Selective stimulation of the hypoglossal nerve with a multi-contact cuff electrode

The feasibility of selectively stimulating the hypoglossal nerve (XII) with a multi-contact flat-interface-nerve-electrode (FINE) was investigated for the potential application of treating obstructive steep apnea (OSA). The main trunk of the XII was stimulated with monophasic cathodic pulses, while the elicited electroneurographic (ENG) and electromyographic (EMG) signals were recorded. Selective fascicular stimulation of the XII was achieved but with certain limitations: branches 1 and 2 could not be independently activated and the ranges of stimulus current associated with selective stimulation were small. Nevertheless, in terms of independently activating the protrudor and retractor muscle groups that are relevant to OSA, the ENG data suggests that sufficient control of pharyngeal airway patency can be achieved with this method. The functional selectivity of the FINE, however, was more difficult to address in these experiments. Selective activation of individual muscle groups was not possible but that of the retractor muscle group itself was observed. The results of this paper raise the issue of how fascicles are recruited when whole nerves are stimulated with multi-contact cuff electrodes. In order to answer this question, modification of the FINE may be warranted.