Screening for critical illness polyneuromyopathy with single nerve conduction studies

The ability to diagnose patients with critical illness polyneuromyopathy (CIPNM) is hampered by impaired patient sensorium, technical limitations, and the time-intensive nature of performing electrophysiological testing. Therefore, we sought to determine whether single nerve conduction studies (NCS) could accurately screen for CIPNM.

Critically ill patients at increased risk for developing CIPNM were identified. Bilateral NCS of six nerves, and concentric needle electromyography were performed within 24 h of meeting inclusion criteria, and subsequently on a weekly basis until CIPNM was diagnosed or the patient was discharged from the intensive care unit (ICU).

A total of 75 patients were enrolled into the study. Patients who developed CIPNM had a higher hospital mortality (50 vs. 13 %, p = 0.002), and fewer ICU-free days (0 vs. 11, p = 0.04). There were no differences between the right and left amplitudes (p = 0.59, 0.91, and 0.21) for nerves that could be simultaneously tested bilaterally (sural, peroneal, and tibial). The amplitudes for each of the six individual nerves were significantly diminished in patients with CIPNM when compared to patients without CIPNM. The nerves with the best diagnostic accuracy were the peroneal nerve [AUC = 0.8856; sensitivity = 94 % (95 % CI = 88–100 %); specificity = 74 % (95 % CI = 63–85 %)], and the sural nerve [AUC = 0.8611; sensitivity = 94 % (95 % CI = 88–100 %); specificity = 70 % (95 % CI = 59–81 %)]. The combined diagnostic accuracy for the amplitudes of the peroneal and sural nerves increased significantly [AUC = 0.9336; sensitivity = 100 % (95 % CI = 100–100 %) and specificity = 81 % (95 % CI = 71–91 %)].

Unilateral peroneal and sural NCS can accurately screen for CIPNM in ICU patients and detect a limited number of patients that would need concentric needle electromyography to confirm a diagnosis of CIPNM. These results identify a more streamlined method to diagnose CIPNM that may facilitate routine diagnostic testing and monitoring of weakness in critically ill patients.