8 - Assessing Fetal-Type Circle of Willis in Puerto Rican Cadavers

Poster Board Number: 8
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Co-authors:

Jaime Arroyo Aviles - San Juan Bautista Medical School; Wilson Veras, MD - Professor, Anatomy, San Juan Bautista Medical School

Abstract Body : Introduction

The Circle of Willis forms a network of interconnected arteries encircling the base of the brain. Karatas et al., 2015, describe that its major role is to provide efficient collateral circulation to cerebral and cerebellar tissue to prevent ischemia, and subsequent transient ischemic attack or stroke. Literature has unveiled a considerable number of variations in its anatomical configuration. One of the most common variants is the Fetal-Type Posterior Circle of Willis (FTPCW) where there is an embryonic derivation of the posterior cerebral artery (PCA) from the internal carotid artery (ICA). This anatomical configuration of the Circle of Willis usually arises after 28 days of embryonic life. Subvariants include a partial FTPCW, in which a small P1 segment between the basilar artery and the post communicating part of the PCA is present, and a full FTP, in which the P1 segment is absent.



Aim

Document the incidence of the Fetal-Type Posterior Circle of Willis and its sub-variants in a sample of dissected brains.



Methodology

An observational study using Puerto Rican cadavers was conducted at the Anatomy Lab at San Juan Bautista School of Medicine. The cause of death and age of the specimens is unknown. The meninges around the interpeduncular fossa were removed to expose the Circle of Willis(CW). The posterior circulation was dissected to identify the PCA. We followed the PCAs on both sides of the CW from their origin to their termination. The variations of PCAs were noted and categorized according to A.Fleur van Raamt classification.





Results

Forty-one brains were assessed; one brain was discarded due to gross damage to the posterior Circle of Willis. A total yield of eighty posterior cerebral arteries (PCA). Results showed an incidence of sixteen Fetal-type PCAs, thirteen of which were classified as partial subtypes. Only one Fetal-type PCA proved to be of the full subtype. We were unable to determine the subtype of two Fetal-type PCAs. Among the brains analyzed, two showed a bilateral partial Fetal-type PCA.



Conclusion



Relevance of this study is rooted in the physiologic understanding of the importance of collateral circulation in cases of ischemic stroke. Studies show an increased risk of intracranial aneurysms due to the presence of FTP (Fleur van Raamt et al., 2006) and a decreased number of collateral circulation. Our study found a high prevalence of fetal configuration of the posterior Circle of Willis within a sample of 41 brain specimens. Data obtained in this study showed a high incidence of FTP, presumably leading to an increase in cerebrovascular accidents in the Puerto Rican population. Nevertheless, there is a need to investigate variations further and determine their prevalence compared to others with a greater sample size and increased statistical certainty.