Stroke Flashcards
Define stroke
Clinical term
Development of focal/global neurological deficit related to vascular event
Can transient clinical events occur due to vascular events?
Yes
Can vascular events go undetected clinically?
Yes
What are the pathological processes involved in stroke?
Infarction
Haemorrhage
Subarachnoid haemorrhage
What percentage of strokes are caused by infarction?
75%
What is an infarction?
Death of tissue due to inadequate blood supply
What percentage of strokes are caused by haemorrhage?
20%
What is a haemorrhage?
Tissue injury due to escape of blood from vessels
What percentage of strokes are caused by subarachnoid haemorrhage?
5%
What is a subarachnoid haemorrhage?
Escape of blood primarily into subarachnoid space
What is the third leading cause of death?
Stroke
What are the risk factors for cerebral infarction?
Ageing Hypertension Cardiac disease; eg: atrial fibrillation Hyperlipidaemia Diabetes Hypercoagulable states Smoking Obesity
What happens in a cerebral infarct?
Necrosis of cerebral tissue in particular vascular distribution
Due to vessel occlusion/severe hypoperfusion
What is cerebral infarction usually related to?
Arterial obstruction
Where can the primary problem causing a cerebral infarct be?
Arterioles
Veins
Heart
What are the possible mechanisms of infarction?
Inadequate supply of blood due to pump failure Inadequate supply of blood due to narrowed vessel lumen - Atherosclerosis - Thrombosis - Hypertensive vessel thickening - Diabetes - Amyloid angiopathy Vessel occlusion by embolus
Why is haemorrhage more likely than infarction if you have an amyloid angiopathy?
Wall thickens > weakens
Lumen narrowed
What can cause a large artery occlusion?
Thrombosis
Embolus
What can cause a small vessel occlusion?
Thrombosis
Embolus
What can cause a venous occlusion?
Thrombosis
How can infective endocarditis cause a cerebral infarction?
Mycotic embolus blocks vessel
What percentage of people have a probe-patent interatrial septum?
30%
What is a probe-patent interatrial septum?
Flap that can be open
How can a probe-patent interatrial septum contribute to a cerebral infarct?
If right heart pressure increased > embolus crosses into left atrium from right > travels up into cerebral vessel > occlusion
What are the common sites of atherosclerosis in the circle of Willis?
Anterior circulation at bifurcation
Vertebral artery
Basilar artery
Internal carotid artery
How do thrombi form in atherosclerotic vessels?
Narrowing of vessel lumen
Irregularities in intima
Lend themselves to thrombus formation
Where is an embolus more common?
In aortic and internal carotid branches than vertebro-basilar system
What does the brain look like within one hour of a cerebral infarct?
Relatively normal
How does cerebral oedema form?
Cells swell because of cytotoxic oedema
Vasogenic oedema in vascularised edges
What does cerebral oedema cause?
Raised intracranial pressure
What happens to the gyri and sulci around the swelling tissue?
Gyri expand
Sulci are obliterated
What does the brain look like macroscopically in the days/weeks after a cerebral infarct?
Clear interface between dead and normal tissue
Liquefactive necrosis
What does liquefactive necrosis look like microscopically?
Massive influx of macrophages
More and more cavitation
Some surviving blood vessels with a little new growth
Neurons don’t regenerate
What does the brain look like in the months/years after a cerebral infarct?
Infarcted area replaced by cavity
What are most cerebral infarcts caused by: thrombus or embolus?
Embolus
How does a haemorrhagic infarct happen?
Embolus lodges > tissue necrosis, damage to blood vessels > embolus removed, naturally/iatrogenically > reperfusion into necrotic area > weakened blood vessels rupture > haemorrhage over necrosis
Why must blood be restored before complete necrosis?
Avoid haemorrhagic infarction
What is hyaline arteriolosclerosis?
Small vessel disease associated with hypertension
What causes lacunar infarcts?
Hyaline arteriolosclerosis
In which areas do lacunar infarcts usually occur?
Basal ganglia
Internal capsule
Why do people with cerebral infarction die?
Most people - Pneumonia - Cardiovascular disease - Pulmonary thromboembolism Involvement of vital centres Cerebral swelling
What are the effects of raised intracranial pressure?
Transtentorial herniation
Brainstem haemorrhages
What are the two most common causes of intracerebral haemorrhage?
Hypertensive small vessel disease
Congophilic/amyloid angiopathy
Which demographic is amyloid angiopathy most common in?
Older people
What are the causes of intracerebral haemorrhage?
Hypertensive small vessel disease Amyloid angiopathy Blood disorders Tumour Vasculitis Vascular malformation Drugs
What is a hypertensive haemorrhage?
Presence of small vessel disease like hyaline arteriolosclerosis
In which sites is hypertensive haemorrhage likely to occur?
Basal ganglia Thalamus Lobar white matter Cerebellum Pons
What is amyloid angiopathy?
Deposition of beta amyloid in walls of superficial supratentorial blood vessels
What type of haemorrhage is amyloid angiopathy associated with?
Superficial haemorrhages
Often multiple and of varying age
Which neurodegenerative disease is amyloid angiopathy associated with?
Alzheimer’s disease
What are the non-traumatic causes of subarachnoid haemorrhage?
Rupture of saccular/berry aneurysm in circle of Willis and its branches Rupture of other aneurysms - Mycotic - Atherosclerotic Extension of intracerebral haemorrhage
What does it mean by a congenital berry aneurysm?
Aneurysm develops at sites of congenital weakness
Aneurysm develops with ageing
What are the risk factors for developing a saccular aneurysm?
Age Polycystic kidney disease Coarctation of aorta Type III collagen deficiency Hypertension Smoking/alcohol
Where do 90% of aneurysms form?
In anterior circulation of circle of Willis
Where are sites of congenital weakness in the circle of Willis?
Arterial bifucations
What are the most common sites of berry aneurysm formation?
Bi/trifurcation of middle cerebral artery
Junction of internal carotid artery and posterior communicating artery
Anterior communicating artery
What are the complications of an aneurysm rupture?
Subarachnoid haemorrhage
Cerebral oedema and raised intracranial pressure
Vasospasm and infarction
Ventricular obstruction > hydrocephalus
