Introduction to Stroke Flashcards
define ischaemia
deficient supply of blood to an organ or tissue due to obstruction of inflow of arterial blood
define occlusion
shutting off or obstruction
define thrombus
a blood clot formed within a vessel and remaining attached to its place of origin
define embolus
a mass, such as an air bubble, detached blood clot, or foreign body, that travels in the blood stream and lodges in a blood vessel thus serving to obstruct or occlude such a vessel
define hypoxia
a deficiency of oxygen reaching the tissues of the body
describe the brain
only 2% of body’s mass
most metabolically active part of the body
requires constant delivery of O2 and glucose to maintain brain cell function
if arterial supply to an area of brain is disrupted brain cells will start to die within minutes of oxygen deprivation
what is a stroke
occurs when the blood supply to the brain is disrupted - either due to occlusion or rupture of bloody vessel supplying or within the brain - brain cells therefore starve of oxygen and die or are damaged
what does TIA stand for
transicent ischaemic attack
what is a TIA
short-lived episode (less than 24hrs) of temporary impairment in brain function caused by insufficient volume of blood supply to the brain due to a temporary or partial blockage of a blood vessel
usually no permanent damage occurs as a result of a TIA
how many of those who have a TIA eventually will have an acute stroke
1/3
what is ischaemic stroke
most common type (80% of all strokes)
occurs when a clot or blockage prevents the flow of blood in the brain
Hyproxia (deprived of O2 and other nutrients), the brain suffers damage and eventually will die as a result of stroke
what may vascular occlusion be caused by - 3 points
thrombus
embolism
general decrease in blood supply - e.g. shock
what is an intracerebral haemorrhage
when blood vessels within the brain become damaged (poss trauma) or weakened due to hypertension, cerebral aneurysm, vascular malformation (inc AVM) - more likely to rupture and cause haemorrhage in the brain
higher fatality rate/ poorer prognosis than ischaemic infarcts
location > size - tends to be greater factor in influencing severity of stroke
what 3 ways can damage be caused in haemorrhagic stroke
blood is prevented from reaching the brain cells beyond the point of rupture leading to hyproxia
leaked blood can irritate and harm the brain cells in the areas where it accumulates
mass effect can damage brain tissue and raise ICP
what is a subarachnoid haemorrhage
a type of intracerebral haemorrhage
bleeding from a damaged vessel causes blood to accumulate in the subarachnoid space - commonly due to rupture of cerebral aneurysm
can also be due to trauma and AVM
often in the circle of willis
commonly present with ‘thunderclap’ headache and photophobia
what are the signs and symptoms of a stroke
vary from person to person
depend on part of the brain affected and extent of damage
main stroke symptoms - FAST
face arms speech time
common clinical indications - 7 points
hemipariesis - muscle weakness on one side of the body
visual field defect
ataxic gait - unsteady walk
dysphagia
dysarthria - difficulty with articulation
aphasia - inability to speak
dysphagia - difficulty speaking, reading, writing due to brain damage
what are the recommended guidelines for stroke - 4 points
rapid diagnosis
admission to specialist stroke unit
immediate brain imaging
thrombolysis where indicated
what are implications from these stroke guidelines - 4 points
services need to be reorganised to allow scanning to be performed urgently when indicated
all hospitals admitting stroke patients have 24 hour access to scanning
scans should scheduled appropriately and running an out of hours service
US and angiography require the same consideration
which is the modality of choice and why
CT relatively inexpensive widely available immediate access speed in scanning patients and results
which modality is less suitable and why
why can this be used
MRI
speed - long acquisition times, sensitive to patient movement artefact
inability to screen acute patient
magnetic field excludes A/E equipment and staff
difficult cases
follow up
functional studies - where thrombolysis is an option
how does an acute ischaemic infarct radiologically present - 2 points
ill-defined/wedge-shaped area of hypo density
affects both grey and white matter
mass effect - effacement of adjacent sulci/ventricle, possible midline shift
how does a chronic ischaemic infarct radiologically present - 4 points
well defined wedge shaped area of low attenuation
CSF fills space where the tissue has died
associated expansion of the ipsi-lateral ventricle and sulcal widening
affects both grey and white matter
how does an acute intracerebral haemorrhage radiologically present - 5 points
hyper density surrounded by brain
possibly rim of hypo density indicating oedema
mass effect - effacement of adjacent sulci/ventricles, possible midline shift
may have intraventricular extension
overtime acute blood = reabsorbed, the tissue has died due to lack of oxygen, and an area of encephalomalacia (dead tissue) remains - appears as a hypodense area
how does a subarachnoid haemorrhage radiologically present
hyperdensity (blood) seen within the subarachnoid spaces
C.O.W in subarachnoid space
typical ‘star of david’ appearance
blood also seen following pattern of ‘sulci/gyri’
why is treatment for each type significantly different
incorrect treatment could have significant life-threatening consequences
imaging critical in order to give quick, reliable diagnosis
allowing the correct treatment ASAP
treatment for acute ischaemic infarct - 4 points
aspirin/anticoagulants - prevent clots/reduce further blood clots occurring
statins - block the liver enzyme that produces cholesterol
diuretics and ACE inhibitors - reduce blood pressure
carotid endarterectomy - incision in neck to open up carotid artery and remove fatty deposits
treatment for intracerebral haemorrhage - 3 points
ACE inhibitors - to lower blood pressure
emergency craniotomy - to evacuate clot and relieve pressure
endovascular emobilsation or surgical clipping - of any aneurysm related to haemorrhage within 48 hrs
describe thrombylisis
brain tissue at periphery of area of infarction remains viable for a short time (ischaemic penumbra) and may recover function if blood is restored
pharmaceutical method used to breakdown clots - only effective if started in first 4 hours after onset - speed of receiving delivery = better chance of recovery
no benefits if after 4 hours of onset
BUT can cause potentially fatal bleeding in brain
what does it require in order to receive thrombylisis - 5 points
accurate knowledge of onset of symptoms
immediate access to specialist stroke centre
no contraindications
expertise in producing and analysing images
specialist trained to administer drug
role of imaging in thrombylisis
function CT and MR perfusion studies demonstrate and evaluate the size of penumbra - potentially viable tissue
images taken during IV admin of contrast media
provide quantitative measurements of CSF flow - critical because it indicates brain tissue viability and haemorrhagic risk
