Hemodynamic response following neuronal activity in cases with severe stenosis of the cervical internal carotid artery and its serial change through carotid artery stenting

Objective: Regional cerebral blood flow (CBF) increasing focally at sites of neural activity is called “hemodynamic response (HDR)”. In cases with severe cerebral ischemia, HDR may be disturbed and cause disruption of normal neuro-vascular coupling. HDR was measured during a motor task using functional near infrared spectroscopy (fNIRS) in cases with severe cervical internal carotid artery (ICA) stenosis before and after carotid artery stenting (CAS). Ischemia and the influence of therapy for it on HDR was analyzed. Methods: Seventeen right-handed patients with severe cervical ICA stenosis admitted for CAS were examined. fNIRS during a motor task was performed and concentration changes in oxygenated hemoglobin (HbO2), deoxygenated hemoglobin (HbR), and total hemoglobin (tHb) were calculated in these patients in addition to routine evaluations. The same measurements were repeated after CAS and serial data were evaluated. In order to analyze the relevance of HDR to CBF status, Xenon-enhanced computed tomography (Xe-CT) was performed before and after CAS. Results: Some abnormalities in the HDR curve and its recovery after CAS were detected, including a delay in peak time of tHb concentration, of more than 10 seconds during the 20 second stimulation, in 9 cases. TTP^0.7 (time to peak) value, defined as the time to reach seventy percent of maximum tHb concentration, was observed to be higher in patients with low CBF at rest before CAS. In the group with a high TTP^0.7 value, CBF at rest before CAS was lower than 35mL/100g/min., significantly lower than the group without a high TTP^0.7 value (P<0.01). Additionally, in the group with a high TTP^0.7 value, CBF increase after CAS was significantly higher than the group with a lower TTP^0.7 value (P<0.01). Conclusions: In some cases with severe ICA stenosis, cortical hemodynamics, and oxygen metabolism during functional activation are disturbed, and CAS can modulate these changes. This result is important in that intervention for cervical IC stenosis can not only reduce ischemic events, but also influence cortical hemodynamics during functional activity.