Introduction The circle of Willis (CoW) is an important factor affecting collateral blood flow to the brain and plays a key role in sustaining sufficient cerebral perfusion especially during instances of impaired flow.² Past studies have indicated that there are variations in CoW composition and that often the various segments of the arteries comprising CoW are either not present or are hypoplastic.^{1 4} This study investigated 1) mean and median age, and 2) gender in patients with complete vs. incomplete circle. In addition, we investigated the association of missing segment(s) with the age and gender in patients with incomplete circle

Methods Study Population

One hundred randomly selected individuals were examined in this study. These patients had undergone CT scans for stroke. Using the enhanced viewer, the circle of Willis was then analyzed to ascertain whether the circle was complete or incomplete. The arteries examined were the anterior communicating artery, the A1 segment of the ACA (horizontal), the A2 segment of the ACA (vertical), the posterior communicating arteries, and the P1 and P2 segments of the PCA in both hemispheres. The results obtained were tabulated and subsequently analyzed.

Results For the comparison of mean age in complete and incomplete circle, a t-test was conducted. The result showed there was no significant difference between the mean values of age (p-value: 0.8122). For the comparison of median age in complete and incomplete circle, a Kruskal-Wallis test was performed. The results also indicated that there was no significant difference (p-value: 0.90574). Chi-square analysis was utilized to compare gender in patients with complete and incomplete circle. There is no significant relationship between gender and circle completion (p-value: 0.98041).We then investigated the association of missing segments with age or gender only. In order to determine the association of missing segments with age, a t-test was performed. Only the variable LA1 demonstrated a significant result (p-value:0.0043). For the association of missing segments with gender, a Chi-square analysis was performed. None of the missing segments has a significant result.Logistic regression was performed to test the influence of gender and age on the missing segments. A likelihood Ratio test was conducted to test the global null hypothesis which concluded that there is no effect of gender and age. Variable LA1 and ACom had significant results (p-value: 0.0378 and 0.0426) which indicates that in general, age and gender have the association with LA1 and Acom.

References

1. Alpers BJ, Berry RG, Paddison RM. Anatomical studies of the circle of willis in normal brain. Arch Neurol Psychiat. 1959;81:409–18.

2. Cieslicki K, Gielecki J, Wilczak T. Redundancy of the main cerebral arteries in morphological variations of the Willis circle. Neurol Neurochir Pol. 1997 May-Jun;31(3):463–74.

3. Krabbe-Hartkamp MJ, van der Grond J, de Leeuw FE, de Groot JC, Algra A, Hillen B, Breteler MM, Mali WP. Circle of Willis: morphologic variation on three-dimensional time-of-flight MR angiograms. Radiology. 1998;207:103–111. doi: 10.1148/radiology.207.1.9530305.

Disclosures M. Khan: None. C. Rupareliya: None. N. Almeida: None. V. Fennell: None. J. Milburn: None.