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Updated: Jun 10, 2026
Manual Muscle Testing: A Method of Measuring Extremity Muscle Strength Applied to Critically Ill Patients
Published on: April 12, 2011
A comparison of EMG and muscle biopsy in ICU weakness
Hakim Raghig1, G Bryan Young, Robert Hammond
1Department of Clinical Neurological Sciences, The University of Western Ontario, London, ON, Canada.
Background:
Patients can become weak in ICU from various etiologies and mechanisms. Establishing the diagnosis is invaluable for prognostic determination and specific management. We evaluated the relative contributions of clinical, laboratory, electomyographic studies (EMG), and percutaneous muscle biopsy (MB) in determining the cause of muscular weakness that developed in a series of patients while in ICU. The principal objective is to determine the concordance between results of the EMG and MB studies in patients with ICU-acquired weakness.
Methods:
We retrospectively reviewed hospital charts for clinical features, and results of laboratory investigations, EMG studies, and MB results in 11 consecutive patients who underwent both EMG and MB while in ICU. We excluded patients with previously diagnosed muscular weakness or neurological conditions prior to ICU admission.
Results:
Electomyographic studies suggested axonal neuropathy in three cases; MB confirmed this in one case, but showed myopathic features in two. EMG showed myopathic features in two cases; MB confirmed this in both cases. EMG suggested neuromyopathy in four cases, confirmed by MB in one case only. One patient, subsequently diagnosed with myasthenia gravis with decrement on repetitive nerve stimulation and positive anti-acetylcholine receptor antibodies, had non-specific findings on MB.
Conclusions:
EMG and MB are complementary investigations. They agreed completely in four cases but in the rest of the cases there was uncertainty as to the primary process based on the results of electrophysiological studies. In only one case was there a clear discordance between electrophysiological studies and muscle biopsy. We suggest that muscle biopsy should be performed more frequently as it establishes the diagnosis and thus the prognosis with more certainty than EMG in some patients. EMG is much more difficult in the ICU and more susceptible to confounding technical factors, but remains indispensable for the diagnosis of neuromuscular transmission defects.
