Up to 80% of patients without a recurrent laryngeal nerve palsy report alteration
in their voice after a thyroid procedure. The aims of this study were (1) to quantify
voice changes after thyroid operation; (2) to correlate the changes to the extent
of operation; and (3) to correlate voice changes to intraoperative recurrent laryngeal
Patients undergoing total and hemithyroidectomy were recruited prospectively from
the Monash University Endocrine Surgery Unit during a 12-month period. Voice quality
was scored subjectively using the Voice Disorder Index (score 0–40, from best to worst)
and objectively using the Dysphonia Severity Index (score −5 to 5, from worst to best),
before and after operation. These assessments were carried out by 2 speech pathologists.
Recurrent laryngeal nerve diameter was measured intraoperatively at the commencement
and conclusion of the lobectomy, using Vernier calipers with a resolution of 0.1 mm.
Statistical methods used included Student t test, χ2, Wilcoxon signed-rank test, and linear regression.
A total of 62 patients were included in the study, with a mean age of 48 ± 16 years
and a female preponderance (6:1). Overall, the voice quality deteriorated both subjectively
(mean Voice Disorder Index 4.2 ± 0.8–9.4 ± 1.2, P < .01) and objectively (mean Dysphonia Severity Index 3.9 ± 0.3–2.8 ± 0.3, P < .01) with thyroid operation. Patients who underwent either hemi- or total thyroidectomy
both reported significant deterioration of voice (mean Voice Disorder Index 5.4 ± 1.5–7.9 ± 1.4,
P = .02 and 3.4 ± 0.7–10.4 ± 1.8, P < .01 respectively). However, on objective assessment, only total thyroidectomy patients
showed significant deterioration (Mean Dysphonia Severity Index 4.0 ± 0.3–2.5 ± 0.3,
P < .01). At 6–12 months, both Voice Disorder Index and DSI returned to preoperative
levels. Intraoperatively, the recurrent laryngeal nerve diameter increased by 0.58 ± 0.05 mm
(1.82 ± 0.05 mm−2.40 ± 0.05 mm; P < .01). In hemithyroidectomy patients, the degree of nerve swelling correlated with
the degree of deterioration in objective voice assessment, in that the greater the
increase in recurrent laryngeal nerve diameter, the worse the Dysphonia Severity Index
score (coefficient −0.4, P = .03). This was not the case in the total thyroidectomy patients.
Voice quality deteriorates with thyroid operation despite functionally intact recurrent
laryngeal nerve. While likely multifactorial, the degree of deterioration is related
to the extent of operation and may also be related to the degree of recurrent laryngeal
nerve swelling. Spontaneous resolution is expected in the majority of patients.