Proceedings of The Physiological Society
University College London December 2005 (2006) Proc Physiol Soc 1, C18
Enhancing cortical excitability and motor behaviour in chronic stroke with theta burst stimulation
Talelli, Penelope; Greenwood, Richard James; Rothwell, John Christofer;
1. Institute of Neurology, London, United Kingdom. 2. The National Hospital for Neurology and Neurosurgery, London, United Kingdom. 3. Institute of Neurology, London, United Kingdom.
Recovery of human hand function after stroke depends on reorganisation of the motor system around the area of the lesion. Recent functional imaging studies have suggested that as patients recover hand movements they show increased activation of perilesional cortex on the stroke hemisphere and reduced activation of the non-stroke hemisphere. Experiments with repetitive transcranial magnetic stimulation (rTMS) in healthy subjects have shown that it is possible to induce changes in the excitability of motor areas of cortex that outlast the stimulation by 30-60 min. The question we ask here is whether we can use these methods to induce optimal patterns of reorganisation after stroke. The present experiments represent a proof of principle study that tests the effectiveness of a single session of rTMS, given using a theta burst protocol (TBS), on physiological and behavioural measures of hand function. Six patients with a first ever supratentorial motor stroke and incomplete recovery of the hand, were studied at least 1 year after the ictus. All patients were tested under 3 conditions: inhibitory TBS over the non-stroke side (continuous pattern, 80% aMT, 300 pulses); facilitatory TBS over the stroke side (intermittent pattern, 80%aMT, 600 pulses); and sham stimulation. Changes in corticospinal excitability were assessed by single pulse TMS both on the stroke (MEP amplitude during rest and contraction, input-output curves at rest) and the non-stroke side (MEP amplitude at rest). The effect on motor behaviour of the hand was tested using two different reaction time protocols(simple and choice reaction times to a somatosensory stimulus applied to the left or right hand). Changes in reaction times were sought at 10, 20 and 30 min after the stimulation. After facilitation (iTBS) of the stroke hemisphere the amplitude of active MEPs on the affected side increased in all patients by up to 50% (P<0.001). Input-output curves were also increased in the majority of the subjects. When compared to the sham condition, the affected hands were slightly but significantly faster in the simple reaction task throughout the testing period (P=0.033), while there was no difference in the choice reaction times. In contrast, inhibition (cTBS) of the non-stroke side had no consistent effect on either the reaction times or the electrophysiology of the affected side even though it suppressed the MEPs evoked in the unaffected hand. There were no adverse events. A single session of facilitatory TBS (iTBS) over the stroke side in chronic patients increased corticospinal excitability and improved simple reaction times in the affected hand for 40 min. In the future we hope to give patients physical therapy during this time window of increased excitability. This may improve or speed up the long term effects of conventional treatment.
Where applicable, experiments conform with Society ethical requirements