Airway management has always been of major importance throughout history [1], and ancient physicians worked on diseases affecting the airway and respiratory system [2]. Vocal fold paralysis (VFP) is a fairly common entity encountered by otorhinolaryngologists & is usually an indicator of an underlying pathology [3]. Detecting the underlying disease is critical in patients with VFP since the primary diseases include many fatal diseases and late detection can cause major complications [4]. By definition, idiopathic etiologies have no cause. The actual incidence of idiopathic RLN paralysis is uncertain, though, because it depends on how comprehensive the investigative evaluation is. With the development of technologies in imaging, fibreoptics, and viral titres, the incidence of idiopathic RLN paralysis has declined [5,6]. Despite being widespread, little is known about idiopathic paralysis, which is believed to be secondary to inflammatory or viral illness [7].

VFP can be a manifestation of numerous diseases that may arise from thorax, head & neck, or even systemic disease. It can be caused by neurological damage or mechanical fixation of the vocal fold due to neoplastic infiltration of the vocalis muscle or cricoarytenoid joint fixation. VFP can occur due to damage to the vagus and recurrent laryngeal nerve along their anatomic course and since these nerves pass through the thoracic cavity, several thoracic and mediastinal diseases can, in turn, cause VFP. Hence, apart from imaging and other investigations of the head and neck, investigation into thoracic causes of VFP should be done alongside. Although chest radiography is an excellent screening tool for identifying thoracic diseases, it still misses out on diagnosing several diseases, especially in the mediastinum and aortopulmonary window [4]. However, computed tomography (CT) can be an extremely useful diagnostic tool in these cases as it can provide more detailed information about the mediastinal structures [8]. The literature about the thoracic causes of VFP is limited, and none is done in the Indian subcontinent [8–10]. The current study was designed to identify the thoracic causes of VFP in the Indian population with the help of chest imaging.

Demographic Data: A total of 147 cases of VFP were included in the study, which included 50 female and 97 male participants. The average age of participants was 51.5 years.

51 participants were current smokers (44 male & 7 females), 33 were former smokers and 63 were never smokers. 38 had a history of alcohol use, 24 of tobacco chewing and 1 had a history of cannabis smoking. The most common co-morbidity was hypertension, seen in 26 patients, followed by diabetes mellitus (n=15), gastroesophageal reflux (n=6), chronic obstructive pulmonary disease (n=5), gout (n=5), and hypothyroidism (n=3). 92 study participants had no active co-morbidity. One patient with right VFP had a history of CAD and had undergone coronary artery bypass grafting (CABG) in the past. 11 patients (7.5%) had a history of pulmonary tuberculosis in the past.

Site: The most common side affected was left (104, 70.7%)) followed by right (34, 23.1%), while 9 patients had bilateral vocal fold paralysis. Most of the participants (132) reported complaints of loss of or change in voice while 8 reported dysphagia, 5 had throat pain, and 2 presented with shortness of breath.

Chest X-ray findings: Out of 147 patients, 116 had a grossly normal Chest radiography. The most common pattern seen on chest radiography was heterogenous opacities (n=16, 10.9%) followed by homogenous opacity (n=9, 6.1%), cavitation (n=4, 2.7%), hyperinflation (n=1), and hilar prominence (n=1). In patients with parenchymal opacities, bilateral involvement was seen in 12 patients, 11 had only the right while 7 had only the left side involved.

Computed Tomography findings: Among 147 study participants, no radiological abnormality was found on CT in 97 participants. Radiological abnormalities found in CT of rest of 47 patients are summarized in Table

Site and cause of VFP: 14 (26.9%) patients had right vocal cord paralysis; 35 (67.3%) patients had left vocal cord involved while 3 (5.8%) patients were of bilateral VFP. The most common thoracic cause for vocal cord paralysis was found to be malignant neoplasm (25 cases) followed by Tuberculosis, including fibrosis (15 cases). Details given in table 1.

Malignant neoplasms of the chest causing VFP: Lung cancer was found in 17 cases (68%), followed by metastatic lymph nodes (4 cases), Oesophageal cancer (3 cases) and mediastinal tumour (single case). Details shared in table 2.

Out of the 52 patients of VFP with thoracic cause 63.5% were male and 36.5% were female. In similar studies done earlier male patients were more than female patients [8,11]. This might be due to the fact that smoking is more prevalent in males than in females [12]. The average age in our study was 57 years which was similar to previous studies [11].

In this study 26.9% subject had right vocal cord paralysis, 67.3% patients had left vocal cord involved while 5.8% patients were of bilateral VFP. In previous studies unilateral VFP was much more common than bilateral VFP [8,11]. Majority of previous studies have also showed left preponderance among unilateral VFP [11–13]. Most common thoracic cause for vocal cord paralysis was found to be malignant neoplasm 48.1% followed by Tuberculosis, including fibrosis 32.7% in our study. In previous studies, majority of the VFP cases due to chest involvement belonged to malignant neoplasm followed by cardiogenic causes such as thoracic artery aneurysm [3,4,13]. This difference might be due to increased prevalence of Tuberculosis in Indian subcontinent [14]. Among malignant neoplasms, majority of the cases in our study were due to Lung cancer (68%), followed by Metastatic lymph node (16%) and Oesophageal cancer (12%). In previous studies majority of malignancy was of Lung cancer followed by Oesophageal cancer [3,11].

Our study has confirmed few observations as observed in previous studies such as, VFP has always been found to be common among male patients than female patients probably due to increased prevalence of smoking in male patients. Unilateral VFP is more common than bilateral VFP and left sided VFP is also more common than right sided VFP. Most common thoracic cause for VFP among malignant neoplasm is Lung Cancer. Our study had some differences from previous done studies such as Tuberculosis was one of the major causes of VFP in our study possibly due to increased prevalence of Tuberculosis and Tuberculosis related complications in our country. Among malignant neoplasm, malignant lymph nodes were a major cause for VFP in our study.

This study shows the difference in causes of VFP due to thoracic disease between Indian subcontinent and the rest of the world. Malignant neoplasm and both active and past infection of Tuberculosis need to be considered in every case of VFP by both otorhinolaryngologist and pulmonologist. The major drawback of our study was a small sample size due to less number of patients.

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