Variation in Calibre of Arteries of Circle of Willis with Age: An MRA Based Study

Objective: To establish reference range for the diameters of arteries forming the Circle of Willis (CoW) and to correlate it with age. Methods: This cross-sectional study was conducted at the Radiology Department from January to July 2018. It comprises of patients referred for MR imaging of brain without any manifestation of cerebrovascular diseases. Patients who were claustrophobic or had a history of atherosclerosis, vasculitis, thrombus, aneurysm, arteriovenous malformation (AVM), intracranial tumour, diabetes and hypertension were excluded. 300 individuals comprising both males and females with mean age of 45 +/- 11.6 (years) were recruited via non-probability sampling technique. Three-dimensional Time of Flight (TOF) Magnetic Resonance Angiography (MRA) was performed. Diameters of all component vessels forming the Circle of Willis were measured. Results: The diameter of the anterior cerebral, anterior communicating, internal carotid, posterior communicating, posterior cerebral and basilar arteries were found to be 1.51 +/- 0.28 mm, 1.05 +/- 0.37 mm, 3.69 +/- 0.23 mm, 1.10 +/- 0.11 mm, 1.85 +/- 0.23 mm, 3.00 +/- 0.11 mm respectively. Spearman correlation demonstrated that the diameters of the arteries were significantly correlated with age in different ways. Significant moderate positive correlations of internal carotid and basilar artery diameters were seen with age. Significant weak negative correlations were seen in anterior and posterior cerebral arteries. Significant very weak negative correlations were seen in anterior and posterior communicating artery diameters and age. Conclusion: The normal reference values for vessels diameter of CoW were determined in general population living in Karachi. Diameter of the arteries showed statistically significant correlation with age in different ways. Knowledge of calibre of the arteries is helpful in cerebrovascular surgeries and radiological neuro interventions.