A topographical and surgical anatomical description of the recurrent laryngeal nerve: Observations from cadaveric dissection and thyroidectomy patients

Background

Recurrent laryngeal nerve (RLN) injuries account for most successful litigations against surgeons following head and neck surgery. Most injuries to the RLN occur during thyroidectomy with the best strategy to reduce injury to the RLN being through intraoperative monitoring of its normal anatomy, extra-laryngeal trajectory and topography. Identification of the RLN during thyroidectomy is possible at the tracheoesophageal groove (TEG), where it crosses the inferior thyroid artery (ITA) and or pierces the suspensory ligament of the thyroid gland (ligament of Berry). The extra-laryngeal course and branching patterns of the RLN are highly variable, increasing the likelihood of iatrogenic injury.

Materials and methods

The current study investigated the extra-laryngeal course, branching patterns and topographical relationships of the RLN in the TEG in adult cadavers and patients who underwent thyroidectomy. The study examined 30 thyroidectomy patients and 50 adult cadavers.

Results

The mean diameters of the RLN were 1.74 ± 0.59 mm and 1.63 ± 0.47 mm on the left and right sides, respectively, with no statistically significant difference between the genders and sides (P ≥ 0.05). The majority of the RLNs on the left side coursed in the first 0–15⁰ relative to the TEG while on the right side the majority deviated from the TEG at an angle ranging between 0 and 30⁰. The distribution of the RLN in relation to the inferior thyroid artery in the cadaveric sample was as follows: 29.6 % posterior to the artery, 33.7 % anterior to the artery and 36.7 % in-between its branches with statistically significant differences between genders (P ≤ 0.05). The majority of the RLN exhibited two or more branches on both sides, with a maximum of four branches being observed. In the surgical cohort, majority of the RLN ran posterior to the ITA followed by the anterior course and least in-between the branches of the ITA.

Conclusions

The present findings augment the vital information about the course, topography and branching patterns of the RLN along the TEG by outlining differences between the a cadaveric and a surgical sample as well as between two major South African population groups in order to minimise the iatrogenic injuries to the RLN and also to improve the diagnoses and management of the disorders of the neck, larynx and voice production.