Radiological classification of azygos anterior cerebral artery and evaluation of the accompanying vascular anomalies

Surg Radiol Anat. 2020 Nov;42(11):1345-1354. doi: 10.1007/s00276-020-02509-4. Epub 2020 May 29.


Purpose: There is not a classification of azygos anterior cerebral artery (ACA) based on anatomical branching levels in the literature. In the present study, a classification of azygos ACA was made based on radiological imaging for a common terminology, and frequency, accompanying vascular anomalies and malformations were investigated.

Methods: A total of 4913 cases who had brain CTA, MRA, contrast-enhanced MRI and DSA in January 2010-January 2020 period were screened for the study. Based on anatomical branching level, azygos ACAs were classified into four groups. Aneurysms, anomalies and malformations accompanying azygos ACA were identified. The associations of azygos ACA types with the presence of aneurysm or ACA A1 segment anomalies were investigated.

Results: Azygos ACA was observed in 57 cases (29 male and 28 female) and frequency of azygos ACA was 1.16%. Average age of the cases with ACA was 56.19 ± 19.65 years. Forty-eight of the cases had type C azygos ACA, four cases type B, four cases type D and one case type A azygos ACA. A total of nine intracranial aneurysms were identified in seven of the cases (12.28%). Five of the aneurysms were located in MCA and four in distal ACA. Most common vascular anomalies accompanying azygos ACA were unilateral vertebral artery hypoplasia and ACA A1 segment hypoplasia. Azygos types did not have significant correlations with the presence of aneurysms or ACA A1 segmental anomalies (p = 0.683 and p = 0.949, respectively).

Conclusion: Azygos ACA is a rare variation, but it could be accompanied by aneurysms or other vascular anomalies.

Keywords: Aneurysm; Azygos anterior cerebral artery; Computerized tomography angiography; Magnetic resonance angiography; Unpaired pericallosal artery.

MeSH terms

  • Adult
  • Aged
  • Anterior Cerebral Artery / abnormalities*
  • Anterior Cerebral Artery / diagnostic imaging
  • Cerebral Angiography / methods
  • Cerebral Angiography / statistics & numerical data
  • Computed Tomography Angiography / statistics & numerical data
  • Contrast Media / administration & dosage
  • Female
  • Humans
  • Intracranial Aneurysm / epidemiology*
  • Intracranial Aneurysm / etiology
  • Magnetic Resonance Angiography / statistics & numerical data
  • Male
  • Middle Aged
  • Retrospective Studies
  • Vascular Malformations / classification
  • Vascular Malformations / complications
  • Vascular Malformations / diagnosis
  • Vascular Malformations / epidemiology*
  • Vertebral Artery / abnormalities*
  • Vertebral Artery / diagnostic imaging


  • Contrast Media