Cerebral Hemispheres & Vascular Supply Flashcards
1
Q
Main Functional Areas of Cerebral Cortex
A
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
3
Q
Anterior & Posterior Circulation
A
4
Q
Anterior & Posterior Circulation
A
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.
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.
7
Q
Figure 10.3 Circle of Willis and Its Main Branches
A
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.
9
Q
Circle of Willis and Its Main Branches
A
10
Q
Circle of Willis and Its Main Branches
A
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.
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.
13
Q
Anterior Cerebral Artery
A
14
Q
Arteries of the Brain
A
15
Q
Territories of 3 Main Cerebral Aa.
Superficial Cerebral Structures
A
•MCA turns laterally & enters Sylvian fissure.
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.
17
Q
Middle Cerebral Artery -MCA
A
18
Q
Arteries of the Brain
A
19
Q
Territories of 3 Main Cerebral Aa.
Superficial Cerebral Structures
A
- PCA curves back with branches over:
- Inferior & middle temporal lobe
- Occipital cortex.
20
Q
Arteries of the Brain
A
21
Q
Arteries of the Brain
A
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
A
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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.
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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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