The diagnostic utility of inspiratory-expiratory radiography for the assessment of phrenic nerve palsy associated with brachial plexus injury

Background: The phrenic nerve is commonly injured with trauma to the brachial plexus. Hemi-diaphragmatic paralysis may be well-compensated in healthy individuals at rest but can be associated with persistent exercise intolerance in some patients. This study aims to determine the diagnostic value of inspiratory-expiratory chest radiography compared to intraoperative stimulation of the phrenic nerve for assessing phrenic nerve injury associated with brachial plexus injury. Methods: Over a 21-year period, the diagnostic utility of three-view inspiratory-expiratory chest radiography for identification of phrenic nerve injury was determined by comparison to intraoperative phrenic nerve stimulation. Multivariate regression analysis was used to identify independent predictors of phrenic nerve injury and having an incorrect radiographic diagnosis. Results: A total of 237 patients with inspiratory-expiratory chest radiography underwent intraoperative testing of phrenic nerve function. Phrenic nerve injury was present in approximately one-fourth of cases. Preoperative chest radiography had a sensitivity of 56%, specificity of 93%, positive predictive negative of 75%, and negative predictive value of 86% for identification of a phrenic nerve palsy. Only C5 avulsion was found to be a predictor of having an incorrect diagnosis of phrenic nerve injury on radiography. Conclusion: While inspiratory-expiratory chest radiography has good specificity for detecting phrenic nerve injuries, a high number of false negatives suggest that it should not be relied upon for routine screening of dysfunction after traumatic brachial plexus injury. This is likely multifactorial and relates to variation in diaphragm shape and position, as well as limitations regarding static image interpretation of a dynamic process.