ABSTRACT
Introduction: A large number of patients with coronavirus disease 2019 (COVID-19) require intensive care unit (ICU) admission. Critically ill patients may develop neuromuscular complications such as critical illness myopathy (CIM) or neuropathy (CIP) or both (CIPM) although there could be other myopathic conditions, possibly caused by ICU stay, inflammatory response to the infection, or direct viral damage to the muscular fibers. Our aim is to detect the presence of myopathies in ICU patients affected by COVID-19 and characterize myopathic conditions, correlating neurophysiological anomalies to muscle biopsy findings. Method(s): We evaluated Sars-CoV2-positive patients, without a history of underlying neuromuscular disorders or risk factors, who developed generalized weakness during ICU stay. If patients presented a significant reduced force (Medical Research Council [MRC] score < 48/60) at least 5 days after ICU admission, they underwent neurophysiological evaluation and muscle biopsy. Electrodiagnosis included motor and sensory nerve conduction studies and F waves evaluation (also after 20 Hz repetitive nerve stimulation for 1 second). Qualitative electromyography (EMG) was performed in at least two muscles and quantitative EMG with multi-motor unit action potential (MUAP) analysis was obtained when possible. Vastus lateralis muscle biopsy samples underwent different histological and histochemical analysis. Based on histological findings, panels of antibodies/microbiological evaluation were chosen to characterize the underlying pathology. Result(s): Ten patients were included in the study. MRC sum score range was between 18 and 45. Nine patients underwent a neurophysiological diagnosis of CIM, while only one showed concomitant sensory involvement (CIPM). The most common neurophysiological abnormality was reduced compound muscle action potentials amplitude with concomitant increased duration. Spontaneous activity was seen in one patient. MUAP analysis showed myopathic changes in 8 out of 10 subjects (reduced mean MUAP duration and/or increased percentage of lower-limit duration outliers) with different severity degrees. One patient presented only increased amount of polyphasic potentials, while one subject had normal needle examination. Muscular histopathological features were consistent with primary myopathy (CIM) in all cases: in particular, all patient presented loss of myosin filaments, muscle fiber necrosis and fiber atrophy. These abnormalities were present in each patient and variably expressed. Conclusion(s): Our study highlights the importance of neurophysiological evaluations in ICU patients to better characterize ICUAW conditions and to identify different electromyographic patterns because different expression of CIM typical histopathological features explains variability in neurophysiological findings. Copyright © 2022