Is there a role of near infrared spectroscopy in predicting the outcome of patients with carotid artery occlusion?

BACKGROUND: Transcranial Doppler (TCD) studies demonstrated that cerebral vasomotor reactivity (VMR) can predict the outcome of carotid artery occlusion (CAO). Near-infrared spectroscopy (NIRS) is a non-invasive optical method for assessing hemoglobin (Hb) oxygenation parameters. The purpose of this study was to evaluate the role of NIRS parameters as prognostic markers of stroke occurrence in patients with CAO. METHODS: Sixty-five patients (46 men, mean age 68.8 years) with CAO were enrolled. Forty-two patients had previous cerebrovascular events (15 TIA, 27 minor stroke), the remaining 23 were asymptomatic. All subjects underwent simultaneous TCD and NIRS examination at rest and after hypercapnia. All patients completed follow-up (median, 36 months). RESULTS: During follow-up, 11 strokes occurred. Cerebral VMR measured by TCD had a prognostic role in stroke occurrence (p=0.042). The increase in Hb oxygen saturation detected by NIRS during hypercapnia predicted the occurrence of new cerebrovascular events, although without an overt significance (p=0.058). Hb oxygen saturation at rest, however, failed to be of prognostic value (p=0.65). CONCLUSIONS: NIRS is potentially useful in monitoring cerebral oxygenation; however, at present NIRS does not effectively predict the outcomes of stroke or vascular death in patients with CAO. This study does confirm the primary role of TCD VMR in the outcome of carotid disease.