202 - Stroke Flashcards
What are the two types of stoke and how common is each?
Ischaemic (85%) - embolic (lodging of a blood clot fat or gas in blood stream) and ‘in situ thrombotic (forming of a blood clot in place)
Haemorrhagic (15%) - burst blood vessel
Define a stroke
A neurological deficit related to a non traumatic vascular event
Define a Transient Ischaemic Attack
A neurovascular event with symptoms lasting less than 24 hours
what are the cardinal features of strokes?
- Focal - particular location
- Negative clinical phenomena - no added signs like twitching
- Relate to arterial anatomy (i.e. not veins)
- Sudden onset
- Px has identifiable vascular risk factors - poor diet, smoking, no exercise
What are the risk factors for embolic strokes?
- Atheromatous disease - smoking, family Hx, diabetes, hypertension
- Cardiac causes - AF, endocarditis, shunts, cardiomyopathy
- Low cardiac output states
What are the risk factors for ‘In Situ’ thrombotic strokes?
- Atheromatous Disease
- Hyperviscosity -excess RBCs
- Vasculitis
- Thrombophilic states - F5 leiden (blood clotting disorder), pregnancy, oral contraceptive pill
- Incr. alcohol intake
What are the risk factors for Haemorrhagic strokes?
- Hypertension
- on anti coagulation drugs
- on thrombolysis drugs
What are the risk factors for venous strokes?
- Dehydration
- Infection
- Heart Failure
- Thrombophilic states - CA, pregnancy, OCP
Describe a Primary Intracranial haemorrhage (PICH)
- Hyper acute and sometimes LOC & headache due to incr. in Intracranial pressure (cushing’s reflex)
- A ruptured vessel in R hemisphere would cause L hemiparesis
Describe a Sub Arachnoid Haemorrhage (SAH)
- Hyper acute & meningism (neck stiffness) & LOC
- Extra-cerebral anuerysm
- Thunderclap headache
Describe Cerebral Venous Sinus Thrombosis (CVST)
- DVT of the brain
- Sub acute / evolving - back pressure in the veins
- Secondary bleeding, incr. in ICP
- Don’t respect arterial territories
- Affects young people, women on OCP
Describe Brainstem and spinal strokes
- Ataxia, diplopia (double vision), dysarthria, lower CNS hemiparesis
- Ipsilateral on face and contralateral on arms and legs
What does optic disc selling indicate?
Incr. BP caused over a long time - therefore not a stroke
Describe the autoregulation of cerebral blood flow.
CBF is maintained at the same rate over a range of blood pressures (50-170 mmHg) by variation in arteriolar control
How does chronic hypertension affect affect autoregulation of CBF?
The range is reset to a higher level. If BP too low arteriolar system no longer compensates and Px blacks out (CBF inadequate for metabollic demands, impaired cellular metabolism & decr. neuronal activity). If BP too high leads to cerebral oedema, hypertensive encephalopathy and hyperaemia.
What can cause the failure of autoregulation?
- Incr. age
- Head Trauma
- SAH or Ischaemic stroke
- Cerebral Hypoxia
- High pCO2
At what percentage fall from the normal range of CBF will tissue be at a risk of ischaemic damage?
50%
Describe what glial cells are and how they metabolise
They are non-neuronal support cells that maintain homeostasis, form myelin and supply lactate to adjacent neurons. They metabolise aerobically and anaerobically.
Describe what neurons metabolise and how they metabolise
They can metabolise glucose but mostly metabolise lactate from the glia. They are obligate aerobes and are very sensitive to ischaemia, suffering irreversible damage after 5-7 mins of hypoxia.
What is the difference between ischaemia and hypoxia?
Ischaemia is a restriction in blood supply that leads to dysfunction +/- damage.
Hypoxia is oxygen deprivation due to low 02 in inspired air, airway obstruction, lung disease, reduced O2 carrying capacity of blood, ischaemia & inhibition of aerobic respiration
What are the effects of ischaemia/hypoxia dependent on?
The degree and duration of ischaemia/hypoxia, temp (low temp prevents damage) and blood glucose (incr. glucose causes incr. damage due to build up of lactic acid that cannot be metabolised.
What is global ischaemia?
Interruption of circulation and general reduction in cerebral profusion due to:
- Cardiac arrest
- Severe hypotension
- Shock
What does global ischaemic lead to?
- Selective neuronal necrosis
- Cortical Laminar Necrosis
- Watershed infarcts - at areas between different arterial supplies due to poor blood supply from distal end arteries
What does global ischaemia cause clinically?
- Transient confusion
- Focal deficits
- Non perfused brain and brain death (ICP>arterial BP)
How is the risk of a stroke affected if a Px has a TIA?
7-10% risk
Where do intracerebral haemorrhages most commonly found?
Thalamus/basal ganglia
What most commonly causes sub arachnoid haemorrhages?
Rupture of saccular Aneurysms.
Aneurysm most commonly occur in anterior circle of willis
What is a Lacunar Infarction?
Ischaemic stroke cause by occlusion of lenticulostriate arteries (arise off MCS). Associated with chronic hypertension and affect the basal ganglia, thalamus, internal capsule and pons leading to formation of a small lacuna (holes)
what causes a stroke secondary to cerebral vasculitis and how is it treated?
inflammation of blood vessel walls in brain often due to rheumatoid arthritis, SLE or drug abuse. Treated by immunosupression (glucocorticoids)
What is Binswager’s disease?
Multi-infarct dementia caused by a combiation of artherosclerosis, embolism, chronic HTN
What imaging technique works best for venous strokes?
CT venography
How are venous strokes treated?
Anticoagulation even if small haemorrhages present as you must remove the thrombus to remove the back pressure first. Thrombolysis if anticoagulation not working.
