To identify whether diaphragm electromyography (EMG) and phrenic nerve conduction studies (NCS) alter diagnosis and/or management of patients with suspected diaphragm paresis.

While diaphragm EMG and phrenic NCS have theoretical diagnostic benefit in suspected diaphragm paresis, there is scant evidence to suggest they guide diagnostic and therapeutic decision making.

We conducted an IRB approved retrospective chart review study of patients who had a diaphragm EMG and phrenic NCS performed in our clinic from 2015 to 2019. The data collected was analyzed by simple statistical methods.

52 patients underwent both phrenic NCS as well as EMG of one or both diaphragms. The results of diaphragm EMG/phrenic NCS were found to be incongruent with the results of pre-procedure imaging studies in 19 patients. Most of the abnormal imaging studies had abnormal electrodiagnostic results. After the procedure, 6 patients were lost to follow up. The diagnosis changed in 10/52 patients and remained unchanged in 30. In the 9 patients diagnosed with a neuromuscular disorder after results of electrodiagnostics, 6 had EMG abnormalities in other limb muscles. In total, a change in management occurred in 13/52 patients. Out of the 10 patients whose diagnosis changed after EMG/NCS, 4 had a change in management. Out of the 30 patients who had no change in diagnosis after the procedure, 7 had a change in management.

Diaphragm EMG and phrenic NCS are of value in guiding diagnostic decisions. The utility of diaphragm EMG may be limited in myopathic processes, particularly if limb EMG reveals a myopathy. In cases of suspected phrenic neuropathy, abnormal imaging studies and abnormal phrenic NCS may be sufficient for diagnosis without the need for diaphragm EMG. Diaphragm EMG and phrenic NCS may have value for surgical planning; due to lack of long-term follow-up data, we were unable to confirm this.