Adaptation in the function of pharyngeal constrictor muscles.

The palatopharyngeus and pharyngeal constrictor muscles were studied by electromyography (EMG) and by direct observation with a flexible fiberoptic scope in the anesthetized as well as in the alert rhesus monkey. The muscles were monitored to determine the change in their discharge with nasal obstruction, head posture, head extension, and swallowing. The results indicated that certain regions of the middle and inferior pharyngeal constrictors never discharged during deglutition. Extending the head could induce a tonic discharge in fibers of the middle pharyngeal constrictor for the duration of head extension. Placement of water in the hypopharynx not only induced a sustained laryngospasm but also a tonic discharge in the select fibers of the superior and middle pharyngeal constrictors. Changing from a supine to an upright posture, or obstructing the nasal cavity, could induce a rhythmic discharge. These studies indicate that there are functional components of fibers within each of the anatomically recognized pharyngeal constrictors.

Laryngeal reinnervation using the split-phrenic nerve-graft procedure.

A new operative procedure for reinnervation of the paralyzed larynx is described. Initial successes in a series of animals have shown that use of the split-phrenic nerve-graft procedure results in functional abduction of the paralyzed vocal cord, while preserving innervation to the diaphragm. Electromyography, microlaryngoscopic movies, chest fluoroscopic examination, and nerve compound action potential recordings were all used to document these findings. This procedure appears to have several advantages over the neuromuscular pedicle operation described by Tucker.