Objective: The Circle of Willis (CW) is a network of anastomotic arteries surrounding the base of brain in the interpeduncular fossa. It provides collateral pathway for the redistribution of blood supply to prevent ischemia. Variations in the CW is being related with cerebral hemodynamic and vessel related diseases, but the exact aetiology remains unclear. The diameter of the arteries is directly proportional to the flow of blood volume. The normal functioning of the circle is its completeness and also the lack of hypoplastic vessels. The present study observes the variation in branching pattern of CW with the presence of hypoplastic vessels and its histological features.
Methods: The CW and its branches were dissected and the variations in the branching pattern were recorded and photographed on 35 cadaveric brains. Diameter of the vessels were measured using digital vernier calliper. The sections of the arteries were taken for histological examination (Masson’s Trichrome staining).
Results: The present study observed that majority of the CW showed anomalies (48.57%). Hypoplasia was the most frequent anomaly observed. Duplication was observed in 28.57% of the vessels. The morphometry of the vessels of CW was taken and tabulated. The histology (Masson’s Trichrome staining) of hypoplastic vessels observed changes in the tunica media of the vessel.
Conclusion: The variations in the CW are known to develop in the early embryonic stages and is probably genetically determined. These anomalies persist in the post-natal life and alter the occurrence, severity of symptoms, treatment and recovery from cerebrovascular disorders. Variations in the communicating arteries are known to cause higher incidence of disorders like migraine, schizophrenia and cerebrovascular disorders due to compromised collateral circulation and poor redistribution of blood. Knowledge of these variations are important for surgical interventions and also to prevent inadvertent vascular trauma during surgeries.
Keywords: anterior cerebral artery; anterior communicating artery; circle of Willis; posterior cerebral artery; posterior communicating artery