Vocal Cord Paralysis –An Etiological Analysis

Introduction: Vocal cord paralysis is the total interruption of nerve impulse resulting in absence of laryngeal muscle movement. The most common type of vocal cord paralysis found is due to recurrent laryngeal nerve injury. The pathology can be either along the course of the tenth cranial nerve from cerebral cortex to neuromuscular junction or could be from mechanical fixation of cricoarytenoid joint. Objective: To study the various etiological factors contributing to vocal cord paralysis. Materials and methods: Patients with vocal cord paralysis [unilateral and bilateral] who were treated at a tertiary institute for a period of 3 years were included. The immobility of cords was assessed with the use of indirect laryngoscopy via mirror or rigid angled telescopy or flexible laryngoscopy. The patients were categorized based on laterality of paralysis as well as based on various etiological factors into groups. Appropriate statistical analysis was done. Results: Among 50 patients, 84 % cases had unilateral vocal cord paralysis. Surgical cause was found to be the most common etiology of unilateral vocal cord paralysis (34%) closely followed by idiopathic (18%) and neoplasm (16%). In bilateral vocal cord paralysis, surgical and neurological causes were found to be the main causative factor. Conclusion: Vocal cord paralysis wide range of factors contributing to its occurrence with surgical cause being a common one. A comprehensive assessment of patient should be performed to determine the cause which facilitates a direct treatment plan.


Introduction
Vocal cord paralysis [VCP] is the total interruption of nerve impulse resulting in absence of laryngeal muscle movement. Vocal cord paresis implies the hypo function or hypo mobility secondary to neurologic injury, whereas vocal cord paralysis is the complete immobility of a muscle. The most common type of vocal cord paralysis found is due to recurrent laryngeal nerve injury [RLN].The left recurrent laryngeal nerve branch is more frequently involved as the intrathoracic course of left RLN is twice more than the right RLN [1]. Left RLN travels into mediastinum and loops around arch of aorta prior to penetrating larynx more vertically. Right RLN loops around subclavian artery and has a shorter course & returns and penetrates horizontally. Paralysis of the left vocal cord is reported 1.4-2.5 times more than right [2]. There are multiple ways of The clinical presentation is based on the type of classification.
The most common symptom is voice change, the severity and degree of which will depend on the position of the vocal cords [3][4]. Other symptoms are stridor, which is seen in bilateral abductor paralysis, aspiration which is usually noted in bilateral adductor paralysis, dysphagia, sore throat, cough. The voice quality also varies as per the type of paralysis. Unilateral vocal cord paralysis can be asymptomatic also. a.

Materials and Methods
Patients with vocal cord paralysis [unilateral and bilateral] from a tertiary institute for a period of 3 years were included in the study. The immobility of cords was assessed with the use of indirect laryngoscopy via mirror or rigid angled telescopy or flexible laryngoscopy. The patients were categorized based on laterality of paralysis as well as based on various etiological factors into groups.
Children less than 15 years of age and inadequate documentation of VC immobility were excluded from the study.

Results
A total number of 50 cases were included in the study. Among which 22 were males and 28 were females.

Discussion
Vocal cord paralysis is a common feature of some underlying disease entity which can even be life threatening at times.
Hence identifying the etiology of vocal cord paralysis plays a significant role in prognosis and treatment outcomes. The clinical presentation depends on the site and severity of injury [6,7]. The age group of 51-60 years is found to be more prone for vocal cord paralysis, probably due to history of chronic smoking and the higher occurrence of malignancy and systemic co morbidities like diabetes and hypertension as per Gupta et al. [8,9]. Our study was also in accordance with the above study wherein average age was found to be 56 yrs. A comparative analysis of incidence of unilateral and bilateral vocal cord paralysis is shown in the table below [ Table   1]. Surgery, neoplasm, and idiopathic causes have been quoted in literature as the common culprits for the occurrence of vocal cord paralysis [ Table 2]. Neoplasm was found to be the most common etiology in earlier studies [3,10,11]. Our study also reinforces the same with surgical cause being the predominant one. The bright side of post thyroidectomy cases of UVCP is the high rate of complete recovery, almost 93% as per studies [12]. The presence of adhesions, anatomical derangement in recurrent goitres and vascular masses obscuring surgical field due to excessive bleeding are few predisposing factors rendering the identification of the recurrent laryngeal nerve cumbersome intra-operatively [9,12].
Other surgeries like oesophageal surgery, cervical spine surgeries, and cardiac surgeries still pose a high risk of VC palsy [1,12,13].

Conclusion
Vocal cord paralysis has a wide range of factors contributing to its occurrence with surgical cause being a common one. The advanced techniques and improved surgical skills can lead to reduction in surgeries being the cause of vocal cord paralysis. The incidence of unilateral vocal cord paralysis is more than bilateral vocal cord paralysis. A comprehensive assessment of patient should be performed to determine the cause which facilitates a direct treatment plan.