Pathogenesis of acute monocular blindness from leaking anterior communicating artery aneurysms: report of six cases.

This report describes six cases of leaking anterior communicating aneurysms, collected over 37 years, that caused acute monocular blindness. In two cases, surgical and pathologic evidence demonstrated the pathogenic mechanism: As the aneurysm enlarges, the down-pointing dome compresses the optic nerve from above and adheres to it. When the aneurysm ruptures through the adherent dome, it bleeds directly into the optic nerve, resulting in severe headache and monocular blindness. The other cases also suggest an alternative mechanism, namely, direct optic nerve compression by the aneurysm.