Vocal cords or vocal folds paralysis is a type of voice disorder associated with neuromuscular diseases that affect your phonation muscles (muscles that help produce sound). It can be unilateral or bilateral. Unilateral vocal paralysis is the most common. Bilateral vocal cord paralysis is rare but can be life-threatening.
Vocal folds are supplied by two branches of the vagus nerve: recurrent laryngeal nerve (RLN) and superior laryngeal nerve (SLN). Damage to this nerve causes vocal fold paresis and vocal fold paralysis.

Anatomy of Vocal Cords

The larynx is an important dynamic structure involved in respiration, deglutition (swallowing), and phonation (sound production). It is located above the trachea (windpipe) and the superior part of the esophagus (food pipe).

Image shows the Anatomy of vocal cords

Vocal cords are bilateral structures within the larynx. During normal breathing, the vocal cords open sideways to facilitate unimpeded airflow. Conversely, during swallowing, they close to prevent food particles from entering the trachea, safeguarding the airway from foreign bodies.

They also play a pivotal role in sound production. Air from the lungs passes through the larynx, where it is transformed into sound with the assistance of laryngeal muscles. Additionally, this sound is modified by the resonators (from downward above the throat, mouth, and nasal passage).

Incidence

The vocal cord paralysis affects your speaking, breathing, and swallowing activity. Left-sided paralysis is more common than right-sided. Most commonly, women are more affected than males, with a ratio of 3:2¹

Pathophysiology:

Injury to the nerves supplying your vocal cords is the most common cause of it, followed by trauma, surgery, or tumor.² Most of the time, the paralysis is surgery-induced due to pressure, heating, or crushing during the operation.
Additionally, there are two types of injuries. These include the following:

Neuropraxia (Schwann Cells Injury):

It is a milder form of injury in which only Schwann cells are injured, and it spares axonal cells. It lasts for 6-8 weeks. However, the recurrent laryngeal nerve (RLN) is most commonly involved in this injury.

Axonotmesis (Axonal Injury):

It is a severe form of injury in which neuron death occurs, resulting in complete loss of mobility of the vocal folds.

What is Unilateral and Bilateral Vocal Cord Paralysis?

Unilateral vocal cord paralysis is the most common form of paralysis.³ About one-third of unilateral vocal cord paralysis is neoplastic in origin (associated with tumors). Another one-third is followed by trauma. Similarly, the last one-third is idiopathic.
However, bilateral vocal cord paralysis is more severe and life-threatening, followed by surgery trauma and neurodegenerative diseases. These surgeries include thoracic and cervical surgeries and tracheal intubation.⁴

Causes of Vocal Cord Paralysis

There can be multiple causes of this. These are surgeries, neoplasms, viral infections, neurodegenerative diseases, and other causes.

Illustration of vocal cord paralysis

Surgery Associated:

Surgery is the most common cause of this paralysis. Recurrent and superior laryngeal nerves are affected during surgery. Therefore, different thorax, trachea, spine, and thyroid surgeries affect your vocal cords. These are:

Thyroidectomy
Tracheostomy
Thoracic surgery
Skull base surgeries
Cervical spine surgeries

Neoplasm Associated:

Some tumors (mostly malignant) affect your vocal cords. These include the following:

Thyroid carcinoma
Small cell lung carcinoma
Esophageal carcinoma
Mediastinal carcinoma

Viral infections :

Viral infections also affect your vocal cords. These infections include:

Herpes simplex infection
Varicella zoster virus
H-influenza virus
Epstein-Barr virus
Cytomegalovirus

Neurodegenerative Diseases:

Some neurodegenerative disease affects the nerve supplying your vocal cords, leading to vocal cord paralysis. The following neurodegenerative diseases are the most common causes:

Multiple sclerosis
Parkinson’s disease
Cerebrovascular attack (CVA)
Myasthenia gravis
Tumors

Other Causes :

Other causes are:

