Rare anastomosis between the bilateral internal carotid arteries via the recurrent arteries branching from the first segment of the ophthalmic artery.

Although anastomoses between the arterial branches arising from the internal carotid artery (ICA) can develop as collateral pathways between the bilateral ICAs in cases of dysgenesis of the ICA, anastomosis of the recurrent arteries branching from the first segment of the ophthalmic artery (OphA) has not been described. Herein, we report two cases of this rare anastomosis. In a 36-year-old man with left segmental dysgenesis of the ICA, an anastomosis between the bilateral ICAs developed around the sella turcica. In a 39-year-old woman with dysgenesis of the bilateral distal ICAs, an anastomosis between the superior hypophyseal trunk and bilateral ICAs was identified. The anastomoses in both cases were also supplied by recurrent arteries branching from the first segment of the OphAs. This is the first report describing recurrent arteries from the OphAs that form the anastomosis between bilateral ICAs.