2025 American Academy of Neurology Abstract Website

Objective:

The objective of this study is to determine the incidence of absent posterior communicating artery (PCOM) segments in the pediatric circle of Willis (CW) using time-of-flight magnetic resonance angiography (TOF-MRA).

Background:

Studies using TOF-MRA have found that variations in the CW, specifically missing or hypoplastic segments, are found in approximately 65% of the general population, most commonly in the communicating arteries. This has led the medical community to consider the absence of PCOMS in neurovascular imaging as typical. However, these studies primarily involved older populations, where vascular diseases such as atherosclerosis may potentially obscure arteries on TOF-MRA imaging. As these diseases are rare in children, it is thus plausible that undetectable arteries are relatively rare in child TOF-MRA.

Design/Methods:

The analysis of 51 healthy school-aged children’s TOF-MRA images was performed by visual inspection and automated segmentation of the CW. Participants were then divided into three groups based on the number of visible PCOMS (A: 2 PCOMS, B: 1 PCOM and C: 0 PCOM) for analysis of the CW arteries diameters, and the intracranial volume.

Results:

The incidence group A (both PCOMs present) was 84% (N=42), 16% for group B (1 PCOM) (N=9) and 0% for group C. When comparing Group A and B, we observed no significant differences in PCOM diameter (p=0.3740), nor in basilar and internal carotid arteries (p=0.0591), suggesting that the number of visible PCOMS is not related to the size of the child in this age range.

Conclusions:

This study suggests that most individuals are born with two PCOMS, and the perception of frequent CW anatomical variations may result from imaging techniques that visualize blood flow rather than the vessels themselves. This aligns with dissection studies, which reveal fewer absent arteries than the imaging studies.