STROKE Patho Flashcards
What is stroke?
A stroke occurs when a blood vessel that carries O2 and nutrients to the brain is either blocked by a clot or ruptures –> brain cannot get the blood (and O2) it needs, so brain cells die
How is stroke characterized?
Neurological deficit caused by an acute, focal injury to the CNS due to a vascular (blood vessels) cause
How is stroke classified?
Ischemic stroke, Hemorrhagic stroke (Intracerebral or Subarachnoid) and TIA
Ischemic stroke
Involves vascular injury (infarct) to the brain, SC or retina related to ischemia with sx persisting for >/= 24 hrs
TIA
A transient episode of neurological dysfunction caused by focal brain, SC or retinal ischemia without acute infarction
Hemorrhagic stroke
Intracerebral –> caused by focal collection of blood within the brain parenchyma or ventricles, not related to trauma (direct bleeding into brain)
Subarachnoid – caused due to bleeding into the subarachnoid space, not related to trauma
Stroke breakdown by gender
- Upto 80 years old, men survive stroke more than women
- After 80, women survive more
- Stroke incidence is same till age 60
-After age 60, men tend to get more strokes than women
-After age 60, incidence of stroke doubles
Why does an ischemic stroke occur?
- Occurs due to blockage resulting from in-situ thrombosis in a blood vessel or clot embolization
- Embolization could occur from a proximal artery to a distal artery or from the heart
- Lack of cerebral blood flow –> neuronal damage and cell death
(Loss of supply of O2 and glucose –> collapse of energy producing processes in neurons –> disintegration of cell structures and membranes leading to necrosis)
What is ischemic core and penumbra?
Ischemic core - tissue that has already experienced irreversible damage and cannot be salvaged
Penumbra –> tissue at risk –> hypo- perfused tissue surrounding the ischemic core –> may be salvaged by acute reperfusion therapy but delay in tx leads to permanent, irreversible damage
Signs of stroke
F - Is face drooping?
A - Can you raise both arms?
S - Is speech slurred or jumbled?
T - time to call 911 right away
What arteries supply blood to the brain?
- Common carotid artery (Internal/anterior and External/various facial structures)
- Vertebral artery (Basilar artery to create vertebrobasilar system - posterior BS)
- Internal carotid arteries and vertebral arteries feed into the circle of willis
- The arteries of the circle of willis connects circulation from the anterior to the posterior portion of the brain
- This collateral circulation allows for blood flow to be redirected in the event of an obstruction –> blood redirected to damaged part of the brain (People with complete circle of willis tend to have better collateral circulation and smaller infarcts in stroke)
Stroke etiology
Ischemic stroke –> Large artery Atherosclerosis, Small artery disease, Cryptogenic, Cardiac embolism, Unusual
Hemmorhagic stroke –> ICH, SAH
Large artery atherosclerosis (patho/most affected areas)
- Includes both extracranial (common and internal carotids, vertebral artery) and intracranial system (circle of willis and proximal branches)
- Most common cause is build of plaque
- May be caused due to in-situ thrombosis in the affected vessel or due to artery to artery embolization
- Intermittent progression of sx –> over several mins to hours
Pathogenesis: plaque forms at branching points and curves of cerebral arteries
Most commonly affected areas-
1. Internal carotid artery at its origin from common carotid
2. Vertebral artery at origin from the subclavian vessels or at its junction to form the basilar artery
3. Main bifurcation of the middle cerebral artery
Cardiac embolism
- Fragment broken away from a thrombus within the heart –> either one of the heart chambers or from a heart valve and blocks arteries in the brain
Thrombus formation may occur due to:
- pre-existing cardiac conditions (Afib)
- valvular heart disease
- patent foramen ovale (hole between left and right side of heart)
May affect any part of the brain
- embolus attaches to a bifurcation point or narrowed vessel
Sx develop rapidly within seconds
Small artery disease
- Caused due to occlusion in the small penetrating branches of the cerebral arteries (0.2-15 mm in diameter) –> deeper parts of the brain
- Necrotic tissue from the infarct is removed by macrophages resulting in the formation of a small cavity or lacune
- Sx appear over few hrs to days and in some cases may be asymptomatic
Pathogenesis of lacunar stroke
Usually caused by:
- thickening of small vessel walls due to lipid build up in the wall structure –> lipohyalinosis (most common)
- atherosclerosis in larger blood vessels that occludes the origin of smaller blood vessels
- entry of small embolic material into smaller blood vessels (rare)
Strong relationship with vascular disease: HTN and Diabetes
Non-modifiable risk factors of ischemic stroke
Age –> risk of stroke increases with age, men tend to have it more after 60
Gender
Ethnicity –> risk twice as high in african americans vs caucasians
INTERSTROKE 2 study
PAR - contribution of risk factor to stroke
HTN –> increases risk of ischemic stroke and intracerebral haemorrhage (more ICH risk)
Good regular physical activity (4 hours of mod-severe in 1 week) will decrease risk of stroke
Smoking mostly increases risk of Ischemic stroke
High hip to waist ratio –> increased stroke
ApoB/A1 –> increases risk of ischemic stroke mostly
History of diabetes or HbA1C >/= 6.5% –> risk of ischemic stroke
Having a good diet decreases risk of stroke
Alcohol can increase risk of stroke but weak association
Psychosocial factors (stress and depression) increase risk of stroke
Cardiac causes (Afib, AFL) increases risk of stroke
Afib affects ischemic stroke
S/S of Ischemic stroke
Depends on area of infarction in the brain but typically involve:
- Numbness/weakness in the face, arm or leg esp on one side
- Sudden confusion, trouble speaking, or difficulty understanding speech
- Trouble seeing in one or both eyes
- Trouble walking, dizziness, loss of balance or lack of coordination
MCA stroke syndrome
MCA provides supply to the frontal, parietal and temporal lobes
Subdivided into 4 main dvisions: M1, M2, M3 and M4
Infarcts occur most commonly in the M1 and M2 sections
Superior division affects broca area(speech), motor and sensory
Inferior division affects visual cortex, wernicke area (language and comprehension), auditory area
What happens if there is occlusion of the main stem? (MCA)
-contralateral hemiplegia involves face, arm and legs (paralaysis)
-contralateral hemianesthesia is the loss of sensation on contralateral side
-contralateral homonymous hemianopia: visual field loss on the same side of both eyes
-deviation of head and eyes to the side of the lesion
-dysarthria (if left hemisphere affected) –> slurred/slow speech
ACA occlusion
Provides circulation to the medial portion of the frontal lobe and the superior medial portion of the parietal lobe
Common features:
- sensorimotor deficits in the contralateral foot and leg, less in upper extremities
-urinary incontinence
-language disturbances (dysarthria or mutism or speak in whispers)
-behavioural disturbances (abulia, distractibility and mood changes)
Abulia: slowness or lack of spontaneity in reactions, reduction in reflexes
PCA occlusion
Provides circulation to the occipital lobe and the medial temporal lobe
Mainly visual field deficits
- contralateral homonymous hemianopia
-partial or complete vision loss and visual hallucinations
Anomia- inability to name objects but can describe them
Short term or long term memory loss due to temporal lobe involvement
Subarachnoid Haemorrhage (SAH)
Extravasation of blood into the SA space resulting in mixing of blood and CSF
Typically occurs in younger pts
80% caused by aneurysmal rupture
Neurologic emergency if bleeding caused by trauma
