Injury to the external branch of the superior laryngeal nerve (EBSLN) can result in detrimental voice changes, the severity of which varies according to the voice demands of the patient. Variations in its anatomic patterns and in the rates of identification reported in the literature have discouraged thyroid surgeons from routine exploration and identification of this nerve. Inconsistent with the surgical principle of preservation of critical structures through identification, modern-day thyroidectomy surgeons still avoid the EBSLN rather than identifying and preserving it.
To describe the anatomic variations of the EBSLN, particularly at the junction of the inferior constrictor and cricothyroid muscles; to propose a systematic approach to identification and preservation of this nerve; and to define the identification rate of this nerve during thyroidectomy.
Materials and Methods
A retrospective review of thyroid lobectomies and total thyroidectomies performed between 1978 and 1997 was carried out. A total of 884 patients were included, with 1057 EBSLNs explored. Intraoperative findings of identification of the EBSLN were recorded and compared on an annual basis for both benign and malignant disease. Overall results were also compared with those found in previous series identified through a 50-year literature review.
The 3 anatomic variations of the distal aspect of the EBSLN as it enters the cricothyroid were encountered and are described. The total identification rate over the 20-year period was 900 (85.1%) of 1057 nerves. Operations performed for benign disease were associated with higher identification rates (599 [86.1%] of 696) as opposed to those performed for malignant disease (301 [83.4%] of 361). Operations performed in recent years have a higher identification rate (over 90%).
Understanding the 3 anatomic variations of the distal portion of the EBSLN and its relation to the inferior constrictor muscle allows for high rates of identification of this nerve. The EBSLN should be explored during thyroid surgery and identification is possible in most cases. Preservation of the EBSLN maintains optimal function of the larynx.