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of or near the head end or toward the front plane of a body
earlier in time (同)prior

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(場所などが)前の,前部の;(…より)前に位置する《+『to』+『名』》 / (時・事件などが)以前の,先の;(…より)前の《+『to』+『名』》

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/06/26 02:07:15」(JST)

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The anterior cerebral artery (ACA) is one of a pair of arteries on the brain that supplies oxygenated blood to most medial portions of the frontal lobes and superior medial parietal lobes. The two anterior cerebral arteries arise from the internal carotid artery and are part of the Circle of Willis.

The left and right anterior cerebral arteries are connected by the anterior communicating artery.

Structure

The ACA is classified into 5 segments with the smaller branches from the ACA "callosal" arteries (supracallosal) considered as the A4 and A5 segments:^[1]

A1: this segment originates from the internal carotid artery and extends to the anterior communicating artery (AComm). The anteromedial central (medial lenticulostriate) arteries arise from this segment as well as the AComm, which irrigate the caudate nucleus and the anterior limb of the internal capsule
A2: this segment extends from the AComm to the bifurcation forming the pericallosal and callosomarginal arteries. The recurrent artery of Heubner (distal medial striate artery), which irrigate the internal capsule, usually arises at the beginning of this segment near the AComm. 4 branches arise from this segment, the:
- Orbitofrontal artery (medial frontal basal): Arises first a small distance away from the AComm
- Frontopolar artery (polar frontal): Arises after the orbitofrontal close to when A2 curves posteriorly over the corpus callosum. Could also originate from the callosal marginal.
A3: Also termed the pericallosal artery this is one of (or the only) the main terminal branches of the ACA, which extends posteriorly in the pericallosal sulcus to form the internal parietal arteries (superior, inferior) and the precuneal artery. This artery may form an anastomosis with the posterior cerebral artery.
- Callosal marginal artery: A commonly present terminal branch of the ACA, which bifurcates from the pericallosal artery. This artery in turn branches into the medial frontal arteries (Anterior, Intermediate, Posterior), and the paracentral artery, with the cingulate branches arising throughout its length. Depending on anatomical variation, the callosal marginal artery may be none discrete or not be visible. In the latter case, the branches mentioned will originate from the pericallosal artery. In a study of 76 hemispheres, the artery was present in only 60% of the cases.^[2] Angiography studies cite that the vessel can be seen 67% ^[1] or 50%^[3] of the time.

Function

Areas supplied by the anterior cerebral artery include:^{[citation needed]}

The medial surface of the frontal lobe by the medial orbito-frontal artery, and parietal lobes
The anterior four- fifths of the corpus callosum
Approximately 1 inch of the lateral surfaces of frontal and parietal lobes, next to the medial longitudinal fissure
Anterior portions of the basal ganglia and internal capsule
Olfactory bulb and tract

Clinical relevance

Occlusion

Occlusion of the anterior cerebral artery may result in the following defects:^[4] If stroke occurs prior to the anterior communicating artery it is usually well tolerated secondary to collateral circulation. Occlusion of A2 segment(Post communal segment of Anterior cerebral artery) the following signs and symptoms may be noted.

Paralysis or weakness of the contralateral foot and leg due to involvement of Motor leg area
Cortical Sensory loss in the contralateral foot and leg
Gait apraxia Impairment of gait and stance
Abulia akinetic mutism, slowness and lack of spontaneity
Urinary incontinence which usually occurs with bilateral damage in the acute phase
Frontal Cortical release reflexes: Contralateral grasp reflex, sucking reflex, gegenhalten(paratonic rigidity)

Additional images

Anterior cerebral artery
Medial surface of cerebral hemisphere, showing areas supplied by cerebral arteries. Areas supplied by the anterior cerebral artery are shown in blue.
Anterior view of cerebral circulation, including rough courses of A1, A2, and A3 with pericallosal and supracallosal branches.
Cerebral arteries seen in mid-line. Anterior cerebral artery visible at centre.
Cerebral arteries seen from beneath. Anterior cerebral artery visible at centre.

References

^ ^a ^b Krayenbühl, Hugo; Yaşargil, Mahmut Gazi; Huber, Peter; Bosse, George (1982), Cerebral Angiography, Thieme, pp. 79–91, ISBN 978-0-86577-067-6
^ SCHNEIDER, MARCO A. STEFANI; MARRONE, ANTONIO C. H.; SEVERINO, ANTONIO G.; JACKOWSKI, ANDREA P.; WALLACE, M. CHRISTOPHER (2000), "Anatomic Variations of Anterior Cerebral Artery Cortical Branches", Clinical Anatomy (13): 321–236
^ Osborn, Anne G.; Jacobs, John M. (1999), Diagnostic Cerebral Angiography, Lippincott Williams & Wilkins, pp. 143–144, ISBN 978-0-397-58404-8
^ Harrison's Principles of Internal Medicine 18th Edition vol. 2 Chapter 370, Cerebrovascular Diseases,page 3286, Fig 370-8

External links

MedEd at Loyola Neuro/neurovasc/navigation/aca.htm
Anatomy photo:28:09-0218 at the SUNY Downstate Medical Center
http://neuroangio.org/anatomy-and-variants/anterior-cerebral-artery/
Atlas image: n3a8p1 at the University of Michigan Health System
Anatomy diagram: 13048.000-1 at Roche Lexicon - illustrated navigator, Elsevier
Anatomy diagram: 13048.000-3 at Roche Lexicon - illustrated navigator, Elsevier

UpToDate Contents

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English Journal

There is No Benefit to Universal Carotid Artery Duplex Screening before a Major Cardiac Surgical Procedure.

