Stroke Flashcards
Define stroke
Obstruction of blood flow to area of brain, also called Cerebrovascular Accident.
Ischemic stroke
This stroke is Thrombotic (blood clot forms in cerebral arteries and blocks ) or it can be embolic (blood clot formed somewhere else in body and travels to the brain and blocks ).
Hemorrhagic strokes
This stroke results from uncontrolled bleeding can create pressure, kill brain cells
Possible causes : hypertension and Aneurysm
Area of damage - Brain stem
Possible effect - uncommon but fatal. This can cause problems with breathing, heart function, balance and coordination, chewing, swallowing, speaking, seeing as well as weakness and paralysis on both sides of body
Area of damage - cerebellum
Possible effect - cause problems such as balance and coordination, dizziness, headaches, nausea and vomiting
Area of damage - cerebrum (left hemisphere )
Possible effect - causes weakness, paralysis on right side of body and cognitive problems like with reading, talking, and thinking and learning, remembering new information
Area of damage - cerebrum (right hemisphere )
Possible effect - cause problems with vision, depth perception, short term memory loss and judgement as well as weakness or paralysis on left side and a tendency to ignore things on your left side including your own left leg and arm
Diagnoses of stroke
CT scan ( to see if a stroke has occurred or not )
MRI ( to visualize any brain damage
Angiography ( to examine blood flow through brain
Blood and Urine test
Echocardiogram ( Shows how well the valves of your heart are working and size of your heart chambers
ECG ( to check electrical activity of heart )
Neurological exam ( To check how brain function has been affected by stroke )
Goal of the stroke treatment
If a stroke is confirmed the bleeding will be controlled to reduce pressure and blood vessel damage will be repaired by surgery
Ischemic core
The area closed to the blocked artery, the cells and neurons in the area die off due to lack of oxygen and glucose in few minutes, severely ischemic
Ischemic penumbra
Peripheral surrounding area around ischemic core, moderately perfused, neurons and cells don’t die right off, this area gets oxygen and glucose through diffusion in surrounding areas / collateral arteries
Ischemic cascade
No blood supply -> anaerobic metabolism begins (produce less ATP and lactic acid) -> Na+ / K+ pump stops working (No more Na+ going out of neuron and K+ going inside neuron without ATP) -> Na+ gets trapped inside the cell -> H2O in outer space rushes into the neuron -> neuron swells up (Cytotoxic edema ) -> potentially causes death
Ischemic cascade
No ATP production -> Na+ / Ca2+ pump stops working ( no more Na+ going inside the cell and Ca2+ going outside the cell ) -> Ca2+ build up inside the cell -> cytotoxicity, chemical messenger like Glutamate exit neurons and excites other nearby neurons because it is excitatory, degradative enzymes get activated ( proteases (break down proteins inside neuron), lipases (breakdown lipids in neurons, cell membrane eventually breaks down), causes generation of free radicals (oxidative reactive species ) leading to further neuron damage. Due to aftermath of stroke and release of unwanted chemicals in the space mitochondria start breaking down releasing apoptotic factors ( cell die)
Post stroke inflammation
As neurons starting to die off -> release damage associated molecular patterns (DAMPS - signals that trigger inflammatory response ) -> macrophages get activated -> once sufficient in numbers many other immune cells got involved -> turn into anti inflammatory -> leads to liquifactive necrosis (neutrophils in the area start to release hydroplanes (break down dead cells, forming a cavity of soft liquified necrotic debri, if its a small stroke then the cavity gets walled off and removed by macrophages, if a large stroke then necrotic area gets isolated / walled off and turn into a cyst and the cyst gets cleared by immune cells creating a hole which will lack portion of brain that won’t be regenerated )
Ischemic stroke
Three ways it can happen - embolic (embolism travels and blocks the blood supply), thrombotic (blockage forms in the area and causes obstruction, likely due to atherosclerosis
Lacunar strokes (blockage in a small blood vessel either through clot or progressive hypertension leading to thickening of blood vessel walls)
