REFLEX RESPONSES AND SPASMIC AFTER-DISCHARGES EVOKED IN THE INTERNAL LARYNGEAL MUSCLES

Abstract

Vocal cord motion reflexly induced by stimulation of the internal branch of the superior laryngeal nerve(SLN)with single or frequent electrical shock was observed.Evoked potentials in the internal laryngeal muscles were recorded.Conclusions are as follows;
1.The vocal cord adducted reflexly by single shock stimulation of the internal branch of the SLN, but returned quickly to the intermediate position.
2.Reflex contraction by single shock stimulation was observed not only in the adductor muscles but also in the abductor.
3.By frequent stimulation of the internal branch of the the SLN, on the othe other hand, adduction of the vocal cord into the midline continued even after some ten seconds of stimulation.The vocal cord became short and the closure of glottis was sphincteric in type.
4.In case of frequent stimulation, reflexly evoked potentials were obserbed only in the adductor muscles.The abductor, on the contrary, was reflexly inhibited.
5.Spasmic-after-discharges were induced mainly in the thyroarytenoid muscle, which play an important role in spasmic closure of the larynx.
6.Origin of spasmic-after-discharge was discussed.