Near-Infrared Transillumination Back Scattering Sounding—New Method to Assess Brain Microcirculation in Patients with Chronic Carotid Artery Stenosis

Abstract

PurposeThe purpose of the study was to assess the responses of pial artery pulsation (cc-TQ) and subarachnoid width (sas-TQ) to acetazolamide challenge in patients with chronic carotid artery stenosis and relate these responses to changes in peak systolic velocity (PSV), cerebral blood flow (CBF), cerebral blood volume (CBV), mean transit time (MTT) and time to peak response (TTP).MethodsFifteen patients with carotid artery stenosis ≥90% on the ipsilateral side and <50% on the contralateral side were enrolled into the study. PSV was assessed using colour-coded duplex sonography, CBF, CBV, MTT and TTP with perfusion computed tomography, cc-TQ and sas-TQ with near-infrared transillumination/backscattering sounding (NIR-T/BSS).ResultsBased on the ipsilateral/contralateral cc-TQ ratio after acetazolamide challenge two groups of patients were distinguished: the first group with a ratio ≥1 and the second with a ratio <1. In the second group increases in CBF and CBV after the acetazolamide test were significantly higher in both hemispheres (ipsilateral: +33.0%±8.1% vs. +15.3%±4.4% and +26.3%±6.6% vs. +14.3%±5.1%; contralateral: +26.8%±7.0% vs. +17.6%±5.6% and +20.0%±7.3% vs. +10.0%±3.7%, respectively), cc-TQ was significantly higher only on the ipsilateral side (+37.3%±9.3% vs. +26.6%±8.6%) and the decrease in sas-TQ was less pronounced on the ipsilateral side (−0.7%±1.5% vs. −10.2%±1.5%), in comparison with the first group. The changes in sas-TQ following the acetazolamide test were consistent with the changes in TTP.ConclusionsThe ipsilateral/contralateral cc-TQ ratio following acetazolamide challenge may be used to distinguish patient groups characterized by different haemodynamic parameters. Further research on a larger group of patients is warranted.

Morphometric evaluation of the delayed cerebral arteries response to acetazolamide test in patients with chronic carotid artery stenosis using computed tomography angiography

“…Therefore our population may be characterised by generally delayed reactivity, while at the same time being relatively well adapted to low CBF. Such reasoning would be in line with results from our previous study on similar population [7]. Taken together, we may observe higher delayed reactivity on the ipsilateral side to stenosis.…”

“…Nevertheless, both Sato et al [16] and Skow et al [17] used Doppler ultrasound and measured CBF velocity as a surrogate of CBF in healthy subjects. Doppler ultrasound as a method to estimate CBF is even more questionable in patients with chronic artery stenosis due to turbulent blood flow in the area of stenosis [7,11,14]. Therefore, our study, to the best of our knowledge, provides morphometric evaluation of the PCAs reactivity for the first time.…”

“…Therefore the delayed response beyond this timeframe remains unknown. We have previously shown that in patients population with chronic carotid artery stenosis (CAS) within the frontal grey matter there are no differences in CBF response to the acetazolamide test in ipsi-and contra-lateral sides to the ICA stenosis [7]. We speculated that the diameter of the ipsilateral anterior cerebral artery (ACA) and middle cerebral artery (MCA) may need to dilate more than the contralateral ACA and MCA to accommodate the increased CBF.…”

Perfusion computed tomography: 4 cm versus 8 cm coverage size in subjects with chronic carotid artery stenosis

“…Owing to strict inclusion criteria consisting of stenosis of .70% within a single ICA with concomitant neurological symptoms (dizziness, tinnitus, visual disturbances and headaches), our population was very homogeneous in terms of cerebral haemodynamic parameters and was characterized by low CBF and low CBV. 13 Although the relatively narrow population can be seen as a limitation of this study, population homogeneity increased the reliability of our results. Patients with bilateral haemodynamically significant (i.e.…”

“…As long as heart rate is within the normal ranges, there are no direct interactions between heart rate and the parameters CBF, CBV, MTT or TTP. 13 Finally, as the choice of reference artery and venous regions are critical in CTP, 19 the arterial input function within the anterior cerebral artery (Segment A2) on the level of the basal ganglia and the venous output region from the superior sagittal sinus were selected in both groups. ROIs were determined at each analyzed level by the two experienced neuroradiologists; large blood vessels, fluid-filled spaces and postinfarct areas were avoided.…”