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Illustrated Encyclopedia of Human Anatomic Variation: Opus II: Cardiovascular System

Fourteen Variations of Circle of Willis and Related Vessels.

Ronald A. Bergman, PhD
Adel K. Afifi, MD, MS
Ryosuke Miyauchi, MD

Peer Review Status: Internally Peer Reviewed


Image of variations of circle of Willis and related vessels

Based on a study of 600 brains.

A: Normal cerebral arterial circle and associated vessels. A Com, anterior communicating; A Ce, anterior cerebral; M Ce, Middle cerebral; P Ce, posterior cerebral; IC, internal carotid stump; P Com, posterior communicating; SC, superior cerebeilar; Ba, basilar; La, labyrinthine; AIC, anterior inferior cerebellar; PIC, posterior inferior cerebellar; V, vertebral; AS, anterior spinal; P, pontine.

B, C: Failure of vertebral artery to unite with the basilar artery (extremely rare anomaly).

D: Inferior union of vertebral arteries to form basilar artery.

E: Double basilar artery with absence of anterior communicating artery (1st description of this anomaly).

F: Failure of left posterior communicating artery to unite with rostral end of basilar artery; all pontine branches arise from left side of basilar artery.

G: A specimen showing underdeveloped anterior cerebral, anterior communicating, and left posterior communicating arteries.

H: Absence of left posterior communicating artery.

I: Both anterior cerebral arteries are related only to the left internal carotid artery.

J: Specimen from a microcephalic idiot showing attenuation of internal carotid arteries and their branches, and a large saccular basilar artery.

K: Absence of both posterior communicating arteries.

L: A plexiform basilar artery (1st description of this anomaly).

M: Specimen showing difference in size of internal carotid, posterior communicating, middle, and anterior cerebral arteries, with right side underdeveloped.

N: A composite drawing showing several variations found in different specimens: (a) anterior inferior cerebellar and internal auditory arteries arise as branches from a common origin; (b) posterior cerebral and superior cerebellar arteries arise from a common origin; and (c) all pontine branches on one side arise from common origin.

Authors' note: Additional reference: Stehlbens, W.E. Aneurysms and anatomical variation of cerebral arteries. Arch. Pathol . 75:45-64, 1963.

Redrawn from McCullough, AN (Rewritten posthumously for the author by Howard K. Suzuki). Some anomalies of the arterial circle (of Willis) and related vessels. Anat. Rec. 142:537-543, 1962.

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