Are brain arteriovenous malformations congenital or developmental? Evidence from paediatric age data

The natural history of paediatric brain arteriovenous malformations (AVMs) remains uncertain, particularly regarding their origin (congenital versus postnatal) and risk of rupture. This study analyses age-related patterns in AVM presentation from a single quaternary referral centre. A retrospective review of 275 paediatric AVM cases from 2009-2022 was conducted using radiological, surgical and hospital records to identify age at first haemorrhage and associated AVM characteristics. Two mathematical models were developed: (i) a congenital model with a variable age-dependent rupture risk; and (ii) a postnatal model of AVM development, assuming age-dependent variable incidence and a constant rupture rate. Data were normalized to institutional age-based presentation rates. Haemorrhagic presentation peaked between ages 7 and 14, before declining sharply, a trend which remained after normalization. A congenital model with age-dependent rupture rate accounted well for the empirical distribution, while the postnatal model overpredicted adolescent haemorrhage and could not account for the observed decline. However, the rising distribution of asymptomatic AVMs with age suggests that a purely congenital model is implausible. The study supports a model where paediatric brain AVMs are largely postnatally acquired, though likely very early, with age-dependent varying annual risk of rupture peaking at age 13, before declining to an adult risk rate.