Paralysis of one or both vocal folds may happen under a number of circumstances. Since the causes, symptoms and treatment of unilateral vocal fold paralysis are so different from those of bilateral vocal fold paralysis, these will be considered separately.
The vocal fold on the right side of this picture is paralyzed, so that the vocal folds do not close completely during phonation.
Normally, open vocal folds form a symmetric "V" shape. The vocal fold on the right side of this picture is paralyzed, so that it cannot move outward or inward.
Unilateral Vocal Fold Paralysis
Unilateral vocal fold paralysis is immobility of one vocal fold because of nerve dysfunction. Although there are other reasons for a vocal fold to be immobile, they are uncommon. The recurrent laryngeal nerve is the main nerve that accounts for most of the movement of each vocal fold. It is called "recurrent," because it travels from the brain into the chest and then back up to the larynx, thus "recurring" in the neck. This nerve can be damaged by various diseases, by certain surgeries, and probably by viral infections. It is important to understand that in the case of surgeries, immobility of the vocal fold does not mean that the nerve was cut. Sometimes even a little bit of handling of the nerve can stop it functioning for a time. The first question to be answered upon diagnosis of vocal fold paralysis is why the nerve is not functioning.
Some operations that can result in vocal fold paralysis:
- Carotid endarterectomy
- Lung operations, particularly on the left side
- Heart operations, especially aortic valve replacement or repair
- Repair of thoracic aortic aneurysm
- Anterior cervical diskectomy
- Mediastinoscopy/mediastinal lymph node biopsy
- Closure of patent ductus arteriosus
- Brain surgery, especially at the base of the brain or brainstem
Some medical conditions that can result in vocal fold paralysis:
- Thyroid cancer
- Tuberculosis, Sarcoid or anything that causes lymph nodes to enlarge in the chest
- Various neurologic diseases, such as Charcot-Marie-Tooth, Shy-Drager, and Multisystem atrophy
Normally the vocal folds are able to open and close symmetrically. With these two motions, they accomplish three tasks: open to allow breathing, close to prevent food from entering the trachea (windpipe) when one swallows, and close to produce voice with air from the lungs.
When one vocal fold is paralyzed, the larynx is unable to completely close. Thus breathing is usually normal, since it depends on the vocal folds being able to open. However, people may find that they occasionally cough or choke when swallowing, particularly when swallowing liquids. The most noticeable symptom is the dramatic voice change: the voice become hoarse, breathy and weak. Speaking at loud volume or over background noise becomes very challenging and effortful.
Some cases of vocal fold paralysis resolve on their own, although it may take weeks to months. In other cases, it is almost always possible to achieve a normal or near normal voice using voice therapy alone or in combination with various types of surgery. No treatment should be undertaken until a thorough search for the cause of the problem is done. Sometimes, this will turn up nothing obvious. In such a case, the cause is deemed "idiopathic," which simply means of unknown cause. Up to one-third of cases of vocal fold paralysis may turn out to be idiopathic. Conditions that must be eliminated as possible causes include lung cancer, particularly if the paralysis is on the left, and thyroid cancer.
Treatment must be individualized for every patient. Treatment depends upon the cause and duration of the paralysis, and the extent of disability it causes. In some cases, an additional diagnostic test called electromyography is recommended. This test may provide information about the likelihood that the nerve will recover on its own. Therefore, it can sometimes play an important role in treatment decision. The goal of treatment is to improve vocal fold closure, because all of the symptoms caused by vocal fold paralysis are due to incomplete vocal fold closure. Difficulty breathing is the most concerning complication of surgical treatment. Usually, this complication can be safely avoided, but this should be carefully discussed with your surgeon. A very brief summary of treatments is presented below.
Voice therapy consists of exercises and techniques to help in vocal fold closure. Under certain conditions, other muscles can be used to increase closure. The voice therapist will teach you to take advantage of these. Unlike the surgical treatments, there is no risk to the airway with voice therapy. In cases where the gap between the paralyzed vocal fold and the working one is small, and sometimes in cases where the paralyzed vocal fold recovers only partially, voice therapy alone may be enough to achieve normal voice. Read more about specific goals and techniques of voice therapy for unilateral vocal fold paralysis.
Injection laryngoplasty is an operation that consists of injection of a material to add bulk to the paralyzed vocal fold so that it can make contact with the working one. The injection is done through the mouth, so that there are no scars, and usually requires general anesthesia. Traditionally, the material injected was Teflon, but experience has shown that it may cause benign growths called granulomas in a substantial number of cases, which can further damage voice and even narrow the airway, making breathing difficult. As a result, Teflon is generally avoided nowadays. Alternatives include collagen, fat from elsewhere in the body, processed connective tissue and other, newer substances. None of these are permanent, and they gradually re-absorb. This is not to say that the voice result cannot be permanent, as there are other variables involved. Speak to your physician about the details of the operation and the specific features of the various materials.
Medialization laryngoplasty describes an operation to implant a small piece of synthetic material, which is permanent (although removable) into the larynx. This serves to bring the vocal fold closer to the midline (medialize the vocal fold). It is generally performed under a local anesthetic in the operating room, though a small incision on the neck over the larynx. It may be combined with a procedure known as arytenoid adduction, which rotates the arytenoid to accomplish the same thing.
Reinnervation is surgery aimed at providing an alternate nerve supply to the vocal fold. It is not expected that this will cause the vocal fold to move again, but rather, that it will restore tone and bulk to a flaccid (limp) vocal fold. Observations have suggested that this may be enough to achieve a good voice result. Reinnervation is currently an investigational therapy, and is not used routinely in most centers.
Because there are many options in the treatment of vocal fold paralysis, it is important to have a detailed discussion of your condition with your physician. In most cases, substantial improvement in laryngeal function can be achieved with treatment. There is no reason to endure the symptoms of unilateral vocal fold paralysis.
Bilateral Vocal Fold Paralysis
When both vocal folds are paralyzed, they are usually immobilized close to the midline. Thus, closure is usually adequate, permitting acceptable voice and swallowing. However, breathing is usually very difficult. This difficulty increases with effort, and people with this condition may find that they are severely restricted in how far they can walk, or in how heavy a load they can carry. Often there is a wheezy noise when breathing, which can cause this condition to be mistaken for asthma. Asthma that fails to improve with appropriate medicines and inhalers requires that a physician examine the larynx and vocal folds.
Bilateral vocal fold paralysis almost always has an identifiable cause - it is rarely "idiopathic" or unknown. Causes include stroke or other neurologic condition (especially a childhood condition known as Arnold-Chiari malformation), thyroid cancer, or surgery such as major brain surgery or thyroidectomy.
The main issue in the treatment of bilateral vocal fold paralysis is whether or not the vocal folds are far enough apart to allow safe breathing. In many cases, the safest initial treatment is a tracheostomy - a breathing hole directly into the windpipe - to guarantee the airway until other plans are made.
There are procedures to allow adequate airway and permit removal of the tracheostomy. However, all of these may cause some deterioration of voice quality, and sometimes, may create problems swallowing. This is because these procedures (such as arytenoidectomy and cordotomy) necessarily increase laryngeal opening.
Treatment of bilateral vocal fold paralysis often requires making some difficult choices. As is true in all voice disorders, nothing can take the place of a detailed discussion with your treatment team.