We report a case of bispectral index (BIS) falling to zero during absolute alcohol embolization of an intracranial arteriovenous malformation (AVM) under anesthesia. This case highlights the unusual effect of a therapeutic dose of parenteral alcohol on the central nervous system using BIS monitoring.A 29-yr-old male with a left parieto-occipital arteriovenous malformation underwent neuroendovascular embolization under general anesthesia. During injection of absolute alcohol injection into the AVM nidus, the patient developed hypertension and tachycardia coincident with a profound and sustained reduction of BIS values to zero, despite a stable level of anesthesia. Immediate angiography revealed no evidence of hemorrhage or new changes in the patient's cerebral vasculature. Post-procedure, the patient remained drowsy for several hours with signs of alcohol intoxication. He had full neurological recovery.In the presence of normal cerebral angiographic findings, suppression of BIS values may serve as an early indicator of CNS responses to intracranial injection of absolute alcohol for embolization of an arteriovenous malformation.