The After-Effect of Accelerated Intermittent Theta Burst Stimulation at Different Session Intervals

Abstract

Objective: The study aims to investigate the after-effect of three sessions of intermittent theta-burst stimulation (iTBS) on motor cortical excitability. The iTBS was induced over the primary motor cortex (M1) at different time intervals. Methods: The study has a crossover design. Sixteen participants were assigned to three groups and received different accelerated iTBS (aiTBS) protocols during each visit: (1) three continuous sessions with no interval (iTBS18000); (2) three iTBS sessions with 10-min intervals (iTBS600 × 3∗10); and (3) three iTBS sessions with 30-min intervals (iTBS600 × 3∗30). As washout period, each visit is separated by at least 7 days. We measured the motor cortical excitability changes and intracortical inhibition. Results: A dose of 1,800 pulses of aiTBS per day is tolerable. The iTBS1800 led to a reduced cortical excitability; whereas iTBS600 × 3∗10 and iTBS600 × 3∗30 enhanced cortical excitability to a differential extent. After a total dose of 1,800 pulses, iTBS600 × 3∗30 exhibited the longer effect and highest percentage of individuals with enhanced cortical excitability. Conclusion: The results suggest that aiTBS protocols at different time intervals result in different motor cortical excitability after-effects.