Addition of an intrafascicular electrode at the site of application of a multipolar nerve cuff enhances the opportunity for selective fascicular activation

Multipolar nerve cuffs are being developed to apply to peripheral trunk nerves in an effort to limit the number of implanted components of an FES system, while at the same time allowing specific fascicles within the cuffed nerve to be independently activated. Because the electrode contact sites of a multipolar circumferential fitted cuff are positioned only at the surface of the cuffed nerve, it is difficult to activate fascicules that are located deep within the nerve. This situation might be improved if one or more additional electrode contacts were provided within the core of the nerve. An obvious choice for such a contact is to use an intrafascicular electrode (IFE) such as. those described by Horch and his colleagues. In our present study we inserted a single IFE into a trunk nerve that subserves the forelimb muscles in an adult anesthetized pig. An 18 pole multichannel nerve cuff was then applied to the nerve at the same site. We stimulated different combinations of the cuff contact sites with and without the IFE while monitoring the evoked EMGs from an array of innervated forearm and shoulder muscles to assess the ability to activate different fascicles independently. The results have shown that the use of the IFE in combination with the normal cuff contacts can afford modest improvements in the degree of selective muscle activation that is possible.