Adams BC1, Clark RM1, Paap C2, Goff JM Jr3.Author information 1Department of General Surgery, University of New Mexico, Albuquerque, NM.2Vascular and Endovascular Therapy Section, Surgical Service, The Raymond G. Murphy Veterans Affairs Medical Center, Albuquerque, NM.3Department of General Surgery, University of New Mexico, Albuquerque, NM; Vascular and Endovascular Therapy Section, Surgical Service, The Raymond G. Murphy Veterans Affairs Medical Center, Albuquerque, NM. Electronic address: james.goff2@va.gov.AbstractBACKGROUND: Perioperative stroke is a devastating complication after cardiac surgery. In an attempt to minimize this complication, many cardiac surgeons routinely preoperatively order carotid artery duplex scans to assess for significant carotid stenosis. We hypothesize that the routine screening of preoperative cardiac surgery patients with carotid artery duplex scans detects few patients who would benefit from carotid intervention or that a significant carotid stenosis reliably predicts stroke risk after cardiac surgery.
Annals of vascular surgery.Ann Vasc Surg.2014 Jan;28(1):93-101. doi: 10.1016/j.avsg.2013.06.018. Epub 2013 Nov 9.
BACKGROUND: Perioperative stroke is a devastating complication after cardiac surgery. In an attempt to minimize this complication, many cardiac surgeons routinely preoperatively order carotid artery duplex scans to assess for significant carotid stenosis. We hypothesize that the routine screening of
PMID 24220649

Modeling the circle of Willis to assess the effect of anatomical variations on the development of unilateral internal carotid artery stenosis.

Zhang C, Wang L, Li X, Li S, Pu F, Fan Y, Li D.Author information Key Laboratory for Biomechanics and Mechanobiology of Ministry of Education, School of Biological Science and Medical Engineering, Beihang University, No. 37 Xueyuan Road, Haidian District, Beijing, 100191, China.AbstractCircle of Willis (CoW) plays a significant role in maintaining the blood supply for the brain. Specifically, when the stenosis occurs in the internal carotid artery (ICA), abnormal structures of CoW would decrease the compensatory capacity, leading to the local insufficiency of cerebral blood supply. The present paper built a series of lumped parameter models for CoW, and simulated the blood redistribution caused by the unilateral ICA stenosis with different severities in cerebral arteries in the normal and abnormal CoW respectively. The results showed that when unilateral ICA stenosis occurred, the collateral circulation was built through the anterior communicating artery and the ipsilateral posterior communicating artery, maintaining the flow in cerebral arteries. The absence of the two communicating arteries would cause an obvious decrease of flow in local cerebral arteries in the anterior circulation. In conclusion, the two arteries play a significant role in maintaining the balance of cerebral blood supply in the development of ICA stenosis.
Bio-medical materials and engineering.Biomed Mater Eng.2014;24(1):491-9. doi: 10.3233/BME-130835.
Circle of Willis (CoW) plays a significant role in maintaining the blood supply for the brain. Specifically, when the stenosis occurs in the internal carotid artery (ICA), abnormal structures of CoW would decrease the compensatory capacity, leading to the local insufficiency of cerebral blood supply
PMID 24211932

The anatomy of vascular compression in trigeminal neuralgia.

Thomas KL, Vilensky JA.Author information Department of Anatomy and Cell Biology, Indiana University School of Medicine, Ft. Wayne, Indiana.AbstractThe etiological basis of trigeminal neuralgia (TN) is unknown but vascular (arterial and venous) compression of the trigeminal nerve roots has emerged as the likely cause in most cases. Here we examine the evidence for the "brain sagging/arterial elongation hypothesis" with reference to the cerebral arteries and veins believed to cause the compression. Most often implicated are the superior cerebellar artery, the anterior and posterior inferior cerebellar arteries, and the superior petrosal vein including several of its tributaries. The reviewed data suggest that the theoretical support for a vascular compressive etiology of TN is weak, albeit the surgical outcome data are relatively convincing. Clin. Anat. 27:89-93, 2014. © 2013 Wiley Periodicals, Inc.
Clinical anatomy (New York, N.Y.).Clin Anat.2014 Jan;27(1):89-93. doi: 10.1002/ca.22157. Epub 2013 Feb 5.
The etiological basis of trigeminal neuralgia (TN) is unknown but vascular (arterial and venous) compression of the trigeminal nerve roots has emerged as the likely cause in most cases. Here we examine the evidence for the "brain sagging/arterial elongation hypothesis" with reference to the cerebral
PMID 23381734

Japanese Journal

30 Study on the Patient Suffering from the Closure of Arteria Cerebri Anterior

Neurologia medico-chirurgica 4, 166, 1962
NAID 110002282674

「前大脳動脈」

Anterior cerebral artery
	Outer surface of cerebral hemisphere, showing areas supplied by cerebral arteries. (Blue is region supplied by anterior cerebral artery.)
	The arterial circle and arteries of the brain. The anterior cerebral arteries (top of figure) arise from the trifurcations of the internal carotid arteries into the anterior cerebral artery, middle cerebral artery and posterior communicating artery on each side.
Details
Latin	arteria cerebri anterior
Source	internal carotid artery
Vein	cerebral veins
Supplies	cerebrum
Identifiers
Gray's	p.571
MeSH	A07.231.114.228.100
TA	A12.2.07.022
FMA	50028
	Anatomical terminology