Journal of Laryngology and Voice

ORIGINAL ARTICLE
Year
: 2021  |  Volume : 11  |  Issue : 1  |  Page : 12--16

Etiology of unilateral vocal cord paralysis: A 16-year retrospective review


Sachin Gandhi, Subash Bhatta, Nilanjan Bhowmick 
 Department of Laryngology, Deenanath Mangeshkar Hospital and Research Centre, Pune, Maharashtra, India

Correspondence Address:
Nilanjan Bhowmick
Department of Laryngology, Deenanath Mangeshkar Hospital and Research Centre, Pune, Maharashtra
India

Abstract

Introduction: Vocal fold paralysis is a common clinical entity. Vocal fold immobility is defined as the restriction of movement of the vocal folds secondary to neuropathy or mechanical fixation. Neurogenic immobility may result from damage to the vagus and recurrent laryngeal nerve. Unilateral vocal cord paralysis (UVCP) is a highly variable clinical entity that warrants a thorough evaluation to assess the functional status of the larynx and to determine the etiology. Vocal fold paralysis is a sign of an underlying disease, not a disease in itself, and finding its etiology determines its prognosis and management options. Aims and Objectives: To study the etiology of unilateral vocal cord paralysis in patients in a tertiary referral centre Materials and Methods: The present study was conducted in a tertiary referral center between January 2003 and December 2019. A retrospective review of the case records of all patients diagnosed with UVCP who presented to us was carried out. A total of 435 cases who met the inclusion criteria were considered. The etiology of UVCP was determined using history, examination and appropriately directed investigations. Observation and Results: The most common identifiable cause of UVCP in our study was found to be surgical trauma, followed by non laryngeal malignancies. Conclusion: Though surgical trauma has been found to be the most common etiological factor in UVCP, a large proportion of patients had idiopathic UVCP and further research as to the pathophysiology of these cases is warranted.



How to cite this article:
Gandhi S, Bhatta S, Bhowmick N. Etiology of unilateral vocal cord paralysis: A 16-year retrospective review.J Laryngol Voice 2021;11:12-16


How to cite this URL:
Gandhi S, Bhatta S, Bhowmick N. Etiology of unilateral vocal cord paralysis: A 16-year retrospective review. J Laryngol Voice [serial online] 2021 [cited 2021 Dec 3 ];11:12-16
Available from: https://www.laryngologyandvoice.org/text.asp?2021/11/1/12/320561


Full Text



 Introduction



Vocal fold paralysis is a common clinical entity. Vocal fold immobility is defined as the restriction of movement of the vocal folds secondary to neuropathy or mechanical fixation. Neurogenic immobility may result from damage to the vagus and recurrent laryngeal nerve (RLN) through surgeries or neoplastic invasion from brainstem to jugular foramen, neck, mediastinum, and aortic arch on left or subclavian artery on right.[1] Mechanical fixation may occur by infiltration of musculature or ankylosis of the crico-arytenoid joint.[2] Symptoms depend on whether the vocal cord paralysis is unilateral or bilateral. It is imperative to distinguish between unilateral or bilateral vocal fold paralysis as the latter may present as an obstruction that would often require intubation or tracheotomy.[2] Unilateral vocal cord paralysis (UVCP) may be asymptomatic or can lead to the varying degree of dysphonia (e.g., simple vocal fatigue to complete aphonia) as well as dysphagia and aspiration.[3],[4] UVCP is a highly variable clinical entity that warrants a thorough evaluation to assess the functional status of the larynx and to determine the etiology. Vocal fold paralysis is a sign of an underlying disease, not a disease in itself, and finding its etiology determines its prognosis and management options.

