Introduction: Unlike the brain, functional imaging of the spinal cord has been elusive. This is due to the small size of the spinal cord and limitations of the neuroimaging techniques. The functional ultrasound imaging (fUSI) is a novel neuroimaging technique with superior spatiotemporal properties that can detect microvascular changes correlated to changes in neural activity. The objective of this study is to determine whether fUSI can detect and characterize the spatial and temporal hemodynamic changes in the human spinal cord in response to bladder filling and emptying. Methods: Four patients, who were undergoing standard-of-care implantation of a spinal cord stimulator, were enrolled in the study. Following exposure of the spinal cord during implantation of the spinal cord stimulator, the fUSI probe was positioned over the spinal cord at thoracic level 10. Images were acquired during two bladder-filling cycles and one emptying cycle with intermittent holding periods. The bladder pressure dynamics and power Doppler signal were correlated to determine the spinal cord regions associated with micturition. Results: Several regions of interest (ROIs) exhibiting differential activation in response to changes in detrusor pressure were identified. The ROIs were primarily localized to the dorsal spinal cord. Most regions exhibited an increase in power Doppler signal during bladder filling and a decrease in signal with bladder emptying. However, other regions exhibited a reverse pattern with signal reduction during bladder filling and signal increase during emptying (Figure 1). Conclusions: This is the first in-human application of ultrafast ultrasound to study the neurovascular coupling changes that occur in the spinal cord as a result of bladder filling and emptying. The ability to characterize and correlate spinal cord hemodynamics to micturition events holds promise to help further understand functional and dysfunctional anatomy associated with lower urinary tract physiology. SOURCE OF Funding: None
