[Investigation of the mechanism of hoarseness after thyroidectomy].

Electromyography of the intrinsic laryngeal muscles and laryngeal function measurements were performed on 34 patients with hoarseness after thyroidectomy. It is believed that mild laryngeal nerve paralysis might not give rise to disturbances in vocal cord movement. Causes of hoarseness after thyroidectomy could be mild recurrent superior laryngeal or combined nerve paralysis. During recovery, the vocal cord moved from paramedian position to middle position. Normal vocal cord movements did not mean complete recovery from paralysis, since electromyogram still showed abnormal potentials. It is suggested that vocal cord paralysis be divided into three types: severe, moderate and mild.