Nerve at Risk – Anatomical Variations of the Intrathoracic course of the Left Recurrent Laryngeal Nerve and its Implications for Thoracic Surgeons

Background:

Recurrent laryngeal nerve (RLN) injury during thoracic surgery results in a high number of postoperative complications including aspiration and pneumonia. Anatomical details of the intrathoracic course of the nerve are scarce in the literature. However, only in-depth understanding of the anatomy will help to reduce nerve injury during lymph node dissection. Aim of this study was to assess anatomic variations of the intrathoracic left RLN in fresh cadavers.

Material and method:

In cooperation with the Institute of Legal Medicine, we dissected left-sided vagal nerves and RLN in 100 consecutive Caucasian cadavers during routine autopsy. Anatomical details were documented. Available demographic data were assessed to look for possible correlations.

Result:

All nerves were identified during dissection. The variant courses were clustered into three different groups according to the level of separation of the RLN from the vagal nerve: (1) above the level of the aortic arch, (2) at the level of the aortic arch, and (3) below the aortic arch. (Figure 1) We found 11% of RLN separate above the aortic arch crossing the aortic arch with a considerable distance to the vagal nerve. 48% of RLN split off at the level of the aortic arch, and 41% leave the vagal nerve below the aortic arch in a perpendicular direction. All nerves crossed the Ligamentum arteriosum on the posterior side. No correlation was found with demographics.

Conclusion:

Lymph node dissection at the anterior mediastinal area in left sided lung cancer puts the RLN at risk. With a more detailed knowledge about its course, it is possible to reduce the risk of RLN injury. Dissection behind the Ligamentum arteriosum should consider the anatomical variations of the RLN.