Non-Neural Post-Thyroidectomy Dysphonia: Long-Term Voice Outcomes in 527 Patients.

OBJECTIVE

To characterize non-neural post-thyroidectomy dysphonia (PTD) by analyzing long-term voice outcomes in patients with no evidence of nerve injury on postoperative laryngoscopy and electromyography (EMG).

STUDY

DESIGN

Retrospective cohort study.

SETTING

Tertiary referral center.

METHODS

We reviewed 527 post-thyroidectomy patients with intact vocal fold mobility and normal EMG results at 2 to 3 months postoperatively. Voice evaluations, including acoustic analysis, voice range profile, aerodynamic study, and VHI-10, were performed preoperatively and 3 days, 2 weeks, 1, 3, 6, and 12 months postoperatively. Linear mixed models and machine learning were used to assess the effects of sex, age, surgical extent, and preoperative fundamental frequency (F0pre) on voice parameters.

RESULTS

Fundamental frequency (F0) and speaking fundamental frequency (SFF) declined immediately after surgery, with more prolonged reduction in older patients (≥45 years) and those with high F0pre. VHI-10 increased during the early postoperative period, particularly after total thyroidectomy, but returned to near-baseline by 6 to 12 months. Older age was associated with delayed VHI-10 recovery. Maximum frequency (Fmax) decreased in the early period after total thyroidectomy. F0pre and age were main predictors of F0 and SFF at 1 and 3 months, while surgical extent predicted VHI-10 and Fmax at 1 month.

CONCLUSIONS

Voice changes may occur even when the recurrent laryngeal nerve and the external branch of the superior laryngeal nerve are preserved during thyroidectomy. Although most alterations improve over time, some voice parameters may not fully recover, with outcomes influenced by sex, age, surgical extent, and F0pre. These findings may aid in counseling patients with non-neural PTD.