<prompt> Choose the appropriate lettered structure in this angiogram of the cerebral vasculature and collateral circulations are discounted. Aneurysm of which artery causes a perichiasmal lesion that may cause nasal hemianopia?ABCD  <response>: d Nasal hemianopia is blindness in the nasal field of vision of the eye because of a perichiasmal lesion such as an aneurysm of the internal carotid artery. 