Higher Efficacy and Less Inter-individual Variability in QPS than TBS: Head to Head Comparison Study

Background: Two distinct protocols of patterned repetitive transcranial magnetic stimulation (rTMS), the theta burst stimulation (TBS) which uses biphasic waveform pulses and quadripulse stimulation (QPS) which uses monophasic waveform pulses, are widely known as effective protocols to induce motor cortical plasticity in humans. However, the interindividual variability of after-effects were also present in both protocols. No data are available concerning the efficacy and the variability comparison between TBS and QPS.
Objective: To compare the efficacy and inter-individual variability between both protocols. We hypothesized that QPS would be more effective and have less variable in comparison to TBS.
Methods: This study directly compared effects between facilitatory iTBS and QPS5 and between inhibitory cTBS and QPS50 in the same 31 healthy participants. Motor evoked potentials (MEPs), measured every 5 min for up to one hour after the intervention, were compared to baseline value taken before the intervention. Interindividual variabilities were categorized to responder, non-responder, and opposite responder based on natural variation responses to sham stimulation from 16 different volunteers (8 sham-TBS and 8 sham-QPS).
Results: One-way ANOVA showed time had significant effects on the size ratio of QPS5, QPS50, and cTBS (p < 0.05). Two-ways ANOVA showed facilitatory effects of QPS5 were greater than those of iTBS (p = 0.036), and inhibitory effects of QPS50 were much stronger than those of cTBS (p = 0.001). The responder rate of QPS was higher than that of TBS (QPS5 vs. iTBS: 68% vs. 39%, QPS50 vs. cTBS: 77% vs. 42%). Opposite-responder rate was smaller in QPS than TBS (QPS5 vs. iTBS: 3% vs. 10%, QPS50 vs. cTBS: 0% vs. 3%).
Conclusions: The present study confirmed the more effectiveness and less variability of QPS as compared with TBS by head to head direct comparisons between these two methods.