A Study on Etiopathogenesis of Vocal Cord Paresis and Palsy in a Tertiary Centre

Abstract

To identify patients of vocal cord paresis and palsy and to establish an etiological diagnosis based on a study performed in a tertiary centre. Study was done prospectively in the Department of ENT in KIMS Hospital, Bangalore, for 1 year, from June 2016 to June 2017. 100 patients with vocal cord paresis and palsy were identified and examined by using various tests and investigations to establish the etiology. Most of the patients presented with complaints of change in voice (92%). Some of the other common presenting complaints included noisy breathing and difficulty in swallowing, difficulty in voice production and vocal fatigue and cough. Unilateral paralysis (82%) was found to be more common than bilateral paralysis (18%), of which left (52%) was more commonly affected than right (48%) vocal cord. The most common age group affected was 51–60 years (24%) followed by 61–70 years (19%). Males (60%) were affected more than females (40%) in a ratio of 3:2 and among the affected males 73% were known smokers. The most common cause of vocal cord paresis and palsy was found to be idiopathic (38%), followed by primary laryngeal growths (27%). Other causes included carcinomas of lung, thyroid and oesophagus, traumatic, inflammatory, systemic diseases like Rheumatoid arthritis, Hypertension leading to stroke. Identifying the exact etiopathogenesis of vocal cord paresis and palsy in patients has been difficult and is very important in order to establish a proper diagnostic and treatment protocol for these patients.

Introduction

Vocal cord paresis and palsy refers to the reduced and absent movement of the vocal cords respectively. It is not a disease per se, but is a common manifestation of numerous diseases, which may be localized to the larynx or may be of the thorax, neck or cranial cavity or even of various systemic diseases [1]. The causes are variable and may be multifactorial and evasive, hence the symptoms also vary from being mild to severe. These depend on the severity of injury caused to the vagus nerve or its branches-recurrent laryngeal nerve and superior laryngeal nerve, which may be unilateral or bilateral. Beyond being neurological, the cause of vocal cord paresis or palsy may also be due to mechanical fixation of vocal cords [2].

Several studies have been done in this field of vocal cord paresis and palsy which have shown the importance of diagnosing the cause to be able to treat and explain the prognosis.

Objective

This study was conducted with a purpose of identifying patients of vocal cord paresis and palsy and to establish an etiological diagnosis based on detailed history, clinical examination findings and investigations.

Materials and Methods

Study was done prospectively in the Department of ENT in KIMS Hospital, Bangalore, for 1 year, from June 2016 to June 2017. 100 patients with vocal cord paresis and palsy were identified. Detailed history was taken, General physical examination and Systemic examination were done for patients who came with voice and throat related complaints. Complete ENT examination was done for these patients which included an Indirect and Video Direct Laryngoscopy and Esophagoduodenoscopy. Following this, patients were sent for blood tests which included routine haematological tests (complete blood picture), renal and liver function tests, serum electrolytes, serology, lipid profile, thyroid function tests and urine tests. For selected patients ANCA and CRP tests were also done. As per requirement, imaging tests like X-Rays, Ultrasound scans (neck) and CT scans (neck, chest) were also done.

Patients who failed to cooperate for our examinations and those who failed to come for follow up were excluded from the study.

Results

Totally 100 patients with vocal cord paresis and palsy were studied. 92% of the patients came with complaints of change in voice. Some of the other complaints the patient came with included difficulty in swallowing (27%), cough and aspiration (27%) and noisy breathing (15%), difficulty in voice production and vocal fatigue (19%) (Fig. 1).

Fig. 1.

Complaints

The most common age group to be affected was 51–60 years (24%) followed by 61–70 years (19%). Next common age group to be affected was 41–50 years (17%) followed by 31–40 years (14%). Least to be affected was patients belonging to the age group of 20–30 years (10%) (Fig. 2).

Fig. 2.

Age

Males (60%) were affected more than females (40%), in a ratio of 3:2. Of the affected males, 73% were chronic smokers (Fig. 3).

Fig. 3.

Sex ratio

On examination, 82% of the patients had unilateral paralysis. Left vocal cord was found to be involved more than the right by 52%. 78% of the unilateral palsy cases, showed the vocal cords to be in paramedian position. 13% of these patients showed intermediate position of vocal cords and 9% showed median position of vocal cords. 88% of the bilateral vocal cord palsy showed vocal cords in paramedian position and 12% were in intermediate position (Fig. 4).