Watershed strokes (area deprived of blood supply due to less total cerebral perfusion / blood volume in brain from a further blockage ( for example - carotid artery blockage )
Hemorrhagic stroke
Internal bleeeding causes pressure but also deprives brain tissue of blood supply, internal bleeding can also cause irritation of nearby blood vessels causing their vasospasm which further reduces perfusion and causes secondary stroke
Major reasons of internal bleeding - aneurysm, arteriovenous malformation ( when arteries are directly connected to veins instead of connecting through capillaries, resulting in high pressure blood getting straight into veins increasing risk of rupture, this is primarily congenital defect )
Common symptoms of stroke
Facial drooping, slurred speech, arm drift. If symptoms go away in about less than or in 24 hours then its a TIA and if not then its a stroke
Other symptoms - numbness (if stroke affected the primary somatosensory cortex - controls feeling), weakness (if stroke affected motor cortex - controls movement ), trouble speech (frontal lobe impacted by stroke ( Broca’s area - fluent speech production) and junction of temporal and parietal lobe gets affected (Wernicke’s area - understanding others and producing meaningful speech), sudden trouble with vision (occipital lobe impacted - controls vision) , sudden loss of balance , dizziness and coordination (stroke impacted cerebellum - coordinate movement and balance) , sudden headache (hemorrhagic stroke - creating pressure )
Diagnoses of the stroke - Imaging
CT scan - immediately done, shows if the stroke has occurred, shows hyper dense sign - blood clot in the brain
Shows hemorrhagic strokes very well
CT angiography - Dye is injected into blood stream so that blood vessels are all lit up in CT scan
MRI scan - shows where stroke has occurred through high resolution images, shows ischemic strokes very well very well
Diagnoses - lab testing
Looks for underlying causes of stroke - test ordered
CBC - looks for thrombocytopenia, polycythemia, both of these conditions can increase the risk of stroke due to RBC and platelets having blood clotting potential and if there is more clotting it can lead to ischemic strokes very well and if there is less clotting there will be hemorrhagic stroke
Electrolyte check - low Na+ can cause imbalance of electrical activity in brain leading to seizure and stroke like symptoms
Hypoglycemia - can also mimic stroke such as showing symptoms like weakness, numbness, trouble speaking, trouble with vision
Coagulation studies - checking for clotting disorders
Toxicology screen - checks for drug usage
Acute treatment for stroke
Through medications - ischemic strokes ( Aspirin (prevent clots from forming further ), Thrombolytic (breaks clot causing stroke , example - Tissue Plasminogen activator (TPA) activates and turns into plasmin (bursts up the clots ) )
Hemorrhagic stroke ( Anti hypertensive (to lower blood pressure), head elevation (to lower cerebral pressure), anticonvulsive (to avoid seizure (could happen due to cerebral pressure) )
Treatment and intervention of stroke
Ischemic stroke-MERCI retriever(mechanical embolus removal in cerebral ischemia) this works to remove clot by entering a wire and the wire hold onto the clot and remove it to resume blood flow) (suction- a tube gets inserted that acts like a suction to suck up and remove the clot and resume blood flow)
Hemorrhagic stroke -(aneurysm clipping -burst aneurysm gets clamped by metal clip at the base and would prevent blood from going towards the bleeding site and stop blood loss) (coil embolization a will get inserted into aneurysm and would release wire and the wire will coil around the aneurysm, bulging site and prevents blood from entering the site, this will also eventually lead to clotting at the site)
Prevention of stroke
Lower blood pressure(regular exercise, reduce salt intake) reduce alcohol consumption, avoid smoking, keep a healthy diet, a healthy body weight, managing medical conditions( diabetes)
Medication: blood pressure lowering meds ( ACE inhibitors) , antiplatelets( aspirin), anticoagulants( warfarins) , lipid lowering drugs(statins,ezetimibe (prevent absorption of cholesterol), Lipitor(prevent liver from forming lipids))
Surgery: plaque removal from carotid arteries (carotid, endarterectomy), widening of carotid artery(carotid stenting)
