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

Abstract 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.