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What is ischemia?
Inadequate blood supply to an area
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What is infarction?
Death of tissue due to ischemia
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"Bleeds"
- Hemorrhage into the brain or subarachnoid space
- Often from aneurysm
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What is an aneurysm?
- Congenital abnormal sac on vessel
- Weakens vessel wall
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"Blocks"
1. Slow
2. Fast
- Occulisve process
- 1. Arteriosclerosis produces thrombus
- 2. Embolus produces sudden occlusion
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Transient Ischemic Attacks
Temporary deficits (cerebral or retinal)
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Transient Global Amnesia
- Temporary Memory disturbance
- Anoxia of the hippocampus
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Major Vertebral A. Branches and supplied areas
- Anterior Spinal Artery - medial medulla
- Bulbar Branches - lateral medulla
- Posterior Inferior Cerebellar Artery - lateral medulla
- Basilar Artery
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What is the result of an Anterior Spinal A. Infarct?
Inferior alternating hemiplegia
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What is the result of a PICA or Bulbar A. Infarct?
- Lateral medullary snydrome of Wallenberg
- - ipsilateral face - pain/thermal loss
- - contralateral body - pain/thermal loss
- - ipsilateral Horner's syndrome
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Major Basilar A. Branches and areas supplied
- Anterior Inferior Cerebellar A. - caudal pons, caudal cerebellum
- Labyrinthine A. - inner ear
- Paramedian A. - medial pons
- Circumferential A. - lateral pontine tegmentum
- Superior Cerebellar A. - rostral pons, rostral cerebellum
- Posterior Cerebral A. - crus cerebri
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What are the symptoms of a Paramedian Infarct?
- Contralateral dorsal column deficits - medial lemniscusContralateral hemiplegia - corticospinal tractCN III, VI, XII effected
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What are the symptoms of lateral Infarcts?
- Ipsilateral Horner's syndrome
- Ipsilateral V deficit
- Contralateral spinothalamic deficit
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Major Branches of the ICA
- Opthalmic
- Posterior Communicating A.
- Anterior Choroidal A.
- Anterior Cerebral A.
- Middle Cerebral A.
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What is the target of the cortical branches of the Circle of Willis?
surface of the cerebral cortex
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What is the target of the central branches of the Circle of Willis?
Deep structures (hypothalams, thalamus, basal ganglia, hippocampus, amygdala, globus pallidus)
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What are the Cortical branches of the Circle of Willis?
- Anterior Cerebral A.
- Posterior Cerebral A.
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Branches and targets of the Anterior Cerebral A.
- Frontopolar A. - orbit and frontal lobe
- Callosomarginal A. - Paracentral lobule and cingulate gyrus
- Pericallosal A. - parietal lobe, precuneus, corpus callosum
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ACA Infarcts
- Personality changes (prefrontal cortex)
- UMN/sensory deficit in contralateral lower extremity (paracentral lobule)
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Branches and targets of the Posterior Cerebral A.
- Anterior Br. - inferior temporal lobe
- Calcarine A. - Primary visual cortex
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PCA Infarcts
Contralateral homonymous hemianopsia (visual field)
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Target of the Middle Cerebral A.
- Inf/middle frontal gyri
- Pre/postcentral gyri
- Sup/middle temporal gyri
- Inf parietal lobule
- Lat occipial lobe
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What is the Sylvian Triangle and what is its significance?
- Insular branches of the MCA create a triangle shape
- If displaced in angiogram, provides location of space-occupying lesion
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What is a "lacunar" infarct and why are we at risk?
- Small, local infarctions due to bleeds or occlusions of small central branches of circle of willis
- These do not anastomose effectively
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Branches and targets of the Medial Central branches of the Circle of Willis
- Anteromedial - ant. hypothalamus and preoptic area
- Posteromedial - post. hypothalamus, anteromedial thalamus, subthalamic nucleus
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Branches and targets of the Lateral Central branches of the Circle of Willis
- Medial Striate (Huebner) - basal ganglia, ant. internal capsule
- Lateral Striate (lenticulostriate) - basal ganglia, internal capsule
- Posterior Lateral (thalamogeniculate) - post. thalamus
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What are the targets of the Anterior Choroidal A.?
- Hippocampus
- Amygdala
- Globus Pallidus
- Post. Internal Capsule
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Capsular Infarcts: affected fibers and resulting deficits
1. Anterior limb
2. Genus
3. Posterior limb
4. Retrolenticular Portion
- 1. corticostriate - dyskinesia2. corticobulbar - central voluntary facial palsy
- 3. corticospinal/somatosensory - contralateral hemiplegia and contralateral sensory loss 4. optic & auditory radiations - contralateral homonymous hemianopsia, contralateral hearing diminution
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