[Experimental investigation of cricothyroid approximation for correction of hoarseness caused by superior laryngeal paralysis].

Twenty-four adult dogs were used for the experiments. Cricothyroid approximation was performed in 17 of them. The bilateral external branches of the superior laryngeal nerves were severed in advance and their phonation under light anaesthesia investigated preoperatively, immediately and 6-20 weeks after operation by sound spectrum in all animals. Following the operation, the animals with cricothyroid approximation got higher pitch and lesser hoarseness than the controls, but would never reach the preoperative mean value. It is considered that the effect of cricothyroid approximation in raising vocal pitch and improving phonation is affirmative but limited.