Multiple causes of UVCP have been reported by different studies, often without agreement on the most common etiology.[2],[3],[4],[5],[6],[7],[8] Studies have demonstrated that the most common etiologies of UVFP vary in both time and/or geographic location. (Kearsley and Havas show that most common etiology changes in Australian study as both study have a difference of 18 year duration) In 1981, Kearsley reported that lung carcinoma was the leading cause of vocal fold paralysis in a study in Australia.[9] Havas et al. demonstrated that iatrogenic causes such as surgery had replaced malignancy as the most common etiology, in another Australian study performed 18 years later.[10] Few studies reported extralaryngeal malignancy as the leading cause of UVCP,[9],[11],[12] whereas other surgical cases may be replacing thyroidectomy as the leading cause of surgical trauma.[1],[2],[8],[11]

In our study, we retrospectively analyzed the patients of UVCP diagnosed at Deenanath Mangeshkar Hospital, Pune from 2003 to 2019 to establish an etiological diagnosis and to evaluate the trends of UVCP within a single institution.

 Materials and Methods



The present study was conducted at the Department of ENT and Laryngology at Deenanath Mangeshkar Hospital, Pune, Maharashtra, India, which is a tertiary referral center between January 2003 and December 2019. A retrospective review of the case records of all patients diagnosed with UVCP who presented to us was carried out. A total of 435 cases who met the inclusion criteria were considered. The medical records of all patients diagnosed with unilateral vocal fold paralysis were obtained from January 2003 to December 2019 from the electronic database. Patient data with regard to age, gender, duration of symptoms, laterality, medical and surgical history, flexible fiberoptic laryngoscopy, videolaryngostroboscopic findings, and imaging studies were reviewed.

The diagnosis of unilateral vocal fold paralysis was based on a detailed history taking and thorough physical and local examination. All patients were subjected to flexible examination and stroboscopic examination to confirm the diagnosis. All patients were investigated to find out the cause of paralysis.

The etiology of UVCP was determined using history, examination, and appropriately directed investigations. Depending on clinical suspicion, further investigations were done. These included chest radiographs to screen for intrathoracic lesion, thyroid sonography, barium swallow, esophagoscopy, bronchoscopy, and fine-needle aspiration cytology when mass lesions were detected and magnetic resonance imaging of the brain when central nervous system lesions were expected. Brain, neck, and/or chest computed tomography was carried out depending on the suspected pathology. Bronchoscopy and esophagoscopy were performed if signs and/or symptoms (dysphagia, odynophagia, unexplained weight loss, hematemesis, hemoptysis, shortness of breath, stridor, unexplained cough, otalgia, lymphadenopathy, and anemia) may indicate the need for these procedures.

A diagnosis of idiopathic UVCP was made when detailed clinical and radiological examination findings were normal, including observation over a 12-month period.

Patients with laryngeal/hypopharyngeal malignancies, intubation trauma, congenital vocal palsy, cricoarytenoid joint ankylosis, and those with incomplete examination and follow-up data were excluded from the study.

The etiologies were categorized to allow comparisons to previous studies.

 Results



We studied a total of 435 cases that fulfilled our inclusion and exclusion criteria. The average age was 48 years, ranging from 2 months to 98 years. Out of this, 276 (63.44%) were male and 159 (36.55%) were female. We had 276 patients with left-sided paralysis and 159 patients with right-sided paralysis.

The etiology of UVCP in our institution is tabulated in [Table 1] and [Table 2]. In patients where no obvious etiology was found after thorough investigations were labelled as idiopathic. The most common causes were idiopathic – 208 patients (47.81%); followed by iatrogenic surgical trauma-105 patients (24.13%) and esophageal malignancy 19 patients (4.36%). This was followed by external neck trauma – 14 patients (3.21%) and cerebral vascular accident (CVA) 14 patients (3.21%).{Table 1}{Table 2}

In our series, nonthyroid surgery cases (n = 65) exceed thyroid surgery cases (n = 40). Thyroidectomy was still the single most common surgical cause for UVCP followed by other nonthyroid neck surgeries and anterior cervical decompression and esophagectomy. Nonthyroidectomy group included other neck surgeries, spine surgeries, thoracic surgeries, and neurosurgery. The most common nonthyroid surgery to cause vocal fold paralysis was anterior cervical decompression. The next most common surgical cause was vagal schwannoma excision followed by esophagectomy and gastric pull up.

