Histological asymmetry of the human recurrent laryngeal nerve.

Histological studies of the human recurrent laryngeal nerves (RLNs) have described differences in fiber length and thickness between the right and left RLNs. This asymmetry is probably involved in the different times of arrival of the stimuli to the laryngeal musculature controlled by each nerve. Histological and structural differences between the right and left RLNs could explain the synchronicity of laryngeal musculature contraction despite the differing nerve lengths. The purpose of this investigation was to shed some light on this paradigm by obtaining estimates of some morphometric parameters, such as intraperineural area, intraperineural perimeter, fiber area, fiber perimeter, fiber density (number of fibers/mm(2)), and total number of fibers in the right and left RLN of humans. Thus, the right and left RLNs were studied in a total sample of eight human specimens obtained from necropsies. The nerves were analyzed using histology, and the morphometric parameters were measured using Image Pro Plus Software 4.1 (Media Cybernetics, Silver Spring, MD, USA). No statistical differences between the two RLNs were observed in the intraperineural area, intraperineural perimeter, density (number of fibers/mm(2)), and total number of fibers. However, the area and perimeter of fibers of the right RLN were statistically larger when compared with those of the left RLN--21% and 11%, respectively. In conclusion, we show that in humans, the area and perimeter of the right RLN are larger than those of the left RLN. This morphological finding is probably related to the different time of arrival of the stimulus to the laryngeal musculature.