Calibre of the Component Vessels of the "Circle of Willis" of the Human Brain

Introduction: The arteries of the circle of Willis (CW) of the human brain show considerable variations of calibre and pattern. Two pair of major arteries-right and left vertebrals; right and left internal carotids deliver all their blood almost exclusively to the brain. This arterial circle equalizes the pressure of the blood flow to the two sides of the brain as it’s the main collateral channel. It provides alternative routes, when one of the major arteries leading into it is blockade. There is considerable individual variation in the pattern and calibre of vessels that make up the circle of Willis.

Material and methods: The calibres of the different segments of the circulus arteriosus vary so much that no two circles are completely identical. Hence a study to determine the length and external diameters of the arteries constituting the CW in the population of Assam will be of utmost importance. The length and external diameters of the arteries forming the circle of Willis were measured. The recorded data were then statistically analysed using Student’s T-test. P value d” 0.05 is considered as statistically significant.

Result: There is a statistical significant difference between diameters of both sided PCoA (t=2.123;P=0.041) and the lengths of both sided A1(t=2.286,P=0.028).

Conclusion: The data obtained in this study will help in certain medico-legal practices. The study may be helpful to neurosurgeons and neurologists in Assam in planning and executing treatment of its population.