Non-recurrent laryngeal nerve

Last revised by Ciléin Kearns on 8 Mar 2023

A non-recurrent laryngeal nerve is an uncommon anatomical variant in which the laryngeal nerve does not descend into and return from the thorax, instead directly entering the larynx from the cervical vagus nerve.

Incidence is rare and varies by study but has been indicated to be as high as 0.57% on the right and 0.07% on left in an observational study of the recurrent laryngeal nerve during neck surgery 1

A right non-recurrent laryngeal nerve usually occurs due to partial regression of the fourth pharyngeal arch, resulting in an aberrant subclavian artery running posterior to the esophagus 2,3. As a result, the nerve does not loop under a normally placed right subclavian artery before returning superiorly to enter the larynx. 

A left non-recurrent laryngeal nerve is very rare, only having been reported a number of times where it accompanied situs inversus 1.

The variant was first reported in the literature in 1823 2,5.

The presence of an non-recurrent laryngeal nerve is considered a major factor for iatrogenic injury during surgery 4. Patients have a near six-fold increase in risk for intraoperative nerve injury in the presence of an undetected non-recurrent laryngeal nerve 2.

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