A1 segment hypoplasia

Case contributed by Dr Mostafa El-Feky


Right sided numbness

Patient Data

Age: 25 years
Gender: Female


Normal MRA of the brain. The following anatomical variants are noted:

  • absent A1 segment of right anterior cerebral artery. A2 segment is perfused through Acom artery
  • fetal origin of right posterior cerebral artery, from right Pcom artery
  • dominant left vertebral artery

Case Discussion

Cerebral MR angiography shows absent right A1 segment, a common variant of circus of willis accounting for 10% of individuals. The contralateral A1 segment supplies ipsilateral A2 segment by a prominent anterior communicating artery.

Fetal origin of right posterior cerebral aretry also incidentally noted, a common variant of the posterior cerebral circulation in which a prominent ipsilateral PCOM supplies the posterior cerebral artery rather than basilar artery. 

This study was done in conjunction with a brain MRI study which was normal.

PlayAdd to Share

Case information

rID: 83365
Published: 27th Oct 2020
Last edited: 28th Oct 2020
Inclusion in quiz mode: Included
Institution: Dar El Ashaa Center

Updating… Please wait.

 Unable to process the form. Check for errors and try again.

 Thank you for updating your details.