What are Vocal Folds? The larynx, housing the vocal folds, sits atop of the trachea,
and is the gateway to the respiratory tract. It serves important biological functions which include allowing air into and out of the lungs during sustained breathing, and protecting the airway from food or liquid entering during the swallow. Central to these functions is the ability of the vocal folds to abduct or adduct. The vocal folds, also known as the true folds, are important for normal phonation. Phonation is the product of vibrating vocal folds, and this occurs within the larynx. Everyone has two vocal folds in their larynx: a right and left vocal fold. This pair of elastic, fibered bands is covered with a mucous membrane and passes horizontally backward from the thyroid cartilage (also known as the Adam’s apple) to insert on the paired arytenoid cartilage. In order to produce sound, adductor muscles are activated, providing resistance to exhaled air from the lungs. When fully approximated there is an increase in subglottal air pressure (below the VF) relative to supraglottal air pressure, the increased subglottal air pressure bursts through the closed vocal folds. The vocal folds vibrate, modulating the flow of air being expelled from the lungs. It is respiration that is the source of energy for speech, while phonation is the source of voice. |
What is Paralysis?Paralysis refers to loss of voluntary motor function, different
from paresis which refers to weakness. Paralysis can arise from damage to the upper motor neurons, which are neurons that arise from the brain and end in the spinal column or brainstem, or damage to the lower motor neurons, which are neurons that leave the spinal column or brainstem to innervate the muscles involved. Vocal fold paralysis may take several forms, depending on the nerve damage. If only one side of the recurrent laryngeal nerve (lower motor neuron) is damaged, the result will be unilateral vocal fold paralysis. Bilateral vocal fold paralysis would result from bilateral lower motor neuron damage. According to Dr. Boone bilateral vocal fold paralysis may be of the abductory or adductory type. If the result of damage is adductor paralysis, the muscles of adduction are paralyzed and the vocal folds remain in the abducted position. If the damage results in abductor paralysis, the individual will not be able to abduct the vocal folds, and respiration will be compromised. |
What are the signs and symptoms of vocal fold paralysis?
According to ASHA, the vocal folds need to vibrate during speech in order to produce voice, if one or both vocal folds are unable to move then the person will experience voice problems, and possibly breathing and swallowing problems. The severity of voice and swallowing problems depends on where the nerve damage occurs. Typical symptoms include:
hoarseness
breathy voice
inability to speak loud
limited pitch and loudness variations
voicing that lasts only for a short time (around 1 second)
choking or coughing while eating
possible pneumonia due to food and liquid being aspirated into the lungs (the vocal folds cannot close adequately to protect the airway while swallowing)
additional symptoms include noisy breathing, shortness of breath, ineffective coughing, and loss of gag reflex
hoarseness
breathy voice
inability to speak loud
limited pitch and loudness variations
voicing that lasts only for a short time (around 1 second)
choking or coughing while eating
possible pneumonia due to food and liquid being aspirated into the lungs (the vocal folds cannot close adequately to protect the airway while swallowing)
additional symptoms include noisy breathing, shortness of breath, ineffective coughing, and loss of gag reflex
Unilateral Vocal Fold Paralysis vs. Bilateral Vocal Fold Paralysis
Disease or damage to the recurrent laryngeal nerve will cause inability to open the folds on one affected side and is referred to as unilateral vocal fold paralysis, which is most common than bilateral vocal paralysis. Because of the extended course of the left RLN, traveling down the neck and looping around the aortic arch in the chest and then traveling up again to the larynx (which is why it is called "recurrent"), the left RLN is more susceptible to traumatic or surgical injury than the right RLN (The right RLN has a different course from the left). When the RLN is compromised to one side, the laryngeal adductor muscles (particularly the lateral cricoarytenoid) are not able to perform their adductory role. This keeps the paralyzed fold fixed in the paramedian position, that is neither fully abducted nor adducted. The paralyzed vocal fold does not move to vibrate with the other fold but vibrates abnormally or does not vibrate at all.
