A comparison of two methods for estimating 50% of the maximal motor evoked potential

作者：Pitcher Julia B^*; Doeltgen Sebastian H; Goldsworthy Mitchell R; Schneider Luke A; Vallence Ann Maree; Smith Ashleigh E; Semmler John G; McDonnell Michelle N; Ridding Michael C

来源：Clinical Neurophysiology, 2015, 126(12): 2337-2341.

DOI：10.1016/j.clinph.2015.02.011

• Corticomotor stimulus-response curves
• Resting motor threshold
• Ageing
• Children
• Motor evoked potential
• First dorsal interosseous

Objectives: Two commonly-used methods for setting stimulus intensities in transcranial magnetic brain stimulation studies were compared to determine which best approximated a motor evoked potential (MEP) of 50% of the maximal MEP amplitude (SI50); a suprathreshold intensity relative to resting motor threshold (rMT) or adjusting the intensity to evoke an MEP amplitude of 1 mV.
Methods: Corticomotor stimulus-response curves and rMT for the right first dorsal interosseous (FDI) muscle of 176 subjects (aged 10-74 years) were retrospectively analysed.
Results: Regardless of subject age or sex, SI50 occurred at 127.5 +/- 11.3% rMT. Except in young children, MEPs of 1 mV were significantly smaller than those evoked at SI50.
Conclusions: In the inactive FDI muscle, a stimulus intensity of 127-128% rMT consistently gives the best approximation of SI50 in most subjects, except perhaps young children.
Significance: Setting TMS stimulus intensities relative to rMT provides a less variable inter-subject comparator, with respect to individual differences in corticomotor input-output characteristics, than adjusting the stimulator output to give an absolute MEP magnitude.

• 出版日期2015-12