True vocal cord paralysis signifies loss of active movement of the “true” vocal cord, or vocal fold, secondary to disruption of the motor innervation of the larynx. Disruption of innervation may occur along the length of the recurrent laryngeal nerves and the vagi and may include damage to the motor nuclei of the vagus. It should be differentiated from fixation of the vocal cord secondary to direct infiltration of the vocal fold, larynx, or laryngeal muscles. It should also be distinguished from fixation at the cricoarytenoid joint, encountered with rheumatoid arthritis or following traumatic intubation.
The site of disruption of the nerve supply leads to a characteristic pattern in the position of the vocal cords. However, distinguishing between recurrent laryngeal nerve paralysis and vocal cord paralysis secondary to disruption of the vagus nerve can be difficult.
Table 32–1 summarizes the main causes of vocal cord paralysis in adults. Once the cause of the vocal cord paralysis is ascertained, the next stage is to consider the rehabilitation and treatment of the patient depending on his or her symptoms.
Table 32–1. Etiology of Vocal Cord Paralysis in Adults. ||Download (.pdf)
Table 32–1. Etiology of Vocal Cord Paralysis in Adults.
|Type of Paralysis||Etiology|
|Bilateral recurrent||Post-thyroid surgery|
|Unilateral vagal||Iatrogenic causes|
|Bilateral vagal||Neurologic causes|
The relevant anatomy of the larynx is best understood in terms of the muscles producing abduction and adduction of the vocal cords and their nerve supply. All the intrinsic laryngeal muscles, except the cricothyroid muscle, which is supplied by the external branch of the superior laryngeal nerve, are supplied by the recurrent laryngeal nerve. The sole abductor of the vocal cords is the posterior cricoarytenoid muscle. Table 32–2 provides a summary of the relevant laryngeal musculature and their innervation.
Table 32–2. Summary of Innervation of the Vocal Cord. ||Download (.pdf)
Table 32–2. Summary of Innervation of the Vocal Cord.
|Adductors (lateral cricoarytenoid, thyroarytenoid, interarytenoids)||Recurrent laryngeal (adductor branch)|
|Posterior cricoarytenoid||Recurrent laryngeal (abductor branch)|
To understand the causes of vocal cord paralysis, it is important to understand the pathways of the vagus and recurrent laryngeal nerves. The course of the vagi in both sides of the head and neck are identical, but the recurrent laryngeal nerves differ significantly in their course once they leave the vagus.
The nuclei lie in the upper medulla and give rise to 8–10 rootlets that lie between the glossopharyngeal nerve superiorly and the spinal root of the accessory nerve inferiorly. The muscles of the pharynx, upper esophagus, larynx, and palate are all supplied by motor fibers originating in the nucleus ambiguus. Most of these fibers join ...