Fig. 4.

Laterality

The most common cause of vocal cord paresis and palsy was found to be idiopathic (37%). The next common cause was benign and malignant growths over the larynx causing mechanical fixation of cords as seen in 28% of patients with vocal cord paresis or palsy, of which majority of patients presented with unilateral vocal cord growth and subsequently palsy. 7 patients with lung carcinoma with secondaries, 2 with thyroid malignancies and 1 case of oesophageal cancer presented with vocal cord palsy (Fig. 5).

Fig. 5.

Causes of vocal cord palsy

Eight patients (6 females and 2 males) presented with unilateral vocal cord paresis, post total or hemi-thyroidectomy procedures, which were transient and recovered completely with proper conservative treatment. 2 patients had come with vocal cord palsy following cerebrovascular accident (stroke) due to uncontrolled hypertension. 4% of the patients presented with vocal cord palsy following intubation. 2 patients were diagnosed to have vocal cord palsy post radiotherapy, both for pyriform fossae growth. 2 patients who were known cases of Rheumatoid arthritis had come with hoarseness of voice and difficulty in breathing and were found to have bilateral abductor palsy. 6 other cases of vocal cord palsy were noted with inflammatory etiology too. 1 patient was referred to our department for difficulty in voice production post oesophagectomy surgery and was diagnosed to have left vocal cord palsy (Fig. 6 and 7).

Fig. 6.

Causes of unilateral vocal cord palsy

Fig. 7.

Causes of bilateral vocal cord palsy

Discussion

Vocal cord paresis and palsy refers to the decreased and absent movements of the vocal cords respectively. It is a very common sign of underlying diseases, which may be evasive and multifactorial. Symptoms include hoarseness of voice (most common), respiratory problems like difficulty in breathing, cough and aspiration, dysphagia and dysphonia [3]. These depend on the severity of injury caused to the vagus nerve or its branches superior laryngeal and recurrent laryngeal nerves.

Most common age group to be affected was the elderly age group of 51-60 years, probably because of the history of chronic smoking and the higher incidence and prevalence of cancer and systemic comorbidities like diabetes and hypertension [1]. Ahmed et al. also reported maximum number of patients in the 5th and 6th decades of life [4]. Our results are also in alliance with Merati, Havas and Glazer who reported the mean age as 53 years [3, 5, 6].

The history of chronic smoking among males may also be a reason for males being affected more than females by a ratio of 3:2. Studies also reason it as males visiting the outpatient department in hospitals more than females, in our country [1]. These results are also in accordance with another study by Nerurkar in which the male to female ratio was 2:1 [7] and Benninger (Males 52.1%, females 47.9%) [2]. A study by Feehery on bilateral vocal cord palsy showed a reversal in the ratio, M:F = 0.3:1 (M—48%, F—52%) [8]. Other studies by Hollinger have also separately reported prevalence to be higher in females [9].

In most patients of unilateral vocal cord palsy, vocal cord is fixed in paramedian position (78%) in our study, followed by intermediate (13%) and median (9%). In patients with bilateral vocal cord palsy, also the vocal cords were mostly in paramedian position (88%). Woodson proposed that the paramedian position was due to robust innervation of thyroarytenoid muscle in patients with recurrent laryngeal nerve injury [10].

Left vocal cord palsy was found to be 1.5–2 times more commonly involved than the right vocal cord due to the long intrathoracic course of the left recurrent laryngeal nerve in the mediastinum [11]. Our study was in concordance with studies performed by Ko et al. reporting nearly 68% paralysis in left side [12] and Srirompotong et al. reporting 73% paralysis on left side [13].

Idiopathic etiologies by definition have no identified cause. Though the incidence of idiopathic vocal cord palsies has reduced with improving imaging and fibreoptic endoscopy, it still remains the most common etiological factor of vocal cord paresis and palsy. In 1973, Bulteau reported the highest incidence of 50% [14], a year after which Maisel reported the lowest incidence of 3.7%. [15].

The next common cause identified in our study was benign and malignant growths leading to mechanical fixation of cords. This was mainly seen in males with the cause being attributed to chronic smoking and poor dietary habits.

