Disrupted functional connectivity in carotid artery stenosis patients: Insights from fNIRS during a vasoreactivity test

Carotid artery stenosis (CAS) reduces cerebral perfusion, which can contribute to neurodegeneration and cognitive decline. While fMRI studies have identified CAS-related disruptions in functional connectivity (FC) associated with neurodegeneration, translating these methods to functional near-infrared spectroscopy (fNIRS) offers a portable, clinically practical alternative. In this study, we assessed FC using fNIRS in 44 CAS patients and 20 controls during breath-holding, a clinical vasoreactivity task. Our results demonstrate clear differences between FC during breath-holding and the resting state, highlighting the task's impact on network connectivity. Patients with unilateral mild stenosis (50–69 % occlusion) exhibited FC patterns comparable to those of controls, whereas patients with bilateral severe stenosis showed a 26 % reduced connectivity and a 14 % lower clustering. When accounting for time delays of 0.9–1.3 seconds, network synchrony was restored across all CAS groups, suggesting that the proposed fNIRS-based method can be used to investigate compensatory hemodynamic delays in CAS. Although sample size limits broader clinical generalizations, this work demonstrates the feasibility of using fNIRS for FC analysis in CAS during a vasodilatory task and provides evidence that fNIRS-based FC metrics are sensitive to CAS severity.