A multivariate analysis of objective voice changes after thyroidectomy without laryngeal nerve injury

Abstract

Objective: To evaluate the impact of thyroidectomy and the possible effects of factors such as patient sex, operation type, and surgeon experience on objective voice parameters of patients undergoing thyroidectomy without laryngeal nerve injury.

Design: Prospective study.

Setting: University hospital.

Patients: Thirty-six patients undergoing primary thyroidectomy because of thyroid disease.

Main outcome measures: The effect of thyroidectomy on voice was examined by recording the voices of the patients before and 1 week after thyroidectomy. The Multi-Dimensional Voice Program was used for capturing and analyzing the voice samples.

Results: On postoperative examination of objective voice changes, thyroidectomy had no multivariate effect on the combination of voice parameters. Patient sex, type of surgery, and surgeon experience had no effect on the combination of voice parameters before and after thyroidectomy. Regardless of within-patient factors (type of surgery, patient sex, and surgeon experience), 4 acoustic parameters (highest fundamental frequency, standard deviation of average fundamental frequency, phonatory average fundamental frequency range in semitones, and degree of subharmonics) significantly decreased after thyroidectomy (P < .05). Although they tended to be worse, none of the acoustic parameters showed significant changes in male patients. However, significant changes in some of the acoustic parameters of female patients were observed. Highest fundamental frequency, standard deviation of average fundamental frequency, phonatory average fundamental frequency range in semitones, absolute jitter, relative average perturbation, pitch perturbation quotient, shimmer in decibels, percentage of shimmer, amplitude perturbation quotient, noise to harmonic ratio, and degree of subharmonics values were all lower in female patients after thyroidectomy (P < .05).

Conclusions: Voice changes may occur after thyroidectomy without any evident laryngeal injury, and deterioration and amelioration of acoustic parameters can be observed to occur differently among male and female patients. Preoperative and postoperative objective voice analyses may be helpful in documenting voice changes.