What is the surgical indication for performing the Hunterian Ligation operation?

Hunterian ligation (parent vessel occlusion) is generally only considered if occlusion of the aneurysm neck is dangerous or impossible. It reduces flow past the aneurysm, often reducing the size of the lesion and even occasionally causing spontaneous thrombosis. Ref: Neurosurgery: Principles and Practice By Anne J. Moore, David W. Newell, 2005, Page 323.