Cerebral Hemispheres & Vascular Supply Flashcards

1
Q

Main Functional Areas of Cerebral Cortex

A
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2
Q

Circle of Willis

A
  • Arterial supply to the cerebral hemispheres.
  • An anastomotic ring giving collateral circulation.
  • Anterior circulation.
  • From brachial cephalic trunk or aorta > internal carotid aa.
  • Posterior circulation.

From subclavian aa. > transverse foramen / vertebral aa. > basilar arter

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3
Q

Anterior & Posterior Circulation

A
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4
Q

Anterior & Posterior Circulation

A
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5
Q

Main Arteries of the Circle of Willis

A
  • Anterior cerebral artery (ACA).
  • Anterior communicating aa. (AComms) link the ACAs.
  • Middle cerebral artery (MCA).
  • Posterior cerebral artery (PCA).
  • Arise from the top of the basilar a.
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6
Q

Main Arteries of the Circle of Willis

A
  • The anterior & posterior circulations are linked via the posterior communicating aa. (PComms).
  • PComms connect internal carotids to PCA.
  • Brainstem branches & cerebellar aa. arise from basilar a.
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7
Q

Figure 10.3 Circle of Willis and Its Main Branches

A
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8
Q

Internal Carotid Artery

A
  • Named segments.
  • Cervical segments.
  • Petrous segment.
  • Cavernous segment (carotid siphon).
  • Passes anterior clinoid process to pierce dura & bed posterior to subarachnoid space as intracranial segment.
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9
Q

Circle of Willis and Its Main Branches

A
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10
Q

Circle of Willis and Its Main Branches

A
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11
Q

Main Branches of Intracranial Segment of Internal Carotid Artery

A
  • OPAAM
  • Ophthalmic a. - enters optic foramen with optic n.
  • Posterior communicating a.
  • .Anterior choroidal a.
  • Anterior cerebral a.
  • Middle cerebral a.
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12
Q

Territories of 3 Main Cerebral Aa.
Superficial Cerebral Structures

A
  • ACA (anterior cerebral artery) travels in interhemispheric fissure and back over corpus callosum.
  • Supplies most of cortex on anterior medial surface from frontal > parietal lobes & medial sensorimotor cortex.
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13
Q

Anterior Cerebral Artery

A
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14
Q

Arteries of the Brain

A
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15
Q

Territories of 3 Main Cerebral Aa.
Superficial Cerebral Structures

A

•MCA turns laterally & enters Sylvian fissure.

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16
Q

Territories of 3 Main Cerebral Aa.
Superficial Cerebral Structures

A
  • MCA turns laterally & enters Sylvian fissure ad then bifurcates into
  • Superior division
  • Inferior division
  • (varies, sometimes into 3 or 4).

The branches form a loop as they pass over the insula and back out Sylvian fissure.

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17
Q

Middle Cerebral Artery -MCA

A
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18
Q

Arteries of the Brain

A
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19
Q

Territories of 3 Main Cerebral Aa.
Superficial Cerebral Structures

A
  • PCA curves back with branches over:
  • Inferior & middle temporal lobe
  • Occipital cortex.
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20
Q

Arteries of the Brain

A
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21
Q

Arteries of the Brain

22
Q

Territories of 3 Main Cerebral Aa.
Superficial Cerebral Structures

A
  • MCA turns laterally & enters Sylvian fissure ad then bifurcates into
  • Superior division
  • Inferior division
  • (varies, sometimes into 3 or 4).
  • The branches form a loop as they pass over the insula and back out Sylvian fissure.
23
Q

Territories of 3 Main Cerebral Aa.
Deep Cerebral Structures

A
  • **MOST IMPORTANT penetrating vessels at the base of brain = lenticulostriate aa.
  • Arise from MCA.
  • Penetrate anterior perforated substance.
  • Supply large part of basal nuclei (ganglia) & internal capsule.
  • Prone to narrowing in HTN > infarct > rupture

> hemorrhage.

