Galen's "anastomosis" revisited.

ABSTRACT

This study aimed to examine the incidence and contribution to the innervation of the larynx from Galen's "Anastomosis" (GA), which is the direct connection between the dorsal branches of the internal laryngeal nerve (ILN) and the recurrent laryngeal nerve (RLN). Fifty adult laryngeal specimens were micro-dissected. The diameter of the ILN and RLN were measured immediately after each had given off their muscular branches to form GA. The incidence of GA was 81%. The average diameter of the ILN after giving off muscular branches to form GA was 1.28 mm (right) and 1.27 mm (left) while the average diameter of the RLN after giving off muscular branches to form GA was 0.65 mm (right) and 0.68 mm (left). The weighted mean incidence of GA (77.3%) calculated from a review of the literature concurred with the present finding of 81%. The ILN and RLN supplied the laryngeal musculature. According to the results obtained; it appears that the ILN may provide a greater contribution to the connection between the ILN and RLN as the morphometric contribution from the ILN was larger in comparison to the RLN. In addition, the authors propose a suitable term viz. the "communicating branch" as opposed to the commonly used misnomer GA to describe the connection between the dorsal branch of the RLN and the ILN, based on the definition that an "Anastomosis" refers to blood vessels and that a single connection exists between the dorsal branch of the RLN and ILN.