Intra subject variation and correlation of motor potentials evoked by transcranial magnetic stimulation

Background Characterising intra and inter-subject variability of motor-evoked potential (MEP) measurements from transcranial magnetic stimulation (TMS) is key to its development as a diagnostic tool. Methods We performed three experiments to elucidate MEP variability within subjects: (i) repeated me...

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Bibliographic Details
Published in:Irish journal of medical science 2011-12, Vol.180 (4), p.873-880
Main Authors: Roy Choudhury, K., Boyle, L., Burke, M., Lombard, W., Ryan, S., McNamara, B.
Format: Article
Language:English
Subjects:
Adult
Analysis of Variance
Electromyography
Evoked Potentials, Motor - physiology
Family Medicine
General Practice
Humans
Internal Medicine
Medicine
Medicine & Public Health
Muscle, Skeletal - physiology
Original Article
Pyramidal Tracts - physiology
Transcranial Magnetic Stimulation
Young Adult
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Summary:Background Characterising intra and inter-subject variability of motor-evoked potential (MEP) measurements from transcranial magnetic stimulation (TMS) is key to its development as a diagnostic tool. Methods We performed three experiments to elucidate MEP variability within subjects: (i) repeated measurements at different levels of stimulation and muscle activation, (ii) simultaneous measurements at pairs of ipsilateral and contralateral muscles, (iii) simultaneous measurements of contralateral muscles when one is activated. Results Cube root transformation of MEP data produces approximately constant coefficient of variation with Gaussian distribution and no significant autocorrelation between repeat measurements. After adjustment of intersubject variability, correlation between simultaneous muscle pairs was insignificant ( p  = 0.36). Highly significant effects were observed due to increase in intensity of stimulation: (0.07, 0.23) mV, p  
ISSN:0021-1265
1863-4362
DOI:10.1007/s11845-011-0722-4