Non-recurrent laryngeal nerve

Last revised by Andrew Murphy on 02 Aug 2021

A non-recurrent laryngeal nerve is an uncommon anatomical variant in which the recurrent laryngeal nerve takes a course that is deviant to its usual descent into the thorax. The non-recurrent laryngeal nerve rather enters the larynx directly from the cervical Vagus nerve instead of coursing inferior and then returning superiorly.

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 rare, only having been reported a number of times, and has always been accompanied by other significant abnormalities (ie situs inversus2.

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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