Intrinsic Susceptibility Of The Left Vs Right Recurrent Laryngeal Nerve To Paralysis: A Systematic Review

Objective Unilateral vocal fold paralysis (UVFP) occurs more commonly on the left than right, a difference historically attributed to greater left recurrent laryngeal nerve (RLN) length and its presence in the thorax with consequential increased exposure to injury. However, considering the importance of mRNA locally transcribed in the distal nerve after nerve injury, there may be other intrinsic neuromuscular reasons for this discrepancy. To investigate whether intrinsic neuromuscular issues influence laterality, this study investigates the rate of paralysis relative to side in idiopathic and short-term intubation cases, excluding cases due to identifiable disease and surgery. Data Sources Embase and PubMed database Review Methods A systematic literature search was performed to capture articles published up until May 2022. Articles were included if laterality and etiology of paralysis were reported. Demographic data was extracted for patients diagnosed with idiopathic paralysis or paralysis after intubation for procedures performed outside the head, neck, and thorax. Study design was collected from included articles. Results Twenty-one studies were included, from which 702 patients were drawn for analysis. Within the idiopathic group, 69.2% were left-sided. Within the post-intubation group, 67.9% were left-sided. Conclusions The available evidence indicates that left-sided paralysis is more common in patients with idiopathic or short-term intubation related UVFP. This suggests intrinsic neuromuscular differences contribute to the left RLN being more susceptible than the right to damage and dysfunction. Further study is needed to identify these differences, which may provide insights into the pathophysiology of RLN paralysis as well possible therapeutic options. ### Competing Interest Statement The authors have declared no competing interest. ### Funding Statement This work funded by NIH grant #R01DC018060 ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The study used ONLY openly available human data that were originally located in peer reviewed journal articles available online and cited in Embase and PubMed databases I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors All data produced in the present work are contained in the manuscript