Azygos anterior cerebral artery

An azygos anterior cerebral artery is uncommon to rare variant of the circle of Willis where the two A1 segments of the anterior cerebral artery (ACA) join to form a single trunk. As a result, there is no anterior communicating artery. This organisation is similar to that seen in lower primates 2.


They are present in approximately 0.4-1% of the population 1.



It is associated with numerous abnormalities, including 1:

Berry aneurysms are often seen at the eventual bifurcation of the single vessel, due to either altered haemodynamics or congenitally abnormal wall, or both. The reported incidence varies widely, from 13 to 71% 1.

As there is frequent hypoplasia of the ACOM and supply of the medial surface of the hemispheres by contralateral ACA branches, confirmation of an azygos ACA can be difficult on angiography 2. Cross compression views can be helpful.

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Article information

rID: 6656
Section: Anatomy
Synonyms or Alternate Spellings:
  • Azygous anterior cerebral artery
  • Azygous ACA
  • Azygos ACA

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Cases and figures

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    Azygous ACA

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    Figure 1: azygos ACA
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    Azygous Aca
    Case 1
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    Conventional ACA ...
    Figure 2: conventional ACA anatomy
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    Case 2: septooptic dysplasia
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    Ribbon lipoma wit...
    Case 3: corpus callosal dysgenesis and lipoma
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    Case 4: syntelencephaly
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    Case 5
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    Case 6
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