VOICE QUALITY BEFORE AND AFTER THYROIDECTOMY

Abstract

Voice disorders are a well-known complication which is often associated with thyroid gland diseases and because voice is still the basic mean of communication it is very important to maintain its quality healthy. The aim of this study referred to questions whether there is a statistically significant difference between results of voice self-assessment, perceptual voice assessment and acoustic voice analysis before and after thyroidectomy and whether there are statistically significant correlations between variables of voice self-assessment, perceptual assessment and acoustic analysis before and after thyroidectomy. This scientific research included 12 participants aged between 41 and 76. Voice self-assessment was conducted with the help of Croatian version of Voice Handicap Index (VHI). Recorded reading samples were used for perceptual assessment and later evaluated by two clinical speech and language therapists. Recorded samples of phonation were used for acoustic analysis which was conducted with the help of acoustic program Praat. All of the data was processed through descriptive statistics and nonparametric statistical methods. Results showed that there are statistically significant differences between results of voice self-assessments and results of acoustic analysis before and after thyroidectomy. Statistically significant correlations were found between variables of perceptual assessment and acoustic analysis. Obtained results indicate the importance of multidimensional, preoperative and postoperative assessment. This kind of assessment allows the clinician to describe all of the voice features and provides appropriate recommendation for further rehabilitation to the patient in order to optimize voice outcomes.

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Abstract

Introduction: Voice disorders are a well-known complication which is often associated with thyroid gland diseases and because voice is still the basic mean of communication it is very important to maintain its quality healthy.

Objectives: The aim of this study referred to questions whether there is a statistically significant difference between results of voice self-assessment, perceptual voice assessment and acoustic voice analysis before and after thyroidectomy and whether there are statistically significant correlations between variables of voice self-assessment, perceptual assessment and acoustic analysis before and after thyroidectomy.

Methods: This scientific research included 12 participants aged between 41 and 76. Voice self-assessment was conducted with the help of Croatian version of Voice Handicap Index (VHI). Recorded reading samples were used for perceptual assessment and later evaluated by two clinical speech and language therapists. Recorded samples of phonation were used for acoustic analysis which was conducted with the help of acoustic program Praat. All of the data was processed through descriptive statistics and nonparametric statistical methods.

Results: Results showed that there are statistically significant differences between results of voice self-assessments and results of acoustic analysis before and after thyroidectomy. Statistically significant correlations were found between variables of perceptual assessment and acoustic analysis.

Conclusion: Obtained results indicate the importance of multidimensional, preoperative and postoperative assessment. This kind of assessment allows the clinician to describe all of the voice features and provides appropriate recommendation for further rehabilitation to the patient in order to optimize voice outcomes.

Keywords: voice quality, thyroidectomy, voice self-assessment, perceptual voice assessment, acoustic voice analysis

Introduction

Thyroidectomy is a surgical procedure which results in total or partial thyroid gland removal (1). The most common thyroid gland diseases, in which thyroidectomy is indicated, are: goiter, hyperthyroidism, autoimmune thyroiditis and thyroid cancer. Total thyroidectomy implies complete removal of both thyroid gland lobes (2), while total lobectomy implies removal of only one thyroid gland lobe. In the past few years more and more surgeons choose total thyroidectomy, even in cases of benign diseases (3). Thyroidectomy aims to remove pathologically altered tissue while preserving parathyroid gland function and to preserve or improve voice, speech and swallowing functions. The number of patients that undergo thyroidectomy has grown over the years and even though it's performed amongst both genders, most of the patients are females (1, 4).

Thyroid gland produces thyroid hormone which has multiple physiological effects and is essential for normal functioning, growth and development of various tissues as well as larynx (5). As a result, thyroid gland diseases can affect almost all structures engaged in voice production, such as: larynx, trachea, laryngeal muscles and nerves (6). Precisely because of such anatomical connection sensorimotor impairment of laryngeal function is a possible thyroidectomy complication (7). Factors associated with higher risk of laryngeal nerve impairment, are: secondary thyroidectomy, malignant cancer diagnosis (8), higher amount of blood loss, longer time and bigger extent of thyroidectomy (7, 9 11), but also the surgeons experience (7, 8).

