A1 segment hypoplasia

Case contributed by Dr Mostafa El-Feky

Presentation

Right sided numbness

Patient Data

Age: 25 years
Gender: Female
MRI

MRA

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.

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