Vocal cord paralysis is the loss of function and movement of the vocal cord as a sequel to dysfunction of the vagus nerve or its distal branch, the recurrent laryngeal nerve. Vocal cord paralysis is a subset of vocal cord or fold immobility which is a broad term for all causes of vocal cord dysfunction.
Clinical presentation of vocal cord paralysis may take two forms: existing stridor which progresses acutely into dyspnea or development of gradual and progressive dyspnea within a few months  which is characterized by absence of significant voice changes.
In all patients with vocal cord immobility, history should consist of the chief symptom, onset of symptoms, voice and airway changes over time, tobacco use, and risk factors such as surgery, chronic inflammatory or fibrotic conditions, and intubation.
On physical examination, the quality patient's voice should be noted; auscultation should take the presence of abnormal airway findings such as stridor into consideration. The breath sounds may be normal. Deglutition challenge should be done to assess the patient's swallowing function and risk of aspiration.
On head and neck examination, the following should be considered: the color and condition of the laryngeal mucosa, stenosis of the posterior glottis, mobility status of the arytenoids, length, muscle bulk, tone and temper of each vocal cord, and the symmetry of the cords.
Fibronasopharyngolaryngoscopy is the standard tool for making a diagnosis of vocal cord immobility. This technique reveals the immobility of both vocal cords. A CT scan imaging of the length of the vagus nerve from the base of the skull to the mediastinum may be necessary if a diagnosis of vocal cord paralysis is inconclusive.
Although in vocal cord paralysis and immobility, the voice quality is not significantly changed, acoustic analysis of the voice may serve as an adjunctive tool to evaluate the recovery or responsiveness of the patient. A detailed neurological examination may be necessary to exclude other neurologic causes of bilateral vocal cord immobility.
Fiberoptic laryngoscopy is the main investigative tool for assessing the clinical status of the patient. Stroboscopic videolaryngoscopy provides more detail about the mobility of the vocal cords if asymmetric mucosal waves are identified. Direct laryngoscopy is done under general anesthesia and it shows details of the posterior glottis, subglottis, trachea, and main bronchi to exclude infiltrative diseases and neoplasms, subglottic stenosis, and other lesions along the airway tract.
Treatment of unilateral vocal cord paralysis mainly centers on the improvement of voice quality. This is achieved through certain techniques including medialization, reinnervation, and augmentation. Augmentation involves the injection of plasticized particles, micronized dermis, autologous fat, or collagen into the paralyzed cord, thereby approximating the cord and improving voice quality and reducing the risk of aspiration. Medialization involves moving the vocal cords medially towards the midline and placing an adjustable spacer lateral to the affected cord.
Bilateral vocal cord paralysis can also be treated surgically via open and endoscopic procedures like arytenoidectomy  . Endoscopic procedures for treating vocal cord paralysis include arytenoidectomy by electrocautery and carbon dioxide laser total arytenoidectomy . Subtotal arytenoidectomy is another conservative technique employed in treating vocal cord paralysis.
Posterior glottic stenosis is much more difficult to treat than vocal cord paralysis. Treatment options for posterior glottic stenosis include endoscopic dilatation, intralesional corticosteroid injections, laryngofissure with posterior cricoidotomy and scar excision with replacement by skin or mucosal grafts .
Implantable stimulators are being investigated as a possible treatment option for vocal cord immobility .
Bilateral vocal cord immobility is a life-threatening condition which requires prompt and accurate diagnosis and treatment. However, vocal cord paralysis needs to be distinguished from other causes of vocal cord immobility, so as to effect the appropriate management plans.
There's currently no definite treatment for bilateral vocal cord immobility. The current treatments approaches seek to restore airway patency, but carry a risk of worsening the glottic sphincteric function and voice quality.
Studies investigating the effectiveness of laryngeal reinnervation have revealed good outcomes of this technique including improved muscle tone, vocal cord bowing, and less atrophy, but no changes in the vocal cord mobility were noted .
In a study conducted by Benninger involving a series of 117 cases, bilateral vocal fold immobility was found to be caused by surgical injury (44%), malignant tumors (17%), endotracheal intubation (15%), neurologic disorders (12%), and idiopathic etiologies (12%) .
A study which reviewed over 800 patients revealed that injuries to the mediastinum and cervical regions during surgeries in those regions were the most important causes of vocal cord paralysis . Surgical injury is responsible for 40% of unilateral vocal cord paralysis and 50% of bilateral vocal cord paralysis. Bilateral vocal cord paralysis was more associated with thyroid surgery while unilateral vocal cord paralysis is caused mostly in association with other neck and mediastinal surgeries such as carotid endarterectomy, open heart surgeries, and anterior cervical spine surgeries. In 20% of cases, unilateral vocal cord paralysis was found to be idiopathic.
Furthermore, in the index study, extralaryngeal malignancies constituted the third commonest cause of unilateral vocal cord paralysis, occurring in 14% of cases. Nonsurgical trauma to the neck accounted for 6% of all cases of unilateral vocal cord paralysis and is frequently linked to endotracheal incubation. Rare causes of vocal cord paralysis include infections, radiotherapy, diseases of the brain or spinal cord, and aortic aneurysm.
The specific etiologies of vocal cord immobility in adults and children differ. In children, the commonest causes include iatrogenic factors, central neurologic diseases, and idiopathic causes.
The incidence rate of vocal cord paralysis is estimated at 42 cases in 10,000 patients. Vocal cord paralysis usually affects adults between the ages of 50 and 60 years.
