Occipital artery–vertebral artery anastomosis visualized by cerebral angiography due to progression of internal carotid artery stenosis: illustrative case

As ICA stenosis progresses, an OA-VA anastomosis that was initially invisible on cerebral angiography may become apparent. Since this anastomosis can serve as a pathway for embolic migration during CAS, which can lead to posterior circulation infarction, it is essential to perform CAS in a manner that prevents embolic migration into the ECA in patients with OA-VA anastomoses. https://thejns.org/doi/10.3171/CASE25187.