Intraspinal stimulation with silicon-based 3D microelectrode array for bladder voiding in cats before and after spinal cord injury

Abstract

Bladder dysfunction is a significant and largely unaddressed problem for people living with spinal cord injury. Intermittent catheterization does not provide volitional control of micturition and has numerous side effects. Targeted electrical microstimulation of the spinal cord has been previously explored for restoring such volitional control in the animal model of experimental spinal cord injury. In this study, the development of the intraspinal microstimulation array technology was continued and evaluated in the feline animal model for its ability to provide more focused and reliable bladder control after a complete spinal cord transection. For the first time, the intraspinal multisite silicon array wad built using novel microfabrication processes to provide custom-designed tip geometry and 3D electrode distribution, better cost efficiency, reproducibility, scalability, and on-the-probe integration of active electronics. Long-term implantation was performed in 8 animals for a period up to 6 months, targeting the dorsal gray commissure area in the S1 sacral cord that is known to be involved in the coordination between the bladder detrusor and the external urethral sphincter. About one third of the electrode sites in the that area produced micturition-related responses. The effectiveness of stimulation increased starting from one month after spinal cord transection (as evaluated in one animal), likely due to supraspinal disinhibition of the spinal circuitry and/or hypertrophy and hyperexcitability of the spinal bladder afferents. Further studies are required to assess longer-term reliability of the developed intraspinal microstimulation array technology in preparation for eventual human translation.