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Origin of ICU acquired paresis determined by direct muscle stimulation

¹ Service de Physiologie – Explorations Fonctionnelles, CHU Henri Mondor, Assistance Publique-Hôpitaux de Paris, Créteil, France
² Service de Réanimation Médicale, CHU Henri Mondor

Correspondence to:
Correspondence to:
Dr Jean-Pascal Lefaucheur
Service de Physiologie – Explorations Fonctionnelles, Centre Hospitalier Universitaire Henri Mondor, 51 avenue du Marechal de Lattre de Tassigny, 94010 Creteil, France; jean-pascal.lefaucheur{at}hmn.ap-hop-paris.fr

Background: Acquired diffuse paresis in an intensive care unit (ICU) can result from critical illness myopathy or polyneuropathy. Clinical examination and conventional neurophysiological techniques may not distinguish between these entities.

Objective: To assess the value of direct muscle stimulation (DMS) to differentiate myopathic from neuropathic process in critically ill patients with diffuse severe muscle weakness.

Methods: 30 consecutive patients with ICU acquired diffuse motor weakness were studied. Responses of the right deltoid and tibialis anterior muscles to DMS and to motor nerve stimulation (MNS) were studied and compared with results of conventional nerve conduction studies and concentric needle electromyography (EMG). An original algorithm was used for differential diagnosis, taking into account first the amplitude of the responses to DMS, then the MNS to DMS amplitude ratio, and finally the amplitude of the sensory nerve action potentials recorded at the lower limbs.

Results: Evidence of neuropathy and myopathy was found in 57% and 83% of the patients, respectively. Pure or predominant myopathy was found in 19 patients. Other results were consistent with neuromyopathy (n = 5) and pure or predominant neuropathy (n = 2). Four patients had normal results with stimulation techniques, but spontaneous EMG activity and raised plasma creatine kinase suggesting necrotic myopathy.

Conclusions: A neurophysiological approach combining DMS and conventional techniques revealed myopathic processes in a majority of ICU patients. Reduced muscle fibre excitability may be a leading cause for this. The diagnosis of myopathy in ICU acquired paralysis can be established by a combination of DMS, needle EMG, and plasma creatine kinase.

Abbreviations: CIM, critical illness myopathy; CIP, critical illness polyneuropathy; CK, creatine kinase; CMAP, compound muscle action potential; DMS, direct muscle stimulation; DMS_amp, response amplitude to direct muscle stimulation; DMS_lat, latency of direct muscle stimulation; ICU, intensive care unit; MNS, motor nerve stimulation; MNS_amp/DMS_amp ratio, ratio of response amplitude from motor nerve stimulation to direct muscle stimulation; MNS_lat, latency of motor nerve stimulation; SNAP, sensory nerve action potential; SNAP_amp, mean amplitude of the sensory nerve action potentials

Keywords: critical care; electromyography; myopathy; nerve conduction; neuropathy

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				B Guarneri, G Bertolini, and N Latronico Long-term outcome in patients with critical illness myopathy or neuropathy: the Italian multicentre CRIMYNE study J. Neurol. Neurosurg. Psychiatry, July 1, 2008; 79(7): 838 - 841. [Abstract] [Full Text] [PDF]

				W. D. Schweickert and J. Hall ICU-Acquired Weakness Chest, May 1, 2007; 131(5): 1541 - 1549. [Abstract] [Full Text] [PDF]

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