Evaluation of normal variants of circle of Willis at MRI


  • Peyush Pattayil Keeranghat Department of Radiodiagnosis, MGMCRI, Pillayarkuppam, Pondicherry, Tamil Nadu, India
  • Jagadeesan D. Department of Radiodiagnosis, MGMCRI, Pillayarkuppam, Pondicherry, Tamil Nadu, India
  • Prakash M. L. Department of Radiodiagnosis, MGMCRI, Pillayarkuppam, Pondicherry, Tamil Nadu, India
  • Radha Gupta Department of Radiodiagnosis, MGMCRI, Pillayarkuppam, Pondicherry, Tamil Nadu, India




Anatomical variations, Circle of Willis, Magnetic resonance 3D-time of flight angiography, Vessel diameters


Background: Anatomy of circle of Willis (COW) shows extensive variations in different individuals and signifies the causation and presentation of clinical disease. The present study aims to evaluate the different anatomical variations of the Circle of Willis (COW) in general population, using magnetic resonance (MR) 3D-time of flight angiography and to correlate the observations with age and gender characteristics.

Methods: This observational clinical study was conducted January 2013 to March 2014 in 503patients who were referred for MRI – Brain. MRI (Philips 1.5 Tesla magnet) with routine brain sequences along with 3D –TOF MRA was done in all patients. The anatomical variants of the anterior and posterior components of the COW were studied. The complete COW was assessed and the diameters of all the components were measured. The correlation between the vessel diameters in relations to age and gender were evaluated.

Results: The mean age group of study participants was 42 years. Male dominance was seen among participants (57.1%). The complete configuration of the circle was seen in 31.6% of population. Most common anterior variant is type A (normal anterior configuration) with a prevalence of 52.9% and posterior variant is type K with a prevalence of 32.9%. Average diameters of the proximal vessels supplying the COW were larger in the older age subjects (centripetal vessels, the right and left ICA s and BA). Statistically significant differences between the mean vessel diameters between males and females were seen in the ICA-RT, ICA-LT, and PCOA-LT.

Conclusions: The present study showed great variability of the anatomy of the COW in asymptomatic person. Various variants of COW can be picked up by MRA which is safer and non-invasive when compared with CTA / DSA. Knowledge of these variations would help in planning surgical procedures as well as preventing unwanted interventions.


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How to Cite

Keeranghat, P. P., D., J., M. L., P., & Gupta, R. (2018). Evaluation of normal variants of circle of Willis at MRI. International Journal of Research in Medical Sciences, 6(5), 1617–1622. https://doi.org/10.18203/2320-6012.ijrms20181497



Original Research Articles