Localized in vivo proton magnetic resonance spectroscopy (1H-MRS) has been used to measure the metabolic status of the human brain in a non-invasive manner; thus, it is often called "a non-invasive biochemical assay". MRS is more sensitive than magnetic resonance imaging (MRI) in detecting ischemic damage by measuring the metabolic changes that occur prior to the anatomic changes. We report a patient who presented with innominate artery occlusion and symptoms of posterior circulation insufficiency and showed favorable metabolic changes by 1H-MRS after revascularization. He showed no visible lesion in brain MRI, but in 1H-MRS, decreased N-acetylaspartate (NAA) signal was noted in a resting state. After revascularization, both symptomatic improvement and recovery of NAA signal were observed. 1H-MRS may provide valuable clinical information in diagnosis and management of cerebral hypoperfusion at a much earlier stage prior to the anatomic changes.