One of the complications Chloe endured after the Arterial Switch Operation was Left Vocal Cord Paresis (weakness in the left vocal fold). Cardiac surgery represents a risk to normal voice function as the nerves serving the larynx (voice box) are routed near the heart. Damage to this nerve during open heart surgery is not uncommon. This nerve is the left recurrent laryngeal nerve – a branch of the vagus nerve that supplies motor function and sensation to the larynx (voice box). The left laryngeal nerve branches from the Vagus nerve to loop under and around the arch of the aorta before ascending, whereas the right branch loops around the right subclavian artery. Chloe’s left recurrent laryngeal nerve was stretched in surgery during the switch. She luckily needed no voice therapy or surgery as it healed on its own. It took a few months to heal but she now has her sweet, soft (and sometimes loud!) voice back.
What Is Vocal Cord (Fold) Paresis?
Vocal Cord Paresis results from abnormal nerve input to the voice box muscles (laryngeal muscles). Paresis is the partial interruption of nerve impulse resulting in weak or abnormal motion of laryngeal muscle(s). Vocal fold paresis can happen at any age – from birth to advanced age, in males and females alike, from a variety of causes. The effect on patients may vary greatly depending on the patient’s use of his or her voice.
What Nerves Are Involved In Vocal Cord Paresis?
Vocal fold movements are a result of the coordinated contraction of various muscles. These muscles are controlled by the brain through a specific set of nerves. The nerves that receive these signals are the:
The superior laryngeal nerve (SLN), which carries signals to the cricothyroid muscle, located between the cricoid and thyroid cartilages. Since the cricothyroid muscle adjusts the tension of the vocal fold for high notes during singing, SLN paresis and paralysis result in abnormalities in voice pitch and the inability to sing with smooth change to each higher note. Sometimes, patients with SLN paresis may have a normal speaking voice but an abnormal singing voice.
The recurrent laryngeal nerve (RLN) carries signals to different voice box muscles responsible for opening vocal folds (as in breathing, coughing), closing vocal folds for vocal fold vibration during voice use, and closing vocal folds during swallowing. The recurrent laryngeal nerve goes into the chest cavity and curves back into the neck until it reaches the larynx. Because the nerve is relatively long and takes a “detour” to the voice box, it is at greater risk for injury from quite different causes – such as infections and tumors of the brain, neck, chest, or voice box; as well as complications during surgical procedures in the head, neck, or chest regions – that directly injure, stretch, or compress the nerve. Consequently, the recurrent laryngeal nerve is involved in majority of cases of vocal cord paresis or paralysis.
What Are The Causes Of Vocal Cord Paresis?
The cause of vocal cord paresis can indicate whether the disorder will resolve over time or whether it is most likely permanent. When a reversible cause is present, surgical treatment will most likely not be recommended given the likelihood of spontaneous resolution of the paresis. Despite advances in diagnostic technology, physicians are unable to detect the cause in about half of all vocal fold paralyses. These cases are referred to as idiopathic (due to unknown origins). In idiopathic cases, paralysis or paresis might be due to a viral infection affecting the voice box nerves (RLN or SLN) or the vagus nerve, but this cannot be proven in most cases.
Known reasons for injury can include:
Inadvertent injury during surgery: Surgery in the neck (surgery of thyroid gland, carotid artery) or surgery in the chest (surgery of the lung, esophagus, heart, or large blood vessels) may inadvertently result in RLN paresis. The SLN may also be injured during head and neck surgery.
Complication from endotracheal intubation: Injury to the RLN may occur when breathing tubes are used for general anesthesia and/or assisted breathing (artificial ventilation). However, this type of injury is rare, given the large number of operations done under general anesthesia.
Blunt neck or chest trauma: Any type of penetrating, hard impact on the neck or chest region may injure the RLN; impact to the neck may injure the SLN.
Tumors of the skull base, neck, and chest: Tumors (both cancerous and non-cancerous) can grow around nerves and squeeze them, resulting in varying degrees of paresis or paralysis.
Viral infections: Inflammation from viral infections may directly involve and injure the vagus nerve or its nerve branches to the voice box (RLN and SLN). Systemic illnesses affecting nerves in the body may also affect the nerves to the voice box.
What Are The Symptoms Of Vocal Cord Paresis?
Paresis of voice box muscles result in voice changes and may also result in airway problems and swallowing difficulties.
Voice changes: Hoarseness (croaky or rough voice); breathy voice (a lot of air with the voice); effortful phonation (extra effort on speaking); air wasting (excessive air pressure required to produce usual conversational voice); and diplophonia (voice sounds like a “gargle”).
Airway problems: Shortness of breath with exertion, noisy breathing (stridor), and ineffective or poor cough.
Swallowing problems: Choking or coughing when swallowing food, drink, or even saliva, and food sticking in throat.
What Is The Treatment For Vocal Cord Paresis?
The two treatment strategies to improve vocal function are voice therapy (the equivalent of physical therapy for large muscle paresis) and phonosurgery, an operation that repositions and/or reshapes the vocal cord(s) to improve voice function. Normally, voice therapy is a first treatment option. After voice therapy, the decision for surgery is dependent on the severity of the symptoms, vocal needs of the patient, position of paralyzed vocal folds, prognosis for recovery, and cause of paresis/paralysis if known.
If you have notice any change in voice quality, immediately contact an otolaryngologist—head and neck surgeon.
Source: American Academy of Otolaryngology
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