The Modulatory Effect of Low-intensity Priming Intermittent Theta Burst Stimulation on Motor Cortex Poststroke: a Concurrent TMS-EEG Study

The Hong Kong Polytechnic University20 enrolled

Overview

Background: The optimization of the intensity of priming theta burst stimulation increases the probability of success in a randomized controlled trial. We hypothesize that priming intermittent theta burst stimulation (iTBS) with a low-intensity continuous theta burst stimulation (cTBS) will yield superior effects than our original priming protocol in healthy adults and patients after stroke. Methods: 20 stroke patients will undergo three separate experimental conditions: a low-intensity priming stimulation (55% resting motor threshold \[RMT\] cTBS+70% RMT iTBS), a conventional-intensity priming stimulation (70% RMT cTBS+70% RMT iTBS), and a nonpriming control. The alterations in cortical excitation/inhibition and its impacts on motor behaviors will be evaluated following stimulation. Significance: The findings will inform future clinical trials investigating the optimized priming iTBS in promoting poststroke recovery.

Study Type

INTERVENTIONAL

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Interventions

Transcranial magnetic stimulationDEVICE

A standard 600-pulse TBS \[16\] will be administrated using a MagPro X100 stimulator (MagVenture, Denmark) and a 65-mm figure-of-eight coil. The measurement of the motor hotspot and individual RMT will be in accordance with our established methodology \[3, 9\]. For patients with stroke, the intensity of real stimulation will be 55% or 70% RMT of the unaffected M1 \[17\], depending on their assigned condition. Sham stimulation will be delivered using the same coil with 20% RMT of the unaffected M1 \[4, 6\]. The priming and conditioning sessions will be delivered to the ipsilesional M1 sequentially. In line with previous works, the interval between them will be 10 minutes \[2, 3\]. For healthy adults, the stimulation will be applied exclusively to the non-dominant (right) M1.

Eligibility

Sex: ALLMin age: 18 YearsMax age: 80 YearsHealthy volunteers:

Medical Language ↔ Plain English

Inclusion Criteria: * (1) have a diagnosis of ischemic or hemorrhagic stroke, with time after stroke onset≥6 months; * (2) aged between 18 and 80 years old; * (3) with residual upper limb functions from 2-7 levels in the Functional Test for the Hemiplegic Upper Extremity, i.e., moderately impaired overall upper extremity functions. * (4) able to give informed written consent to participate in the study. Exclusion Criteria: * (1) any contraindications to TMS (screened by the safety checklist by Rossi \[12\]); - * (2) any concomitant neurological disease; * (3) any sign of moderate-to-severe cognitive problems, i.e., Montreal cognitive assessment (MoCA)\<19/30 * (4) Modified Ashworth score\>2 in hand, wrist or elbow extensor muscle in the hemiparetic upper extremity. In addition, a group of age-matched, right-hand dominant healthy adults without any known neurological diseases will be enrolled. Healthy adults with any contraindications to TMS will be excluded.

Outcomes

Primary Outcomes

The isometric force control task

Force data will be collected using a load cell (Force sensor ZNHM, Chino sensor, China). To assess maximal voluntary contraction (MVC) of the hand grip, three trials will be conducted using both paretic and nonparetic hands (or the dominant and non-dominant hands for healthy controls). Subsequently, separate tests will be performed to measure submaximal isometric force at 20% and 50% of the maximal voluntary force (MVF). Each trial will last for 20 seconds, with a 60-second intertrial interval to prevent fatigue. A total of 5 trials will be conducted for each level of muscle contraction. Muscle strength will be evaluated by calculating the mean force output, while the variability of force control will be assessed by calculating the coefficient of variation of force, i.e., the standard deviation of force/mean force output × 100%.

Time frame: Baseline

The isometric force control task

Time frame: 15-min after completion of stimulation sessions

Transcranial magnetic stimulation-evoked potential

Single pulses evoked an initial response in electroencephalogram, followed by a series of time- and phase-locked positive and negative deflections which could spread to the connected brain areas. The evoked potential is called transcranial magnetic stimulation-evoked potential.