Vulnerability of the Recurrent Laryngeal Nerve in the Anterior Approach to the Lower Cervical Spine

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Abstract
To perform anatomic dissections and measurements of the recurrent laryngeal nerve between the inferior thyroid artery and superior border of the clavicle (mid-portion) on both sides. To determine quantitatively the differences in course and location between the recurrent laryngeal nerves on both sides and to relate this to the vulnerability of the recurrent laryngeal nerve during an anterior approach to the lower cervical spine. The midportion of the recurrent laryngeal nerve is usually encountered in the anterior approach to the lower cervical spine, especially on the right side. No quantitative regional anatomy describing the course and location of the mid-portion of the recurrent laryngeal nerve is available in the literature. Fifteen adult cadavers were used for dissections of the recurrent laryngeal nerve. The length of the recurrent laryngeal nerve between the superior border of the clavicle and the inferior thyroid artery, and the angle of the recurrent laryngeal nerve with respect to sagittal plane, were measured bilaterally. In addition, six cross-sections at C7 were obtained to determine the linear distances between esophagotracheal groove and the recurrent laryngeal nerve. The recurrent laryngeal nerve on the right runs in a superior and medial direction, with an angle of 25.0° ± 4.7° relative to sagittal plane, compared with 4.7° ± 3.7° on the left. The length of the recurrent laryngeal nerve between the superior border of the clavicle and the inferior thyroid artery is 23.0 ± 4.4 mm on the left, and 22.8 ± 4.3 mm on the right. The recurrent laryngeal nerve lies deep within the esophagotracheal groove on the left, but 6.5 ± 1.2 mm anterior and 7.3 ± 0.8 mm lateral to the esophagotracheal groove on the right. The recurrent laryngeal nerve on the right side is highly vulnerable to injury if ligature of the inferior thyroid vessels is not performed as laterally as possible or if retraction of the midline structures along with the recurrent laryngeal nerve is not performed intermittently. Avoiding injury to the recurrent laryngeal nerve, especially on the right side, is a major consideration during an anterior approach to lower cervical spine.