Most common secondary cause of vocal cord palsy was lung cancer with secondaries which most commonly affected the left vocal cord, probably due to the direct compression of the recurrent laryngeal nerve by the cancer mass. Other causes also included thyroid malignancy and esophageal cancer causing the same. Invasion of the nerves could also be a reason in these cases for persistent palsy [16]. Chen et al. had reported lung cancer as the etiology of vocal cord paralysis in 34 cases [17]. Our study is in concordance with a study done by Ko et al. showing lung and thyroid tumours to be the most common sites of tumour origin in cases of vocal cord palsy [12].

Studies state that the most popular causes of vocal cord palsy following surgery are thyroid, oesophagus and heart surgeries [18, 19]. It occurs due to injury to the recurrent laryngeal nerve or external branch of superior laryngeal nerve. Usually, it is unilateral and may be bilateral rarely in cases of total thyroidectomy of which the incidence reported is 0.58% [20].

The incidence of post-thyroidectomy vocal cord paralysis has been reported in the range of 3.5–6.6%, and 93–100% of these patients are reported to make complete recovery [18]. It is a common complication during thyroidectomy procedures and a study has reported the incidence as 50% [21]. Amongst patients of post thyroidectomy vocal cord palsy, majority of the patients were females, owing to the high incidence of thyroid diseases in females [1]. Causes of vocal cord palsy following thyroid surgery include the presence of adhesions, derangement of normal anatomy in recurrent goitres and a huge multinodular goitre (highly vascular mass) that can bleed massively during surgery obscuring the surgical field, making identification of the nerve intraoperatively difficult [18]. A small nodule or cyst located strategically at the tracheoesophageal groove can cause compression of the nerve as well [22]. Transient vocal cord palsy post thyroid surgery was also seen in case of extra laryngeal ramification of recurrent laryngeal nerve in the past [23]. Another possible cause of the same is neaurapraxia while searching for the nerves [24]. Post esophagectomy recurrent laryngeal nerve injury can also be due to the same reasons.

Studies state incidence of intubation related vocal cord palsy as 0.2% [25]. Risk factors in these cases include: size of endotracheal tube, cuff pressure, duration of intubation, hypotension during surgery, neck in prolonged hyperextension position, patient being a smoker and associated co morbidities like diabetes and hypertension [26]. There is a three-fold rise in vocal cord palsy in patients being intubated after the age of 50 years, two fold rise in patients with hypertension and diabetes and 15-fold rise if the ventilator support is for more than 6 h [27]. Over-extension of neck during intubation can cause stretching of both the vagus nerves [28]. The cuff of endotracheal tube pressurizes the anterior branch of recurrent laryngeal nerve between the endotracheal tube and thyroid cartilage causing degeneration and paralysis compromising microcirculation and causing ischaemic degeneration of recurrent laryngeal nerve. Lack of intermittent deflation of cuff can cause pressure neurapraxia leading to vocal cord palsy [29].

Age is also a risk factor considering tissue degeneration with age which may cause cord damage easily as compared to the younger patients. In hypertensive patients with atherosclerosis vessels, microvasculature is more vulnerable to mechanical damage caused by cuff that is inflated. Diabetic patients are more prone to vocal cord palsy as they develop peripheral neuropathy [28].

Cerebrovascular accidents (stroke) due to uncontrolled hypertension can affect nucleus ambiguous and nucleus solitarius, the central connections of vocal cords, which can lead to vocal cord palsy. Bilateral vocal cord palsy in cases of rheumatoid arthritis can be explained to be due to arthritis of the cricoarytenoid joint.

Beyond the above explanations given for the etiopathogenesis of unilateral and/or bilateral vocal cord paresis and palsy, there are many more yet to be studied about and explained.

Conclusion

Vocal cord paresis and palsy have got variable etiologies which vary with age, sex, presence of systemic diseases, side of lesion etc. Hence, an integrated diagnostic and treatment programme is necessary for patients presenting with vocal cord paresis and palsy.

Compliance with Ethical Standards

Conflict of interest

Authors declare that they have no conflict of interest.

Ethical Approval

This article does not contain any studies which experiments with human participants or animals and all institutional and international ethical standards have been followed.

Informed Consent

Informed consent was obtained from all individual participants included in the study.