Unilateral vocal fold paralysis (UVFP) occurs from a dysfunction of the recurrent laryngeal or vagus nerve innervating the larynx. It causes a characteristic breathy voice often accompanied by swallowing disabilty, a weak cough, and the sensation of shortness of breath. This is a common cause of neurogenic hoarseness. When this paralysis is properly evaluated and treated, normal speaking voice is typically restored.
Examples of vocal fold paralysis can be seen in the image and video below.
History of the Procedure
Unilateral vocal fold paralysis (UVFP) most commonly occurs following a surgical iatrogenic injury to the vagus or recurrent laryngeal nerve. Thus, a history of head and neck, skull base, brainstem or chest surgery should be obtained. Specifically, thyroidectomy, carotid endarterectomy, anterior cervical spine surgery, thoracic, or mediastinal surgery most often result in a presentation of UVFP. In a study of 100 children, the incidence of vocal fold immobility after cardiothoracic surgery was 8%. These 8 patients were younger and weighed less than patients with normal vocal fold movement. 
The differential diagnosis for an acute UVFP should always include recent upper respiratory tract or viral infection and recent intubation for any surgical procedure. Procedures aimed at restoring glottic competence include permanent and temporary vocal fold injections, as well as laryngeal framework surgery, including medialization laryngoplasty (type 1 thyroplasty) and arytenoid adduction or arytenopexy.
Normal vocal fold function is reliant on vocal fold glottal closure that results from bilateral adduction of the vocal folds. Normally, this vocal fold adduction behavior, in combination with subglottic airflow, induces vocal fold vibration. Unilateral vocal fold paralysis (UVFP) results in glottal incompetence, either partial or complete, resulting in a weak or absent vocal fold vibration that leads to dysphonia. Significant muscle tension is often seen in the larynx as a compensatory mechanism for the glottal gap. Patients with UVFP often describe pain in the throat or neck after voice use, which is likely due to the excessive muscle tension.
See the list below:
Surgical iatrogenic injuries resulting in vocal fold paralysis include thyroid surgery, anterior cervical disc surgery, carotid surgery, or chest surgery.
Blunt trauma to the neck or chest.
When a clear-cut etiology for the unilateral vocal fold paralysis (UVFP) is not found, it is classified as idiopathic. These cases can be attributed to a viral or inflammatory process, but this is usually a presumptive diagnosis.
The recurrent laryngeal nerve is responsible for both abduction and adduction of the vocal fold. The recurrent laryngeal nerve originates from the vagus nerve, which originates from the brainstem (nucleus ambiguous in the medulla) and travels along the carotid sheath (with the jugular vein and internal carotid artery). The left vagus nerve gives rise to the left recurrent laryngeal nerve as the vagus crosses the arch of the aorta. The left recurrent laryngeal nerve then loops under the ligamentum arteriosum and travels cephalad in the tracheoesophageal groove until it penetrates the larynx to innervate the intrinsic muscles of the larynx. The right vagus nerve delivers the recurrent laryngeal nerve branch at the level of the subclavian artery. The right recurrent laryngeal nerve loops around the subclavian artery and proceeds cephalad to the larynx.
The recurrent laryngeal nerve, just prior to its entrance into the larynx, runs deep to the inferior cornu of the thyroid cartilage. For a short section, the nerve is in a space between the cricoid and thyroid cartilage. This is thought to be the space where the nerve is vulnerable to compression from the cuff on an endotracheal tube that is either overinflated or positioned too far cephalad. Because of the circuitous nature of the recurrent laryngeal nerve, multiple disease processes and operative procedures put these important nerves at risk, often resulting in vocal fold paralysis.
Patients with unilateral vocal fold paralysis (UVFP) typically present with a fairly sudden onset of breathy, weak, low-pitched dysphonia. In some cases, however, the dysphonia can be high-pitched because of a compensated lengthening of the vocal folds to achieve better glottic closure. Often, UVFP is associated with dysphagia, specifically with liquids, because the resultant glottal incompetence can lead to aspiration. This is especially true if the UVFP is due to a high vagal lesion that results in both a recurrent laryngeal nerve and superior laryngeal nerve palsy. The latter results in significant anesthesia of the pharynx, contributing to the patient's dysphagia and increased risk for aspiration.
