Clinical Significance of Asymmetry on Electrodiagnostic Testing to detect Polyneuromyopathy in Critically Ill Patients: a cross-sectional study

Background: In search of simplified nerve conduction studies as screening electrophysiological tests in Intensive Care Unit (ICU), previous studies have suggested that unilateral electrophysiological evaluations may be sufficient for screening probable critical illness polyneuro and/or myopathy (CIP/CIM) in ICU - also called as neuromuscular electrophysiological disorder (NED) - since quantitative statistical analyses did not detect significant bilateral differences, at first reinforcing its symmetrical manifestation as established. This study aimed to investigate the presence of asymmetry in the onset of NED and the relevance of bilateral electrophysiological assessments for correct screening to avoid diagnostic and analysis errors. We also investigated possible effects of laterality and focal lesions of the central nervous system on NED. Methods : From Abril to October 2024, a cross-sectional observational study of critically ill patients admitted in ICU was conducted. All participants underwent bilateral nerve conduction study for the motor peroneal nerve to investigate asymmetry. Different from previous studies, bilateral Compound Muscle Action Potential (CMAP) records were analyzed based on the electrodiagnostic criterion for asymmetry. Results: 41 patients were enrolled, in which 82 assessments were carried out. NED was identified in 34 (83%) participants. Based on electrodiagnostic criterion, asymmetries were observed in 12 (29%) participants, with diagnostic divergence in 5 (12%), in which NED could be overlooked if the evaluation were unilateral. Patients with NED had a two-fold odds ratio of asymmetry between bilateral electrodiagnostic assessments compared to patients without NED. We also identified a possible match between brain anatomical landmarks and the worst CMAP on the contralateral side, with an attributable risk of 17% in patients with NED. Conclusion: This study suggests that electrodiagnostic screening tests for neuromuscular electrophysiological disorders in critically illness participants in ICU should be performed bilaterally to avoid diagnostic error and analysis bias, due to the clinical relevance of asymmetry in the development of this dysfunction. The impact of cerebral laterality and focal brain lesions on electrodiagnostic asymmetry in the early phase of NED needs to be further studied.