(E-185) Functional Ultrasound Imaging Reveals Dynamics of Micturition in the Human Spinal Cord

Introduction:The spinal cord is traditionally neglected in the study of neural function because it is predominantly viewed merely as a pathway between the brain and the peripheral nervous system. As a result, its anatomy and physiology are not well understood as those of the brain. While strong evidence from preclinical work exists for the presence of regulatory neural-network-circuits that are responsible for vital motor, sensory and autonomic functions, its demonstration in humans has been challenging. The facial enclosures and the small cross-sectional dimension of the spinal cord combined with susceptibility to artifacts make it an unfavorable target for traditional neuroimaging techniques. The lack of knowledge in humans consequently, results in suboptimal therapeutic strategies for treating dysfunctions associated with disease or injury to the spinal cord – with devastating health and cost burdens. For instance, current care for urinary dysfunction that affect over 30 million Americans relies mostly on symptomatic management with the use of catheters to empty the bladder. Given this context, there is a distinct need for developing neurotechnologies that make the functional study of the human spinal cord more accessible.


Materials and Methods:: Herein, we investigate the human spinal cord hemodynamic response to bladder filling and emptying, by leveraging the superior spatiotemporal properties of functional ultrasound imaging (fUSI). We characterize the spatial and temporal hemodynamic responses to bladder filling and emptying using simultaneous fUSI spinal cord images acquired from 6 patients. Utilizing 2 bladder-filling cycles and 1 emptying cycle, interspersed by hold periods, we also decode the bladder pressure dynamics from the power Doppler (pD) (i.e.,fUSI) signals to detect spinal cord regions associated with micturition.

Results, Conclusions, and Discussions:: Our findings reveal that responses to bladder filling and emptying reflect a spatiotemporal modulation of human spinal cord hemodynamics not previously evident – with region-specific spinal cord states that show strong correlation with the temporal bladder pressure dynamics (r = 0.86 ± 0.03, Mean ± SE), during filling and emptying (Fig. 1A). Additionally, we extend these results utilizing combined classwise principal component analysis (cPCA) and a support vector machines (SVM) model, to decode the bladder pressure state with high accuracy solely from fUSI pD signal. (Fig. 1C).
Our study presents the first in-human application of fUSI to study the hemodynamic response of the spinal cord during bladder filling and emptying. The ability to characterize and correlate spinal cord hemodynamics as well as decode bladder state opens avenues to investigate spinal cord function and an essential component for building spinal cord machine interface for patients with urinary dysfunctions. Ultimately this is vital for translational development of real-time closed-loop neurorehabilitation systems to restore urinary functions.

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