Voice changes after thyroidectomy are more often associated with recurrent (inferior) laryngeal nerve impairment and rarely with superior laryngeal nerve impairment (4). Posterior branch of recurrent laryngeal nerve innervates adductor muscles which enable vocal folds to open, while the frontal branch innervates adductor muscles which enable vocal folds to close (1). External branch of superior laryngeal nerve is responsible for innerving cricothyroid muscle (12, 13) whose role is to actively stretch vocal folds during phonation to increase their tension (14). 22.2 % of all thyroidectomy complications are recurrent laryngeal nerve impairments, while 3.7 % are external branch of superior laryngeal nerve impairments (15). Prevalence of laryngeal nerve impairments in total thyroidectomy is 1.9% and in partial thyroidectomy 2.4 % (2). Impairments of laryngeal nerve functions are mostly transitory and rarely permanent, which is why postoperative evaluation is important as well as time in which assessments of laryngeal nerve impairment are conducted. The percentage of patients with laryngeal nerve paresis after thyroidectomy declines in time (16).

Laryngeal nerve impairment can cause different vocal and laryngeal symptoms during thyroidectomy (10), such as: changes in voice, respiration, swallowing and coughing which is usually ineffective and silent (7). Voice changes can vary from mild to severe aberrations or from dysphonia to aphonia. Laryngeal dysfunction can lead to transitory or permanent disorders of vocal folds mobility (13). Disorder of vocal folds mobility includes unilateral or bilateral vocal fold paresis or paralysis. Voice disorders after thyroidectomy can significantly affect the quality of life (17). No matter how much individuals depend on their voice in their profession, quality of life is disrupted as long as they use their voice in everyday communication. In that way, dysphonia affects not only the professional, but also the social aspect of life.

Voice disorders could also be the result of thyroid gland dysfunction and be present before thyroidectomy (6). Endocrine dysfunction, like hypothyroidism (5) or hyperthyroidism, usually leads to milder voice disorders, meaning too low or too high fundamental frequency, vocal fatigue, vocal folds swelling and increasing in mass (18). Voice disorders which are present before thyroidectomy can refer to presence of malignant or benign cancers that apply pressure on laryngeal structures and disrupt normal laryngeal function. In these cases, thyroidectomy can lead to voice improvement (6). The removal of thyroid gland and existing cancer results in pressure reduction and improved vibration of vocal folds (13).

Although in a large number of patients voice alterations appear preoperatively and postoperatively, standard guidelines for prevention, assessment and evaluation of voice are still not fully defined.

This study was focused precisely on detecting whether a voice disorder is present before thyroidectomy or if changes in voice quality are a direct consequence of thyroidectomy itself.

Methods

Participants

This scientific research included 12 participants, aged between 41 and 76 (average age of 58). Included criteria were: female gender and indicated and performed thyroidectomy. The main reason for exclusive choice of female gender is that thyroidectomy is more often performed in females than males (1), ratio 4:1 (4).

Among all participants thyroidectomy was indicated by a surgeon, ENT specialist. Diagnoses were: goiter, autoimmune thyroiditis (Hashimoto), benign thyroid cancer, cancer of unknown etiology, hypothyroidism and hyperthyroidism. Nine participants had one diagnosis: goiter (N=4), autoimmune thyroiditis (N=2), benign thyroid cancer (N=2) and cancer of unknown etiology (N=1). Three participants had double diagnosis, in combinations: goiter and hyperthyroidism (N=1), autoimmune thyroiditis and cancer of unknown etiology (N=1) and autoimmune thyroiditis and hypothyroidism (N=1). Total thyroidectomy was performed on a larger number of participants (N=9), whereas lobectomy was performed on other participants (N=3). All participants that underwent total lobectomy had the left lobe of thyroid gland removed.

Measuring instruments

Preoperative and postoperative voice assessment was conducted with all participants. For that purpose voice self-assessment method or method of establishing bio-psycho-social influence of voice quality on quality of life was applied, which was tested by a Croatian version of Voice Handicap Index (VHI) questionnaire (19). In this study total results of three questionnaire subscales (F-VHI, P-VHI, E-VHI) and total questionnaire result were observed (T-VHI).

