Stroke territories Flashcards
What are the 2 main group that stroke can be divided into?
- Ischaemic
- constitutes about 85-90% of water - Haemorrhagic
What are 2 overlapping areas of Ischaemic group?
- Thromboembolic
- Haemodynamic
Interplay between them in stroke setting
When does Ischaemia occur?
When the blood flow through one or more your coronary arteries is decreased
Perfusion drops to a certain threshold
Nutrient supplied to the brain, oxygen and glucose, drops to a critical level
What is the consequence of nutrients dropping to a critical level?
- Decoupling of potassium-ATPase pump of the cell
What are 2 major processes of de-coupling of potassium-ATPase pump?
- Influx of calcium into the cells
2. Release of glutamate into the synaptic cleft
What leads to further increase in intracellular calcium and ventral cellular death?
Attachment of NADPH receptors which is a irreversible process
Further increase in intracellular calcium
Ventral cellular death - end result of ischaemic process
What is the most vulnerable to the effect of blocked artery?
Tissue closest to the blocked artery
Become infarcted tissue
What can be supported for longer by collateral circulation?
Surrounding tissue away from area of infarction
What happens to the tissue if blood supply is reversed?
Will recover
If occlusion persists - get infarcted tissue
The lower the perfusion areas, less time is needed before infarction occurs
What are 2 parameters that infarct are dependent on?
- Severity of blood supply
2. Duration
What is the most used modality in acute setting?
CT
Looking for signs of acute stroke
What is CT scan used to look for?
To exclude haemorrhage
What looks at major blood vessels?
- CTA
2. Angiogram
What is intraluminal thombus in a vessel?
Looking for dense MCA
What happens when you lose perfusion?
Lose grey matter interface
Anterior circulation is lost in that area
What is the posterior circulation constituted by?
Vertebral-basilar circulation
What is anterior circulation constituted by?
Anterior middle cerebral arteries arising from termination of internal carotid arteries
Where does midline anastomosis occur?
between anterior circulation and anterior communicating arteries
There is further anastomosis communication of the anterior and posterior by the posterior communicating arteries
What are the 3 major arterial territories?
- Middle cerebral artery (MCA) -largest
- Anterior cerebral artery (ACA) - paramedially
- Posterior cerebral artery (PCA) - posteriorally
What has invariable supply from anterior circulation by recurring arteries of hebru?
Caudate
What is supplied by MCA?
Some of the lenticulate striate
What is difficult in their supply?
Middle deep grey structures
What is basilar arteries involved in?
Brainstem and cerebellar hemisphere
What is CT fogging?
Equalisation of the cellular fluid shifts as they shift back to more conventional depositions
(Day 3-5)
What is a finding on an enhanced CT scan?
Look for thrombus within vessel that is blocked
What is MCA dot sign?
early marker of thromboembolic occlusion of the distal MCA branches seen in the sylvian fissure
Principally affected area of the brain is the Insula
what does MCA supply?
Deeper ganglionic structures
- Thalami
- Caudate
- Lenticulostriates structures
Example of PCA infarct
- Paramedian-dorsally
2. Also extending along the inferior temporal lobe
Example of Basilar arteries
Involves the:
- Brainstem
- Cerebellar hemispheres
What involves all of the territories ?
Central cause of ischaemia/Infarction
Loss of grey/white matter interface both hemispheres
Cant appreciate the deeper ganglionic structures
Paroxysmal prominence of the tentorium
Why is CT perfusion used?
To scrutinize what is happening at the physiological level
Take sequential volumetric imaging through a slab of tissue - level of roughly MCA
Formation of 2 curves - arterial curve and venous curve
Derive from that parametric graphs:
- MTT
- CBF
- CBV
Relative increase in cerebral blood flow
Pertains to pneumbral tissue rather than infarcted tissue
What is CBV useful for ?
Triaging patients where there is uncertainty about the extent of infarcted tissue
Paucity of vessels
A borderzone between anterior and middle cerebral arteries
There is also an area of low density vessels from MCA - deep water shed zone
- cortical - between anterior and middle cerebral arteries
- Deeper areas - cortical and proximal M1 segments of MCA
What is watershed zones infarcts?
Occur at the border between cerebral vascular territories where the tissue is furthest from arterial supply and thus more vulnerable to reductions in perfusion
What does the sub-cortical areas incorporate?
Deeper ganglia as you work your way through top to bottom of the brain
What does MRI help with
Help patients that present with stroke
DWI
Looking for an increase in signal
ADC map
Looking for a decrease in signal
what are TIA?
Mini strokes
What happens following a TIA?
The likelihood of having a formal stroke is highest in the first few days then 7 days then 14 days after
How can you further classify patients presenting with TIA?
ABCD2 score A- Age > 65 B - BP > 140/95 C - Paresis - Speech/Visual D - symptom pathology > 1 hour Also if you are diabetic
A score of 4 on the ABCD2 scale?
risk is smaller in the next 7 days of developping the stroke
A score of 5 on the ABCD2 scale?
Risk drops quite remarkably to 12%
What is a common cause of stroke?
Atherosclerosis
What are the 3 classifiers of stroke?
- NASCET
- ECST
- CC
What are the 2 complicastions of Carotid dissection?
- Thromboembolic
2. Haemodynamic - narrow lumen and reduce the blood flow
What is the treatment for Carotid dissection?
- Medical
Initial stage of patient presenting with ischaemic stroke
- Clinical examination and rapid radiological assessment
- Imaging in the form of CT is required
- Medical –> Thrombolysis [within time scale]
What are 2 major studies of ischaemic stroke?
- NINDS trial - within 3 hours of onset
2. ECLAS3 - within 3-4.5 hours off onset
Endovascular Stroke Management
- Proximal vessel occlusion
What are the 3 major studies published ?
- MR CLEAN
- EXTEND-IA
- ESCAPE
shows efficacy in selected patients in the vascular treatment for stroke
MR CLEAN
most of the control group were in the proximal or ICA/MCA
between intervention and control group there is a shift of MRES group of better outcome
What strategies can be used for endovascular stroke
- Chemical
2. Mechanical - stent
What are the 2 classifications of Intracranial Haemorrhage?
- Intraxial
2. Extra-axial
What are examples of Extra-axial Haemorrhage?
- Sub-dural
- Extra-dural/epidural
- Subarachnoid
What is an example of surgical emergency?
Epidural
lots of mass effect