Bilateral vocal fold paralysis is usually the result of lesions high in the trunk of the vagus nerve or at the nuclei of origin in the medulla. As mentioned earlier, bilateral paralysis of the vocal folds may be of the abductory or adductory type, and both are recognized as life threatening. Voice per se is of secondary concern to respiratory survival and feeding. In bilateral adductor paralysis, neither vocal fold is capable of moving to the midline, thus making phonation impossible and placing the individual at risk for aspiration. In abductor paralysis, the vocal folds remain at the midline, causing serious respiratory problems for which most patients will need a tracheostomy.
Bilateral vocal fold paralysis is usually the result of lesions high in the trunk of the vagus nerve or at the nuclei of origin in the medulla. As mentioned earlier, bilateral paralysis of the vocal folds may be of the abductory or adductory type, and both are recognized as life threatening. Voice per se is of secondary concern to respiratory survival and feeding. In bilateral adductor paralysis, neither vocal fold is capable of moving to the midline, thus making phonation impossible and placing the individual at risk for aspiration. In abductor paralysis, the vocal folds remain at the midline, causing serious respiratory problems for which most patients will need a tracheostomy.
What Causes Vocal Fold Paralysis?
Many potential causes of vocal fold paralysis include: strokes, tumors (cancerous and noncancerous), surgery, intubation, traumatic injury, viral infection(i.e. Lyme Disease), neurodegenerative and neuromuscular diseases (i.e. Multiple Sclerosis, Parkinson's Disease) and some are reported as idiopathic (unknown causes). In a research article titled "Extralaryngeal Causes of Vocal Fold Paralysis: CT Evaluation" reveals that a variety of extralaryngeal diseases can affect the recurrent laryngeal branch of the vagus nerve and result in vocal fold paralysis. Computed tomography (CT) was found to be a valuable tool in demonstrating these laryngeal abnormalities. The study included 33 patients (22 men and 11 women), all complained about hoarseness lasting from 1 week to 1 year. The region that was scanned depended on the patient's clinical history (left or right vocal fold paralysis). Results revealed that the most common cause of extralaryngeal vocal fold paralysis was malignant neoplasms(http://www.rightdiagnosis.com/medical/malignant_neoplasm.htm). From this, the most common malignancy was caused by bronchogenic carcinoma, with the left recurrent laryngeal nerve found to be most frequently involved. The author states that infections and neurological diseases count for less than 10% of cases of unilateral vocal fold paralysis and about 10-30% of vocal fold paralysis reported as idiopathic. It was found that many patients with no apparent etiology to have spontaneous resolution of the paralysis; presumably some of these causes are caused by viral infections.
Risk Factors Of Vocal Fold Paralysis
Factors that may increase the risk of developing vocal fold paralysis include:
1) Being female: Women are slightly more likely to develop vocal fold paralysis
2) Undergoing throat or chest surgery: People who need surgery on their thyroid, throat or upper chest area have an increased risk of vocal fold nerve damage. Sometimes breathing tubes used in surgery or to help them breathe if they're having serious respiratory trouble can damage the vocal fold nerves.
3) Having a neurological condition: People with certain neurological conditions - such as Parkinson's disease, Multiple Sclerosis or Myasthenia Gravis - are more likely to develop vocal fold weakness or paralysis.
1) Being female: Women are slightly more likely to develop vocal fold paralysis
2) Undergoing throat or chest surgery: People who need surgery on their thyroid, throat or upper chest area have an increased risk of vocal fold nerve damage. Sometimes breathing tubes used in surgery or to help them breathe if they're having serious respiratory trouble can damage the vocal fold nerves.
3) Having a neurological condition: People with certain neurological conditions - such as Parkinson's disease, Multiple Sclerosis or Myasthenia Gravis - are more likely to develop vocal fold weakness or paralysis.
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Watch as Dr. James Thompson, a laryngologist, briefly summarizes what vocal fold paralysis is. The video also presents an individual with unilateral paralysis of the right vocal fold.
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