How Can We Predict the Recovery from Pitch Lowering After Thyroidectomy?

Background: Some of patients are suffered from pitch lowering of voice after thyroidectomy. We sought to identify factors predictive of a recovery from lowered pitch voice after thyroid surgery.
Methods: We retrospectively reviewed the records of 133 patients who underwent total thyroidectomy to treat papillary carcinoma between January 2012 and February 2013. Of these, we enrolled 78 who exhibited a lower-pitched voice (SFF fall > 12 Hz) at 2 weeks post-operatively than pre-operatively and investigated pitch recovery after 3 months. We subclassified patients into recovery and non-recovery groups and compared videostroboscopic findings, acoustic voice data, and thyroidectomy-related voice questionnaire scores pre-operatively and 2, 8, and 12 weeks post-operatively.
Results: Vocal cord asymmetry on videostroboscopic examination at 2 weeks post-operatively (odds ratio 19.056, p = 0.001*) was more frequent in the non-recovery group. In acoustic analysis, mean pre-operative SFF was higher in the non-recovery group than the recovery group (190.9 ±  27.5 and 180.9 ±  24.6 Hz, respectively; p = 0.030*). Also, a reduction in the SFF of > 19.6 Hz, at 2 weeks post-operatively versus pre-operatively, predicted non-recovery of pitch-lowering in patients with reduced SFF within post-operative 3 months, with 72.0% sensitivity and 71.2% specificity. After 6 months of follow-up, no patient who exhibited an SFF fall > 19.6 Hz recovered to within 10 Hz of the pre-operative value.
Conclusion: A reduction in the speaking fundamental frequency (SFF) > 19.6 Hz at 2 weeks post-operatively predicted persisting lowering of voice pitch after thyroidectomy among those with lower-pitched voices after surgery. Pre-operative high SFF and post-operative stroboscopic findings including vocal cord asymmetry at 2 weeks post-operatively also predicted persisting lowering of voice pitch for 3 months.