Surgical anatomy of the extralaryngeal aspect of the superior laryngeal nerve

Objectives: To describe the topography of the superior laryngeal nerve (SLN) and to evaluate the influence of gender, ethnicity, side of the neck, and individual height on the topography of the SLN. Design: Anatomical study of human cadavers. Subjects: Fifty fresh human cadavers (19 female subjects and 31 male subjects; age range, 22-89 years; mean age, 61 years) were randomly selected for this study. The subjects were divided into nonwhite (n= 18) and white (n=32) ethnic groups. The t test and linear regression were used for statistical analysis of data. Results: All SLNs emerged medially to the vagus nerve. The SLNs mostly divided into internal (ibSLN) and external (ebSLN) branches distally from their origin (94%). The mean SE length of the SLN trunk was 16.7+/-0.9 mm and was affected by gender (P=.01) but not ethnicity (P=.57), side of the neck (P=.96), or individual height (R-2=0.01; P=.33). The length of the ibSLN reached 44.9+/-1.0 mm and was unaffected by gender (P=.91), ethnicity (P=.24), side (P=.40), or height (R-2<0.01; P=.71). The length of the ebSLN measured 62.6+/-1.2 mm and was unaffected by gender (P=.69), ethnicity (P=.42), side (P=.26), or height (R-2<0.01; P=.85). The mean+/-SE angle between the ibSLN and the tracheoesophageal sulcus was 49degrees+/-1degrees and was unaffected by gender (P=.35), ethnicity (P=.11), side (P=.26), or height (R-2+/-<0.01; P=.96). Only I subject demonstrated a bilateral anatomical variation of the ibSLN close to its entrance into the thyrohyoid membrane. Conclusions: The topography of the SLN has a few anatomical variations and is unaffected by gender, ethnicity, side of the neck, and individual height, except that the SLN is longer in males than in females. These findings are important in that they can help in the prevention of SLN injuries during operations such as laryngectomy and neck dissection, as well as in the planning of laryngeal reinnervation and transplantation.