Neurodegeneration One - Vascular Stroke Flashcards
(37 cards)
Define stroke
Damage to the brain or spinal cord caused by abnormality of its blood supply
How is stroke recognized?
1) Sudden onset of focal neurological symptoms over a few seconds or minutes that persist for more than 24hrs
2) Symptoms and signs of a focal brain lesion (subarrachnoid hemorrhage is an exception)
Whats the stroke incidence in nz?
8000 per year
mean age for stroke is 73 years
25% occur in under 65
Third most common cause of death
What are the type of stroke?
1) Ischemic stroke (infarction)
2) Intracerebral hemorrhage (ICH)
3) Subarrchnoid hemmorhage (SAH)
What are the characteristics of an ischemic stroke?
- causes 80-85% all strokes
- Caused by loss of blood flow to part of brain or spinal cord which deprives the area of oxygen, glucose and leads to infarction (necrosis)
What are the characteristics of an ICH?
- causes ~15% all strokes
- Bleeding into the brain parenchyma
- Usually from a small artery supplying the deep WMT or basal ganglia
- Results in a heamatoma causing symptoms by cutting off pathways in the brain and by exerting pressure on the surrounding brain tissue
What are the characteristics of SAH?
- Least common (<5%)
- Mostly younger people
- Bleeding into the subarrachnoid space around the brain and spinal cord
- Typically caused by blood leaking out of blood vessel, usually an aneurysm (Berry)
- Different symptoms to other strokes.
What are the different symptoms of SAH?
- Patients have sudden onset of extremely severe headache (thunderclap) +/- abrupt loss of consciousness
- Headache usually severe in the back of the head
- Associated with neck stiffness due to irritation of the meninges
How can the symptoms of a ischaemic stroke differ?
The symptoms depend on which blood vessels are occluded and the part of the brain that those arteries supply
What are the three possible areas of circulation that could be occluded in an ischaemic stroke?
- Anterior circulation (FC,T,P)
- Posterior circulation (Brainstem, T, SC)
- Lunar infarcts (penetrating arteries into deep WM)
What are the three main causes of ischaemic stroke?
- Arterial disease
- Embolism
- Reduced systemic perfusion pressure
What is the most common type of arterial disease that causes ischaemic stroke?
Atherosclerosis
What does atherosclerosis mainly effect?
Bifurcation of arteries
what are four ways atherosclerosis can causes ischaemic stroke?
- Ulceration of endothelium -> plaque forms -> parts break off travels downstream and blocks smaller art. (thromboembolism)
- Adhesion of platelets to wall can trigger coagulation cascade = occlusive thrombosis, can propogate and block art.
- Low flow and perfusion pressure from occluded art. = infarction of that part of brain
- Haemorrhage into a plaque occludes lumen.
How does an embolism cause ischemic stroke?
Thrombus or other material in the heart may break loose and block brain art.
thrombus may be caused by atrial fibrillation, heart valve disease, infection of heart valve, infarction of heart
what are the causes of reduced systemic perfusion pressure?
Pump failure
Shock - dehydration, blood loss
Therefore perfusion pressure in some areas of the brain are reduced and die.
What is the pathophysiological cause of stroke?
- Brain doest store ATP
- Needs constant ATP
- Produces ATP from GLUCOSE only
- Brain recieves 20% blood flow for this purpose (50ml per 100g brain)
-Damage occurs at <5ml/100g though EEG activity falls at 20ml/100g
In the brain what does loss of ATP production cause?
No ATP =
- No ion gradient
- redistribution of ions (esp Ca in) compromises metabolic function
- Oxygen free radicals form and destroy organells
- Loss of cell polarity means lots of excitatory neurotransmitter release
== Irreversible damage (necrosis) even if reperfusion
- If ischaemic but not enough to cause necrosis, apoptosis can occur
What is the degree of ischemia determine by?
How low the perfusion is
Surrounding the central ischemic infarct zone is?
Zones of low perfusion with EEG + Metabolic failure = known as the ischaemic penumbra
What is the fate of the ischaemic penumbra?
The fate of the ischemic penumbra is determined by the duration, intensity of ischemia
- If reperfused early enough it can be salvaged
- If biochemical damage is too severe then necrosis occurs
What are the clinical syndromes of ischaemic stroke?
- Total Anterior Circulation Infract (TACI)
- Partial Anterior Circulation Infarct (PACI)
- Posterior circulation infarct (POCI)
- Lunar Infarct (LACI)
What cause TACI?
Occlusion of internal carotid artery or middle cerebral artery
What are the symptoms of TACI?
- Focal higher cerebral dysfunction (PIMB)
- Homonymous visual field defect (optic art is branch of carotid)
- Unilateral motor and/or sensory deficit in at least two of the following : face, arm, legs
