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Transcranial Theta-Burst Stimulation

Transcranial magnetic stimulation (TMS) has already been described in section 2.6. Transcranial theta-burst stimulation (TBS) differs from TMS in that the stimulation includes patterned (vs non-patterned in repetitive TMS) bursts of shorter duration pulses. Conceptually, intermittent TBS (iTBS, Martin JH 2016; Huang YZ et al 2005) may produce a more robust strengthening of synaptic activity in residual neural pathways.

Table 9 Studies of Transcranial Theta-Burst Stimulation for Reducing Spasticity

Author Year

Country
Research Design

Score
Total Sample Size

MethodsOutcome
Gharooni et al. 2018

UK

RCT Crossover

PEDro=6

NInitial=11

NFinal=10

 

Population: SCI (n=10): Mean age=46.8±11.9yr; Gender: males=8, females=2; Level of injury: C=10; Mean time since injury=0.95±1.18; AIS scale: B=1, C=4, D=5.

Intervention: Participants were randomized to receive either intermittent transcranial theta-burst stimulation (iTBS) or sham first. A 90 mm circular coil placed on the Cz position of the skull delivered iTBS. Three stimuli at 50 Hz were repeated at 200 millisecond intervals for 2 seconds. An inter-train interval of 8 seconds was repeated 20 times for a total of 600 pulses in 200 seconds. Stimulator output intensity was determined as 80% of the resting membrane threshold as observed by a muscle twitch in the upper limbs during resting state. Sham iTBS consisted of the same protocol with the exception that the coil was turn 90 degrees about its vertical midline axis to ensure no brain stimulation. A 2-wk washout period was used in between crossover. Each condition consisted of 10 sessions over 2 wk. Outcome measures were assessed at baseline and 2 wk post intervention.     

Outcome Measures: Combined upper-limb Modified Ashworth Scale of bilateral elbow and wrist extension and flexion (MAS); Leeds Arm Spasticity Impact Scale (LASIS); Visual Analogue Scale for spasticity (VAS-S).

1.     While there was an observed reduction in MAS, it does not appear to be large enough to improve participants’ perception of spasticity or improvement in function as measured by LASIS and VAS-S.

2.     Intervention effects (adjusted for baseline) include; mAS=-2.67 (CI: -5.17 to -0.17), LASIS=0.16 (CI: -0.18 to 0.48), VAS-S=-1.99 (CI: -21.00 to 17.01).

Nardone et al. 2017

Austria

RCT Crossover

PEDro=7

N=10

 

Population: SCI (n=10): Mean age=42.8±11.9yr; Gender: males=7, females=3; Level of injury: C=6, T=4; Mean time since injury=8.3±4.5yr; AIS scale: C=4, D=6.

Intervention: Participants were randomly allocated to receive either intermittent theta burst stimulation (iTBS) or sham iTBS first. Interventions were separated by a wash out period of at least 2 mo. iTBS was delivered over the scalp site corresponding to the motor cortex area of the dominant leg at an intensity of 80% active motor threshold. Ten bursts (composed of 3 stimuli at 50 Hz) were repeated with a theta frequency of 5 Hz every 10 seconds for a total of 600 stimuli/200 seconds. The same protocol was utilized for the sham iTBS, except that the coil was rotated by 90 degrees so that no current was induced in the brain. Both interventions were administered daily for 10 days each. Outcome measures were assessed at baseline, post intervention, and at 1-wk and 4-wk follow ups.    

Outcome Measures: Spinal Cord Assessment Tool for Spasticity (SCAT); modified Ashworth Scale (mAS).

1.     Results indicate a significant treatment X time interaction effect for mAS and SCAT (p<0.001 for both).

2.     There was also a significant time effect for mAS and SCAT in the iTBS group (p<0.001 for both). More specifically, there was a decrease in mAS and SCAT followed by a return to baseline.

3.     There were no significant time effects for the sham iTBS group for both mAS and SCAT (p>0.05).

Discussion

Intermittent theta-burst stimulation is a new intervention being applied to people with incomplete cervical SCI to potentially improve upper limb spasticity, pain and sensorimotor function. Gharooni et al (2018; RCT) administered a total of 600 pulses in 200 seconds 3 stimuli at 50Hz, repeated at 200 ms intervals for 2 seconds and interspersed by 8 seconds between pulse trains). Sham iTBS was the same except with the stimulation coil rotated 90° from the participants midline axis to ensure no brain stimulation. Sessions of iTBS (or sham iTBS) were delivered 10 times over 2 weeks with a 2-week washout period before crossover to the alternative intervention. Three spasticity outcome assessments (modified Ashworth Scale (MAS), Leeds Arm Spasticity Impact Scale (LASIS) and a Visual Analogue Scale for spasticity (VAS-S)) were applied to bilateral elbow and wrist extension and flexion. Results were reported to support a non-significant reduction in MAS compared to sham iTBS and that were not of a magnitude that could be perceived by participants as improved function (via VAS-S and LASIS).

Nardone et al (2017), using SCAT (Spinal Cord Assessment Tool for Spasticity) and MAS and a stimulation protocol as described above (Gharooni et al 2018) with the exception that the washout period was 2 months (vs 2 weeks), found a significant reduction of upper extremity spasticity (p<0.001 for both SCAT and MAS) that returned to baseline within one week.

Conclusions

There is level 1b evidence (Nardone et al 2017; RCT) that iTBS reduces upper extremity spasticity for up to 1 week.

Treatment with intermittant theta-burst stimulation is likely to reduce upper extremity spasticity for up to 1 week.