Sarcoidosis
Aortic aneurysm
Tuberculosis
Systemic lupus erythematosus (SLE)
Pneumoconiosis

Symptoms of Vocal Cord Paralysis

The larynx muscle allows movement of your vocal cords (abduction and adduction). In this paralysis, cord movement is lost, affecting respiration, phonation (production of voice), and the swallowing process. Moreover, in recurrent laryngeal nerve paralysis, vocal folds move when you speak (phonation) but not during inspiration. Hence, in unilateral vocal cord paralysis, there is only hoarseness of voice, which does not affect your respiration.⁵
However, bilateral paralysis affects the process of respiration, phonation, and swallowing.
Symptoms are :

Change in intensity and pitch of sound
Breathing difficulty (dyspnea)
Swallowing difficulty
Stridor
Aspiration of food or foreign particles (choking)
Noisy breathing
Loss of gag reflex
Coughing

When to see your Doctor?

Immediately book an appointment with a medical specialist when you have persistent hoarseness of voice for more than 3-4 weeks. Additionally, if you feel a change in your voice or have swallowing difficulty, it is critical to consult a doctor.⁶

Diagnosis of Vocal Cord Paralysis

Patients suspected of this condition are diagnosed with a detailed history and physical examination followed by laboratory and radiological investigations.⁷

History:

The initial stage in diagnosing any illness involves gathering a patient’s medical history, which helps identify the patient, the disease’s origins, and related factors. In this initial phase, your doctor will inquire about various aspects, including:

Your biodata, such as your name, place of residence, and age.
Have you experienced any hoarseness of voice?
Have you noticed any changes in the quality of your voice?
Do you encounter difficulty breathing?
Are there any existing medical conditions?
Do you struggle with swallowing?
Is there any pertinent family medical history?
Can you provide details about your past medical history
Lastly, any significant aspects of your social history should be shared.

Physical Examination:

A complete physical examination from head to neck is required to see:

Any scar marks (previous surgery)
Any tenderness
Any swelling
Cranial nerve examination
Direct visualization
Thyroid examination
Mobility of vocal cords should be assessed during phonation.

Laboratory Investigation:

Laboratory tests are necessary to exclude other medical conditions. Some common tests include:

Complete blood count (CBC) with erythrocyte sedimentation rate (ESR)
Liver function tests (LFTs)
Renal parameters (RFTs)
Serum electrolytes
Thyroid profile (serum TSH, T3, and T4)
Serum ACE

Endoscopy (Stroboscopy):

Endoscopy or stroboscopy is an investigation of choice that is performed with the help of a camera endoscope (rigid or flexible). This endoscope uses pulse light to better evaluate inside structures and captures high-quality images. In addition, stroboscopy provides useful information regarding the pattern of glottic closure, symmetry of vocal cords, and mucosal wave.

Radiological Investigations:

If there is a suspicion of complete paralysis, diagnostic imaging is required.⁸ The following radiological investigations help with the diagnosis of this condition:

A chest X-ray rules out any pulmonary diseases.
CT scan from the skull base through the chest to trace the path of the vagus nerve and its branches. It is the most favored investigation.
MRI brain rules out other intracranial pathologies such as multiple sclerosis (MS)
Ultrasound of the neck and larynx can assess vocal cords’ movement and diagnose surrounding pathologies.

Laryngeal Electromyography (LEMG)

Laryngeal electromyography is the gold standard investigation to diagnose this paralysis. In this procedure, your doctor uses a needle electrode to check the activity of muscle fibers. Besides this, it estimates the injury’s severity and the disease’s prognosis.

Treatment of Vocal Cord Paralysis

Treatment⁹ of vocal cord paralysis depends on the type of paralysis, the cause of paralysis, and the severity of the disease. Speech therapy is the best way to treat this condition. Surgical interventions are preferred in severe cases.

Speech Therapy:

Speech therapy is the best way to treat your vocal paralysis on its own. It includes voice therapy sessions, exercises, or other activities that help to strengthen your vocal cords and reduce tension. However, this therapy aims to improve your breathing activity, speech activity, and swallowing problems.

