Review ArticleRecurrent laryngeal nerve paralysis: anatomy and etiology
Section snippets
Anatomy
The axons of the recurrent laryngeal nerve are myelinated and are grouped within the vagus nerve. As the vagus nerve exits the medulla oblongata, this group is anteriorly situated along the vagus. As the vagus courses inferiorly, these fibers rotate medially until they ultimately separate from the vagus. The jugular ganglion (superior ganglion) is found in the jugular foramen and contains the cell bodies of parasympathetic and sensory nerves that run with the vagus. Within the foramen, cranial
Mechanisms of nerve damage
Injury to the recurrent laryngeal nerve or vagus nerve anywhere along its course usually results in impaired vocal function. Vascular insults, viruses, bacterial infections, neurotoxic drugs, tumors, and trauma have all been implicated in nerve injury. The exact incidence of recurrent laryngeal nerve paralysis is unknown.
The recurrent laryngeal nerve is inevitably at risk in surgery of the neck, chest, and skull base, and damage to the nerve may be the cause of litigation. Neural disruption
Etiology
Determining a precise incidence for recurrent laryngeal nerve paralysis is difficult, partially because of underdiagnosis. It is well known that some patients can be asymptomatic despite an immobile vocal fold. One group has estimated that as many as 30% to 50% of patients with paralysis may be asymptomatic [9]. Although this proportion seems unusually high to this author, the incidence of asymptomatic recurrent laryngeal nerve paralysis is not 0%. Many surgeons do not evaluate patients with
Surgical etiologies
Comparing many series, surgery is still responsible for more recurrent laryngeal nerve paralysis than tumor (see Table 1). Anterior approaches to the cervical spine, carotid endarterectomy, thyroid surgery, and skull base operation are the most common operations causing damage. In a review of 289 patients with recurrent laryngeal nerve paralysis [24], 22 had undergone thyroidectomy, 13 had carotid endarterectomy, and 16 had anterior approaches to the cervical spine. Although thyroid surgery
Neoplastic etiologies
Nonlaryngeal tumors account for 17% to 32% of the reported cases of recurrent laryngeal nerve paralysis [12], [13], [16], [17], [18], [19]. In Furukawa et al's study of 69 tumors causing paralysis [89], 28 (41%) were thyroid, 21 (30%) were lung, 14 (20%) were esophageal, and 3 (4%) were mediastinal. The findings in Yamada et al's series [12] were similar. In contrast, Benninger et al [13] found that 80% of the neoplastic cases were pulmonary or mediastinal in origin.
The possibility that a tumor
Endotracheal intubation
Endotracheal intubation accounted for 7.1% to 11% of recurrent laryngeal nerve paralysis in several larger series (see Table 1) [12], [13], [16], [19] and has been explained by others [93], [94], [95]. The anterior branch of the recurrent laryngeal nerve can be compressed between the lateralized arytenoid cartilage, thyroid cartilage, and an inflated cuff from an endotracheal tube [96]. When recurrent laryngeal nerve paralysis is suspected after intubation, nerve compression must be
Idiopathic etiology
Idiopathic etiologies, by definition, have no obvious causes. The adequacy of the workup also determines the incidence of idiopathic cases. This may explain a high incidence of idiopathic etiology in earlier series. Improved imaging, fiberoptic endoscopy, and laboratory determination of viral titers have decreased the incidence of so-called “idiopathic paralysis.” From 10% to 27% of reported cases are listed as idiopathic in origin in the English literature [98], whereas the Japanese literature
Viral etiologies
Among the causes of the recurrent laryngeal nerve injury, viruses are the least reported and least studied. Herpes simplex virus [99], [100], [101], [102], varicella zoster [103], [104], [105], Epstein-Barr virus [106], [107], influenza virus [108], [109], [110], and cytomegalovirus [111] associated with human immunodeficiency virus have all been cited. Demonstrating a viral etiology is difficult, because positive viral titers do not necessarily prove neural involvement. Without a nerve
Drug-induced etiologies
Lead, arsenic, and alcohol intoxication have been linked to cases of vocal fold paralysis through toxicity to the central nervous system [116]. Injections of local anesthetics into tonsillar fossae and during carotid surgery have caused temporary recurrent nerve paralysis [43], [117], [118].
Cisplatin-induced bilateral vocal fold paresis has been reported in a patient, which proved reversible on cessation of the drug [119]. The best-known drugs to cause recurrent neuropathy are the vinca
Miscellaneous etiologies
The traditional tripartite division of etiology for vocal fold paralysis—tumor, surgery, and idiopathic—does not encompass all causes. Diabetes can cause neuropathy and has been associated with vocal fold paralysis. Radioactive iodine ablation after thyroid cancer surgery [130], vagal nerve stimulation for seizure control [131], jugular vein thrombosis [132], [133], and central venous access procedures [134] have all been reported to cause vocal fold immobility.
Summary
Etiologies of adult vocal paralysis are varied by the site of the lesion as well as the extent and cause of the damage. Most large series point to surgery and neoplastic causes for recurrent nerve paralysis. A detailed history is important when working up a patient with this voice disorder. Knowledge of the anatomy of the head, neck, and chest as well as the mechanisms behind vocal fold paralysis is essential in the evaluation and treatment of recurrent nerve paralysis. Many of the surgical and
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