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brainstem. Therefore, central nervous system (CNS) insults and anomalies can cause a high vagal injury that can affect the RLN as well as innervation of the pharynx. In high vagal injuries, the pharyngeal muscles and uvula may also be affected, and the uvula will deviate toward the contralateral side of the injury. VFP from a CNS lesion may also occur because of compression or traction on the vagus nerve at the level of the brainstem in the setting of hydrocephalus, a space-occupying CNS lesion, and Arnold-Chiari malforma tion. (16) CNS lesions can lead to bilateral or unilateral VFP and no reported side effect predilection has been reported. After the paired vagus nerves exit the skull base through the jugular foramens, they travel inferiorly along the neck along the carotid arteries. The RLNs branch off from the vagus nerve in the mediastinum. The Figure demonstrates that typically the right RLN loops under the right subclavian artery and the left RLN loops under the aortic arch; they both then travel cephalad in the tracheoesophageal groove to innervate the larynx. The left RLN travels a longer distance through the mediastinum, closely associated with the duc tus arteriosus and aortic arch, and farther along the trache oesophageal groove. As a result, the left RLN is at increased risk for iatrogenic injury during cardiac and thoracic surgery.

Table 2 summarizes the relative proportions of the most common causes of VFP in infants. Cardiothoracic surgery is the most common cause in most studies, though this is contingent upon the presence of an active cardiothoracic service. (9) Large administrative database analyses have identi fi ed a 5% to 9% incidence of VFP after cardiac surgery in infants. (17)(18)(19) An earlier meta-analysis reported a pooled proportion of 9.3% overall and 28% among infants who underwent postoperative evaluation for VFP. (20) Because of this high incidence of VFP, many authors have stated that an infant with a hoarse cry or stridor after cardiothoracic surgery has VFP until proven otherwise. Cardiothoracic surgery involving the aortic arch or patent ductus arteriosus (PDA) has a higher incidence because of the surgical dissection near the course of the left RLN. (21) The Norwood procedure and other aortic arch repairs have an especially high incidence of 48% to 59%. (22)(23)(24) The incidence is 16% to 21% after PDA ligation. (25)(26)(27) VFP is signi fi cantly more common after PDA ligation in preterm (28) as well as extremely low birthweight (ELBW) infants. (29)(30) The incidence increases to 31% in preterm infants (31) and 40% in ELBWinfants. (30) As the survival of very preterm and ELBW infants continues to improve, the

Figure. Schematic of the course of the left and right vagus nerves and the recurrent laryngeal nerves. The left recurrent laryngeal nerve is at particular risk for iatrogenic injury as it loops around the aortic arch and ductus arteriosus. The right recurrent laryngeal nerve loops around the brachiocephalic artery. Both nerves then travel along the tracheoesophageal groove up into the larynx. (Printed with permission from Christine Gralapp, MA, CMI Medical Illustration, Fairfax, CA.)

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