Early Acoustic Voice Changes After Thyroidectomy Without Laryngeal Nerve Injury

The incidence of thyroid cancer has been increasing annually, and surgery remains the primary therapeutic approach. Clinically, postoperative voice disorders may occur in patients undergoing thyroidectomy, even in the absence of intraoperative injury to the laryngeal nerves. This retrospective study aimed to objectively evaluate postoperative acoustic voice alterations after thyroidectomy using Praat software in patients with confirmed preservation of recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN) function. The study focused on changes in acoustic parameters within 72 hours after surgery and explored associated influencing factors, providing a reference for early and accurate assessment, identification, and intervention of postoperative voice impairment to facilitate patient recovery.

A total of 68 patients diagnosed with papillary thyroid carcinoma who underwent total thyroidectomy or thyroid cancer radical surgery at our hospital between October 2025 and January 2026 were retrospectively enrolled. Acoustic analyses were performed using Praat software at three time points: T0 (1-3 days before surgery), T1 (18-24 hours after surgery), and T2 (66-72 hours after surgery). Sustained phonation of the vowel /a/ was recorded in a quiet room with the microphone positioned 10 cm from the participant's mouth using a digital recorder and microphone system. Acoustic parameters, including fundamental frequency (F0), jitter, shimmer, and the maximum phonation time (MPT), as an indicator of respiratory phonatory function, were extracted. Clinical characteristics, surgical-related variables, and perioperative data were collected through structured questionnaires and medical records to analyze the current status of postoperative voice impairment and potential influencing factors.

The results demonstrated that jitter at T2 exhibited the highest sensitivity to surgical trauma among the evaluated acoustic parameters. Intraoperative blood loss exceeding 20 mL was identified as an independent influencing factor for postoperative jitter variation (β = 0.600, P < 0.001). Fundamental frequency (F0) was primarily affected by sex (β = 0.390, P = 0.001). However, shimmer and MPT showed no significant predictive value during the hyperacute postoperative period.

Voice abnormalities occurring after thyroidectomy in papillary thyroid carcinoma patients without intraoperative nerve injury are reversible. The severity of postoperative voice alterations is associated with sex, the extent of intraoperative lymph node dissection, and intraoperative blood loss. This study supports an evaluation strategy based on the matching of specific acoustic indicators with appropriate postoperative time windows for detecting thyroidectomy-related voice impairment. Early identification of voice changes during the hyperacute postoperative phase and implementation of targeted interventions for high-risk patients may reduce the severity of voice dysfunction and improve phonatory recovery.