Expansion
Right hooks the pipe, left loops the arch, right's the short cut, left's the long march
Mnemonic
“The left goes lower”:
- Left recurrent laryngeal hooks under the aortic arch, at the ligamentum arteriosum, so it descends into the thorax
- Right hooks under the right subclavian artery, so it stays in the root of the neck
The asymmetry comes from the embryonic aortic arches: both nerves hook under the sixth arch artery, which persists on the left as the ductus arteriosus but regresses on the right, letting the right nerve rise to the fourth arch.
The left nerve is therefore the one affected by thoracic disease: lung cancer at the left hilum, aortic arch aneurysm, mediastinal nodes, and left atrial enlargement in mitral stenosis, all causing hoarseness (Ortner’s syndrome).
All intrinsic laryngeal muscles are supplied by the recurrent laryngeal nerve except cricothyroid, which takes the external branch of the superior laryngeal nerve.
Expansion
- Right recurrent laryngeal nerve - loops under the subclavian artery
- Left recurrent laryngeal nerve - loops under the aortic arch, longer course