This project is evaluating chronic neuromuscular stimulation using a neuroprosthesis for treatment of central motor control disorders affecting swallowing. It involves a Cooperative Research and Development Agreement with Medtronic, Inc. The implanted system is radio frequency controlled, contains 8 electrodes, and has capability for 2 different programs. Chronic neuromuscular stimulation of the thyroarytenoid, lateral cricoarytenoid and mylohyoid muscles are evaluated in an animal model. The implanted system remained viable and maintained the same movement threshold, displacement and velocity for up to 15 months with intermittent stimulation of the thyroarytenoid muscle. While bilateral thyroarytenoid stimulation achieved adequate glottic closure for airway protection, mylohyoid muscle stimulation was shown to elevate the larynx. Lateral cricoarytenoid stimulation was found to produce arytenoid adduction. On 3 dimensional reconstruction of CT scans conducted with and without thyroarytenoid muscle stimulation, muscle stimulation reduced both glottal and supraglottal airway opening. Based on the studies conducted in the last year, the following conclusions can be reached: 1. Inferior thyroarytenoid muscle stimulation has a lower threshold and equivalent or greater adduction than the superior thyroarytenoid muscle stimulation. 2. Intermittent stimulation routines do not alter muscle kinematics, do not change muscle fiber type, and do not interfere with muscle reinnervation following nerve injury. 3. Mylohyoid muscle stimulation can raise the larynx and shorten and widen the hypopharynx, dependent upon electrode placement. 4. Laryngeal elevation with mylohyoid stimulation does not alter the glottal opening: both vocal fold adduction and laryngeal elevation are required for airway protection.
