Monitoring cerebral tissue oxygen saturation at frontal and parietal regions during carotid artery stenting

Cerebral oximetry is normally placed on the upper forehead to monitor the frontal lobe cerebral tissue oxygen saturation (SctO₂). We present a case in which the SctO₂ was simultaneously monitored at both frontal and parietal regions during internal carotid artery (ICA) stenting. Our case involves a 79-year-old man who presented after a sudden fall and was later diagnosed with a watershed ischemic stroke in the distal fields perfused by the left middle cerebral artery. He had diffuse atherosclerotic occlusive lesions in the carotid and cerebral arterial systems including an 85 % stenotic lesion in the left distal cervical ICA. The brain territory perfused by the left ICA was devoid of collateral flow from anterior and posterior communicating arteries due to an abnormal circle of Willis. During stenting, the SctO₂ monitored at both frontal and parietal regions tracked the procedure-induced acute flow change. However, the baseline SctO₂ values of frontal and parietal regions differed. The SctO₂–MAP correlation was more consistent on the stroked hemisphere than the non-stroked hemisphere. This case showed that SctO₂ can be reliably monitored at the parietal region, which is primarily perfused by the ICA. SctO₂ of the stroked brain is more pressure dependent than the non-stroked brain.