The nonlaryngeal malignancies accounted for 10.34% (n = 45) of the cases which included esophageal carcinoma (n = 17), lung carcinoma (n = 11), breast carcinoma (n = 5), non-Hodgkin's lymphoma (n = 4), Hodgkin's lymphoma (n = 1), metastatic neck nodes (n = 6), and nasopharyngeal carcinoma (n = 1). Central or neurological etiology was identified in 28 cases, out of which we had one case of motor neuron disease, two cases of myasthenia gravis, 8 cases of the postviral neuritis and 14 cases of CVA, one case of malignant otitis externa, one case of pontomedullary glioma, one case of neural invasion along arch of aorta. The other benign lesions accounted for 23 cases, which included pulmonary tuberculosis (n = 11), colloid cyst of the thyroid (n = 1), cardiac anomalies such as coarctation of aorta (n = 1), tetralogy of Fallot (n = 1), right ventricular hypertrophy secondary to pulmonary hypertension (n = 1), left ventricular hypertrophy (n = 1), abnormal variant of azygous system (n = 1) and enlarged prevascular lymph node (n = 1), aortic aneurysm (n = 1), Ortner's syndrome (n = 4), tuberculous cervical lymph node (n = 2), and mediastinal lymph node enlargement (n = 2).

 Discussion



UVCP is not an infrequent problem encountered in an otolaryngology practice.

Unilateral paralysis of the vocal folds may have many causes but generally, it happens due to one of three reasons: Nerve injury during surgeries of the thyroid and other head-and-neck procedures, malignant growth causing pressure on the nerve, or inflammatory process usually caused by a viral infection. These three reasons account for more than 85% of cases of paralyzed vocal folds.[3]

UVCP must be regarded as a sign of underlying disease, not simply a diagnosis unto itself. It is imperative to determine the cause of UVCP, as understanding the etiology of vocal fold paralysis should play a significant role in the prevention and management of paralysis.

Although a number of studies discuss the etiology of UVCP, most of them are Western studies. The current study attempted to evaluate the common causes of UVFP in the Indian subcontinent.

In our series of 435 cases of unilateral vocal fold paralysis that presented from January 2003 to December 2019, were studied to ascertain the etiological factor.

There was a male predominance in our series with a ratio of 1.73:1.0. Our results are in accordance with the study of Gupta et al.[4] (M:F = 2.3:1) from Dehradun, India, and Ahmad et al.[5] (M:F = 3.1) from Srinagar, India.

Left-sided paralysis is more common than the right side, because of the longer and more tortuous course of the RLN on the left. In our study, 276 patients had a left-sided palsy and 159 patients with right-sided palsy, which was in accordance with the studies done by Gupta et al.[4] and Srivastava et al.[13] and Myssiorek.[14]

The etiology can be found in the thoracic cavity, neck, and mediastinum or in the cranial cavity along the course of corresponding recurrent or inferior laryngeal branch of the Vagus nerve. The left vocal cord is more involved because of the longer intra-thoracic course of the left recurrent laryngeal branch of the Vagus nerve, and consequent greater vulnerability to disease and surgery. The recurrent nerve may be subjected to a variety of mechanical trauma. It may be sectioned during surgery. It may be stretched or compressed acutely during surgical manipulation or chronically by a mass growing adjacent to the nerve. It may be invaded by malignancy, and it may be devascularized as a result of nearby surgical dissection. Radiation produces fibrosis in and around nerves that may result in neuropathy as well. The various etiological factors for vocal cord paralysis are idiopathic, iatrogenic trauma, accidental trauma, neurologic, malignancy, congenital, infectious, and postradiation.

[Table 3] shows the distribution of the various causes of UVCP in a few recent studies. We found 47.81% of our cases of UVCP to be idiopathic. This is consistent with those of Cunning[6] (31%) and Ahmad[5] (38.18%).{Table 3}

Surgical trauma was the most common identifiable cause of UVCP in our study. Data now suggest that nonthyroid surgeries account for more cases of UVFP.[1],[2] Our data does support this changing trend. In our series, the proportion of nonthyroid surgical procedures accounted for 61.9% of cases of all surgical causes for UVCP. This changing trend is probably due to better training, familiarity with the anatomy of the neck, and experience of specialists dedicated to the thyroid and parathyroid surgery. Surgeons in other specialties operating along the course of the laryngeal nerve can inadvertently injure them. Familiarity with the possible mode of injury (ligation, stretching, direct pressure from retractors, ventilation tube, intracranial hemorrhage, etc.,) can decrease the chances of injury and early referral to an otolaryngologist will help in confirmation of injury and institution of early treatment.

