Blood supply and stroke Flashcards
What percentage of the cardiac output is used by the brain?
15%
What do the right and left vertebral arteries join to form?
Basilar artery
What arteries make up the anterior circulation of the brain?
Branches of the internal carotid arteries:
- Middle Cerebral Artery
- Anterior cerebral artery
- Perforating branches (striate, leticulochoroidal arteries, etc.)
What does the anterior circulation of the brain supply?
- Anterior 3/5s of the cerebrum
- Diencephalon
What arteries make up the posterior circulation of the brain?
Vertebrobasilar arteries Main branches: - Cerebellar (PICA, AICA, SCA) - Pontine - Posterior cerebral arteries - Striate and thalmic branches
How does the brain regulate cerebral blood flow despite variations in blood pressure?
Autoregulation - blood vessels respond to changes in BP to maintain a safe and steady flow rate
What happens when blood pressure is extremely low (below 50mmHg)?
Arteries collapse and ischaemia occurs
What happens if blood pressure is too high in the cerebrum (above 150mmHg)?
Force-mediated dilation increased flow, vasogenic oedema
If blood flow into brain is compromised how should you check BP?
Bilaterally
What are the common symptoms of stroke?
- Sudden onset
- Facial asymmetry
- Speech disturbance (dysphasia)
- Asymmetrical weakness in muscles
What is the definition of a stroke?
- Interruption of the blood supply to a focal part of the brain causing loss of neurological function
- Symptoms last > 24 hours or lead to death with no apparent cause other than that of vascular origin
What is a Transient ischaemic attack (TIA)?
- The same as a stroke although the symptoms last less than 24 hours
How are strokes classified?
- Ischaemic: 80-85%
- Haemorrhagic: 15%
- Subarachnoid haemorrhage 5%
What are the causes of haemorrhagic stroke?
- Hypertension
- Tumour
- Bleeding disorders
- Vascular malformation (AVM)
- Amyloid angiopathy
What is the primary brain damage of a haemorrhagic stroke?
- Mechanical damage associated with the mass effect
- Within minutes to hours from the onset of bleeding
What is the secondary brain damage of a haemorrhagic stroke?
- Surrounding oedema
- Oxidative stress and inflammation
What is an ischaemic stroke caused by?
A blood clot obstructing an artery
What is the most common origin of an embolism that causes ischaemic stroke?
Heart (cardio-embolism)
- Asssociated with Atrial fibrilation
What are the different causes of ischaemic stroke (origins where clots can arise)?
- Large vessel atheroma / thrombosis
- Cardio-embolism
- Hypoperfusion
- Small vessel disease
What is a lacunar stroke?
Type of ischaemic stroke (most common) that occurs in deep areas of the brain where small perforating branches are obstructed by microatheroma
What is the “core” in an ischaemic stroke?
Where the permanent damge of a stroke is - everything is dead here
What is the ischaemic penumbra?
Surrounds core - neurons which can be saved (aka area of salvagable damage)
What are watershed area (border zones) most vulnerable to?
Hypoperfusion (furthest away from source) - areas which will dies first
What are the different watershed areas (border zones)?
- Cortical border zone (between ACA and MCA)
- Internal Border Zone (between LCA and MCA)
- Cortical Border Zone
(between MCA and PCA)
What can reducing the blood pressure to greatly after an ischaemic stroke result in?
Watershed infarcts (malpractice issue)
What are the most common arteries affected by stroke?
- 51% Middle Cerebral artery
- 13% Small Vessels
- 7% Anterior cerebral artery
- 5% Posterior cerebral artery