MIDDLE CEREBRAL ARTERY (MCA)• Supplies most of the temporal lobe, anterolateral frontal lobe, and parietal lobe.• Perforating branches supply the posterior limb of the internal capsule, part of the head and body of the caudate and globus pallidus.• Unilateral occlusion of Middle Cerebral Arteries at the stem (proximal M1 segment) results in: • Contralateral hemiplegia affecting face, arm, and leg (lesser). • Homonymous hemianopia - Ipsilateral head/eye deviation. • If on left: global aphasia.• Usually occlusion is embolic in nature - thrombotic occlusion more common in carotids.
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.
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 (Meyers loop: optic radiations affected).
MCA – (M 2) Sylvian segment• 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
MCA – (M 2) Sylvian segment• 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.
MCA – (M 3) Cortical segment• Distal branches of MCA course laterally to insular cortex and loop around operculum - "Candelabra" effect seen on lateral angiograms.• Embolization of individual cortical branches can produce highly circumscribed infarctions accompanied by specific neurologic deficits.
ANTERIOR CEREBRAL ARTERY (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 caudate and anterior globus pallidus.
ANTERIOR CEREBRAL ARTERY (ACA)• Bilateral occlusion of Anterior Cerebral Arteries at their stems results in infarction of the anteromedial surface 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 humunculus)
ACA – A 1 SEGMENT• From Internal Carotid Bifurcation to Anterior Communicating Artery.• A1 Branches: Anterior Communicating Artery (connects both sides of anterior circulations). Medial Lenticulostriate Arteries(supply basal ganglia, anterior limb of internal capsule). Recurrent Artery of Heubner(supplies head of caudate and anteroinferior internal capsule)
ACA – Anterior communicating art• Connects bilateral anterior circulations. Common location for cerebral aneurysms.
ACA – Recurrent artery of Heubner• Supplies head of caudate and anteroinferior internal capsule.
ACA – Pericallosal artery• Continuation of the Anterior Cerebral Artery as it arches superiorly and posteriorly. Supplies the medial surface of the cerebral hemispheres and corpus callosum.
ANTERIOR CHOROIDAL ARTERYArises from ICA (rarely from MCA also)The anterior choroidal artery serves many structures in thecerebrum:• 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• crus cerebri
ANTERIOR CHOROIDAL ARTERYLesions lead to:Contralateral hemiplegiaContralaterial hemi-hypoaesthesiaHomonymous hemianopsiaDue to ischemic involvement of:Internal capsuleThalamusOptic chiasm/Optic tract
CIRCLE OF WILLIS• Communication between the anterior and posterior circulations
WATERSHED AREASThere are two patterns of border zone infarcts:Cortical border zone infarctions:Infarctions of the cortex and adjacent subcortical white matter located at theborder zone of ACA/MCA and MCA/PCAInternal border zone infarctionsInfarctions of the deep white matter of the centrum semi-ovale and coronaradiata at the border zone between lenticulostriate perforators and the deeppenetrating cortical branches of the MCA or at the border zone of deep whitematter branches of the MCA and the ACA