Background
Thyroidectomy is one of the most common neck surgery done worldwide. It is associated with debilitating post-operative voice changes even without recurrent laryngeal nerve (RLN) injury. Aims and Objectives: To study the impact of thyroidectomy on voice parameters in the absence of Recurrent Laryngeal Nerve and External Branch of Superior Laryngeal Nerve injury and comparison between the pre and post-operative changes in the subjective and objective voice parameters. Methodology: Patients fulfilling the inclusion criteria underwent thyroidectomy. The Subjective voice assessment was done using Voice Impairment Score (VIS) and objective parameters were analyzed using Multi-Dimensional Voice Program (MDVP) pre-operatively and post-operatively at 1 week, 1 month and 3 months interval. Results: On MDVP analysis of patients, a fall in Mean F0 (Hz), Minimum F0 (Hz) and Maximum F0 (Hz) values was noted at 1 week after surgery. But a trend toward the pre-operative values was observed at 3 months post-operatively.
Keywords: Thyroidectomy, Voice change, RLN injury
Introduction
Thyroidectomy is one of the most common surgical procedures undertaken worldwide [1]. Although it is associated with low morbidity, debilitating post-operative voice changes are reported even in the absence of recurrent laryngeal nerve (RLN) injury [2,3]. The literature describes various causes like laryngeal edema, vocal fold bowing, orotracheal intubation trauma, extra-laryngeal strap muscles damage or temporary malfunction of these muscles, and laryngotracheal fixation [2,4–9]. The most usual complaints are roughness, volume alteration, and vocal fatigue, which might have an important impact on the patient’s professional and social life [2,10,11]. These symptoms should be regarded as true complication of thyroid surgery and treated appropriately by the consulted physicians.
Aims and Objectives
-
I.
To study the impact of thyroidectomy on voice parameters in the absence of Recurrent Laryngeal Nerve and External Branch of Superior Laryngeal Nerve injury.
-
II.
Comparison between the pre-operative and post-operative changes in the subjective and objective voice parameters.
Material and methods
A prospective observational study comprising of 20 patients was conducted in our hospital from 1st January 2016 to 30th June 2017. The patients who presented to our out-patient department with complaint of neck swelling underwent ultrasonography and fine needle aspiration cytology (FNAC) examination. The diagnosed cases of benign thyroid pathology were enrolled in the study. The patients with a history of previous neck surgery, malignant pathology of thyroid gland, any benign or malignant lesion of vocal cords or vocal cord paresis/paralysis were excluded from our study. A written and informed consent was taken from the patients. All cases underwent stroboscopic assessment to look for function of RLN and EBSLN. Pre-operatively, all patients underwent perceptual and acoustical analysis for voice parameters to achieve baseline voice parameters. The impairment/handicap perception was evaluated by using the voice impairment score (VIS) questionnaire, which consists of 10 questions, each on a 5-point scale that varies from \never" to\always" including functional, emotional, and physical aspects related to voice dysfunction. The VIS vary from a minimum score of 0 (no voice alterations) to a maximum of 40 (highest voice impairment). Acoustic Voice Analysis was performed by using MDVP (Multi-Dimensional Voice Program). The microphone was set at a distance of 15 cm from the oral cavity and a vowel of “a” was recorded for 3 s. The acoustic parameters assessed were fundamental frequency (F0/Hz), Mean F0, jitter – pitch perturbation quotient (PPQ/%), shimmer – amplitude perturbation quotient (APQ/%), noise to harmonic ratio (NHR), Maximum F0 (Hz), Minimum F0 (Hz) and Maximum Phonation Time.
All patients underwent thyroidectomy, under general endotracheal anesthesia. To maintain the uniformity of procedure, all surgeries were done by same primary surgeon. The nerve monitoring was used intra-operatively to assess the intactness of RLN and EBSLN. During the dissection, the strap muscles were divided and not cut. For better tissue handling the use of monopolar cautery was prohibited. The dissection was done meticulously and both RLN and EBSLN were identified, preserved and assessed using stimulator probe during surgery. All the surgeries went uneventful and none of the patient developed any complication in post-operative period. Post-procedure, the status of vocal cords was assessed using stroboscope to confirm the status of RLN and EBSLN. The same set of voice tests were conducted at an interval of 1 week, 1 month and 3 months post-operatively.
