Transcranial Doppler and Near-Infrared Spectroscopy Can Evaluate the Hemodynamic Effect of Carotid Artery Occlusion

Abstract

Background and Purpose-Cerebral hemodynamic and metabolic changes can compensate for the decrease in cerebral blood flow occurring in patients with carotid occlusive disease. At present, a complete assessment of the cerebral adaptive status is only possible with positron-emission tomography. Near-infrared spectroscopy (NIRS) is a noninvasive technique that, providing a real time assessment of fluctuations in cerebral hemoglobin, has been used to estimate the cerebral blood volume and to measure cerebral vasomotor reactivity (VMR). Moreover, NIRS technology, by allowing the absolute measurement of absorption and scattering coefficients of brain, can determine the oxyhemoglobin and deoxyhemoglobin concentrations in situ in the blood stream. Methods-In order to evaluate different aspects of the cerebral hemodynamic status, 27 subjects with symptomatic and asymptomatic carotid artery occlusion and 30 healthy subjects underwent a simultaneous examination by means of transcranial Doppler (TCD), able to reliably detect collateral circulation and VMR, and NIRS at rest condition and during CO 2 reactivity test. Results-The main finding of this study was the demonstration of a difference between asymptomatic and symptomatic patients in terms of mean flow velocity increase (52.4% versus 21.0%; PϽ0.001) estimated by TCD and of hemoglobin saturation increase measured by NIRS (6.8% versus 3.8%; Pϭ0.015). Conclusions-The opportunity to perform NIRS and TCD simultaneously provides useful information about both hemodynamic and metabolic cerebral adaptive status in patients with occlusive disease in a simple, noninvasive, and reliable way.

Cerebral Hemodynamic Changes in Stroke During Sleep-Disordered Breathing

“…Alternative explanations for our findings could be: reduced cerebral metabolism 6 ; alteration of the "neurovascular unit," including postischemic vasoparalysis with maximal vasodilatation 11 ; and impaired cerebral vasomotor reactivity to hypercapnia 3 with intracerebral blood steal to the unaffected hemisphere. 12 Minor hemodynamic changes of the affected hemisphere could therefore reflect its diminished cerebral metabolism, or a detrimental vascular "storm" induced by SDB.…”

“…2 Cerebral NIRS coupled with transcranial Doppler (TCD) during the breath-holding test in patients with carotid occlusion distinguished symptomatic patients for their insufficient cerebrovascular autoregulation. 3 NIRS also proved the inability of cerebral autoregulation to prevent hypoxia in patients with severe obstructive SDB. 4 …”

Improved Cerebral Vasomotor Reactivity After Exercise Training in Hemiparetic Stroke Survivors

“…24 -28 It exhibits diurnal variations, reaching low points during morning hours when stroke events are most prevalent. 29 Both symptomatic and asymptomatic carotid artery stenosis are well-known contributors to impaired cVMR, 30 with vasomotor response to CO 2 lower on the stenotic side and improving after carotid endarterectomy. 27 Previous investigations report that impaired cVMR predicts higher stroke risk, 8,9,31 although one recent study suggests basal MCA-BFV is more important to stroke risk than cVMR.…”

Partitioning of Physiological Noise Signals in the Brain with Concurrent Near-Infrared Spectroscopy and fMRI

“…These fluctuations primarily affect the cerebral blood volume and CBF, which are better detected using the D[HbO] waveform; moreover, the effects of global blood-oxygen saturation variations over time are also captured in this signal. (Tong and Frederick, 2010;Vernieri et al, 2004). Therefore, to correlate accurately between the NIRS signal and BOLD, the temporal trace of…”