Thyroidectomy was still the single most common surgical cause for unilateral vocal cord palsy followed by other nonthyroid neck surgeries (22%), anterior cervical decompression (10.47%) and esophagectomy (5.7%). RLN palsy in anterior cervical spine surgery occurs most often from stretch induced neuropraxia[15] and endotracheal tube mediated compression of the RLN during retraction[16] rather than direct surgical injury. New causes have also been revealed, for example, Bentall's surgery (for dilatation of aortic root, ascending aorta and arch of aorta) and CONE reconstruction for tricuspid valve repair in CCHD Ebstein's anomaly was reported in our study one case each.

Nonlaryngeal malignancy contributed to 10.34% of the cases in our study. Another study by Ko et al. found an 11.80% incidence of nonlaryngeal malignancy.[17] In our study, carcinoma esophagus (n = 17) was the most common malignancy associated with unilateral vocal cord palsy, followed by carcinoma lung (n = 11). This was contrary to many other previous studies where lung carcinoma was found to be the most common malignancy to cause UVCP.[8],[18]

Among the neurological cases, CVA (n = 14) accounted for most cases followed by postviral neuritis (n = 8). Vocal fold paralysis may appear in stroke, almost always in conjunction with other deficits.[19] Lateral medullary infarct (Wallenberg syndrome) is a well-known complex of neural injury featuring vocal fold paralysis, dysphagia, ataxia, Horner's syndrome, and hemifacial sensory deficit and/or pain.

There is a decreasing trend of vocal fold paralysis due to nonmalignant medical conditions. According to Bryson Delevan,[20] fixation of the left side of the larynx was almost proof positive of the presence of an aortic aneurysm, though we found only one case of aortic aneurysm.

The other benign diseases that cause vocal cord paralysis in our study included pulmonary tuberculosis, colloid cyst of the thyroid, cardiac anomalies such as coarctation of aorta, tetralogy of Fallot, right ventricular hypertrophy secondary to pulmonary hypertension, left ventricular hypertrophy, an abnormal variant of the azygous system and enlarged prevascular lymph node, aortic aneurysm, Ortner's syndrome, tuberculous cervical lymph node, and mediastinal lymph node enlargement.

Hoarseness due to left RLN paralysis caused by an identifiable cardiovascular disease is referred to as Ortner syndrome. It was first described in a patient with severe mitral valve stenosis by Ortner in 1897. Left atrial enlargement can compress or stretch the nerve. Other causes of Ortner syndrome include mitral valve prolapse, aortic aneurysm, and septal defects.[21]

In chronic pulmonary disease, paralysis may be caused by three possible mechanisms that exert effects on the nerve: (1) The nerve may be passing through or maybe adjacent to a mass of caseating nodes, (2) the nerve may be trapped in the dense fibrous pleural thickening or in the chronic fibrosing mediastinitis that may occur, and (3) the nerve may be stretched due to retraction of the left upper lobe bronchus pulled towards the apex.[22]

Radiation causes fibrosis in and around the nerve which may interfere with blood supply, compress the nerve, or otherwise compromise axonal flow. Cases have been documented following mediastinal irradiation for the treatment of mediastinal tumors or breast cancer.[23],[24] In our series we found 3 cases of post-radiation vocal cord palsy, 2 were radiated for metastatic breast carcinoma, and 1 for metastatic buccal carcinoma.

 Conclusion



The anatomical course of RLN determines the potential causes of vocal fold paralysis, which varies considerably from series to series based on local variations. Unilateral vocal fold paralysis is an evolving condition and is an important sign of various underlying diseases. Despite a lot of clinical experience, significant questions remain about the pathophysiology underlying idiopathic paralysis and recovery rates.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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