Extracranial to intracranial (EC-IC) bypass surgery with an autologous venous graft significantly increases the cerebral blood flow (CBF) as compared with superficial temporal artery to middle cerebral artery (STA-MCA) anastomosis.
When the ipsilateral CBF via the anterior communicating artery (ACoA) and/or posterior communicating artery (PCoA) is not sufficient after the carotid ligation, this procedure is protection against cerebral ischemia by supplying the blood through the venous graft.
On the contrary, when the ipsilateral CBF via the ACoA and/or PCoA is not reduced effectively by the carotid ligation, meaning that the blood flow to the aneurysm is still maintained, this bypass surgery can prevent the aneurysm from rupturing by diverting the blood from the lesion.
In conclusion, in addition to the conventional methods of internal carotid ligation and STA-MCA anastomosis, EC-IC bypass surgery with an autologous venous graft is recommended as one of the useful procedures for the inoperable giant internal carotid aneurysms.