A Fully Implantable Stimulator For Experimental Use In Epidural Spinal Cord Stimulation

Epidural Spinal Cord Stimulation (ESCS) uses electrodes which can be implanted inthe spinal canal to stimulate central neural system directly. ESCS combined with partialweight bearing therapy (PWBT) has been reported to facilitate recovery of functionalwalking for individuals after chronic incomplete spinal cord injury. However, the definiteregulatory mechanism of ESCS is still unknown. Meanwhile, ESCS system which can beused in the research of animal experiments is required to be developed. Further more, thecommercial stimulator for human use is expensive, which usually are powered by batteries.It makes the real service life of an implantable device is short because of the limitedbattery capacity.In view of existing situation that the ESCS device for animal experiments is requiredto be developed and the bottlenecks in power supply for implantable devices need to besolved, this paper describes a low cost, fully implantable, advanced ESCS stimulator thatcan be manufactured in a research laboratory for use in small animals under the supportfrom National Natural Science Foundation (Program NO.:60874035).In this thesis, the theory of ESCS and the research focus in this field at present areintroduced. The generation and transmission of nerve impulse, the structure andphysiological function of the spinal cord are also referred. Then, this thesis describes thedesign process of the ESCS system which can be used in animal research in detail.The system is composed of four main parts: an external personal digital assistant(PDA), an external controller, an implantable pulse generator (IPG), lead extension andelectrode. The PDA allows the experimenter to program the stimulation parametersthrough a user-friendly graphical interface. The external controller placed on the rat backcommunicates with PDA via RF telemetry. The IPG generates the biphasiccharge-balanced voltage-regulated pulses, which are delivered to the bipolar electrode bythe lead extension to achieve chronic ESCS in freely moving rats. A RF carrier from theClass-E amplifier in the external controller provides both data and power for the implantedcircuitry through a closely coupled inductive link. The IPG is hermetically packaged usinga silicon elastomer and measures22mm×23mm×7mm with a mass of3.78g.Finally, this thesis gives the results of the testing of this ESCS system. The wholesystem works stably and the wireless communication has low error rate and the output of the biphasic charge balanced circuit is definite. The stimulator output ranges from50mVto10V (step10mV,100mV and1V), and the frequency from0Hz to200Hz (step1Hz,10Hz and100Hz), while the pulse width from400μs to1200μs. The duration of thestimulation can be set from10s to60min.