Vocal Fold Motion Impairment
The vocal folds, because of their position in the airway, play a vital role in speech, swallowing and breathing. In order to perform these functions normally, the laryngeal muscles must be able to abduct (open) and adduct (close) the folds. Impairment of these functions may occur on one side (more common) or both sides. These two types of impairment in vocal fold motion differ in their seriousness, symptoms and treatment.
Symptoms: Patients with unilateral paralysis may exhibit a weak and "breathy" voice, and speaking may require considerable effort. Because the vocal folds are unable to close completely during swallowing, patients may also experience coughing and choking while eating or drinking. Patients with bilateral paralysis may experience these symptoms, but the possibility of a blocked airway is a more serious threat. The muscles that normally open the folds and provide for an unrestricted airway are unable to function. Thus, the folds may remain closed in the airway and block normal breathing.
Causes: The most common cause of vocal cord motion impairment is injury to the recurrent laryngeal nerve, the nerve responsible for controlling the muscles of the larynx. This may be the result of trauma, compression during anesthesia, surgery, or other less frequent causes. Occasionally, injury or diseases of the brain, including stroke, may also affect this nerve's function and result in impaired motion.
Mechanical obstruction can also result in vocal fold motion impairment. The arytenoid cartilages, to which the vocal folds attach, can become "locked" and restrict movement. Scar tissue may also accumulate and inhibit vocal fold movement.
Treatment: Treatment options for unilateral motion impairment include:
- Medialization thyroplasty
- Injection laryngoplasty
- Laryngeal reinnervation
In medialization thyroplasty, a surgeon makes a small incision in the skin near the larynx and removes a small piece of thyroid cartilage. A small block, usually made of silicone, is carved, inserted and secured in the cartilage. This block acts as a shim, which pushes the paralyzed vocal fold toward the midline, helping to enhance closure with the other vocal fold. This procedure is relatively quick and painless and is usually performed under local anesthesia.
The images below depict the medialization thyroplasty procedure. The image on the left shows the placement of the shim in the thyroid cartilage. The image on the right demonstrates how this shim, when correctly placed, can help push a motion-impaired vocal fold toward the midline.
The second treatment for unilateral vocal fold motion impairment involves the injection of small amounts of materials directly into the vocal fold. Again, the goal is to push the paralyzed fold medially so the normal cord can close the glottis. This technique, although effective, is limited by the difficulty of controlling the placement and volume of the injected material.
Less commonly, a third option is to "reconnect" nerve tissue to the affected area.
Several options exist for the treatment of bilateral vocal fold motion impairment. All of these treatments seek to improve the restriction of breathing that this condition may produce. All procedures try to balance the need for a larger airway with the quality of the voice: The larger the airway, the weaker the voice.
A tracheostomy is a standard and commonly performed procedure in which the larynx is bypassed by opening the trachea and bringing it out to the surface of the neck. A transverse cordotomy is another option and involves removing a small portion of the vocal fold from one or both sides. If breathing is seriously compromised, a cordectomy, or surgical removal of the vocal folds, may be undertaken. Newer procedures for dealing with bilateral vocal fold motion impairment have recently emerged. One of these, a posterior cricoid split, involves splitting the cricoid cartilage and inserting a cartilage graft between the arytenoid cartilages. This allows for a larger opening of the vocal cords posteriorly and can help to relieve the symptom of vocal fold motion impairment. An even newer technique still in the experimental stages, laryngeal pacing, involves implanting a small device that causes coordinated movement of the vocal folds during breathing.