Visualization of the diaphragm muscle with ultrasound improves diagnostic accuracy of phrenic nerve conduction studies


  • This article includes Supplementary Material available via the internet at

  • Disclosure: The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Center for Research Resources or the National Institutes of Health.

  • This study was supported by by the National Center for Research Resources (8UL1TR000105, formerly UL1RR025764) and the National Institutes of Health (T32NS007338-22).


Introduction: Evaluation of phrenic neuropathy (PN) with phrenic nerve conduction studies (PNCS) is associated with false negatives. Visualization of diaphragmatic muscle twitch with diaphragm ultrasound (DUS) when performing PNCS may help to solve this problem. Methods: We performed bilateral, simultaneous DUS–PNCS in 10 healthy adults and 12 patients with PN. The amplitude of the diaphragm compound muscle action potential (CMAP) (on PNCS) and twitch (on DUS) was calculated. Results: Control subjects had <38% side-to-side asymmetry in twitch amplitude (on DUS) and 53% asymmetry in phrenic CMAP (on PCNS). In the 12 patients with PN, 12 phrenic neuropathies were detected. Three of these patients had either significant side-to-side asymmetry or absolute reduction in diaphragm movement that was not detected with PNCS. There were no cases in which the PNCS showed an abnormality but the DUS did not. Conclusions: The addition of DUS to PNCS enhances diagnostic accuracy in PN. Muscle Nerve 49: 669–675, 2014