Anatomic Course of the Recurrent Laryngeal Nerve

Origin and General Course

The recurrent laryngeal nerve (RLN) is a mixed nerve with sensory and motor fibers that originates from the thoracic portion of the vagus nerve, with the left and right nerves following different anatomical paths to reach the larynx 1
The RLN is a branch of the vagus nerve containing both sensory and motor fibers that innervate the intrinsic laryngeal muscles (except the cricothyroid muscle) and provide sensory innervation to the vocal folds and upper esophagus/trachea 1
The right RLN follows a more superficial course along the lateral esophageal edge, while the left RLN loops around the aortic arch and ascends in the tracheoesophageal groove in a deeper position 1
Both nerves ultimately penetrate the cricopharyngeal membrane to innervate the laryngeal muscles 1

Three critical anatomical landmarks for identifying the RLN during surgery include:

The relationship between the RLN and inferior thyroid artery (ITA) is highly variable and critical for neural identification during surgery 1

The anterior extralaryngeal branches are generally motor fibers that may be stretched during Berry's ligament dissection 1

Non-recurrent laryngeal nerve is a rare variant (incidence 0.3-1.6%) observed more frequently on the right side 1
Two types of non-recurrent laryngeal nerve anomalies exist:
A non-recurrent laryngeal nerve often occurs in conjunction with an anomalous (retro-esophageal) right subclavian artery 2

Knowledge of RLN anatomy is crucial for surgeons performing thyroid and parathyroid procedures to prevent nerve injury 3, 2
RLN injury can result in vocal fold immobility, causing dysphonia, breathing difficulties, and dysphagia with aspiration risk 3
Re-operative procedures carry a significantly higher risk of RLN injury (up to 30%) 1

RLN injury impairs vocal cord function, compromising airway protection during swallowing, which can lead to aspiration of food and liquids into the trachea 4, 5
The RLN innervates all intrinsic laryngeal muscles except the cricothyroid, controlling vocal fold movement crucial for both phonation and swallowing 6
Following RLN injury, patients experience impaired ability to cough effectively in the early post-injury period, further compromising airway protection 7

In cases of significant aspiration risk, a tracheostomy may be considered to protect the airway and improve pulmonary toilet 7
Most unilateral RLN injuries show compensation from the opposite vocal cord over time 7
For persistent dysphagia, interventions such as thyroplasty or vocal cord injections may be considered, though these are rarely required 7
Electrical stimulation of the recurrent laryngeal nerve via an implanted electrode is a promising but experimental approach for severe dysphagia 8

Risk of RLN injury is higher during certain procedures, particularly thyroidectomy, with injury rates of 0.3-3% for permanent and 6-8% for transient damage 9
The left RLN is particularly vulnerable during mediastinal lymphadenectomy due to its longer course around the aortic arch 7
Re-operative procedures carry a significantly higher risk of RLN injury (up to 30%) 9
Bilateral RLN injury presents a medical emergency due to potential complete airway obstruction 9