Recurrent Laryngeal Nerve: Identification During Thyroid and Parathyroid Surgery

Abstract

\n,MD, C\l=e'\sarGavil\l=a'\n,MD \s=b\ Intraoperative identification of the recurrent laryngeal nerve (RLN) is mandatory in surgery of the thyroid and parathyroid glands to avoid surgical damage. Several methods have been proposed for identifying and localizing the RLN based on vocal cord motion produced by electrical stimulation of the nerve. Most of them require complex instrumentation, while others are in contradiction with anatomical basis. We present a safe and simple method for identifying the RLN during thyroid and parathyroid gland surgery, which requires no additional surgical instruments and can be performed as a routine procedure. Nonetheless, thorough knowledge of cervical anatomy still remains the most important point in this surgery.In 1933, Prioleau1 stated that in thy¬ roid surgery, a recurrent nerve seen is injured. Eleven years later, Lahey2 opened a new era in thyroid surgery by advocating the systematic intraoperative identification of the recurrent laryngeal nerve (RLN) in thyroidectomy. Nowadays, most au¬ thors agree with the principles proposed by Lahey in 1944, and the inci¬ dence of permanent surgical damage to the RLN in primary operations of the thyroid and parathyroid glands can be as low as 0.1 %.3 In 1956, Riddell" reported a decrease in surgical injury to the RLN, from 6% for un¬ identified nerves to 2% for 1056 iden¬ tified nerves. The incidence of RLN damage increases in reoperative pro¬ cedures.5·6The RLN runs upward, more or less in the groove between the trachea and the esophagus, and is closely related to the inferior thyroid artery and the posterior aspect of the thyroid gland. The right nerve is more commonly anterior (26% to 33%) or passes between the branches of the artery (47% to 50% ), while the left RLN is more commonly posterior (50% to 55% ) to the inferior thyroid artery.7 It is usual for the RLN to divide before entering the larynx,810 but the branches to the laryngeal muscles leave the RLN inside the larynx.11 The intrinsic muscles of the larynx are innervated by the RLN and the supe¬ rior laryngeal nerve. The cricothyroid is the only muscle innervated by the external branch of the superior laryn¬ geal nerve, while the other intrinsic muscles are innervated by the RLN.12 Apparently, the RLN sometimes may also help to supply the cricothyroid muscle,12 but this must be considered an exception rather than the rule.We present a method for intraoper¬ ative identification of the RLN, based on direct electrical stimulation of the nerve with a disposable nerve stimu¬ lator and palpation of the response of the posterior cricoarytenoid muscle (posticus). MATERIALS AND METHODSAfter division of the middle thyroid vein(s), the posterolateral surface of the thyroid gland is exposed, and the inferior thyroid artery is identified and used as a landmark. The suspected location of the RLN caudal to the artery is carefully explored using blunt dissection and an extremely meticulous surgical technique to obtain a bloodless field. Once the structure supposed to be the RLN is located,...

Recurrent Laryngeal Nerve Injury in Thyroid Surgery

“…Therefore, methods that can reduce the incidence of this complication are of great interest. 11 An almost certain way to ensure the integrity of the RLN is to always identify the nerve during all surgical procedure on thyroid and parathyroid glands. 12,13 The aim of the present study is to assess the factors influencing the risk of RLN injury during thyroid surgery.…”

Recurrent Laryngeal Nerve Monitoring in Thyroid and Parathyroid Surgery: The University of Michigan Experience

“…Intraoperative monitoring of the RLN is becoming increasingly accepted during operative procedures that place this important neural structure at risk for iatrogenic injury. These procedures include thyroidectomy, parathyroidectomy, 3 tracheal resections, and anterior cervical spine surgery including discectomy and corpectomy. 4 Monitoring of the RLN can be accomplished by visual or electromyographic techniques.…”

A Comparison of Direct, Indirect, and Fiberoptic Laryngoscopy to Evaluate Vocal Cord Paralysis after Thyroid Surgery

“…Electrostimulation with single or double cuff endotracheal tube and pressure recordings, possibly combined with electromyography, are complicated; they require instrumentation and, therefore, are not easily used in routine clinical practice (21,22). Electrostimulation and palpation of the cricoarytenoid muscle seem effective but may increase the edema by the retrocricoid manipulation (23). Electrostimulation with laryngoscopy can also be performed.…”