Results and analysis
The patients were divided into three age groups for our study purpose. A large segment was in the age group of 40–50 years i.e., 11(55.00%), followed by 30–40 years i.e., 07(35.00%). Age group of 18–30 years had only 02(10.00%) patients (Table I). A total of 20 patients were taken in the study which included 18(90.00%) females and 02(10.00%) males with M: F ratio of 1:9. Chi-square test reveals that there is a statistical significance between age and sex distribution of the participants in the study.
Among 20 patients, on ultrasonography, 15(75.00%) patients were reported as TIRADS-2 and remaining 5(25%) were reported as TIRADS-3. On FNAC, 17(85%) patients were reported as Bethesda II and 3(15%) patients were reported as Bethesda III. On pre-operative stroboscopic evaluation, all 20 patients showed intact function of RLN and EBSLN. All patients underwent documentation of subjective and objective acoustic test scores.
Table II shows interpretation of VIS at 1 week, 1 month and 3 months. In our study on performing subjective voice evaluation using Voice Impairment Score (VIS), the score increased significantly at 1 week and 1 month after surgery. A fall in score was noted at 3 months after surgery but remained higher than pre-operative values.
Table III shows comparison made between the values of objective parameters pre-operatively, at 1 week, 1 month and 3 months post-operatively. A significant increase in Habitual F0 (Hz), Jitter (%), Shimmer (%), NHR (dB) and MPT (sec) values was noted at 1 week and 1 month post-operatively. A fall in Mean F0 (Hz), Min F0 (Hz) and Max F0 (Hz) values was noted at 1 week after surgery. But a trend toward the pre-operative values was observed at 3 months post-operatively.
Discussion
The mechanism of post-thyroidectomy voice alteration without injury to the laryngeal nerve is not well understood. Possible causative factors include laryngotracheal fixation with impairment of vertical movement, cricothyroid muscle dysfunction, operative injury or temporary dysfunction of extra-laryngeal strap muscles, orotracheal intubation trauma and laryngeal edema, severe retractile cervical scar, local neck pain, and psychological factors. The results of this study confirmed that thyroidectomy frequently results in subjective and objective vocal alterations, even in the absence of laryngeal nerve injury. One of the accepted theories is that the strap muscles have a positive relation to pitch elevation. After thyroidectomy, the larynx and trachea adhere to the strap muscles because of scar formation, and the strap muscle and subcutaneous soft tissue also adhere to each other. Therefore, movement of the larynx and trachea during speech is impaired, resulting in defective pitch control during speech or singing [8].
In this study 20 patients, aged between 18–50 years were included, 02(10.00%) males and 18(90.00%) females, with a ratio of 1:9. A large proportion were in age group of 40–50 years i.e., 11(55.00%) patients, followed by 30–40 years i.e., 07(35.00%) patients. Only 02(10.00%) among 18–30 years group (Table 1). Similar results were found in a study conducted by Irene de Pedro Netto in 2006 on voice and vocal self-assessment after thyroidectomy and found that among a total of 88 patients, 77(87.5%) were females and rest 11(12.5%) were males [12].
Table 2.
Interpretation of VIS at various follow-Ups
| Question | Pre-op | At 1-week post-op | At 1 -month post-op | At 3 -months post-op |
|---|---|---|---|---|
| My voice is hoarse | 01 (05%) | 14 (70%) | 8 (40%) | 02 (10%) |
| My voice is breathy and weak | 00 (00%) | 06 (30%) | 04 (20%) | 02 (10%) |
| I have difficulty in singing and yelling | 02 (10%) | 11 (55%) | 06 (30%) | 03 (15%) |
| The pitch of my voice is lowered | 02 (10%) | 07 (35%) | 03 (15%) | 02 (10%) |
| My voice is monotonous | 00 (00%) | 07 (35%) | 02 (10%) | 01 (05%) |
| I run out of air when I talk | 01 (05%) | 10 (50%) | 04 (20%) | 02 (10%) |
| My voice changes during the day | 02 (10%) | 12 (60%) | 05 (25%) | 03 (15%) |
| I use a great effort to speak | 02 (10%) | 07 (35%) | 02 (10%) | 01 (05%) |
| The clarity of my voice is unpredictable | 00 (00%) | 07 (35%) | 01 (05%) | 00 (00%) |
| I feel vocal fatigue | 02 (10%) | 10 (50%) | 05 (25%) | 02 (10%) |
Table 3.
