective vulnerability?
In mild ischaemia, when neuronal populations are lost preferentially
What is selective neuronal necrosis?
In severe ischaemia, when neurons are targeted and the glia and vascular cells are spared
What is pannecrosis?
Complete, permanent ischaemia affecting all cells, ultimately producing chronic cavitary lesions
i.e. infarction
Name some of the key non-modifiable risk factors of stroke?
Older age, male sex, African American ethnicity, genetics, low birth weight
Name some of the key modifiable risk factors for stroke?
Hypertension, smoking, diabetes, atrial fibrillation, recent infection, physical inactivity, low SES, alcohol intake, cholesterol, sickle cell disease
Does the size of a stroke equate to the size of the deficit?
No!
What are the two main types of primary haemorrhagic stroke?
▪️ Intraparenchymal
▪️ Subarachnoid
What are the main causes of ischaemic stroke?
▪️ Atherosclerosis (arteriogenic emboli and hypoperfusion)
▪️ Penetrating artery disease (lacunes)
▪️ Cardiogenic embolism (a-fib, valve disease, ventricular thrombi, etc)
▪️ Cryptogenic stroke
▪️ Other (e.g., dissections, drug abuse, prothrombic states)
What is carotid stenosis?
Narrowing of carotid artery
(can cause haemodynamic insufficiency or be caused by emboli)
What is a large artery stroke?
▪️ Occlusion or narrowing in large extra or intracranial cerebral artery
▪️ Ischaemia in arterial territory
What is a cardioembolic stroke?
One of more of:
▪️ heart valve
▪️ a fib
▪️ MI
▪️ congestive heart failure
▪️ endocarditis
▪️ etc
What is a lacunar stroke?
▪️ Stroke in small penetrating artery
▪️ Lacunar syndrome = pure motor, pure sensory, ataxic hemiparesis, clumsy hand dysarthria
▪️ No lesion on imaging or deep infarct
▪️ Syndrome linked to location
What factors contribute to plaque instability?
▪️ Ulceration
▪️ Lipid content
▪️ Haemorrhage
▪️ Fibrous cap thickness
▪️ Inflammation
▪️ Embolisation
What factors in atherosclerosis contribute to risk of stroke?
▪️ Plaque formation
▪️ Platelet aggregation and attachment at side of endothelial injury
▪️ Increased formation of clots (thromboli) - mechanical obstruction
▪️ Vasoconstriction
How does carotid stenosis affect risk of stroke?
Increases risk, particularly when very severe (90-99%)
What is the prenumbra?
▪️ Area surrounding ischaemic core
▪️ Functional impairments and symptoms
▪️ BUT still likely reversible if treated
What is the oligemia?
Area surrounding penumbra
▪️ Hypoperfusion but not quite severe
▪️ May resolve spontaneously
What happens as a stroke progresses?
Ischaemic core gets bigger
How is severity of carotid stenosis measured?
▪️ Percentage area
▪️ Percentage diameter
What might occur with chronic SVD?
Leukoaraoisis - white matter appears hypodense or hyperintense, predominantly around lateral ventricles
What might occur with chronic carotid stenosis?
Cerebral hypoperfusion
What are the two main forms of chronic cerebrovascular disease that contribute to risk of stroke?
▪️ Carotid stenosis
▪️ Small vessel disease
What cerebral artery is predominantly implicated in haemorrhagic stroke?
The middle cerebral artery
What is an aneurysm?
A bulge in a blood vessel caused by a weakness in the vessel wall, most commonly where it branches (i.e. where one artery meets another)
Blood pressure pushes it out, dangerous if ruptures
How is incidence of previous subarachnoid haemorrhage associated with probability of another?
▪️ Increased as years pass
▪️ Larger aneurysm associated with greatest risk
What are the main causes of haemorrhagic stroke?
▪️ Primary (e.g., hypertension, amyloid angiopathy)
▪️ Secondary (e.g., aneurysm, AVM, neoplasm)
▪️ Coagulopathy
▪️ Drugs or alcohol
▪️ Haemorrhagic ischaemic stroke
▪️ Dural venous sinus thrombosis
▪️ Vaculopathy
▪️ Arterial dissection
▪️ Pregnancy and eclampsia
What is cortical superficial siderosis?
Distinct pattern of blood-breakdown product deposition (iron) in cortical sulci
