Clin Exp Otorhinolaryngol.  2017 Jun;10(2):168-173. 10.21053/ceo.2015.01585.

Changes in Oral Vowel Sounds and Hyoid Bone Movement After Thyroidectomy

  • 1Department of Otolaryngology-Head and Neck Surgery, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea.
  • 2Speech Therapy, Research Institute of Clinical Medicine of Chonbuk National University-Biomedical Research Institute of Chonbuk National University Hospital, Jeonju, Korea.


Voice and speech alterations after total thyroidectomy may be associated with other extralaryngeal factors, such as neck muscle dysfunction and neck scar contracture. We evaluated the acoustic characteristics of oral vowel sounds and changes in hyoid bone movement before and after thyroidectomy.
Twenty-nine female patients undergoing total thyroidectomy were included. Fundamental frequencies (Fo), formants and vowel space areas were evaluated before surgery and 7 days and 3 months after surgery to acoustically analyze the oral vowel sounds. Videofluoroscopic images were taken at the same times to evaluate hyoid bone movement.
The Fo levels of seven vowels decreased significantly after surgery. The vowel formant changes the F1 of vowel /[e]/ decreased significantly from baseline at 3 months postoperatively, and the F3 of vowel /[i]/ decreased significantly from baseline 7 days postoperatively. The change in the vowel space area was not observed. The Y coordinate of the vowels /[i]/ and /[e]/ decreased significantly from baseline 7 days postoperatively due to changes in hyoid movement.
The damage to the neck muscles after thyroidectomy changes in Fo, formant and hyoid bone position. These quantitative results could be used as basic data for voice management in patients who undergo thyroidectomy.


Thyroidectomy; Oral Vowel; Hyoid Bone Movement

MeSH Terms

Hyoid Bone*
Neck Muscles


  • Fig. 1. Anterior and inferior regions of the 4th cervical vertebra were set as the origin “O” of the coordinate, and starting from the origin, the straight line connecting the anterior and inferior regions of the 2nd cervical vertebra was set as the y-axis. With the y-axis passing the origin as the center, the perpendicular line was set as the x-axis vertebra, and the x-axis was the line perpendicular to the y-axis.

  • Fig. 2. Changes in formant frequencies (F1 and F2) according to the time of surgery, (A) for F1 and (B) for F2.

  • Fig. 3. Mean values of 7-vowesl space area according to the time of surgery.

  • Fig. 4. Changes in hyoid bone movements, (A) for X-axis and (B) for Y-axis.


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