Acute weakness in the ICU-electrophysiological and pathological findings

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Objective

To describe electrophysiological and histopathological findings in patients with acute weakness, which developed in the ICU during the course of critical illness.

Materials and methods

During a 15 month period, all patients with clinical signs of acute onset quadruparesis were studied prospectively. In nine critically ill patients of mean age 55 (21–78) years, clinical examination, electrophysiological studies (conduction studies of peripheral motor and sensory nerves, needle electromyography, repetitive stimulation) and skeletal muscle biopsies were performed. None of the patients had any neuromuscular abnormality in anamnesis.

Results

Clinical examination: all of our patients had signs of quadruparesis and generalized hypo- or areflexia of tendon reflexes and prolonged dependence on the ventilator. Electrophysiology: compound muscle action potentials (CMAP) were markedly reduced (mean 18 ± 15% of normal values) or totally absent in all patients. Sensory nerve action potentials (SNAP) were reduced or absent in six patients, only two patients had normal SNAP. Motor nerve conduction velocities were normal or slightly reduced in six patients, two patients had significantly lower motor nerve conduction velocities. Sensory nerve conduction velocities were normal, there was only slight reduction in one patient. Needle electromyography showed fibrillations and positive sharp waves in eight patients. No pathology in repetitive stimulation was found. Histopathology: all skeletal muscle biopsies showed pathologic alterations. Fiber diameters varied from atrophy to normal. In muscle fibers, internal nuclei, fiber splitting and focal regressive changes with increased activity of lysosomal acid phosphatase were found. In 50% of cases, regenerating fibers were present. Endomysial fibrosis was common. All the changes were classified as myogenic, no convincing signs of neurogenic atrophy were noticed. One patient revealed disuse atrophy.

Conclusions

We found electrophysiologic signs of axonal sensory-motor polyneuropathy in all our patients. In spite of that, no neurogenic changes in the muscle were found in the biopsies, the changes in skeletal muscles had a myopathic pattern. These data suggest that in acute quadruplegia of the critically ill, both the nerve and the muscle are affected simultaneously.