Patients with UVFP often report shortness of breath or a feeling of running out of air. Very little negative physiological impact upon pulmonary function actually occurs in patients with UVFP; however, because of the glottal incompetence, they experience significant air wasting and, thus, experience the sensation of shortness of breath and running out of air during speech. In addition, glottal closure is required for individuals to create positive end expiratory pressure (PEEP). Thus, some patients with an immediate postoperative UVFP can experience decreased pulmonary function because of loss of the natural PEEP that occurs with glottal closure. The glottic closure that allows a forceful cough is also compromised and thus a weak, unsuccessful cough is often reported by patients.
The indications for treatment of unilateral vocal fold paralysis (UVFP) are usually the resultant dysphonia or an ineffective cough in a patient at risk for aspiration or pulmonary compromise. If patients experience dysphagia, then they are at risk for aspiration pneumonia and treatment should be implemented as soon as possible. Improving glottic closure in the setting of UVFP and dysphagia often strengthens the voice and cough; however, it does not always correct the swallowing issue. Other sensory branches affecting the laryngopharynx may also be affected by the injury that caused the UVFP in the first place. Thus, patients should not be guaranteed improvement in their swallowing after augmentation of their vocal fold.
For dysphonia related to UVFP, treatment should be determined based on the patient's functional needs and demands, as well as on a new body of evidence that suggests early augmentation of an immobile vocal fold leads to better long-term voice outcomes (with or without return of physiologic function). 
Some patients do not notice any significant functional limitation related to their UVFP. This minimal functional limitation results because of the person's minimal voice demands or comorbidities that occur during postoperative recovery. A temporary injection is often given to allow for an immediate return of glottic competence while the nerve potentially recovers.
Electromyelography (EMG) can be used to determine the prognosis of RLN recovery, even if a temporary injection has occurred. If motion does not return and serial laryngeal electromyography shows no chance for meaningful recovery of vocal fold motion, then a permanent injection of fat, a semipermanent injection of calcium hydroxylapatite, or a medialization laryngoplasty can be offered.
In addition to patient history regarding functional aspects of voice use and voice demands, a standardized voice-related outcome measure can be used to assess the patient's vocal limitations and disability. The voice handicap index has been shown to be a reliable and useful patient-based survey instrument, quantifying the patient's voice handicap due to their voice disorder.
Nonsurgical treatment can be offered to patients with UVFP, especially those who are unwilling or unable to proceed with surgical treatment. However, with more evidence demonstrating better long-term voice outcomes when early temporary augmentation is given, it may be best to offer this to all patients with a vocal fold immobility less than 6 months in duration. 
The anatomy of the vagus/recurrent laryngeal nerve has been outlined above (see Pathophysiology), and its understanding is crucial to the evaluation of the potential etiology for patients who present with unilateral vocal fold paralysis (UVFP).
An understanding of both the internal and external laryngeal anatomy is important for the surgical treatment of UVFP. For patients who receive a vocal fold injection, an appreciation and thorough understanding of the anatomy of the membranous vocal fold, vocal process of the arytenoid cartilage, and paraglottic space is crucial for successful treatment.
Laryngeal framework surgery for the treatment of UVFP requires an understanding of the relationship and anatomy of the thyroid cartilage and cricoid cartilage. This is especially true regarding the relationship of the membranous vocal fold and paraglottic space to the external landmarks of the thyroid cartilage. For the more advanced laryngeal framework surgery techniques (eg, arytenoid adduction, cricothyroid subluxation), thorough knowledge of the anatomy of the cricothyroid joint and cricoarytenoid joint are required to be successful.
No contraindications exist for the nonsurgical treatment of unilateral vocal fold paralysis (UVFP) other than the patient not indicating or realizing the need for treatment. Contraindications for the surgical treatment of UVFP can include medical problems, such as severe cardiac or pulmonary limitations, or anticoagulation therapy. Although it carries a higher risk of non–life-threatening bleeding, injection of an anticoagulated patient has been routinely performed successfully in the author’s practice. Performing injections on a patient via a transoral or transcutaneous route under local or MAC anesthesia can also be done routinely in the riskier patient. 
A careful and detailed medical history and evaluation are required prior to deciding on surgical treatment for UVFP. Often, the most complete history is obtained in conjunction with an internal medicine physician and an anesthesiologist. A poorly abducting contralateral vocal fold is a relative contraindication for surgical treatment of UVFP because of the airway reduction that occurs with surgical medialization of the paralyzed vocal fold.
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