The Infundibulum-Aneurysm Conundrum: A Longitudinal Single-Center Analysis
Year: 2025
Type: article
Study design: Observational Study
Abstract: ABSTRACT BACKGROUND AND PURPOSE: This study aims to characterize the natural history and diagnostic variability of unequivocal intracranial infundibula and diagnostically uncertain outpouchings labeled “aneurysm vs infundibulum.” MATERIALS AND METHODS: We retrospectively analyzed 665 intracranial outpouchings detected on CTA, MRA, or DSA at a single center (2013-2018). Radiology reports classified lesions as unequivocal infundibula (n=321) or as conundrums with an explicit label of “aneurysm vs infundibulum” (n=344). Follow-up imaging through December 2023 was reviewed for growth, rupture or aneurysmal transformation. Ten conundrums with later DSA follow-up also underwent blinded image re-review. A logistic model tested clinical and radiographic predictors of diagnostic ambiguity, and a literature review contextualized anatomic prevalence. RESULTS: Of 321 unequivocal infundibula, 146 (45%) had follow-up imaging. Among 344 conundrums, 208 (61%) were followed, yielding 1040 lesion-years of surveillance across both cohorts. No complications or morphological changes were observed in either group. Median follow-up among followed infundibula and conundrums was 2.26 (IQR 0.32 – 5.34) and 2.31 (IQR 0.20 – 5.43) years, respectively. Conundrums were more likely than unequivocal infundibula to undergo follow-up imaging (p<0.001). Non-Pcomm location (OR 7.4; 95% CI 5.11 – 10.63) and presence of comorbid aneurysms (OR 1.9; 95% CI 1.15 – 2.96) independently predicted a conundrum label. Surveillance declined steeply after 5 years, with only 13.4% of infundibula and 17.2% of conundrums still imaged at that horizon. Secondary reassessment of 10 conundrums revealed 100% concordance with DSA when morphological criteria were rigorously applied. Literature review reaffirmed the predominance of infundibula at the posterior communicating artery but highlighted inconsistent terminology and sparse long-term outcome data. CONCLUSIONS: In the largest single-center cohort to date, both classic infundibula and radiologically ambiguous conundrums remained stable over medium-term follow-up. Diagnostic uncertainty appears to stem mainly from interpretive variability rather than true biological risk. Structured reporting combined with location-informed heuristics could reduce unnecessary surveillance. ABBREVIATIONS: Acomm＝ anterior communicating artery; CE-MRA＝ contrast-enhanced MRA; Pcomm = posterior communicating artery.
DOI: 10.3174/ajnr.a9135
Language: English
Subfield: Neurology
Field: Medicine
Domain: Health Sciences
Open Access status: hybrid
OpenAlex ID: W4417280154