Voice Changes Without Laryngeal Nerve Alterations After Thyroidectomy: The Need For Prospective Trials - A Review Study

BACKGROUND

Thyroidectomy is a commonly performed surgical procedure that is offered for different thyroid pathologies. The most frequent complication after total thyroidectomy is transient or permanent hypoparathyroidism followed by transient or permanent recurrent laryngeal nerve palsy. Patients may experience voice impairment despite intact laryngeal nerve function. These patients are of special interest because they experience subjective symptoms which are difficult to measure and therefore to treat.

SUMMARY

The Voice Handicap Index (VHI) and VHI-10 are the most commonly used subjective questionnaires. Their results correlate with objective findings. Female sex, in particular after menopause, is a dominant factor for developing voice impairment after thyroidectomy. The extent of neck surgery and the weight and volume of the removed thyroid correlates directly with both objective and subjective voice impairment after surgery. Videolaryngostroboscopy should be considered to examine vocal cord pathologies in this patient group. Surprisingly, there are no studies showing that speech and voice therapy are beneficial for patients with voice alterations but with intact laryngeal nerves.

CONCLUSIONS

While recurrent laryngeal nerve (RLN) paralysis can be evaluated by objective exams postoperatively, we are still left with the issue of possible partial or complete external branch of superior laryngeal nerve (EBSLN) injury. It is therefore quite difficult to segregate neural (RLN and EBSLN) and non-neural voice change populations, regardless of the method of literature evaluation. Perhaps patients' perspectives on how they experience voice functionality should play a superior role in deciding which patients should be investigated further with laryngoscopy, acoustic or perceptual analysis, and which patients should be offered treatment.

Unilateral Laryngeal Pacing System and Its Functional Evaluation

Goal. To establish a reliable instrumental system for synchronized reactivation of a unilaterally paralyzed vocal fold and evaluate its functional feasibility. Methods. Unilateral vocal fold paralysis model was induced by destruction of the left recurrent laryngeal nerve (RLN) in anesthetized dogs. With a micro controller-based electronic system, electromyography (EMG) signals from cricothyroid (CT) muscle on the ipsilateral side were recorded and used to trigger pacing of paralyzed vocalis muscles. The dynamic movement of vocal folds was continuously monitored using an endoscope, and the opening and closing of the glottis were quantified with customized imaging processing software. Results. The recorded video images showed that left side vocal fold was obviously paralyzed after destructing the RLN. Using the pacing system with feedback triggering EMG signals from the ipsilateral CT muscle, the paralyzed vocal fold was successfully reactivated, and its movement was shown to be synchronized with the healthy side. Significance. The developed unilateral laryngeal pacing system triggered by EMG from the ipsilateral side CT muscle could be successfully used in unilateral vocal fold paralysis with the advantage of avoiding disturbance to the healthy side muscles.

Comparing the morbidity of external laryngeal nerve injury in thyroid surgery with and without identifying the nerve using intraoperative neuromonitoring

OBJECTIVE

To describe and determine the possibility of surgical trauma to the external branch of the superior laryngeal nerve and to assess the role of intraoperative neuromonitoring in thyroid surgery.

DESIGN AND SETTING

Prospective, randomized, controlled study in a teaching Hospital Universiti Sains Malaysia (HUSM), Kota Bharu, Kelantan, Malaysia.

SUBJECTS

Forty two patients of both genders, whom underwent thyroid surgery divided into two groups (21 patients control group and 21 patients study group) in HUSM and were randomly selected for our study.

METHODS

The use of nerve monitoring and proper surgical technique of upper thyroid pole dissection followed by its lateralization and exposure of cricothyroid space were performed in each subject in study group in order to preserve EBSLN after its identification. In control group upper thyroid vessels were ligated close to the upper thyroid pole without any effort of EBSLN identification.

RESULTS

Total of 42 (35 females and 7 males) patients who underwent thyroid surgery in a period of 2 years. Evaluation of all subjects 1 case in control group presented with symptoms of EBSLN injury.

CONCLUSION

Intraoperative identification and neuromonitoring can avoid injury to the EBSLN and prevent its sequential changes in voice especially for those who professionally depend to their voice.