The diagnostic relevance of recording motor evoked potentials after magnetic stimulation of midclavicular point was evaluated in 47 healthy adults and 2 patients with brachial plexus lesion. The object of this study was to establish a normal protocol and values for magnetic stimulation of the brachial plexus region.
Compound muscle action potentials were obtained with abductor pollicis brevis, abductor digiti minimi, biceps, triceps, deltoid, infraspinatus, latissimus dorsi, and rhomboid major recordings bilaterally.
The results were as follows:
1) The onset latencies of compound muscle action potentials(CMAP) obtained by magnetic stimulation on midclavicular point showed no significant difference between two sides.
2) The amplitudes obtained with magnetic stimulation showed no significant difference between two sides.
3) The onset latencies of compound muscle action potentials obtained by magnetic stimulation on midclavicular point in 2 patients showed absence of CMAP with abductor digiti minimi recording and prolonged latencies for abductor pollicis brevis, biceps, triceps, deltoid recordings. These findings were consistent with clinical topography and severity of brachial plexus.
The magnetic stimulation can be used in addition to electrodiagnostic tests currently available for the evaluation of the brachial plexus.
