ABSTRACT
To identify the anatomical variations in cerebral arterial circle of Willis. Descriptive study. Department of Anatomy, University of Health Sciences, Lahore, from February 2009 to January 2010. Human brains were removed from fifty-one consecutive cadavers at the time of autopsy from Forensic Department, King Edward Medical University, Lahore, to observe anatomical variations in the cerebral arterial circle regarding its completeness, pattern and symmetry. The individual cerebral vessels were also noted for the presence, origin, caliber and symmetry. Pictures from each dissection, showing the complete circle were taken. The variations of the circle as whole and segmental variations were studied and described in percentage. Thirty-seven [72.5%] of the 51 [100%] cerebral arterial circles were complete; 15 subjects [29.4%] had typical configuration; 25 [49%] had symmetrical arrangement and 39 subjects [76.4%] had different types of variations in their component vessels. Variations were most common in the posterior communicating artery followed by anterior communicating artery, pre-communicating segments of the posterior cerebral and pre-communicating segments of anterior cerebral arteries. No circle was found with aneurysm. Different variations in the formation of circle of Willis and in its component vessels are common in the local adult population of Pakistan. These should be taken into consideration during angiographic evaluation and neurosurgical procedures on the anterior circulation