Anatomical and surgical considerations of the external branch of the superior laryngeal nerve: a systematic review.

The anatomical course of the external branch of the superior laryngeal nerve (EBSLN) is variable, and a consistent approach to its preservation during thyroid surgery is needed to reduce risk of post-operative voice impairment. Despite agreement that careful dissection in the region of the superior thyroid pole is required, there is no accepted 'best' approach, nor any universal acknowledgement that location of the EBSLN is actually necessary. The popular cernea classification of EBSLN has limitations, including its decreased reliability with increased thyroid size and its irrelevance in cases of 'buried' variants. * Recent work has identified factors such as ethnicity and stature in the prevalence of EBSLN variants. Consistent approaches to the post-operative detection of EBSLN injury are needed to build an accurate picture of the incidence of surgical nerve injury. Then a standardised approach to EBSLN preservation may emerge.