Vocal cord paralysis more commonly affects males than females, in a male to female ratio of 3:1. The left vocal cord is more commonly affected than the right one.
Bilateral vocal cord paralysis presents initially with dysphonia. This is attributable to the large distance between the vocal cords. With time, both vocal cords approximate and the patient's voice are restored and may come down with cough regardless of the stridor and bilateral vocal cord paralysis. This is because, the more the vocal cords approximate, the better the voice, but the more compromised are the airways. Unilateral vocal cord immobility is more commonly associated with voice changes while bilateral vocal cord immobility or paralysis is associated with breathing difficulties. Vocal cord paralysis may also result in dysphagia and aspiration.
Vocal cord paralysis may be prevented if the risk factors are avoided: Avoiding cigarette smoking and cessation for smokers; these serve to reduce the risk of airway malignancies, using seat belts during driving, and wearing protective wears during sports to minimize risk of injuries to the head, neck, and chest.
Vocal cord paralysis is caused by diseases which cause vagal nerve or recurrent laryngeal nerve dysfunction. Vocal cord paralysis falls within the scope of vocal cord or fold immobility. It is the result of a spectrum of diseases which cause fixation or immobility of the vocal cords.
The vocal cords play a major role in speech production or phonation. The muscles which move the vocal cords for phonation are supplied by the recurrent laryngeal nerves which are branches of the vagus nerve. Therefore, intracranial and extracranial vagus nerve injuries, and recurrent laryngeal nerve injuries cause paralysis and dysfunction of the vocal cords.
The most common cause of vocal cord paralysis and immobility are iatrogenic injuries from surgical procedures such as cervical spine surgery, mediastinal and thyroid gland surgeries. Other causes include endotracheal incubation, malignancies, neurological conditions, and in some cases the cause is undetermined.
The main clinical presentations of vocal cord paralysis include stridor, breathing difficulties, and significant voice changes if only one of the vocal cords is affected. A breathy quality in the voice, loss of pitch, and difficulty in phonating are the significant voice changes in vocal cord paralysis. Vocal cord immobility and paralysis are life-threatening conditions because of the complicating airway compromise, therefore prompt diagnosis and treatment of vocal cord immobility is crucial.
Diagnosis of vocal cord paralysis involves workup via fibronasopharyngolaryngoscopy. Pulmonary function tests and acoustic analysis are adjunctive diagnostic modalities in the management of vocal cord immobility.
Unilateral vocal cord immobility is more common than bilateral vocal cord immobility. Treatment of unilateral vocal cord immobility involves restoration of voice quality via several techniques including augmentation, medialization, and reinnervation.
Bilateral vocal cord immobility is treated with several invasive and endoscopic surgical procedures . The aim of treatment of bilateral vocal cord paralysis is to reestablish airway patency, maintain voice quality, and preserve glottic sphincteric control . Surgical treatment options for bilateral vocal cord paralysis include tracheotomy, subtotal arythenoidectomy, vocal fold lateralization, transverse cordectomy, and reinnervation techniques  .
The vocal cords, also called vocal folds, are a pair of mucous membranes extending between the walls of the larynx or the voice box where they vibrate and modify the passage of air through the voice box when one speaks. They are, therefore, essential in speech production.
Vocal cord paralysis is a condition characterized by damage to the nerves which supply the muscles which control the vocal cords. However, vocal cord immobility is a spectrum of all diseases which cause immobility of the vocal cords and vocal cord paralysis is a subset of this group of disorders.
The commonest cause of vocal cord paralysis is injury to the nerves during certain surgical procedures. Examples of these surgeries include thyroid removal, surgery involving the spine at the neck region and surgeries of the heart and central part of the chest. Among other causes of vocal cord paralysis are infection of the nerves, damage to the nerves by cancerous and noncancerous tumors, and substances that are toxic to the nerves such as lead, arsenic, and mercury. However, in some people, the cause cannot be determined.
It may vary depending upon paralysis of one or both vocal cords. When both the vocal cords are damaged, it may cause a life-threatening difficulty in breathing. Vocal cord paralysis causes an inability of the cords to move, therefore, interfering with swallowing, speaking, and breathing.
In cases where only one of the vocal cords is paralysed, the voice may become breathy and hoarse, but there may be no breathing difficulties. If both vocal cords are affected, there may be significant breathing problems with little voice changes.
Doctors can make a diagnosis of vocal cord paralysis by asking several questions including history of exposure to toxic chemicals like lead, mercury, and arsenic, use of drugs such as phenytoin and vincristine, alcoholism, cigarette smoking, and history of chronic connective tissue disorders.This detailed history is coupled with physical examination of the vocal cord and voice box with a device called a laryngoscope.
Treatment of vocal cord paralysis depends on the number of vocal cords damaged. In cases where just one of the cords is affected, treatment is centered on improving voice quality. The procedures which may be employed to achieve an improved voice quality include injecting certain substances which move both cords closer together, and manually moving the cords closer together by way of a surgical technique.
Treatment of both the vocal cords is possible by using several surgical procedures, example of which are arytenoidectomy whereby both vocal cords are permanently pulled apart to allow better airflow, and tracheotomy in which an opening is made in the trachea from the front side of the neck. Laser therapy is, however, preferred to both surgical techniques. Laser helps to widen the airway with less complications while restoring voice quality.
Vocal cord paralysis can be prevented by avoiding the risk factors for the condition. The preventive measures include smoke cessation and wearing a seat belt while driving. Doctors can also prevent this condition in patients by preventing damage to the vocal cord nerves during neck and chest surgeries.