Perceptual voice assessment which was made with the help of recorded reading samples was also conducted. Every participant was presented with a text about the city of Zagreb which consisted of 154 words divided into three equal segments. The text was presented on a white A4 paper, black printed letters, Times New Roman font, size 16, line spacing 1,5 with justify alignment. Every participant was asked to read the whole text out loud with normal frequency and voice intensity. Participant's voices were evaluated by two speech and language therapists with grades form 0 to 4 where 0 marked no dysphonia and grades 1, 2, 3 and 4 marked mild, moderate, severe and very severe dysphonia. Assessor's grades were added up and an average grade was calculated for every participant. In this kind of assessment one variable was used: general grade of dysphonia (G). The inter-rater ICC for the G was 0.81 (95% confidence interval [CI] = 0.56-0.92). This result demonstrates very strong inter-rater reliability. Objective voice assessment was also conducted based on three recorded phonations. Acoustic analysis was performed in the middle part of the second phonation that lasted 5 seconds. That part of phonation was analyzed by Praat program (20) where the following acoustic parameters were observed: fundamental frequency in Hz (F0), frequency variations of vocal folds vibrations in % (JITT), intensity variations of vocal folds vibrations in dB (SHIMM), harmonic-to-noise ratio in dB (HNR), and the number of voice breaks (NVB).

Data collecting

Participants were selected at Clinical Hospital "Sveti Duh", at ENT department (Clinic for otorhinolaryngology and head and neck surgery). Conduction of this study was approved by the hospital ethical commission. Data collecting was conducted in two time points - just before and two months after thyroidectomy. Study draft was discussed with all potential participants before assessments. Subsequently all participants agreed to participate and they gave written approval for their participation in this study. Demographic and basic data from medical documentation (name and surname, age, diagnosis, type and date of planned surgery and date of preoperative and postoperative voice assessment) was collected for every participant. Firstly, participants filled out a VHI questionnaire with a pen. After that, voice samples for perceptual assessment and acoustic analysis were recorded. Recorded voice sample of every participant was consisted of recorded reading sample and three recorded phonation samples (vowel /a/). Recording was performed with the help of digital recorder TASCAM DR-05 Built-in Stereo Condenser Omnidirectional Microphones with sensitivity up to 125dB SPL. Recorded voice samples were transferred from recorder to computer with USB cable in WAV format. Recorded reading samples were coded and transferred to a CD and then randomly presented to two speech and language therapists with vast experience in the field of voice disorders.

Data analysis

All of the data was processed through the SPSS program. In this study, basic statistical parameters were calculated through descriptive statistic which was conducted. Normality of distribution was tested with Shapiro-Wilk test in order to determine further statistical procedures. Nonparametric Wilcoxon Signed Rank test was used for determining statistically significant differences between first and second measuring point and nonparametric Spearman test was used for determining statistically significant correlations between variables of voice self-assessment, perceptual voice assessment and acoustic analysis. Default level of significance for all statistical analyses that were conducted was p<0,05.

Results

Table 1 contains results of descriptive statistical analysis for voice self-assessment variables. Difference between results before and after thyroidectomy can be observed: postoperative measurements show higher maximum results on all voice self-assessment variables, except for variable which represents emotional subscale of the VHI questionnaire (E-VHI). One can also notice higher standard deviation of results in the postoperative measurement. The largest maximum result was achieved on the physical VHI subscale (P-VHI) in both preoperative and postoperative measurement. The lowest maximum score in preoperative measurement was also obtained on the functional VHI subscale (F-VHI) and in postoperative measurement for the emotional VHI subscale (E-VHI).

Table 2 shows results of the Wilcoxon Signed Rank test used to examine the significance of differences between the mean scores on voice self-assessment variables before and after thyroidectomy. Significant differences were found between preoperative and postoperative mean scores on functional (F-VHI-F-VHI2) and physical (P-VHI-P-VHI2) VHI subscale, as well as between preoperative and postoperative mean total VHI socres (T-VHI-T-VHI2). The mean score on the emotional VHI subscale before and after thyroidectomy (E-VHI-E-VHI2) was not signifficantly differrent.

