Voices of 47 female patients were analyzed before and after thyroidectomy, with preservation
of the recurrent and superior laryngeal nerves and normal vocal fold motility during
the observation period. A mean decrease of the speaking fundamental frequency (SFF)
of 12 Hz was found on day 4; in 8 patients the postoperative vocal pitch was more
than 2 semitones lower. The distance between the highest and lowest F0 during speaking
was diminished (speech was more monotone) and the vocal jitter was elevated. In the
frequency spectrum, there was a diminished prominence of the harmonics. The other
spectral parameters (as the slope of the spectrum and the H1/H2 ratio) were unchanged.
All changes had disappeared the fifteenth day, except for a lower SFF (> 2 semitones)
in 2 cases. It is concluded that after normal dissection of the laryngeal nerves,
and in the absence of vocal fold paresis, other reasons for voice changes immediately
after thyroidectomy remain: alterations in the neck muscles, in the laryngeal mucosa,
and in the patient's general condition. Although the effects seem limited and of short
duration, knowledge of them is helpful when informing the patient before thyroid surgery.