24
Q

Figure 10.7 Lenticulostriate Arteries

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Territories of 3 Main Cerebral Aa. Deep Cerebral Structures
* Anterior choroidal a. arises from internal carotid aa. * Globus palladus, putamen, thalamus, (lateral geniculate nucleus?), posterior limb internal capsule (corticospinal & corticobulbar tracts). * Infarct of lenticulostriate or anterior choroidal aa. territories often=contralateral hemiparesis.
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Figure 10.8 Blood Supply to Deep Cerebral Structures (Part 1)
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Figure 10.8 Blood Supply to Deep Cerebral Structures (Part 2)
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Territories of 3 Main Cerebral Aa. Deep Cerebral Structures
* Branches of ACA. * Recurrent a. of Heubner. * Supplies head of caudate nucleus, anterior putamen, globus palladus & internal capsule. * Thalamoperforator aa. * Thalamus & maybe post. limb int. capsule.
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Figure 10.9 Summary of Superficial and Deep Blood Supply to the Cerebral Hemispheres (Part 1)
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Figure 10.9 Summary of Superficial and Deep Blood Supply to the Cerebral Hemispheres (Part 2)
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Clinical Syndromes
* MCA infarct & ischemia is common - and more common than ACA & PCA. * MCA in 3 regions: * Superior division. * Inferior division. * Deep territory. * Aphasia, hemineglect, hemianopia, face-arm or face-arm-leg sensorimotor loss. -Gaze toward side of lesion acutely
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Major Clinical Syndromes of the MCA
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Major Clinical Syndromes of the MCA
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Clinical Syndromes
* ACA * UMN lesion weakness & cortical type sensory loss affecting contralateral leg more than face or arm. * Large ACA stroke can give contralateral hemiplegia.
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Major Clinical Syndromes of the MCA, ACA, PCA
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Clinical Syndromes
•PCA . Contralateral homonymous hemianopia. •Small penetrating branch can infarct thalamus, posterior limb of internal capsule with sensory loss, contralateral hemiparesis or a thalamic aphasia (so can mimic MCA).
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Watershed Infarcts
* When blood supply to 2 adjacent arteries are compromised, region between 2 vessels are susceptible to ischemia/infarct. * Watershed zone. * Bilateral watershed infarcts in both ACA-MCA & MCA-PCA watershed zones can occur with severe drop in systemic BP. * Occlusion of internal carotid a. or drop in BP in patient with carotid stenosis can cause ACA-MCA watershed infarct.
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Watershed Infarcts
* Proximal arm & leg weakness (“man in a barrel syndrome”). * In dominant hemisphere – transcortical aphasia syndromes. * MCA-PCA infarct can cause higher order visual processing.
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Figure 10.10 Watershed Zones for the Major Cerebral Arteries
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Transient Neurological Episodes
* Common, motor, somatosensory, visual, auditory, olfactory, kinesthetic, emotional, or cognitive. * Most common causes: * Transient ischemic attack (TIA). * Migraine. * Seizure. * Cardiac arrhythmia. * Hypoglycemia.
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TIA
* Neurological deficit lasting less than 24 hours. * Most typical less than 10 minutes. * More than 10 minutes; some permanent cell death. * More than 1 hour usually small infarct; sometimes complete functional recovery within 24 hours. * Caused by temporary brain ischemia. * \*\* Warning sign. * Neurological emergency.
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TIA
* 15% will have a stroke within 3 month with persistent deficits. * ½ of these occur within 48 hours. * Urgent referral, admittance, & evaluation for treatment.
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* 15% will have a stroke within 3 month with persistent deficits. * ½ of these occur within 48 hours. * Urgent referral, admittance, & evaluation for treatment.
* Without other focal features… * Most commonly by cardiogenic syncope. * Vasovagal transient episodes of hypotension. * Arrhythmias. * Other non-neurogenic causes. * Neurologic causes: * Seizures.
44
Ischemic Stroke
* 3rd leading cause of death in U.S.A. * Major cause of permanent disability. * Acute diagnostic & therapeutic management essential, treated like severity of cardiac emergencies. * Ischemic strokes can lead to hemorrhagic conversion. * Inadequate blood supply causing tissure death. * Embolic infarct. * Thrombotic infarct.
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Common Stroke Risk Factors
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Carotid Auscultations
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Circle of Willis
* Complete the following learning module on the Circle of Willis. * http://www.neuroanatomy.ca/flex\_labs/Circle\_Willis/story\_html5.html
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Ischemic Stroke | (Use Blumenfeld pp 405 - 409.)
* For the following, define & discuss the mechanisms of pathology: * Embolic infarcts & cause. * Thrombolic causes and mechanism. * Large vessel infarct. * Small vessel / lacunar infarct. * Cortical vs. subcortical. * Hemispheric vs. brainstem lesions. * Stroke risk factors. * Treatment & diagnostic workup.
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Stenosis & Dissection, Thrombosis | (Use Blumenfeld pp 410 – 411, 413.)
* For the following, define & discuss the mechanisms of pathology: * Carotid stenosis. * Dissection of the carotid & vertebral aa. * Sagittal sinus thrombosis.
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