Control of paralysed axial muscles by electrical stimulation.

The function of a paralysed axial (laryngeal, facial, extraocular) muscle could conceivably be restored if it were made to contract again like its contralateral partner. A muscle stimulation device was designed and constructed so that the stimulus delivered to a given paralysed muscle was modulated by a signal reflecting the contractile state of its contralateral partner. Studies in dog larygneal muscles indicate that paralysed muscles stimulated by such an open-loop device could mimic their partners. However, their tracking accuracies were limited by the nature of their stimulus-reponse characteristics. On the other hand, significantly greater tracking accuracies were observed if a closed-loop device was employed, that is, if feedback information from the stimulated muscles was also used to control the device stimulus level. Considerations in implanting such a (closed-loop or open-loop) device in paralysed axial muscles for chronic stimulation are discussed.