Impact of Young Age on the Presentation of Saccular Intracranial Aneurysms: Population-Based Analysis of 4082 Patients

BACKGROUND: Formation and rupture of saccular intracranial aneurysms (sIAs) may have different pathobiologies in patients with younger age at first diagnosis of sIA disease. OBJECTIVE: To study the phenotype of sIA disease and formation of new (de novo) sIAs in patients below 40 yr. METHODS: A population-based cohort study was conducted in 613 young ( 40-yr-old patients (unruptured and ruptured). Smoking was very prevalent in <40-yr-old patients (33% in SAH, 68% unruptured). SAH patients <40 yr more often had family history of sIA, and lower PHASES scores (age omitted, P < .001). Ruptured sIAs were small (<7 mm) in 33% of 39 to 30 yr patients, in 44% of 29 to 20 yr patients, and 57% of <19 yr patients. Their shape was irregular in 90%, 94%, and 95%, respectively. Smoking history (hazard ratio [HR] 2.8, 95% confidence interval [CI] 1.2-7.0), family history for sIAs (HR 3.1, 95% CI 1.3-7.7), and age at presentation (HR .91 per year, 95% CI .85-.98) were risk factors for de novo sIA formation, diagnosed in 4% even after 20 yr (median 11.8 yr). CONCLUSION: Smoking and family history are risk factors for sIA formation and aneurysmal SAH at young age. Young aneurysmal SAH patients had lower PHASES scores and often rupture from a small sIA, suggesting need for more aggressive management.