Stroke Flashcards
Define an ischaemic stroke
Cerebral loss of blood flow to part of the brain caused by interruption of blood supply.
Results in hypoxia which can stress brain cell metabolism which can lead to anoxia. Anoxia leads to infarction which results in a stroke
What is the most modifiable risk factor when it comes to stroke?
Hypertension
How does hypertension cause stroke?
Stroke is related to blood pressure. Chronic hypertension worsens atheroma and affects small distal arteries
Define ischaemia
Lack of blood flow
Define Hypoxia
Lack of oxygen
Define the relationship between ischaemia and hypoxia
Ischaemia causes hypoxia
Define the term ‘stroke’
A focal neurological deficit due to disruption of blood supply
What causes stroke?
Interruption of supply of nutrients and oxygen, causing brain tissue damage
What are the causes of interruption of blood supply?
Changes in:
- vessel wall
- blood flow
- blood constituents
What are the three main causes of interrupted blood supply?
- Atheroma + thrombosis of artery (Ischaemia)
- Thromboembolism (Ischaemia)
- Ruptured Aneurysm (haemorrhage)
What is atheroma and thrombosis?
Narrowing and thrombosis of artery
Which arteries are usually affected by atheroma and thrombosis?
Internal carotid artery thrombosis causes ischaemia in middle cerebral artery region
What is the pathogenesis of ischaemic stroke?
- a few seconds of hypoxia or anoxia = ischaemia which can lead to infarction
- infarction = damage to neurones permanent and they will not regenerate
Describe a regional cerebral infarct
A wedge shaped reflection of arterial perfusion territory. It goes soft and becomes cystic
When is thrombosis of atrial appendages common?
In patients with arrhythmia of AF
How does thromboembolism affect stroke?
- heart with LA appendage thrombosis throws a clot into aorta and carotid arteries
- Embolism reaches right middle cerebral artery and blocks it = ischaemia
Why do vessels rupture?
Vessel walls weaken and hypertension causes an aneurysm to form
How do ruptured vessels cause haemorrhage and distal ischaemia ?
Artery spasms = haemorrhage and decreased blood flow
Name 2 common sites of ruptured vessels which cause Hemorrhagic stroke?
Basal ganglia and circle of willis
Give examples of situations where levels of o2 in blood are low?
CO poisoing, near drowing, resp arrest
Give examples of situations where blood supply isn’t adequate
Cardiac arrest, hypotension, brain swelling
Define Watershed infarcts
A zonal pattern of ischaemia and infarction at interface of territories
When do Watershed infarcts occur?
When prolonged HYPOTENSION occurs
What occurs in complete loss of perfusion and oxygen?
CORTICAL INFARCTION
What is a TACS?
Total Anterior circulation stroke
- Unilateral weakness of face,arm and leg
- Homonymous Hemianopia
- Higher cerebral dysfunction (dysphasia and visuospatial disorder)
What is a PACS?
Partial anterior circulation stroke
Unilateral weakness of face,arm and leg
- Homonymous Hemianopia
- Higher cerebral dysfunction (dysphasia and visuospatial disorder)
2/3 MUST BE PRESENT FOR PACS CLASSIFICATION
What is a POCS?
Posterior circulation syndrome
- cranial nerve palsy
and a contralateral motor/sensory deficit - Bilateral motor/sensory deficit
- Conjugate eye movement disorder
- Cerebellar dysfunction (vertigo, nystagmus,ataxia)
- Isolated homonymous hemianopia
ONLY ONE NEEDS TO BE PRESENT
What is a LACS
Lacunar syndrome
- Pure sensory stroke
- Pure motor stroke
- Senori-motor stroke
- Ataxic hemiparesis
