27A Ischemic Stroke Flashcards
TIA symptoms occur within what time frame?
1 hr
Non-modifiable stroke risk factors:
- Age (doubles each year after 55)
- Gender (M 1.5x > than F)
- Rcae (AA = 2x)
- Family hx
Modifiable stroke risk factors:
HTN DM hyperlipidemia Smoking Carotid a stenosis Afib Obesity Phys inactivity
What modifiable risk factors have a high relative risk? Which are more prevalent?
Afib (RR = 5-17)
HTN (RR=3-5)
HTN»_space; smoking, hyperlip, inactivity
2 conditions which exacerbate brain injury:
- hyperglycemia (increased lactic acid)
2. hyperthermia (accelerates damage)
What is core ischemia?
central area of ischemia (no collateral flow); tissue dies in <1hr, permanent damage
What is penumbra?
peripheral areas of moderate ischemia; tissue dies in 4-6h, so CAN be salvaged with intervention
Why does acute stroke intervention have a 4-6h time frame?
time from of the evolving ischemic infarct ~4-6h
Cerebral blood flow is proportionally related to:
MAP/CVR
*cerebral vasc resistance
The relationship between CBF and MAP for the normal individual is a sigmoid curve with a plateau of CBF between MAPs of ___ and ___ mm Hg.
What does this demonstrate?
55 and 155 mmHg
in this range, CBF is pretty independent of MAP
How does CBF change with daily activities?
in normal individuals, it doesnt
this is because CBF is pretty independent of MAP when in the normal range
What happens when the MAP falls below 55 or climbs above 155 mm Hg?
CBF becomes proportionally related to MAP
- -> syncope (if below 55)
- -> hypertensive encephalopathy (if above 155)
How does chronic HTN affect the CBF?
shifts to the R
(The critical point at which CBF becomes proportionately related to MAP has been raised from 55 to approximately 75 mm Hg)
How does chronic HTN change the effects of a low-end of nml MAP?
decreased CBF
What happens when CBF drops below 20?
brain tissue will develop an infarction
**ischemic tissue loses all autoreg control
Anterior circulation strokes involve occlusion of:
internal carotid, middle cerebral, anterior cerebral arteries or any of their branches
Posterior circulation strokes involve occlusion of:
posterior cerebral, superior cerebellar, anterior inferior cerebellar, posterior inferior cerebellar, or vertebro-basilar arteries or any of their branches
What functional brain areas are supplied by the middle cerebral artery?
frontal eye fields
motor + sensory (to hip, trunk, shoulder, arm, hand, neck, face)
**also Broca’s, Wernicke’s???
What are the small penetrating branches of the MCA?
lenticulostriate arteries
Why shouldn’t you quickly lower the BP of someone with uncontrolled HTN to 120/80?
decreasing the MAP that significantly would proportionally reduce CBF causing low perfusion
Arteries supplying the mid-pons:
basilar
circumferential basilar
Arteries supplying the caudal pons:
basilar
ant inf cerebellar
Arteries supplying the rostral medulla:
ant spinal
post inf cerebellar
Medullary stroke syndrome (Wallenberg) results from ischemia in what arteries?
post inf cerebellar
vertebral
What are the associated lesions and symptoms associated with Wallenberg syndrome?
- spinal trigeminal nucleus + tract (ipsalateral pain/temp loss to face)
- nucleus ambiguous (dysarthria and dysphagia)
- spinothalamic tract (contralateral pain/temp loss to body)
- spinocerebellar tract (gait ataxia to ipsalateral body)
Pontine stroke syndrome results from ischemia in what arteries?
small penetrating arteries off of basilar artery
What are the associated lesions and symptoms associated with pontine stroke syndrome?
- medial longitudinal fasciculus CNVI (gaze disorders)
- medial lemniscus (contralateral loss of vibrational, proprioception, etc to body)
- corticospinal tract (contralateral hemiparesis)
- pontine nuclei + transverse cerebellar fibers (bil cerebellar symptoms?)
Midbrain stroke syndrome (Benedikt’s) results from ischemia in what arteries?
PCA
What are the associated lesions and symptoms associated with Benedikt’s stroke syndrome?
- Oculomotor complex and Edinger-Westphal Nucleus (ipsalateral palsy and loss of constriction)
- medial lemniscus (contralateral loss of discriminative touch)
- red nucleus (contralateral tremor and ataxia)
Principle signs and symptoms of anterior circulation strokes:
- contralat gaze paresis
- contralateral motor or sensory deficit
- aphasia in dominant hemisphere or neglect in nondominant hemisphere
- ipsalateral blindness or contralateral inf quadrantanopsia
Principle signs and symptoms of posterior circulation strokes:
- Weakness/sensory deficits (unilateral, bilateral or crossed face/body)
- Contralateral homonymous hemianopsia or superior quadrantanopsia
- Vertigo, NV, gait ataxia, diplopia, Horner’s, dysphagia
- altered consciousness or amnesia
What are lacunar strokes?
small areas of ischemic infarction caused by occlusion of small, penetrating brain arteries
What are the 4 lacunar syndromes?
- pure hemiparesis
- pure hemisensory deficit
- ataxia hemiparesis
- dysarthria-clumsy hand syndrome
Most common sites for lacunar strokes causing pure hemiparesis and pure hemisensory deficits?
internal capsule and pons (or VPL if hemisensory)
Most commons sites for the formation of atherothrombotic plaques:
- origins of carotid and vertebral arteries
- bifurcation of common carotid arteries
- int carotid (at siphon, and at branch points of ant and middle cerebral)
- M1 segment of middle cerebral arteries
- basilar artery
Pathogenesis of lacunar strokes?
- microatheroma
- microemboli
- lipohyalinosis
- fibrinoid necrosis
What are lipohyalinosis and fibrinoid necrosis?
histological transformation, occurs in the smooth muscle and intima of small penetrating cerebral vessels as a consequence of chronic hypertension
Major causes of cardiogenic emboli that travel to brain?
afib
valvular heart disease
mural thrombus
CNS vasculitis causes:
segmental narrowing and MULTIfocal occlusions of small and medium-sized vessels
Causes of CNS vasculitis?
- collagen vasc disease
- Giant cell (Temporal) arteritis
- infectious
