Are the variants of the circle of willis determined by genetic or environmental factors results of a twin study and review of the literature

Bianka Forgo, Adam Domonkos Tarnoki, David Laszlo Tarnoki, Daniel Tamas Kovacs, Laszlo Szalontai, Aliz Persely, Anita Hernyes, Marcell Szily, Levente Littvay, Emanuela Medda, Adam Szabo, Lajos Rudolf Kozak, Gabor Rudas, Attila Sas, Marianna Sepsi, Laszlo Kostyal, Csaba Olah

Research output: Contribution to journalReview articlepeer-review


Background: Anatomic variants of the circle of Willis (CW) are commonly observed in healthy subjects. Genetic and environmental factors influencing these variants remain unclear. Our aim was to assess the genetic and environmental background affecting variant CW phenotypes. Methods: A total of 122 adult healthy twins from the Hungarian Twin Registry (39 monozygotic (MZ) and 22 dizygotic (DZ) pairs, average age 49.7 ± 13.4 years) underwent Time-of-Flight magnetic resonance angiography and transcranial Doppler sonography. We investigated the anterior and posterior CW according to morphological categories. Prevalence and concordance rates of CW variants were calculated. MZ twins discordant for CW variants were analyzed for cardiovascular risk factors and altered blood flow. Results: Complete CW (45.0%) and bilaterally absent posterior communicating artery (PCoA) (22.5%) were the most prevalent variants in the anterior and posterior CW, respectively. There was no significant difference regarding the prevalence of variants across zygosity except for bilaterally hypoplastic PCoA (p =.02). DZ concordance was higher compared to MZ twins regarding morphological categories of the CW. Cardiovascular risk factors were not significantly associated with variant CW in MZ twins discordant to CW morphology. Flow parameters did not differ significantly among MZ twins discordant to CW variants. Conclusion: CW variants may not be determined by substantial genetic effects and are not influenced by altered blood flow in healthy individuals. Further investigations are needed to identify potential environmental factors affecting these variants.

Original languageEnglish
Pages (from-to)384-393
Number of pages10
JournalTwin Research and Human Genetics
Issue number5
Publication statusPublished - Oct 1 2018


  • Cerebrovascular development
  • Cerebrovascular variants
  • Circle of willis
  • Collateral flow
  • Genetic
  • Twin
  • Variant

ASJC Scopus subject areas

  • Pediatrics, Perinatology, and Child Health
  • Obstetrics and Gynaecology
  • Genetics(clinical)


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