Surgical Interventions:

Surgical interventions are suitable when severe symptoms are not settled down independently. There are different surgical options depending on the type of paralysis.

Treatment of Unilateral Vocal Cord Paralysis

In this paralysis, surgery aims to bring the cords close together to each other to improve your speaking and swallowing activity. However, the surgical procedures include the following:

Bulk Injection Therapy or Augmentation Therapy:

The laryngologist brings your cords closer with the help of bulk injection therapy. It is the first line of treatment in people with temporary unilateral vocal cord paralysis. In this therapy, a bulk that can be a fat, collagen deposit, or any filler that approximates the size of two vocal cords is added to your paralyzed vocal cord.

Vocal Cords Repositioning:

It is a surgical procedure in which your surgeon moves the window of your tissue from outside to your voice box. Moreover, this procedure allows the unparalysed vocal cord to work better against the paralyzed one.

Reinnervation:

It is most usually suitable for non-recoverable paralysis of vocal cords. However, this procedure restores the tone and positioning of the affected vocal cord but does not restore the motion.

Treatment of Bilateral Vocal Cord Paralysis

In bilateral vocal cord paralysis, surgery aims to maintain the airway. Partial endoscopic cordectomy is a preferable surgery for this condition.

Partial Endoscopic Cordectomy:

It is a minimally invasive surgical procedure to treat patients who require tracheostomy. Tracheostomy is a surgical procedure in which the surgeon gives an incision in the trachea to provide an alternative breathing pathway. In addition, during partial endoscopic cordectomy, a small portion of the vocal cords is cut away to create a hole and reduce tension, but it increases the risk of aspiration. ¹⁰

Difference between Vocal Cord Paresis and Vocal Cord Paralysis

Vocal cord paralysis occurs when both recurrent and superior laryngeal nerves sustain an injury, resulting in a complete loss of mobility in the vocal folds, usually due to neurological issues. On the other hand, vocal cord paresis is characterized by decreased mobility of the vocal cord, typically caused by neurological injuries or weakness in the recurrent or superior laryngeal nerve.

Conclusion

To conclude, it is usually associated with a neuromuscular disorder. It can be unilateral or bilateral, although bilateral paralysis is rare. Vocal cord paralysis disrupts the mechanism of respiration, production of voice, and swallowing. If you or your loved ones have vocal cord paralysis, consult a healthcare practitioner for timely diagnosis and treatment. Your doctor will take a detailed history, perform a physical examination, and prescribe some investigations to confirm the diagnosis. However, the treatment plan depends on the severity of paralysis and whether it is unital or bilateral.

Refrences

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Williamson, A. J. (2023, August 8). Unilateral vocal cord paralysis. StatPearls – NCBI Bookshelf. https://www.ncbi.nlm.nih.gov/books/NBK535420/
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Born, H. L. (2023, August 29). Vocal cord paralysis. MSD Manual Professional Edition. https://www.msdmanuals.com/professional/ear,-nose,-and-throat-disorders/laryngeal-disorders/vocal-cord-paralysis
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Dankbaar, J.W., & Pameijer, F.A. (2014). Vocal cord paralysis: anatomy, imaging, and pathology. Insights Imaging, 5, 743–751. https://doi.org/10.1007/s13244-014-0364-y
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Faanp, J. S. L. M. A. (2020, July 20). What Can I Offer the Patient with this condition? Medscape. https://www.medscape.com/viewarticle/559976_2
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Vocal Cord Paralysis Treatment NYC. (n.d.). Mount Sinai Health System. https://www.mountsinai.org/locations/grabscheid-voice-swallowing-center/conditions/vocal-cord-paralysis#:~:text=Vocal%20cord%20paralysis%20occurs%20when,more%20than%20just%20produce%20sound.

Vocal Cord Paralysis: Causes, Symptoms & Treatment Options

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