Reduced vasomotor reactivity in cerebral microangiopathy - A study with near-infrared spectroscopy and transcranial Doppler sonography

Background and Purpose-Reduction of cerebral blood flow and vasomotor react ivity (VMR) are thought to play an important role in the pathogenesis of ce rebral microangiopathy. The aim of our study was to determine whether near- infrared spectroscopy (NIRS) can detect a reduced VMR in patients with micr oangiopathy, whether NIRS reactivities correlate with VMR assessed by trans cranial Doppler sonography (TCD), and whether the differing extents of pati ents' microangiopathy demonstrated on MRI or CT can be distinguished by bot h noninvasive techniques. Methods-We compared the VMR of 46 patients with cerebral microangiopathy wi th 13 age-matched control subjects. Patients were classified with the Erkin juntti scale. We monitored cerebral blood flow velocity (CBFV) in both midd le cerebral arteries by TCD, changes in concentration of oxyhemoglobin (Hbo ,), deoxyhemoglobin (Hb) and blood volume (HbT) by NIRS, mean arterial bloo d pressure, and end-tidal CO2 (Etco(2)) during normocapnia and hypercapnia. VMRs were calculated as percent change of CBFV (NCR) and as absolute chang e in concentration of HbO(2), Hb, and HbT per 1% increase in Etco(2) (CR-Hb O(2), CR-Hb, CR-HbT), Results-NCR and NIRS reactivities were significantly reduced in patients wi th cerebral microangiopathy. CR-HbO(2) and CR-Hb showed a close correlation with NCR, and NCR and NIRS reactivities were related to the severity of ce rebral microangiopathy according to the Erkinjuntti scale. Validity of NCR and NIRS reactivities were similar. Conclusions-VMR is reduced in patients with cerebral microangiopathy and ca n be noninvasively assessed in basal arteries (with TCD) and brain parenchy ma (with NIRS). Reduction of CO2-induced VMR, as measured by NIRS and TCD, may indicate the severity of microangiopathy.