Variations in the Circle of Willis by MR Angiography

The arterial Circle of Willis at the base of the brain serves as a potential collateral pathway, which will maintain adequate cerebral perfusion in the case of diminished afferent blood supply through internal carotid and basilar arteries¹.

In the present study, Circle of Willis of 100 healthy persons were examined with the help of 3D-TOF MR Angiography of brain. (74 individuals aged 18–60 years and 26 aged above 60 years of either sex.) All component vessels of the circle were assessed by measuring the diameter. Sections of the vessels that were visualized as continuous segment for at least 0.8mm in diameter were considered to be normal and those smaller than 0.8mm in diameter were considered hypoplastic.

Variations most commonly found in communicating arteries, less commonly in cerebral arteries and very rarely noted in internal carotid artery. Most common type of variation found in vessels is hypoplasia and absence. The present study is an observational study; the data of this study will be helpful to the neurosurgeon in the selection of patient as well as assessing the feasibility of shunt operation.