Table 3 contains results of descriptive statistical analysis for variables representing perceptual voice assessment before and after thyroidectomy. Minimum and maximum scores, mean scores and standard deviations were equal for both preoperative and postoperative measurement, indicating that there were no differences between preoperative (G) and postoperative (G2) perceptual assessment. This was confirmed by results of the Wilcoxon Signed Rank test, which are presented in Table 4.

Table 5 presents results of descriptive statistical analysis of acoustic data collected before and after thyroidectomy. The minimum and mean values of fundamental frequency were higher in postoperative measurement (F02), opposed to maximum fundamental frequency value and fundamental frequency standard deviation, which were higher preoperatively (F02). In contrast to results of preoperative measurement (NVB), mean value, standard deviation and maximum number of voice breaks were all higher in postoperative (NVB2) measurement. Minimum and maximum jitter and shimmer values, mean jitter and shimmer values and their standard deviations were all lower in postoperative (JITT2, SHIMM2) measurement, which was not the case for variables representing harmonic-to-noise ratio before and after thyroidectomy (HNR, HNR2). Minimum and maximum values, mean values and standard deviations of harmonic-to-noise ratio variable (HNR, HNR2) were all higher in postoperative measurement (HNR2), i.e. after thyroidectomy.

Table 6 contains results of the Wilcoxon Signed Rank test, used to test significance of differences in acoustic voice parameters before and after thyroidectomy. Statistically significant difference was found between mean shimmer value before (SHIMM) and after (SHIMM2) thyroidectomy, and between mean harmonic-to-noise ratio before (HNR) and after thyroidectomy (HNR2). Significant differences between preoperative (F0, NVB, JITT) and postoperative measurements (F02, NVB2, JITT2) were not observed.

Table 7 presents results of Spearman test used to examine correlations between variables of perceptual voice assessment, voice self-assessment variables and variables representing acoustic voice parameters before thyroidectomy. Moderate positive correlation between perceptual voice assessment (G) and shimmer (SHIMM), and moderate negative correlation between perceptual voice assessment (G) and harmonic-to-noise ratio (HNR) can be noticed. This indicates that the increase of shimmer value and the reduction of harmonic-to-noise ratio leads to the increase of perceptual voice assessment score, or that poorer mean subjective voice assessment score is related to greater amplitude variations between fundamental frequency periods and poorer harmonic-to-noise ratio.

Table 8 shows results of Spearman test used to examine correlations between variables of the perceptual voice assessment, voice self-assessment variables and variables representing acoustic parameters of voice after thyroidectomy. Moderate positive correlation between perceptual voice assessment (G2) and jitter (JITT2) can be observed, indicating that the increase in jitter value leads to the increase of mean perceptual voice assessment score, or that poorer mean subjective voice assessment score is related to greater fundamental frequency variation.

Discussion

Increased mean values of all voice self-assessment variables after thyroidectomy, with the exception of emotional VHI variables (E-VHI and E-VHI2), point out poorer postoperative voice self-assessments. Also, postoperative voice self-assessment was characterised by greater standard deviation values of all self-assessment variables, suggesting greater heterogeneity of individual responses after thyroidectomy. Differences found between preoperative and postoperative voice self-assessment were confirmed as statistically significant for the functional and physical VHI subscale and for the final VHI score. These findings are supported by results of research performed by Kuhn, Bloom and Myssiorek (21), in which 85.9% of subjects reported poorer voice quality after thyroidectomy, as well as occurrence of postoperative hoarseness and other voice problems. Voice problems were most often described as inability of shouting, singing, or a loss of volume, which is consistent with results of this study. In this study, the most reported voice problems, both before and after thyroidectomy, were related to the physical VHI subscale. The least of the reported problems before thyroidectomy were related to the functional VHI subscale and after thyroidectomy to the emotional VHI subscale. Rohde et al. (17) report that all respondents who participated in their study, in late postoperative period (more than one year after thyroidectomy), reported some impact of dysphonia on the quality of life.

Results of the perceptual voice assessment before and after thyroidectomy did not differ. This finding could be explained by the fact that some patients do not experience voice symptoms, in both early postoperative period (one week after thyroidectomy) and late postoperative period (three months after thyroidectomy) (4). Also, this finding could be explained by the assumption that, although the ear of an experienced and trained clinician is a valuable tool in detecting of even minimal changes in voice quality (18), there are certain limitations of perceptual voice assessment. These limitations apply to: different experience and training of assessors, their different internal criteria, terminological diversity, lack of standard materials and instructions for recording, different intensity of recordings and other. Because of these limitations, it is certainly advisable to make an objective, acoustic voice analysis. In fact, their complementary relationship increases accuracy in assessing and determining variation in voice quality, which facilitates treatment and evaluation of progress (22).

