Abstract
Vocal affection in thyroid surgery
Voice production results from the complex function of the vocal mechanism. The vocal mechanism involves the larynx (commonly called the “voice box”) and the infralaryngeal, supralaryngeal and circunlaryngeal structures. The thyroid gland embraces the larynx and trachea, and laryngeal neurovascular structures are deeply connected to the thyroid gland.
Thyroid pathology may induce changes in laryngeal function from anatomical and/or functional compromise. In modern medicine, when proposing thyroid surgery to a patient, the goal is focused both on disease control and in quality-of-life preservation or improvement strategies. Focusing on the patients´ needs in thyroid surgery involves voice quality preservation, because this is a pre-operative concern in self-aware patients and therefore a patient related outcome measure (PROM) to be taken into account.
The importance of early diagnosis of laryngeal dysfunction in thyroidectomy patients derives from the reduced quality of life these patients experience from symptoms such as voice and swallowing disorders. Mechanisms of vocal affection in thyroid surgery are still not clear.
This study wants to quantify pre-operative and post-operative long term voice changes in thyroidectomy patients without vocal fold (VF) immobility and to confirm the hypothesis that an increased thyroid volume is a risk factor for post-operative voice changes.
The clinical practice improvement pretended with this investigation was the need to stratify risk factors more finely in statement 2b from 2010 American Academy of Otolaryngology – Head and Neck Society published guideline “Best Practice Guidelines for Voice Preservation in Thyroid Surgery”, establishing whether goiter surgery should be included in the conditions to refer for pre-operative laryngeal assessment in voice preservation strategies.
If bigger thyroid volume in goiter relates to increased risk for voice change post-operatively, then early referral to voice clinics of patients with increased volume thyroids, submitted to surgery, should be promoted, permitting timely intervention for better voice outcomes.
The more relevant conclusions from this PhD research work were the following:
1.
There are relevant voice and laryngeal changes pre-operatively in patients proposed for thyroidectomy.
2.
Most patients who seek medical advice related to voice changes post-operatively don´t have vocal fold mobility impairment.
3.
Patients without thyroid cancer have more voice changes pre- and post-operatively than patients with thyroid cancer. This factor should prompt a revision of statement 2b, including non-malignant thyroid disease in peri-operative voice evaluation in thyroidectomy. 4.
In patients with dysphonia, but without post-operative VF immobility, dysphonia in the first post-operative year is more frequent in the first three months.
5.
In patients with dysphonia but without post-operative VF immobility, the voice improves to a level better than the pre-operative voice condition 6 months after surgery. Follow up and intervention for these patients is probably cost-effective in the first 3 post-operative months because, 6 months after surgery, voice improves in every patient without post-operative VF immobility, comparing to the first 3 post-operative months.
6.
Post-operative dysphonia in thyroidectomy patients without VF immobility is characterized by reduced f0/a/ and reduced HPf0/i/ comparing to pre-operative results. These data confirms that dysphonia perceived by patients without VF immobility is objectively caused by a quantifiable change in objective voice analysis parameters.
7.
Mean HPf0/i/ reduction post-operatively in patients without VF immobility is 60Hz. Reduced HPf0/i/ post-operatively is certainly one of the factors causing reduced singing ability perceived by the patients, when high pitch tones are required.
8.
In patients without post operative VF immobility, both dysphonia, reduced f0/a/ and HPf0/i/ correlate to bigger thyroid volumes
9.
Thyroid volume (cc) and weight (gram) is correlated to thyroid echography volume determination (cc) and both measures directly correlate to dysphonia, reduced f0/a/ and HPf0/i/ post-operatively.
10.
These findings provide justification for considering increased echography thyroid volume as a risk factor for voice compromise in thyroidectomy patients. Increased thyroid volume pre-operatively should prompt early referral for voice clinics in the peri-operative period aiming at early and tailored voice re-habilitation when proven necessary, promoting a better voice related quality of life (QoL) in thyroidectomy patients.
11.
Statement 2b in Best Practice Guidelines for Voice Preservation in Thyroid Surgery should include patients with increased volume goiter in peri-operative laryngeal evaluation.
12.
Even without loss of sign (LOS) in intra-operative neuromonitoring (NIM) of recurrent nerve in thyroidectomy, patients with goiter should be referred for voice and laryngeal evaluation post-operatively
