[The topographical anatomy of the external branch of the superior laryngeal nerve and its importance in thyroid surgery: a cadaver study].

OBJECTIVES

We investigated topographical anatomic features of the external branch of the superior laryngeal nerve (SLN) in relation to the superior thyroid artery (STA) and its vulnerability to injury in individuals with a normal thyroid size.

STUDY DESIGN

Thirty fresh cadavers (18 females, 12 males; age range 20 to 50 years) with a normal thyroid size and no signs of abnormality in the neck were studied. The external branch of the SLN was identified and classified according to the system proposed by Cernea et al.

RESULTS

The topographical relationship between the external branch of the SLN, the STA, and the upper pole of the thyroid gland was identified in 54 thyroid lobes (90%). Identification was not possible in six lobes because of bleeding or injury. The location of the external branch of the SLN was consistent with type 1 in 28 lobes (51.8%) and type 2 in 26 lobes (48.2%; type 2a in 37.1% and type 2b in 11.1%). No significant relationships existed between the type of the nerve, gender, and age, nor was there any symmetry with regard to the location of the external branch of the SLN in the same subject.

CONCLUSION

Nearly half of the Turkish population with a normal thyroid gland size present high surgical risks during thyroid surgery because of the course of the external branch of the SLN.