Lecture 8: Brain Circulation and Stroke Flashcards
What is a stroke?
acute neurological impairment due to brain ischemia or brain hemorrhage
What is an ischemic stroke?
a clot blocks blood flow to an area of the brain
acute onset of neurologic deficits caused by impaired blood flow to the central nervous system
leading cause of disability
30% impaired activities of dally living
20% impaired ambulation
16% require institutional care
What is an hemorrhagic stroke?
bleeding occurs inside or around brain tissue
on an MRI blood shows white
What is the epidemiology of strokes?
60,000 strokes occur in Canada each year
5th leading causes of mortality
1st leading cause of adult disability
men > women at younger age
women > men at older age
What is the pathophysiology of an ischemic stroke?
blood flow to brain from 2 carotid arteries and 2 vertebral arteries (only blood sources to the brain)
What causes impaired blood flow to brain?
vessel problem: atherosclerosis, vasculitis, dissection, lipohyalinosis
heart problem: atrial fibrillation (most common), valvular disease, cardiac ischemia
blood problem: hypercoagulable state (more easily form blood clots)
mitochondrial disease (very rare, if they can’t generate enough energy)
What happens to the brain when it is ischemic?
cellular injury and death
death of neurons, astrocytes, oligodendrocytes, endothelial cells
blood brain barrier disrutption
What is the mechanism of cell injury and cell death?
apoptosis, autophagy, necrosis
excitotoxicity (glutamate)
inflammation
oxidative stress/reactive oxygen species
mitochondrial dysfunction
How are brain vessels different than other blood vessels?
blood brain barrier/neurovascular unit (limits entry of blood products into brain, endothelium, astrocytes, pericytes, neurons)
autoregulation: neuronal regulation, pCO2 neuropeptides, cytokines
no external elastic lamina
What is the presentation of brain ischemia?
TIA (Transient Ischemic Attack): complete recovery of symptoms in 24 hours, no infarct on CT or MRI
Ischemic stroke: persisting neurological deficit > 24 hours, infarct on CT or MRI
What are lacunar strokes?
small and hard to see
in the small arteries caused by high blood pressure or diabetes
What is acute stroke mangement?
ABCs, reperfusion, neuroprotection
prevent complications (seizures, infection)
rehabilitation
What is stroke prevention?
treat vascular risk factors (hypertension, diabetes, hyperlipidemia, smoking, atrial fibrillation)
antiplatelet or anticoagulant
treat underlying cause
What are the steps of acute stroke treatment?
- ABCs
- Recanalization: time is brain (~1.9 million neurons lost / minute), IV TPA (tissue plasminogen activator), endovascular therapy (stent retriever)
- Neuroprotection: no approved neuroprotective drug, 120 trials, prevent hyperglycemia, hypoxia, hypoperfusion, hyperthermia
What is tissue plasminogen activator?
tPA activates plasminogen to form plasmin
plasmin degrades fibrin based blood clots
What are the effects of tissue plasminogen activator on ischemic stroke?
absolute benefit 11-13%
30% better chance of mild neurologic deficit at 3 months
risk of brain hemorrhage 6.4%
What is endovascular therapy?
EVT removes blood clot
EVT reduces those dead or dependent from 71% to 47%
How are patients selected for endovascular therapy?
time is brain (early reperfusion better)
small core infarct (ASPECTS, Perfusion Imaging (CTP))
large artery occlusion (CTA, MRA, NIHSS>8, LAMS>4)
How is further brain injury prevented after a stroke?
blood pressure (not too high and not too low)
glucose (hyperglycemia worsens stroke)
infection (prevent pneumonia, dysphagia screen, NPO)
temperature (euthermia, brain cooling ICTUS trial, works well on animals puts humans at risk for infections, don’t do it in clinics)
What examples of stroke prevention?
diet: low fat, low salt
exercise: >30 minutes, 3-4 times per week
smoking cessation: cuts stroke risk in half
stop heavy consumption
hypertension (top risk factor for stroke)
diabetes: goal euglycemia
hyperlipidemia: stains prevent stroke
What is carotid atherosclerosis?
artery-artery embolism
fatty streak –> fibrous plaque –> plaque rupture –> thrombosis
carotid disease stenosis >50%
treatment: carotid endarterectomy or stent
What is intracranial atherosclerosis?
treatment: medical management
angioplasty/stenting only for patients refractory to medical management
What is carotid or vertebral dissection?
subintimal hematoma of carotid of vertebral artery
associations: trauma, connective tissue disease, atherosclerosis
angiogram: string sign, smooth tapered occlusion
treatment: antiplatelet or anticoagulation
What is a small vessel lacunar stroke?
microvascular disease: lipohyalinosis or microatheroma
caused by long standing hypertension, diabetes
treatment: antiplatelet (controlling blood pressure, diabetes)
What are cardioembolic stroke?
15-20% of ischemic strokes
clots forms in heart, embolizes to brain
What is atrial fibrillation?
atrium (on top) is contracting irrhythmically
causes formation of clots and stroke
What is anticoagulation indicated for?
atrial fibrillation, left ventricular thrombus, mechanical valve
What are antiplatelets indicated for?
for all TIAs or Ischemic stroke unless anticoagulation indicated
What are the types of hemorrhagic stroke?
epidural hemorrhage (on top of dura)
subdural hemorrhage (subdural space)
subarachnoid hemorrhage (pia mater)
intracerebral hemorrhage (inside brain)
What is an intracerebral hemorrhage?
hemorrhage into brain parenchyma (blood vessel bursts and leaks blood to the brain)
neurological deficits similar to ischemic stroke, cannot distinguish by clinical presentation
headache
altered level of consciousness
What are causes of intracerebral hemorrhage?
hypertension
amyloid angiopathy
vascular malformation
brain tumor
coagulation related
brain trauma
drug (amphetamine, cocaine)
vasculitis
What are treatments of intracerebral hemorrhages?
treat underlying causes
blood pressure control
correct coagulation of abnormal
intracranial pressure management
seizures
What are subarachnoid hemorrhages?
hemorrhage into subcortical space, can become subdural, intracerebral, or intraventricular
sudden onset worse headache of life
neck stiffness
altered level of consciousness
cranial nerve III palsy
graded by Hunt + Hess scale
What is the cause of subarachnoid hemorrhages?
intracranial aneurysm rupture
