Hyperventilation and breath-holding test with indocyanine green kinetics predicts cerebral hyperperfusion after carotid artery stenting

Quantification of the Tissue Oxygenation Delay Induced by Breath-Holding in Patients with Carotid Atherosclerosis

Carotid artery stenosis (CAS) is a common vascular disease with long-term consequences for the brain. Although CAS is strongly associated with impaired cerebral hemodynamics and neurodegeneration, the mechanisms underlying hemodynamic impairment in the microvasculature remain unknown. In this work, we employed functional near-infrared spectroscopy (fNIRS) to introduce a methodological approach for quantifying the temporal delay of the evoked hemodynamic response. The method was validated during a vasodilatory task (breath-holding) in 50 CAS patients and 20 controls. Our results suggest that the hemodynamic response to breath-holding can be delayed by up to 6 s in the most severe patients, a significant increase from the median 4 s measured for the control group (p = 0.01). In addition, the fraction of brain regions that responded to the task decreased as the CAS severity increased, from a median of 90% in controls to 73% in the most severe CAS group (p = 0.04). The presence of collateral circulation increases the response to breath-holding and decreases the average time delays across the brain, although the number of communicating arteries alone cannot predict these fNIRS-based hemodynamic variables (p > 0.09). Overall, this work proposes a method to quantitatively assess impaired cerebral hemodynamics in CAS patients.

Lawrence K, Tachtsidis I, Tong Y, Torricelli A, Urner T, Wabnitz H, Wolf M, Wolf U, Xu S, Yang C, Yodh AG, Yücel MA, Zhou W. Optical imaging and spectroscopy for the study of the human brain: status report

This report is the second part of a comprehensive two-part series aimed at reviewing an extensive and diverse toolkit of novel methods to explore brain health and function. While the first report focused on neurophotonic tools mostly applicable to animal studies, here, we highlight optical spectroscopy and imaging methods relevant to noninvasive human brain studies. We outline current state-of-the-art technologies and software advances, explore the most recent impact of these technologies on neuroscience and clinical applications, identify the areas where innovation is needed, and provide an outlook for the future directions.

Arterial transit artifacts on arterial spin labeling MRI can predict cerebral hyperperfusion after carotid endarterectomy: an initial study

OBJECTIVES

To investigate whether preoperative arterial spin labeling (ASL) MRI can predict cerebral hyperperfusion after carotid endarterectomy (CEA) in patients with carotid stenosis.

METHODS

Consecutive patients with carotid stenosis who underwent CEA between May 2015 and July 2021 were included. For each patient, a cerebral blood flow ratio (rCBF) map was obtained by dividing postoperative CBF with preoperative CBF images from two pseudo-continuous ASL scans. Hyperperfusion regions with rCBF > 2 were extracted and weighted with rCBF to calculate the hyperperfusion index. According to the distribution of the hyperperfusion index, patients were divided into hyperperfusion and non-hyperperfusion groups. Preoperative ASL images were scored based on the presence of arterial transit artifacts (ATAs) in 10 regions of interest corresponding to the Alberta Stroke Programme Early Computed Tomography Score methodology. The degree of stenosis and primary and secondary collaterals were evaluated to correlate with the ASL score. Logistic regression and receiver operating characteristic curve analyses were performed to assess the predictive ability of the ASL score for cerebral hyperperfusion.

RESULTS

Of 86 patients included, cerebral hyperperfusion was present in 17 (19.8%) patients. Carotid near occlusion, opening of posterior communicating arteries with incomplete anterior semicircle, and leptomeningeal collaterals were associated with lower ASL scores (p < 0.05). The preoperative ASL score was an independent predictor of cerebral hyperperfusion (OR = 0.48 [95% CI [0.33-0.71]], p < 0.001) with the optimal cutoff value of 25 points (AUC = 0.98, 94.1% sensitivity, 88.4% specificity).

CONCLUSIONS

Based on the presence of ATAs, ASL can non-invasively predict cerebral hyperperfusion after CEA in patients with carotid stenosis.

KEY POINTS

• Carotid near occlusion, opening of posterior communicating arteries with incomplete anterior semicircle, and leptomeningeal collaterals were associated with lower ASL scores. • The ASL score performed better than the degree of stenosis, type of CoW, and leptomeningeal collaterals, as well as the combination of the three factors for the prediction of cerebral hyperperfusion. • For patients with carotid stenosis, preoperative ASL can non-invasively identify patients at high risk of cerebral hyperperfusion after carotid endarterectomy without complex post-processing steps.

Hypocapnia Induced by Hyperventilation with Indocyanine Green Kinetics Detects the Effect of Staged Carotid Angioplasty to Avoid Hyperperfusion in Patients with Impaired Cerebral Hemodynamic Reserve

Cerebral hyperperfusion syndrome (CHS) is a serious complication following carotid artery stenting (CAS). Staged angioplasty (AP) could potentially prevent CHS and hyperperfusion phenomenon (HPP) after revascularization. However, methods for measuring the effects of staged AP on cerebral hemodynamic reserve have not been established. Here, we evaluated whether indocyanine green kinetics and near-infrared spectroscopy (ICG-NIRS) with hypocapnia induced by hyperventilation can detect the effects of staged AP on hemodynamic reserve to prevent CHS after CAS. Participants comprised 44 patients at high risk of CHS, whose ipsilateral cerebrovascular reactivity (CVR) was impaired on preoperative single photon emission computed tomography (SPECT). Patients were divided into a staged AP group (n=13) and a regular CAS group (n=31). In the staged AP group, stenting was performed 3 weeks after staged AP. In the regular CAS group, 16 cases (52%) showed HPP, and five (16%) presented with CHS after CAS, while no HPP or CHS occurred in the staged AP group (p=0.001). Changes in blood flow index (BFI) and time to peak (TTP) ratio during hypocapnia calculated from ICG-NIRS indicated a significant linear relationship with preprocedural CVR on SPECT (r=-0.710, 0.632, respectively; p<0.0001 each). BFI and TTP ratios during hypocapnia were significantly improved after staged AP (p<0.001 each). Furthermore, significant linear correlations were observed between BFI and TTP ratio during hypocapnia and postoperative asymmetry index AI (r=0.405, -0.475, respectively; p<0.01 each). Hypocapnia induced by hyperventilation under ICG-NIRS appears useful for detecting the effects of staged AP on hemodynamic reserve in patients at high risk of CHS.