Areas n Ant Circ

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12/8/12

Dr.Mohammed Sadiq AzamPostgraduate, Prof.Sirajs unit, M:I

Deccan College of Medical Sciences

FUNCTIONAL ANATOMY OF THE

CEREBRAL HEMISPHERES &

ANTERIOR CIRCULATION


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BRAIN FUNCTIONAL

ANATOMY


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BRODMANNS AREAS


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ANTERIOR CIRCULATION

Internal Carotid Artery -

main artery

Terminates into :

Anterior cerebralartery

Middle cerebral artery

Forms the crux of the

anterior circulation.


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MIDDLE CEREBRAL ARTERY

(MCA)


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MIDDLE CEREBRAL ARTERY

(MCA)

Supplies most of the temporal lobe, anterolateralfrontal lobe, and parietal lobe.

Perforating branches supply the posterior limb ofthe internal capsule, part of the head and body ofthe caudate and globus pallidus.

Unilateral occlusion of Middle Cerebral Arteriesat the stem (proximal M1 segment) results in:

Contralateral hemiplegia affecting face, arm, andleg (lesser).

Homonymous hemianopia - Ipsilateral head/eye

deviation.

If on left: global aphasia.

Usually occlusion is embolic in nature -thrombotic occlusion more common in carotids.


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MCA (M 1) Horizontal segment Branch: Lateral lenticulostriate a

Unilateral occlusion of

Proximal M1 Segment

results in deficits in:

MOTOR

Contralateral Hemiplegia

(face and arm, lower extremity less affected.

SENSORY

Homonoymous Hemianopia + Deviation of head/eyes toward the

side of the lesion.

LANGUAGE

LEFT lesions: Global aphasia.

RIGHT lesions: Anosognosia.


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MCA (M 1) Lateral

lenticulostriate art.

Branch of M1 Segment of MCA.

Supplies basal ganglia structures:

Part of head and body of caudate, globus pallidus, putamen,and the posterior limb of the internal capsule.

Effect of lesion:

Damage to the internal capsule resulting in contralateral

hemiparesis and sensory deficit.

Speech may be affected (medial temporal lobe) as well as

visual function (Meyer's loop: optic radiations affected).


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MCA (M 2) Sylvian segment


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Divides into superior and inferior divisions: can be a site

for an embolus to lodge.

Branches supply:

Temporal Lobe and Insular Cortex (sensory language area

of Wernicke)

Parietal Lobe

(Sensory cortical areas)

Inferolateral frontal lobe


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Superior Division Infarction:

"Brachiofacial paralysis"Sensorimotor deficit involving face and arm, leg

to a lesser extent. Foot is spared.

Ipsilateral deviation of head/eyes.

With Left lesion may have initial global aphasia

-> motor aphasia.

No impairment of alertness.

Inferior Division Infarction:

Rarer than Superior Division Infarctions.Superior quadrantanopia / homonymous

hemianopia.

LEFT lesion: Wernicke aphasia (deficit in

comprehension of spoken/written language)

RIGHT lesion: Left-sided visual neglect.


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MCA (M 3) Cortical segment

Distal branches of MCA

course laterally to insular

cortex and loop around

operculum - "Candelabra"

effect seen on lateralangiograms.

Embolization of

individual cortical

branches can produce

highly circumscribed

infarctions accompanied

by specific neurologic

ANTERIOR CEREBRAL ARTERY


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(ACA)



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(ACA)

Supplies most of the medial surface of the

cerebral cortex (anterior three fourths), frontal

pole (via cortical branches), and anterior

portions of the corpus callosum.

Perforating branches (including the recurrent

artery of Heubner and Medial Lenticulostriate

Arteries) supply the anterior limb of the internal

capsule, the inferior portions of head of the



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(ACA) Bilateral occlusion of Anterior Cerebral Arteries at

their stems results in infarction of the anteromedialsurface of the cerebral hemispheres:

Paraplegia affecting lower extremities and sparing

face/hands.

Incontinence

Abulic and motor aphasia

Frontal lobe Symptoms: personality change,

contralateral grasp reflex.

Unilateral occlusion (distal to Ant. Comm. origin) of

Anterior Cerebral Artery produces contralateral

sensorimotor deficits mainly involving the lower

extremity with sparing of face and hands (think of the


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ACA A 1 SEGMENT

From Internal Carotid Bifurcation

to Anterior CommunicatingArtery.

A1 Branches:Anterior Communicating Artery

(connects both sides of anteriorcirculations).

Medial LenticulostriateArteries(supply basal ganglia,anterior limb of internal capsule).

Recurrent Artery ofHeubner(supplies head ofcaudate and anteroinferiorinternal capsule)


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ACA Anterior communicating art

Connects bilateralanterior circulations.

Common location forcerebral aneurysms.

ACA R t t f


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ACA Recurrent artery of

Heubner

Supplies head ofcaudate and

anteroinferiorinternal capsule.


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ACA Pericallosal artery

Continuation of theAnterior CerebralArtery as it arches

superiorly andposteriorly.

Supplies the medialsurface of thecerebral

hemispheres andcorpus callosum.


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ANTERIOR CHOROIDAL ARTERY

Arises from ICA (rarely from MCA also)

The anterior choroidal artery serves manystructures in the cerebrum:

choroid plexus of the lateral ventricle and third

ventricle

optic chiasm and optic tract

internal capsule

lateral geniculate body

globus pallidus

tail of the caudate nucleus, hippocampus,

amygdala

substantia nigra

red nucleus


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ANTERIOR CHOROIDAL ARTERY

Lesions lead to:

Contralateral hemiplegia

Contralaterial hemi-hypoaesthesia

Homonymous hemianopsia

Due to ischemic involvement of:

Internal capsule

Thalamus

Optic chiasm/Optic tract


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CIRCLE OF WILLIS

Communication between the anterior and posterior

circulations


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WATERSHED AREAS


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WATERSHED AREAS

There are two patterns of border zone infarcts:

Cortical border zone infarctions:

Infarctions of the cortex and adjacent subcortical white matter

located at the border zone of ACA/MCA and MCA/PCA

Internal border zone infarctions

Infarctions of the deep white matter of the centrum semi-ovale

and corona radiata at the border zone between lenticulostriate

perforators and the deep penetrating cortical branches of the

MCA or at the border zone of deep white matter branches of

the MCA and the ACA

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