The recurrent laryngeal nerve (RLN) is important for functions involving the larynx, also known as the voice box. It controls muscles essential for voice production and breathing. Proper function is integral for clear communication and maintaining an open airway, affecting daily activities like speaking and swallowing.
The Nerve’s Journey
The recurrent laryngeal nerve is an offshoot of the vagus nerve (Cranial Nerve X). Unlike most nerves, the RLN follows a unique “recurrent” path, looping into the chest before ascending to the larynx. This distinctive course differs between the left and right sides of the body.
On the left, the nerve descends and loops underneath the aortic arch, a major blood vessel near the heart. It then travels upwards, in a groove between the trachea (windpipe) and esophagus (food pipe). The right recurrent laryngeal nerve takes a shorter path, looping around the right subclavian artery, a vessel supplying blood to the right arm, before ascending to the larynx. Both nerves ultimately enter the larynx below the inferior constrictor muscle.
How We Speak and Breathe
The recurrent laryngeal nerve controls most intrinsic laryngeal muscles, which are responsible for vocal cord movement. These muscles, including the posterior cricoarytenoid muscles, open and close the vocal cords and adjust their tension. Voice production (phonation) relies on precise muscle coordination to bring the vocal cords together and vibrate as air passes through.
Beyond speech, the nerve’s control over vocal cord movement is also important for breathing and protecting the airway. During inhalation, the posterior cricoarytenoid muscles, solely controlled by the RLN, pull the vocal cords apart, creating an open pathway for air to enter the lungs. When swallowing, the vocal cords close tightly to prevent food or liquids from entering the trachea and lungs, averting aspiration. The RLN also has sensory functions, relaying information from the mucous membranes below the vocal cords to the brain.
When the Nerve is Impaired
Damage or dysfunction of the recurrent laryngeal nerve can lead to symptoms due to impaired vocal cord movement. A common consequence is hoarseness or a breathy voice (dysphonia), occurring when one or both vocal cords cannot move properly to produce clear sound. The voice may also experience changes in pitch.
Difficulty swallowing (dysphagia) can also arise if the vocal cords cannot close adequately to protect the airway during eating or drinking, potentially leading to aspiration. In more severe cases, particularly with bilateral nerve damage, breathing difficulties like stridor (a noisy, high-pitched sound) or shortness of breath may occur, as vocal cords can obstruct airflow. This happens because the sole muscles responsible for opening the vocal cords, the posterior cricoarytenoid muscles, become paralyzed.
Common Reasons for Impairment
Impairment of the recurrent laryngeal nerve can stem from various causes, with surgical complications being a frequent factor. Procedures in the neck and chest, particularly thyroid, parathyroid, and cardiac surgeries, place the nerve at risk due to its close proximity. For example, thyroid surgery has a reported incidence of vocal cord paralysis ranging from 1.5% to 14%.
Tumors are another cause of nerve impairment, as growths in the head, neck, or chest can compress or invade the nerve. Examples include lung, thyroid, or esophageal cancers. Trauma to the neck or chest, such as from accidents, can directly injure the nerve. Additionally, infections, like viral neuritis, and certain neurological conditions can affect nerve function. Endotracheal intubation, where a breathing tube is inserted into the windpipe, can also lead to nerve injury.