Phonatory characteristics of patients undergoing thyroidectomy without laryngeal nerve injury.

Complications that arise after thyroid surgery may be associated with infection, hemorrhage, hormonal problems, and laryngeal nerve injury. Voice alteration after thyroidectomy is usually caused by recurrent or superior laryngeal nerve injury. This voice dysfunction may also be associated with laryngotracheal fixation with impairment of vertical movement or by temporary malfunction of the strap muscles after surgery. In this study, we evaluated the voice function phonetically before and after thyroidectomy in 54 patients, although function of the recurrent and superior laryngeal nerves was normal. During surgery, the superior and recurrent laryngeal nerves were identified and protected, and after surgery electromyographic testing of the cricothyroid muscle was performed. Typical voice symptoms after surgery were easy fatigue during phonation and difficulty with high pitch and singing voice. Acoustic analysis revealed that the phonation time and fundamental frequency were not changed after surgery, but the speaking fundamental frequency, range of speaking fundamental frequency, and vocal range were significantly diminished after surgery. These data allowed us to suggest that the cause of voice dysfunction is not seen in neural lesions, but in a disturbance of the extralaryngeal skeleton. These voice changes emphasize the importance of the extralaryngeal mechanism for pitch control.