Department of Exercise Sciences


Combining Theta Burst Stimulation With Training After Subcortical Stroke

Suzanne J. Ackerley, Cathy M. Stinear, P. Alan Barber and Winston D. Byblow.
Published in Stroke (2010) 41, 1568-72.

Introduction

One of the most pressing challenges for neurorehabilitation is to develop practical ways to promote neural plasticity to improve recovery after stroke. Theta burst stimulation (TBS) is a form of non-invasive brain stimulation that can modulate primary motor cortex (M1) activity but its effects when combined with motor training, akin to its potential use in rehabilitation, had not been explored.

 

Aim

The aim of this study was to determine the clinical and neurophysiological effects of M1 TBS and standardised motor training on upper-limb function of patients with chronic stroke.

 

Method

  • Patients: 10 hemiparetic stroke patients. See Table.
  • Intervention: Intermittent TBS of the ipsilesional (stroke-affected) M1, continuous TBS of the contralesional (opposite) M1 and sham TBS were delivered in separate sessions in conjunction with standardised training of a precision grip task with the paretic upper limb.
  • Assessment: Before and after TBS and training: grip-lift kinetics (preload duration and force) were measured with a grip-lift device; corticomotor excitability (how easy it is to activate neurons in the cortex) was measured by evaluating motor evoked potential (MEPs) elicited from first dorsal interosseous (FDI) muscles with single-pulse transcranial magnetic stimulation (TMS); and upper-limb function was measured with the action research arm test (ARAT).
Ackerley-2010-Table

 

Results

  • Training after real TBS improved paretic-hand grip-lift whereas training after sham TBS resulted in deterioration of grip-lift (see Figure 2A and B). Preload force (the amount of force, in N, placed on the device before lifting) increased when training followed sham TBS (P < 0.05), indicating fatigue, but not following real TBS (P > 0.05). Preload duration (the time taken, in ms, to establish grip) shortened after cTBS and training (P = 0.026), with a similar trend after iTBS (P = 0.058).
  • Corticomotor excitability of ipsilesional M1 increased after intermittent TBS (P = 0.029) but decreased after continuous TBS to the opposite M1 (P = 0.049, not significant corrected).
  • Action Research Arm Test scores deteriorated when training followed continuous TBS of the contralesional M1, and this was correlated with reduced ipsilesional corticomotor excitability.
Ackerley-2010-Figure-2

 

Interpretation

Generally, TBS and training led to task-specific improvements in grip-lift. Specifically, continuous TBS of the contralesional M1 led to an overall decrement in upper-limb function, indicating that the contralesional hemisphere may play a pivotal role in recovery after stroke. Work needs to be undertaken to identify patients who might benefit the most from receiving TBS before therapy.

 

Acknowledgements

We would like to thank Lynley Bradnam and Denise Miller for assistance during data collection. This research was funded by the Neurological Foundation of New Zealand and the Auckland Medical Research Council.