Cross-talk in Nerve Root Stimulator Implants

Implanted stimulators of motor nerve roots have been used for functional restoration in paraplegia since many years. While the high root density of the cauda equina limits the surgery to one field, it also presents the problem of cross-talk stimulation: unwanted activation of a root lying near an active set of electrodes. The Lumbar Anterior Root Stimulator Implant (LARSI) did exhibit cross-talk, and we have hypothesized that this is because the anodes in all the slots were connected together, causing virtual cathodes outside the active slot. In this paper, we report in vitro experiments suggesting that, with a better design, we can improve the cross-talk ratio (out-of-slot threshold/in-slot threshold) from <10 to >80.