Samusyte, G;
Bostock, H;
Rothwell, J;
Koltzenburg, M;
(2018)
Short-interval intracortical inhibition: Comparison between conventional and threshold-tracking techniques.
Brain Stimulation
, 11
(4)
pp. 806-817.
10.1016/j.brs.2018.03.002.
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Abstract
BACKGROUND: Short-interval intracortical inhibition (SICI) is conventionally measured as the relative amplitude reduction of motor evoked potentials (MEPs) by subthreshold conditioning stimuli. In threshold-tracking SICI (T-SICI), stimulus intensity is instead adjusted repeatedly to maintain a constant MEP and inhibition is measured as the relative threshold increase. T-SICI is emerging as a useful diagnostic test, but its relationship to conventional amplitude SICI (A-SICI) is unclear. OBJECTIVE: To compare T-SICI and its reliability with conventional A-SICI measurements. METHODS: In twelve healthy volunteers (6 men, median age 30 years), conventional and T-SICI were recorded at conditioning stimuli (CS) of 50-80% resting motor threshold (RMT) and interstimulus interval of 2.5 ms. Measurements were repeated on the same day and at least a week later by a single operator. RESULTS: Across the CS range, mean group T-SICI showed a strong linear relationship to the mean group values measured by conventional technique (y = 29.7-0.3x, R2 = 0.99), but there was considerable interindividual variability. At CS 60-80% RMT, T-SICI had excellent intraday (intraclass correlation coefficient, ICC, 0.81-0.92) and adequate-to-excellent interday (ICC 0.61-0.88) reproducibility. Conventional SICI took longer to complete (median of 5.8 vs 3.8 min, p < 0.001) and tended to have poorer reproducibility (ICC 0.17-0.42 intraday, 0.37-0.51 interday). With T-SICI, smaller sample sizes were calculated for equally powered interventional studies. CONCLUSION: The close relationship between conventional and T-SICI suggests that both techniques reflect similar cortical inhibitory mechanisms. Threshold-tracking measurements of SICI may be able to improve reproducibility, to shorten acquisition time and to reduce sample sizes for interventional studies compared with the conventional technique.
| Type: | Article |
|---|---|
| Title: | Short-interval intracortical inhibition: Comparison between conventional and threshold-tracking techniques |
| Location: | United States |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1016/j.brs.2018.03.002 |
| Publisher version: | https://doi.org/10.1016/j.brs.2018.03.002 |
| Language: | English |
| Additional information: | Copyright © 2018 The Authors. Published by Elsevier Inc. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). |
| Keywords: | Threshold-tracking TMS, Short-interval intracortical inhibition, Reliability, Intraclass correlation coefficient, Coefficient of repeatability |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology UCL > Provost and Vice Provost Offices > School of Life and Medical Sciences > Faculty of Brain Sciences > UCL Queen Square Institute of Neurology > Clinical and Movement Neurosciences |
| URI: | https://discovery.ucl.ac.uk/id/eprint/10046683 |
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