Introduction: Critical illness patients may show marked weakness acquired in the Intensive Care Unit (ICU). There are some disagreements about the myopathic versus neuropathic damage in this condition, presumably due to the lack of reliable diagnostic criteria.
Aims: To report the neurophysiological findings in critical patients, to classify them in groups according to the electro-physiological data of myopathy, and to ascertain the rapport between the neurophysiological classification of myopathy and the muscle biopsy results.
Patients and methods: A prospective assessment of 33 ICU patients with marked weakness by means of needle electro-myography, electroneurography, and percutaneous muscle biopsy was carried out. Direct muscle stimulation was performed in 9 patients and repetitive nerve stimulation in 14 cases. RESULTS. According to neurophysiological criteria, patients were classified in 3 groups: definite (33%), probable (46%), and uncertain (21%) myopathy. The most conspicuous myopathic pathological findings including fibrillar atrophy and necrosis, vacuoles, and myosin and mitochondrial anomalies, were observed in both, definite and probable groups (26 patients). In 17 of these cases, low amplitude of the compound motor action potentials and normal sensory nerve action potentials were found. Axonal sensory-motor neuropathy was present in 11 patients, concomitant with neurophysiological data of myopathy in 7 cases.
Conclusions: Based on the neurophysiological criteria for the assessment and classification of acquired weakness in critically ill patients, myopathy is highly predominant over the neuropathic impairment. Histopathological findings are closely related to the electrophysiological diagnosis of myopathy. Neither neurophysiological nor pathological data support a hypothetic motor axonal neuropathy in this series.