Topographic anatomy of the recurrent laryngeal nerve

Laryngeal Nerves and Voice Change in Thyroid Surgery

The low incidence of injury to the recurrent laryngeal nerve (RLN) and external branch of the superior laryngeal nerve (EBSLN) quoted in the literature is derived from expert series. The exact incidence of nerve injury of a thyroid surgeon will be revealed only if pre-operative and post-operative laryngoscopy is becoming routine practice. It is found that the injury rates are increased with routine post-operative laryngoscopy. Subjective voice change occurred in one third of patients all whom had normal vocal cord motion. Therefore, it is important to take written informed consent for voice change in addition to identification of both nerves and documenting it.

Surface Electromyographic Activity in Total Laryngectomy Patients following Laryngeal Nerve Transfer to Neck Strap Muscles

Hands-free triggering and pitch control would improve electrolarynx devices, which are inconvenient to use and sound unnatural. The present study tested the strategy of salvaging voice-related neural signals for hands-free electrolarynx control either by transferring cut recurrent laryngeal nerves (RLNs) to denervated neck strap muscles or by preserving strap muscles with their normal innervation. An RLN nerve transfer was performed at the time of total laryngectomy in 8 individuals, and in 5 of these subjects, strap muscles with intact ansa cervicalis innervation were also preserved for comparison. Neck surface electromyography performed over the strap muscles was used periodically for more than 1 year on phonatory and nonphonatory tasks. Signals were eventually obtained in all subjects from both RLN-innervated and ansa-innervated strap muscles that correlated with speech production. After 1 year, RLN-driven signals were larger than ansa-driven signals in magnitude, and their timing appeared better correlated with intended phonation. The results show that neck surface electromyography is an effective control source for hands-free electrolarynx activation, and that RLN transfer may provide the best approach for obtaining phonation-related activity.

A Closer Look at the Recurrent Laryngeal Nerve Focusing on Branches & Diameters: A Prospective Cohort Study

AIM

We aimed to investigate the anatomical characteristics of the recurrent laryngeal nerve (RLN) highlighting on its diameter and branching pattern.

MATERIALS AND METHODS

We prospectively collected 215 patients (178 female, 37 male) who underwent thyroid/parathyroid surgery during over a 2-year period. Apart from demographic features and surgical data, diameter of RLNs, and their branches and as well as branching distance (distance between the point of bifurcation and the laryngeal entry of RLN) were recorded.

RESULTS

In 215 patients, 378 RLNs were assessed and 42% (n = 159) bifurcated RLNs were observed. The bifurcation rate was similar on the right and left side(s) of the neck (40% and 44%, respectively; p = 0.47). In those, who underwent bilateral exploration, in the case of bifurcation on the first side of the neck, the possibility of contralateral bifurcation was approximately 50%, whereas this rate was found to be only 30% in those with nonbranching RLNs. Mean branching distance was 18 ± 9 mm, and it was similar on the right and left sides (17 and 19 mm, respectively). Approximately 80% of bifurcations were observed within 5-24 mm of the RLN. Mean diameter of the anterior branches was found to be significantly larger compared to posterior branches (1.09 ± 0.35 and 0.82 ± 0.36 mm, respectively; p < 0.01).

CONCLUSIONS

There is great variability in RLN branching. We observed that approximately two out of three bifurcations were unilateral and anterior branches were thicker compared to posterior branches. These findings should be taken into consideration to avoid any damage to the RLN during thyroid and parathyroid surgery.

Ansa cervicalis nerve: review of the topographic anatomy and morphology

In recent years, there has been a proliferation of techniques utilizing the ansa cervicalis nerve to reinnervate the paralyzed larynx. The anatomic course and morphology of the ansa cervicalis are complicated by the variable course and location along the great vessels of the neck, as well as the significant differences observed in the arrangement of its contributing roots and regional branching patterns. Herein, we review the surgical anatomic course of ansa cervicalis and its innervation of the muscles of the neck, and develop specific recommendations with respect to the use of this nerve in laryngeal reinnervation.