An Implantable Sacral Nerve Root Recording and Stimulation System for Micturition Function Restoration

Yuan WANG  Xu ZHANG  Ming LIU  Weihua PEI  Kaifeng WANG  Hongda CHEN  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E97-D   No.10   pp.2790-2801
Publication Date: 2014/10/01
Online ISSN: 1745-1361
DOI: 10.1587/transinf.2013EDP7395
Type of Manuscript: PAPER
Category: Biological Engineering
Keyword: 
neural prosthesis,  functional electrical stimulation,  closed-loop bladder control,  acute animal experiment,  spinal cord injury,  

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Summary: 
This paper provides a prototype neural prosthesis system dedicated to restoring continence and micturition function for patients with lower urinary tract diseases, such as detrusor hyperreflexia and detrusor-sphincter dyssynergia. This system consists of an ultra low-noise electroneurogram (ENG) signal recording module, a bi-phasic electrical stimulator module and a control unit for closed-loop bladder monitoring and controlling. In order to record extremely weak ENG signal from extradural sacral nerve roots, the system provides a programmable gain from 80 dB to 117 dB. By combining of advantages of commercial-off-the-shelf (COTS) electronics and custom designed IC, the recording front-end acquires a fairly low input-referred noise (IRN) of 0.69 μVrms under 300 Hz to 3 kHz and high area-efficiency. An on-chip multi-steps single slope analog-to-digital converter (ADC) is used to digitize the ENG signals at sampling rate of 10 kSPS and achieves an effective number of bits (ENOB) of 12.5. A bi-phasic current stimulus generator with wide voltage supply range (±0.9 V to ±12.5 V) and variable output current amplitude (0-500 μA) is introduced to overcome patient-depended impedance between electrode and tissue electrolyte. The total power consumption of the entire system is 5.61 mW. Recording and stimulation function of this system is switched by control unit with time division multiplexing strategy. The functionality of this proposed prototype system has been successfully verified through in-vivo experiments from dogs extradural sacral nerve roots.