Analysis and Prevention of Voice Morbidity in Thyroidectomy Patients: A Prospective Study

INTRODUCTION

Altered voice is a common problem after thyroid surgery. Previous studies demonstrate that 25–90% of patients report abnormal voice within the first few weeks after operation and 11–15% of patients report persistent voice problems 3–6 months after thyroidectomy.^1,2 Major laryngeal nerve injuries account for a large portion of this incidence and are well-established and feared complications of thyroidectomy.^3,4 But many patients suffer long-term negative voice outcomes (NVOs) and have no evidence of laryngeal nerve injury.⁵ Various non-neurogenic mechanisms have been postulated to account for postthyroidectomy voice changes, including the effects of endotracheal intubation⁶ and other alterations in normal anatomy and mechanical factors.⁷

Our study was aimed at the ability to identify early changes in voice indicative of durable dysfunction (both neurogenic and non-neurogenic). This would facilitate early referral for comprehensive voice evaluation aimed to improve quality of life, prevent secondary injuries, and identify patients who might benefit from vocal fold augmentation.^8,9 All patients in this study were subjected to videolaryngoscopic examination, assessment of fundamental frequency of voice, and maximum phonation duration preoperatively and postoperatively.^10–12 Patients with voice change were subjected to early voice therapy and the outcome was assessed.

MATERIAL AND METHODS

This study is a prospective study conducted in a tertiary care teaching hospital, from December 2011 to May 2013. Patients of both sexes of all age groups with preoperative normal vocal cord mobility undergoing thyroidectomy were included for study. Patients with vocal cord paralysis preoperatively and patients with a past history of neck surgeries were excluded from the study. One hundred and eighteen patients who fulfilled the inclusion criteria were enrolled in the study after getting the informed consent during the study period.

Preoperative voice assessment was done for all the study patients with videolaryngoscopy, analysis of maximum phonation duration (MPD), and fundamental frequency (Fo). Postoperatively, VLS, MPD and Fo were repeated at the second and sixth month in patients with voice change. Videolaryngoscopic examinations were done for all patients using an Atmos stroboscopic unit. Voice was recorded using a microphone, by asking the patient to say constant syllable and the fundamental frequency was evaluated. Maximum phonation duration was measured by asking the patient to take a deep breath and say a constant syllable.

Subjective voice change is assessed by GRBAS (Grade, Roughness, Breathiness, Asthenia, and Strain), an auditory–perceptual evaluation method for hoarseness. Voice therapy given by voice pathologists following eclectic approaches which include vocal hygiene, abdominal support/breath control, intrinsic laryngeal muscle exercises, accent method, head and neck relaxation, and resonant voice/humming. Data regarding age, sex, final diagnosis, malignant nature of tumors, type of surgery, and percentage of EBSLN were collected. Distribution of the sample according to subjective voice change, cause of subjective voice change, and voice rehabilitation was also studied. VLS, Fo, MPD were compared at different intervals of time.

RESULTS

The results are as follows after analysis of data (Tables 1 to 12).

DISCUSSION

Preservation of voice is an important concern for patients undergoing thyroid surgery. However, vocal and laryngeal symptoms appear to be common following thyroidectomy.¹³ The outcomes of injury to RLN and EBSLN are well known and preservation of these nerves is the major point in modern thyroid surgery.¹⁴ However, the etiology of postthyroidectomy voice disturbances for patients with preserved nerve function has not been widely studied.¹⁵ The objective of our study was early identification of the voice related problems in postthyroidectomy patients and starting voice rehabilitation as early as possible, in order to prevent faulty voice production techniques in them.^16,17

Out of 118 patients, 13 patients who underwent hemithyroidectomies had no voice changes. Thirty-three of the 105 patients (31.43%) underwent total thyroidectomy and had subjective voice change in the early postoperative period. Only 4 patients (3.4%) out of 105 underwent total thyroidectomy and had voice change after 6 months. In all patients, recurrent laryngeal nerve (RLN) was identified and was well preserved. In spite of the proper preservation, 4 patients (3.3%) had RLN palsy postoperatively. Patients with postoperative videolaryngoscopic (VLS) features like posterior glottic rotation, bowing of vocal folds, asymmetrical mucosal folds vibration were considered as EBSLN palsy.¹⁸ Twenty-two patients had EBSLN palsy. Seven patients had voice change without any obvious abnormality in VLS. Their fundamental frequency increased after two months. Voice change in these patients may be due to forceful retraction, the application of cautery near cricothyroid muscle.¹⁹

The most common course of EBSLN observed in our study is type I which was 72%, followed by IIA in 10% and IIB in 9.5% of patients. EBSLN could not be identified in 8.5% of patients. It was observed that patients with type IIB course of nerve are more prone for injury. Hence, postoperative vocal cord examination is advisable for patients with type IIB course and in patients for whom EBSLN is not identified.²⁰

The preoperative video-strobo-laryngoscopic examination of vocal cords of all patients was normal. Early postoperative period shows abnormality in 26 patients which includes complete immobility of the vocal cords, restricted vocal cord mobility, anterior glottis rotation, bowing of vocal folds, and absent or asymmetrical mucosal folds vibration. Early postoperative videolaryngoscopic findings are statistically significant as p value is less than 0.05. After postoperative initiation of voice rehabilitation therapy, VLS examination after 2 months showed abnormal findings in 7 patients. Late postoperative evaluation after 6 months showed abnormal findings in 4 patients, including restricted vocal mobility of vocal cord which was completely immobile previously in 2 patients and minimal bowing of vocal cord in 2 patients.

The mean fundamental frequency (Fo) of voice was 214.3 Hz preoperatively. The preoperative value of each patient was considered to be their normal value. Early postoperative mean Fo was 207.1 Hz. Mean Fo at the 2-month postoperative period was 210.5 Hz. The late postoperative mean Fo was 211.9 Hz. The value was more than that of the early postoperative mean Fo but did not equal the preoperative value. The improvement was statistically significant as p < 0.01.

Maximum phonation duration was 16.2 seconds preoperatively. Early postoperative value was 15.6 seconds. Late postoperative values were 15.7 and 15.9 seconds at 2-month and 6-month periods, respectively. This change was statistically significant as the p value was less than 0.001. At 6 months, only 4 patients had subjective voice change, compared to 33 in early postoperative period. The changes in fundamental frequency and maximum phonation duration compared to preoperative period were statistically significant (p < 0.01). None of our patients was in need of vocal fold augmentation therapy. This study shows there was improvement in subjective voice and fundamental frequency and maximum phonation duration of the patients with voice therapy.

CONCLUSION

Voice change in early postoperative period after thyroidectomy is a common problem. Early identification of the problem and initiation of voice rehabilitation therapy will considerably reduce the voice morbidity in thyroidectomy patients.

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