Background Vein of Galen aneurysmal malformations (VGAMs) are congenital disorders that may require emergency treatment and some may cause sudden death before medical attention is provided. Some patients also have a spontaneous thrombosis.

Objective To understand the natural progression of VGAMs through a systematic literature review.

Methods We examined PubMed to identify studies published between July 1973 and March 2015. We determined the proportion of patients with VGAM who died before receiving medical attention, who received emergency treatment, or had a spontaneous thrombosis. We pooled estimates of proportions with corresponding 95% CIs calculated using the raw (ie, untransformed) proportions.

Results The 31 studies obtained described the outcome of 754 patients with VGAM. The probability of sudden death risk was 4% (95% CI 1% to 7%; I²=51.6%); of an emergency operation was 46% (95% CI 34% to 58%; I²=93.2%); and of spontaneous thromboses 1% (95% CI 0% to 2%; I²=0%) of cases. Differences between age and clinical outcomes of patients with spontaneous thromboses were significant according to the rank test (Mann–Whitney U test, Z=−2.398, p=0.016), both having a linear correlation (χ² test, p=0.022).

Conclusions Over time, the rate of preoperative sudden death in patients with VGAM gradually declined and the rate of emergency operations gradually increased. The outcome of patients with early spontaneous thromboses was good. Our study provides a definitive description of the natural progression of VGAMs and the need for urgent medical attention.