THE EXTERNAL BRANCH OF THE SUPERIOR LARYNGEAL NERVE - ITS TOPOGRAPHICAL ANATOMY AS RELATED TO SURGERY OF THE NECK

Objective: To determine the possible courses of the external branch of the superior laryngeal nerve (EBSLN) and its relationship to the supe rior thyroid artery (STA) to improve the chances of identifying and sa ving the nerve during head and neck surgery. Design: Anatomical analys is of the exact topography of the EBSLN. Subjects: Thirty-one perfusio n-fixed human cadavers (ie, 62 preparations) of both sexes ranging in age from 50 to 94 years (mean, 78 years) with neither enlarged thyroid glands nor any other signs of abnormality in this region. Results: Fo ur types of relationship between the EBSLN, the upper pole of the thyr oid gland, and the STA were found. In 23 preparations (42%), the EBSLN crossed the STA more than 1 cm above the upper pole of the thyroid gl and (type 1). In 15 preparations (30%), the EBSLN crossed the STA less than 1 cm above the upper pole of the thyroid gland (type 2). In 7 pr eparations (14%), the EBSLN crossed the STA under cover of the upper p ole of the thyroid gland (type 3). In 7 preparations (14%), the EBSLN descended dorsal to the artery and only crossed the branches of the ST A immediately above the upper pole of the thyroid gland (type 4). Conc lusion: The description of the variable course of the EBSLN and its ca tegorization may help minimize the risk of iatrogenic lesions of the n erve during surgery.