P 163 Combining TMS and EEG – a new tool to assess motor system integrity after stroke

摘要

Background Despite the wealth of neuroimaging studies regarding stroke pathophysiology and recovery after stroke, there is still a lack of clinically relevant biomarkers that allow to predict the potential of functional recovery and treatment response at individuals’ level. Anovel approach is to test motor system integrity by means of combining transcranial magnetic stimulation (TMS) and electroencephalography (EEG). By recording TMS-evoked potentials (TEP), the cortical response to TMS, both local and network responses can be recorded and analyzed in individual subjects (). Thus TMS-EEG could not only provide information about neuronal properties in lesioned regions but also yield to information about the integrity of the entire motor system. We therefore used TMS-EEG to investigate TEPs in the lesioned hemisphere and their spread to contralesional motor regions in early subacute stroke. Moreover these changes are linked to patients’ behaviour and clinical state in order to draw conclusions about the relationship of TEPs, current impairment and motor recovery. Methods Ten first-ever stroke patients (time since stroke: 10 days) with hand motor deficits and a group of aged-matched healthy controls participated in this study.Motor impairment and neurological status was determined by relative grip strength, standardized motor scores (Motricity Index (MI), Action Research Test (ARAT)) and the clinical National Institute Health Stroke Scale (NIHSS). TMS-EEG was recorded online using a TMS-compatible 64-channel EEG-System (BrainProducts). Neuronavigated TMS was applied as single pulses with 80% of resting motor threshold (RMT) over the ipsilesional primary motor cortex (M1). After preprocessing, TMS pulses were averaged and TEP components were analyzed under the coil over the electrode (C3/C4) representing ipsilesional M1. Results For the ipsilesional hemisphere we found a significant between-group difference with respect to the amplitude of the N45 TEP component. Stroke patients showed a less pronounced N45 than healthy controls ( p 0.005).The amplitude of N45 correlated negatively with the motor scores achieved at the MI ( r = ?0.7, p = 0.05), i.e., more impaired patients had a less pronounced ipsilesional N45 amplitude. In addition the amplitude of P30 correlated negatively with the NIHSS at admission to the hospital ( r = ?0.736, p = 0.015). Furthermore, we found a between-group difference regarding the N100 amplitude, which was significant smaller in stroke patients compared to controls ( p 0.05). Interestingly, changes in N100 were not correlated with motor impairment. Conclusion We here found evidence that especially early components of the TMS-evoked potential are strongly linked to the motor impairment of stroke patients, while later components like the N100seem to reflect a more general disturbance of neural processing after stroke. Hence, TMS-EEG has the potential to provide novel biomarkers to assess and monitor stroke recovery. ]]>