Strokes Flashcards
ischemia
inadequate blood supply (including O2 and glucose)
prolonged ischemia results in ____
infarction (cell death)
anoxia
inadequate oxygen supply
what can cause a stroke?
- ischemia: result of occlusion (blocked a due to atherosclerosis or blood clot)
- hemmorrhage (bleeding a due to ruptured aneurism or hypertension)
- hypotension
what is the cause of the majority of strokes?
ischemia (caused by clotting)
what are the types of blood clots that cause ischemic stroke?
- thrombotic (eg. lacunar)
- embolic
when does a thrombotic stroke usually occur?
when a large artery to the brain is blocked by a blood clot (thrombus) that forms as a result of atherosclerosis
(occurs at site of formation)
atherosclerosis is a chronic inflammatory response where ____ and ____ are released
macrophages
neutrophils
the immune system releases ____ in response to inflammatory mediators of atherosclerosis, which function to…
cytokines
attract more white blood cells and perpetuate the cycle
in atherosclerosis, injured arterial walls fail to produce enough ____, which leads to…
- nitric oxide (maintains BV elasticity)
- arteries become calcified & lose elasticity
how does a thrombus form?
- atherosclerosis -> macrophages & neutrophils
- immune system -> cytokines
- injured walls -> insufficient NO -> calcified aa
- arterial walls stenose -> occlusion of blood flow
in atherosclerosis, arterial walls…
stenose: slowly thicken, harden & narrow until blood flow is reduced
Lacunar stroke
thrombotic stroke of small branches of large vessels that supply the brain
a lacunar stroke may cause…
clumsiness
weakness
emotional variability
(depending on branch affected)
an embolic stroke is usually caused by an ____
embolus: a dislodged blood clot that has traveled through the blood vessels, leading to embolic stroke
what are 4 possible causes of an embolus?
- atrial fibrillation: blood pooled in atria forms clots which break off and travel to brain as emboli
- artificial heart valves or heart valve disorders
- heart attack or failure
- emboli formed from fat particles, tumor cells, or air bubbles that travel through the blood stream (rare)
in a healthy brain, neurons are protected from exposure to blood by the ____
blood-brain barrier
what is the blood-brain barrier?
a wall of tiny vessels and astrocytic feet
what occurs in a hemorrhagic stroke?
- arteries weaken & break open
- blood-brain barrier is broken
- accompanied by a catastrophic headache
name 2 location-based categories of hemorrhagic strokes
- intracerebral or parenchymal (bleeding within cerebrum)
- subarachnoid (bleeding into subarachnoid space)
what causes hemorrhagic strokes?
weakened arteries break open due to:
- aneurysms
- arteriovenous malformations (AVM)
- hypertension
what is an aneurysm and how does it cause a hemorrhagic stroke?
- balloon-like dilations of arteries
- dome of dilation is fragile and may rupture and cause bleeding
what is an arteriovenous malformation and how does it cause a hemorrhagic stroke?
- abnormal connection between arteries & veins
- if it occurs in the brain & ruptures, may cause hemorrhagic stroke
hypertensive hemorrhages tend to be ____
intracerebral
what is hypotension and how does it cause a stroke?
- low BP can occur from heart attack, major bleeding, major infection, surgical anesthesia, or overtreatment of high BP
- extreme hypotension can reduce O2 supply to brain and cause stroke
name the risk factors for stroke
- age
- gender
- ethnicity
- geography
- hypertension
- atrial fibrillation
- smoking
- diabetes & insulin resistance
- obesity & sedentary lifestyle
- cholesterol & lipids
- alcohol, coffee, drug abuse
- genetics
- heart disease & treatment
- mental & emotional
- migraine
- homocysteine & vit B deficiency
stroke risk factor:
Age
- adults over 65 years most at risk, especially with 2+ risk factors
- 28% victims are <65 years
stroke risk factor:
Gender
mortality higher in women
stroke risk factor:
Ethnicity
higher risk in minority groups, especially middle-aged African Americans
stroke risk factor:
Geography
- highest risk in Southeastern US
- also high in lower Mississippi valley & Southern California
stroke risk factor:
Hypertension
- contributes to 70% of all strokes
- wider spread between systolic & diastolic = greater risk
stroke risk factor:
Atrial Fibrillation
1 in 6 strokes due to A-fib
stroke risk factor:
Smoking
- pack a day = 2.5x greater risk as non-smokers
- increases both hemorrhagic & ischemic stroke risk
stroke risk factor:
Obesity & sedentary lifestyles
weight centered around abdomen = high association w stroke & heart disease
stroke risk factor:
Cholesterol & other lipids
- HDL important for preventing strokes
- hypertensive pts with overall cholesterol levels <180mg/dl = risk for hemorrhagic stroke
stroke risk factor:
Alcohol, Coffee, & Drug abuse
- alcohol: heavy use = higher risk of ischemic & hemorrhagic; mild/moderate = lower risk ischemic, higher risk hemorrhagic
- coffee: 3+ cups/day = higher risk in older men w/hypertension
- Drug abuse (ie., cocaine, methamphetamine, steroids)
stroke risk factor:
Mental & emotional factors
- Stress: men w/ intense response to stress, chronic or frequent stress (higher BP) = higher risk
- Depression: higher risk of stroke and lower survival rates
stroke risk factor:
migraines
- migraine/severe headache = higher risk, especially before age 50 (diminishes with age)
- oral contraceptives = higher risk in young women who have auras
- taking decongestants may increase risk in those w migraines
stroke risk factor:
Homocysteine & vitamin B deficiencies
- abnormally high homocysteine levels occur with deficiencies of vit B6, B12, & folic acid = high risk of CAD & stroke
- homocysteine = major risk factor (second to high BP)
stroke risk factor:
infections
may play a role in atherosclerosis and heart disease & stroke (inflammatory response)
- Lung infections (chlamydia pneumoniae)
- Periodontal (gum) disease
- Vericella Zoster Virus (chicken pox & shingles)
what is a transient ischemic attack?
- a focal loss of neurological function that usually resolves within 24hrs
- mini-ischemic stroke, usually caused by tiny emboli that lodge in artery to brain
- blood supply quickly restored = no residual damage/symptoms
- warning sign for ischemic stroke
silent brain infarctions
- small strokes that cause no apparent symptoms but are major contributors to mental impairment in elderly (multi-infarct dementia)
- up to 31% of elderly people
- higher risk in smokers & hypertension
what is syncope?
sudden reversible loss of consciousness and postural tone (fainting) that results from temporary global cerebral ischemia
what can cause syncope?
- hypotension
- decreased cardiac output
- blood & metabolic disorders
- CNS disorders
