Stevens et al listed criteria for the diagnosis of Critical Illness Myopathy (CIM) in a patient with intensive care unit-acquired weakness. The authors are from the Johns Hopkins University, Uniformed Services University of Health Sciences, Ohio State University, Centre Hospitalier de Poissy-Saint-Germain and University of Versailles Saint-Quentin en Yvelines Garches.


The criteria are modified from those of Lacomis et al.


Diagnostic criteria for CIM:

(1) The patient meets the criteria for ICUAW (see previous section).

(2) Sensory nerve action potential (SNAP) amplitudes are greater than 80% of the lower limit of normal (LLN) in 2 or more nerves.

(3) Needle electromyogram shows short duration, low amplitude motor unit potentials with early or normal full recruitment in >= 2 muscle groups.

(4) Direct muscle stimulation shows reduced excitability in >= 2 muscle groups.

(5) A muscle biopsy shows hisotlogic changes consistent with myopathy.



• The needle electromyograms may (or may not) show fibrillation potentials.



1 and 5

probable CIM

1 and 2 and (3 or 4)

probable CIM

1 and 2 and (3 or 4) and 5

definite CIM


Differential diagnosis:

(1) cachexia

(2) rhabdomyolysis

(3) disuse muscle atrophy

(4) decompensation of a primary muscle disorder

(5) steroid myopathy


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