Cerebrovascular disease Flashcards
Cerebrovascular disease comes in two forms
- Localised interruption of blood or oxygen supply (Stroke)
- Generalised interruption of blood or oxygen supply
Define a stroke?
A focal neurological deficit caused by disruption of supply oxygen and/or nutrient supply causing damage to brain tissue
What could cause a stroke?
Vessel Wall:
- Aneurysm
- Atheroma
- Vasculitis
- Strangulation
Blood Constituents
- Thrombosis
- Bleeding due to anticoags or reduced platelet/clotting factors
Blood flow:
- Hypotension
- Hypertension -> Bursting
So what are the 3 main causes of localised interrupted blood supply to the brain (Stroke)?
Ischaemic:
- Atheroma and thrombosis
- Thromboembolism (E.g. from Afib)
Haemorrhagic:
- Ruptured Aneurysm
Whats the difference between a TIA & Stroke?
Both are ischaemia to a localised section of brain tissue
TIA:
- <24 hour symptoms
- Reversible Ischaemia
- Tissue still viable
Stroke:
- Symptoms last >24 hours
- Irreversible ischaemia
- Localised brain death (i.e. infarct)
What happens to the brain tissue during a regional cerebral infarct?
The region is classically wedge shaped reflecting the in->out arterial supply.
The tissue becomes soft, yellowy discoloured and begins to disintegrate typically in a cystic appearance
There may be visible congested vessels and swelling around the area
How does infarcted brain tissue appear histologically?
Visibly lost neurons
Foamy macrophages - Part of the repair process prior to gliosis (Scar tissue formation)
Why are cerebral arteries so likely to have aneurysms?
They are very thin walled due to their lack of muscle.
This is so that there’s no way cerebral blood can be diminished .
This when coupled with hypertension leads to aneurysms which can burst
How does a ruptured aneurysm cause localised interruption of blood flow?
The haemorrhage means blood doesnt get through and compresses the brain
Can also get distal ischaemia due to arterial spasm
Where do cerebral aneurysms most often form?
- Microaneurysms in the Basal Ganglia
- Berry Aneurysms in the Circle of Willis
What are the main causes of a generalised Interrupted blood supply or hypoxia?
- Low O2 in the blood (Hypoxic Hypoxia) e.g. CO poisoning or resp arrest
- Inadequate supply of blood e.g. Cardiac arrest, swollen brain or hypotension
- Rarely an inability to use the O2 such as cyanide posioning
What are the main types of Generalised interrupted blood supply?
- Hypotension
- Cardiac Arrest
- Complex Case (Combines various types of ischaemia form multiple causes)
What pattern of infarction could be caused during an Operation in which there is a prolonged period of hypotension?
Generalised interrupted blood flow
- -> poor Perfusion to the borders between arterial territories in the brain
- -> So you get a pattern of ischaemia and infarction at the interfaces between these area (watershed infarcts)
IF someone goes into cardiac arrest and is resuscitated after several minutes, describe their pattern of ischaemia?
They go several minutes with no supply of blood (Generalised interruption)
Causes infarction all over the brain
They get Laminar (lined) cortical necrosis i.e. large areas of grey matter thin and necrose
Lets say a women comes in with a known Coronary artery disease, bouts of pneumonia and suffers a cardiac arrest, describe her patterns of ischaemia?
This is known as a Complex Case, she has multiple different sources of ischaemia causing different patterns in her brain:
- Watershed infarcts from her time poorly ventilated due to pneumonia
- Regional infarcts related to localised loss of blood flow from atheromatous disease
- Laminar Cortical infarcts due to complete cessation of blood flow during cardiac arrest
