Features of “false positive” unruptured intracranial aneurysms on screening magnetic resonance angiography

BACKGROUND: Physicians can find it challenging to decide whether confirmative digital subtraction angiography (DSA) should be performed in patients who present with “suspicious small aneurysm-like structures” on magnetic resonance angiography (MRA). Factors associated with “false positive aneurysms on MRA” (FPAMs),” which are finally confirmed as negative on DSA, have rarely been reported. This study aimed to identify the clinical or radiologic clues indicative of FPAM on DSA. METHODS: Patients who had undergone DSA between 2016 and 2019 for suspicious aneurysm-like structures < 5 mm in size on MRA were enrolled. Patient demographics and the details regarding the geometry of the structures were retrospectively reviewed. Univariate and multivariate logistic regression analyses were conducted to identify the associated factors. Receiver operating characteristic curve analysis was performed to assess the clinical implications. RESULTS: Of the 107 suspicious structures, 46 were indicated as being false positive on DSA (42.96%). Location (positive on C7 and negative on C5-6 ICA) and lower dome to neck ratio were found to be significant parameters in the multivariate analysis. The dome to neck ratio threshold value was 0.99. CONCLUSION: Suspicious aneurysm-like structures located not on C5-6 but on C7 ICA and having wide neck morphologies (dome to neck ratio < 0.99) are highly likely to be negative on DSA.