3-2-07. Clinical application of the measurement of muscle fiber conduction velocity using direct muscle stimulation for critical illness myopathy (CIM)

Abstract

Measurement of the muscle fiber conduction velocity (MFCV) using direct muscle stimulation has been considered to be useful for the evaluation of critical illness myopathy (CIM), although there are rather few reports on this issue. Subjects consisted of 2 normal volunteers, 4 patients with myositis, and 1 patient with CIM. Stimulation was given to the muscle using a monopolar needle and the muscle fiber action potentials (MFAPs) was recorded using a concentric needle electrode. MFCV was calculated based on the onset latencies of the MFAPs recorded at different intramuscular locations. As results, MFCV was 4–5 m/s in the CIM patient. It was 4.2 and 4.8 m/s on average in control subjects, and was 3.6–4.3 m/s in patients with myositis. The CIM patient presented with markedly prolonged duration of the compound muscle action potential (CMAP). Normal MFCV in the CIM patient may suggest that the prolonged CMAP duration in CIM may not be due to the slowed MFCV, but to other mechanisms. MFCV measurement is a difficult technique, and its diagnostic role is yet to be documented, including for CIM.