Comparison of preoperative, 1 week, 1 month and 3-month postoperative results of MDVP analysis
| Parameter | Pre-operative (Mean) | At 1 week | At 1 month | At 3 months | P value |
|---|---|---|---|---|---|
| Habitual (F0) | 160.9 | 167.5 | 166.2 | 163.7 | 0.004 |
| Jitter (%) | 0.40 | 0.51 | 0.49 | 0.42 | 0.001 |
| Shimmer (%) | 2.8 | 3.4 | 3.5 | 2.7 | 0.000 |
| Mean F0 (Hz) | 211.47 | 203.29 | 204.15 | 207.15 | 0.000 |
| Min F0 (Hz) | 168.4 | 161.9 | 163.6 | 166.3 | 0.000 |
| Max F0 (Hz) | 403.6 | 379.5 | 350.9 | 396.4 | 0.009 |
| NHR (dB) | 0.14 | 0.16 | 0.17 | 0.17 | 0.000 |
| MPT (sec) | 18.56 | 18.62 | 18.80 | 19.38 | 0.000 |
Table 1.
Distribution of patients according to age and sex
| Age Group (in years) | Male | Female | Total | |||
|---|---|---|---|---|---|---|
| No. of males | %age | No. of females | %age | No. of respondents | %age | |
| 18–30 | 00 | 00.00 | 02 | 10.00 | 02 | 10.00 |
| 30–40 | 01 | 05.00 | 06 | 30.00 | 07 | 35.00 |
| 40–50 | 01 | 05.00 | 10 | 50.00 | 11 | 55.00 |
| Total | 02 | 10.00 | 18 | 90.00 | 20 | 100.00 |
In our study, the VIS showed worsening at 1 week and 1 month but reverted to near normal at 3 months. Similar trend was reported by Celestino Pio Lombardi et al. in 2006 in their study, Voice and swallowing changes after thyroidectomy in patients without inferior laryngeal nerve injuries. They found that the voice changes gradually improved over time. The mean VIS was significantly increased at 1 week and 1 month following surgery. At 3 months after surgery, the VIS remained higher than that at preoperative levels, but the difference was not significant. After an initial impairment, the VIS showed a trend toward the preoperative levels. At 3 months after surgery, the patients’ VIS values were significantly improved with respect to those obtained at 1 week and 1 month after total thyroidectomy [13].
Our study showed that at 3 months post-operatively most of the parameters had returned to baseline value. The difference between the pre-operative and 3 months post-operative values was not significant for jitter (0.41 vs 0.43), shimmer (2.8 vs 2.7) and Minimum F0 (168.4 vs 166.3). But significant alteration from baseline was noted for Maximum F0 (405.6 vs 396.4), Mean F0 (210.83 vs 207.15) and MPT (18.56 vs 19.38). The values for Maximum F0 and Mean F0 post-operatively were reduced than pre-operative values whereas post-operative MPT value was higher than pre-operative value. Similar pattern was observed in a study performed by Celestino Pio Lombardi et al. in 2006 on Voice and swallowing changes after thyroidectomy in patients without inferior laryngeal nerve injuries. They noted that the mean MPT was 19.1 s before surgery and 19.7 s 3 months later. No significant differences were found among the preoperative and postoperative mean values of the MDVP and VRP parameters before and after TT [13].
In our study subjective impairment of voice after thyroidectomy was evaluated with a questionnaire. Patients showed subjective impairment of voice up to 1 month after surgery but showed improvement 3 months after surgery. However, the objective parameters obtained from the MDVP showed no significant difference in postoperative outcomes. The patients reported short term voice changes after thyroidectomy in the form of voice fatigue, roughness, low voice pitch, and volume reduction. The small sample size is a limitation of this study but VIS and MDVP seem to be reliable measures for voice assessment.
Conclusion
Dysphonia is generally reported by patients after thyroidectomy. The most common cause known is the injury of recurrent laryngeal nerve. This study focuses on other parameters that cause alteration in voice after thyroid surgery. The subjective and objective parameters studied here showed altered values in post-operative period but mostly were reverted to pre-operative values when noted at 3 months post-operative interval. On MDVP analysis of patients a fall in Mean F0 (Hz), Minimum F0 (Hz) and Maximum F0 (Hz) values was noted at 1 week after surgery. But a trend toward the pre-operative value was observed at 3 months post-operatively. So, factors like scar formation, post-operative edema and post intubation can be accounted for voice change in patients after thyroid surgery.
Footnotes
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