Singing voice range profile: New objective evaluation methods for voice change after thyroidectomy

Background After surgery in the thyroid region, patients may present with phonation or singing difficulty, even within their vocal range. We designed a novel voice evaluation method that reflects subjective and objective voice complications of the surgery. Methods This tool recorded patients' voice ranges while singing, which was named the singing voice range profile (singing VRP). Patients were asked to sing "Happy Birthday," which has a one-octave scale, at a comfortable tone and intensity. The singing VRP, standard VRP and voice handicap index-10 (VHI-10) results were recorded before thyroidectomy and 1 and 3 months after thyroidectomy for 128 patients. For subgroup analysis, a group where the maximum F-0 of standard VRP in 1 month postoperatively was lower than the highest singing F-0 of the preoperative singing VRP was defined as "Collapsed group" and the other group was "Preserved group." Results The changes in the highest, lowest and range of singing fundamental frequency (F-0) had decreased at 1 month postoperatively. Subsequently, they had improved significantly at 3 months postoperatively but were lower than those preoperatively (all P < .05, except for the change in the lowest singing F-0 between 1 and 3 months postoperatively, P = .274). In the subgroup analysis, the singing range of the collapsed group (n = 65) showed significantly lower VHI-10 scores, range of vocal F-0 and singing F-0 than those of the preserved group (n = 63) at 1 and 3 months postoperatively (all P < .001). At 3 months postoperatively, the singing F-0 range in the preserved group had recovered to the range before surgery (13.0 +/- 1.3 vs. 13.1 +/- 1.4, P = .746 for the preserved group, and 13.0 +/- 1.3 vs 11.5 +/- 2.4, P < .001 for the collapsed group). Conclusions Parameters measured by singing VRP showed a trend similar to the change in VHI-10 and the maximum F-0 of standard VRP. In addition, singing VRP allowed a qualitative classification of the postoperative voice function when combined with standard VRP. Therefore, it can be used as a supplementary voice evaluation tool to reflect the physiologic and functional aspects of voice.