Proposed diagnostic criteria for intracranial infectious aneurysms

Background: We propose a set of criteria for diagnosis of intracranial infectious aneurysm (IA). The proposed diagnostic criteria contain a mandatory criterion ( demonstration of intracranial aneurysm by neuroimaging) and 12 supportive criteria drawn from three domains. Domain A encompasses infection, such as infective endocarditis, meningitis, cavernous sinus thrombophlebitis or orbital cellulitis. Domain B encompasses angiographic features of the aneurysm, such as multiplicity, distal location, fusiform shape, change in size or appearance of new aneurysm at follow-up angiogram. Domain C encompasses other features, such as age,45 years, recent history of fever, lumbar puncture or cerebral haemorrhage. Each criterion is given 1 point and the sum under each domain (A(sum), B(sum) and C(sum)) and total score are calculated. Methods: We evaluated these criteria in 25 patients with confirmed IA and in another 111 consecutive patients with non-infectious aneurysm. The sensitivity, specificity and receiver operator characteristic (ROC) curves were calculated for these cohorts. Results: The highest ROC was for total score (0.997). A total score of 3 had high sensitivity (96%) and specificity (100%), as well as a positive predictive value of 100% and negative predictive value of 99.4%. A total score of 2 had high sensitivity ( 100%) but low specificity ( 87.4%). Other combinations had lower ROC areas, sensitivities and specificities. Conclusion: Diagnosis of IA would be clinically compelling if three or more of the proposed supportive criteria are satisfied, or clinically probable if two proposed supportive criteria are satisfied apart from the mandatory criteria.