Results of objective voice analysis showed differences in mean values of all of the acoustic variables before and after thyroidectomy. However, these differences confirmed to be statistically significant only for mean shimmer values and harmonic-to-noise ratio, but not for mean values of the fundamental frequency, the number of voice breaks and jitter. Significantly lower value of shimmer and significantly higher harmonic-to-noise ratio suggest postoperative improvement of voice quality. Lower values of shimmer subjectively manifest as a reduction in hoarseness of voice, while higher harmonic-to-noise ratio is subjectively perceived as an increase in voice resonance. This finding is not impossible, because certain number of patients after thyroidectomy demonstrates improvement in voice quality (6). Namely, voice problems that are present before thyroidectomy may indicate the presence of malignant or benign cancer, which interferes with proper laryngeal function (23). In such cases, thyroid gland and existing cancer are surgically removed, which enables better vibration of vocal folds (13). However, Soylu et al. (10) noticed poorer voice quality after the surgery in all patients who participated in their study. They found significant difference between preoperative and early postoperative results of acoustic voice analysis in all of patients. They concluded that significant decrease in mean fundamental frequency and significant increase in mean values of jitter, shimmer and harmonic-to-noise ratio indicates poorer quality of voice after thyroidectomy. These postoperative changes are reported to be short-termed for mean values of jitter, shimmer and harmonic-to-noise ratio, but long-termed for mean fundamental frequency (10, 14). Therefore, depending on preoperative voice status, thyroidectomy may lead to improvement or deterioration in voice quality (6, 24). This study showed that voice quality of patients after thyroidectomy was objectively somewhat better, but results of voice self-assessment were not in accordance with results of acoustic voice analysis.

In this research, statistically significant correlations were found between results of perceptual voice assessment and acoustic voice analysis (G and SHIMM, G and HNR, G2 and JITT2). Yu et al. (25) reported that mean values of acoustic and aerodynamic parameters vary in accordance with results of perceptual voice assessment. Santosh and Rajasekhar (13) reported significant correlation between results of perceptual voice assessment and acoustic voice analysis. However, some previous studies suggests that acoustic correlates of perceptual voice ssessment are not clear and unambiguous (22). Also, this study have specific limitation because the number of participants is very low and the clear statement can't be made.

Conclusion

High percentage of changes in voice quality after thyroidectomy, their negative impact on life of individuals and also the lack of research of these issues in Croatia were main triggers for this study. In order to examine the impact of thyroidectomy on voice quality, three methods of voice evaluation were employed: voice self-assessment, perceptual voice assessment and acoustic voice analysis.

This research showed significant differences between voice self-assessments before and after thyroidectomy which indicate poorer voice self-assessment after thyroidectomy. Significant differences were also found between acoustic analysis before and after thyroidectomy, indicating improvement in acoustic voice parameters after thyroidectomy. Statistically significant correlations were found between perceptual voice assessment and acoustic voice analysis.

Obtained data suggest importance of preoperative and postoperative voice assessment in order to determine improvement or deterioration in voice quality after thyroidectomy. In addition, results of this research underline the need for multidimensional approach, which delivers more detailed information about all of voice characteristics and provides timely advice and recommendations for further rehabilitation procedures to the patient.

Conflict of interests

Authors declare no conflict of interests.

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Dora CVELBAR

Ana BONETTI1

Boris SIMUNJAK2

1University of Zagreb, Faculty of Education and Rehabilitation Sciences, Department of Speech and Language Pathology, Zagreb, Croatia

2Clinical Hospital "Sveti Duh", Department of Otorhinolaryngology and Head and Neck Surgery, Zagreb, Croatia

Recived: 30.11.2015

Accepted: 30.01.2015

Scientific Article

Corresponding address:

Dora CVELBAR

Ilirska 95, 31 000 Osijek, Croatia

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Email: [email protected]