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

Abstract

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 cere- brovascular diseases. Patients who were  claustrophobic  or  had  a  history  of  atherosclerosis,  vasculi-  tis, 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 commu- nicating 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.