Altered neurovascular coupling in neuromyelitis optica.

Neurovascular coupling reflects the close relationship between neuronal activity and cerebral blood flow (CBF), providing a new mechanistic insight into health and disease. Neuromyelitis optica (NMO) is an autoimmune inflammatory demyelinating disease of the central nervous system and shows cognitive decline-related brain gray matter abnormalities besides the damage of optic nerve and spinal cord. We aimed to investigate neurovascular coupling alteration and its clinical significance in NMO by using regional homogeneity (ReHo) to measure neuronal activity and CBF to measure vascular response. ReHo was calculated from functional MRI and CBF was computed from arterial spin labeling (ASL) in 56 patients with NMO and 63 healthy controls. Global neurovascular coupling was assessed by across-voxel CBF-ReHo correlations and regional neurovascular coupling was evaluated by CBF/ReHo ratio. Correlations between CBF/ReHo ratio and clinical variables were explored in patients with NMO. Global CBF-ReHo coupling was decreased in patients with NMO relative to healthy controls (p = .009). Patients with NMO showed decreased CBF/ReHo ratio (10.9%-17.3% reduction) in the parietal and occipital regions and increased CBF/ReHo ratio (8.0%-13.3% increase) in the insular, sensorimotor, temporal and prefrontal regions. Some of these abnormalities cannot be identified by a single CBF or ReHo analysis. Both abnormally decreased and increased CBF/ReHo ratios were correlated with more severe clinical impairments and cognitive decline in patients with NMO. These findings suggested that patients with NMO show abnormal neurovascular coupling, which is associated with disease severity and cognitive impairments.