Differentiation of Critical Illness Myopathy and Critical Illness Neuropathy Using Nerve Ultrasonography

PURPOSE: Intensive care unit-acquired weakness occurs frequently in intensive care unit patients, including critical illness myopathy (CIM) and critical illness polyneuropathy (CIPN). The authors present a prospective study to assess the ultrasound pattern sum score to differentiate between confirmed CIM, sensory neuropathy, and CIPN cases.METHODS: Cross-sectional areas of 12 predefined nerve segments in 16 patients were sonographically examined. Single-nerve cross-sectional areas and ultrasound pattern sum score values were compared; results are given as P-values and receiver operating characteristic area under the curve (AUC).RESULTS: In neuropathy, significant single-nerve cross-sectional area enlargement was observed in the median (P = 0.04), ulnar (P = 0.04), and fibular nerves (P = 0.0003). The ultrasound pattern sum score could reliably differentiate between pure CIM and neuropathy (P = 0.0002, AUC 0.92), CIM and sensory neuropathy (P = 0.001, AUC 0.88), and CIM and CIPN (P = 0.007, AUC 0.92), but not between sensory neuropathy and CIPN (P = 0.599, AUC 0.48).CONCLUSIONS: Nerve ultrasonography reliably identifies neuropathy in intensive care unit-acquired weakness, yet cannot differentiate between sensory neuropathy and CIPN. A standardized ultrasound algorithm can serve as a fast bedside test for the presence of neuropathy in intensive care unit-acquired weakness.