1022. Analysis of 406 Mirror Intracranial Aneurysms: Anatomic Characteristics and Risk Factors

Authors: Alexandra Santos; Jefferson Rosi Junior, MD, PhD; Saul Almeida da Silva, MD; Ricardo Iglesio, MD; José Guilherme Caldas, MD, PhD; Manoel Teixeira, MD, PhD; Eberval Figueiredo, MD, PhD (Sao Paulo, Brazil)

Introduction: Mirror Intracranial Aneurysms (MIA) are present in about 40% of patients diagnosed with multiple aneurysms, and it accounts for 5% of all intracranial aneurysms. They usually are a challenge to the neurosurgeon, many times requiring two different approaches. The aim of this study was documenting the incidence, size and location of MIA, as well as investigating possible risk factors. Methods: We studied 1404 patients with intracranial aneurysms followed in the Hospital das Clinicas of the University of Sao Paulo, a referral hospital for treatment of cerebrovascular diseases in Brazil. Patients admitted from September 2009 to August 2018 were included. MIA was defined as one pair of aneurysms involving bilateral corresponding arteries. We divided patients according to sex, age, arterial hypertension, and habit of smoking. Results: A total of 406 aneurysms were identified as MIA (203 pairs, 18%) of 2254 diagnosed aneurysms. Female sex increased risk to MIA ( p< 0.001, OR= 2.828, 95% CI= 1.725-4.636), while advanced age, smoking and hypertension didn’t have significant results ( p= 0.163, p= 0.055, p= 0.781, respectively). Middle cerebral artery was the most common site of MIA (37.4%), followed by internal carotid artery in the segments posterior communicating (20.7%), cavernous (18.7%), and ophthalmic (14.3%). The remaining documented sites obtained less than 5% of frequency. Concerning their size, 28.8% were less than 3 mm of diameter, the majority (56.4%) were 3-10 mm, 8.6% were 10-25 mm, and 6.2% with a diameter bigger than 25 mm. Conclusion: Mirror intracranial aneurysms were most found in female and factors as age, smoking, and hypertension appears to be unrelated to MIA occurrence. Most of the mirror aneurysms were less than 10 mm, and were more often of anterior cerebral circulation.