Annals of Neurology: Volume 89, Number 5, May 2021

A photograph of the brain of a mouse perfused with blue latex and clarified to visualize the entire vascular system. This mouse had received an injection of a viral vector targeting vascular endothelium with a mutation of the KRAS gene that was recently implicated in the genesis of arteriovenous malformations (AVMs) in humans. The tangles of blue dye seen in multiple locations in the brain represent AVMs. This method allows the detailed investigation of the development of AVMs. See Park et al., (pp. 926–941, this issue) for details.