Event Abstract

Transcranial magnetic stimulation combined with electroencephalography in severely brain-injured patients: methodological aspects

  • 1 Coma Science Group, Cyclotron Research Center and Department of Neurology, University of Liège and University Hopital of Liege, Belgium, Belgium
  • 2 Department of Clinical Sciences “Luigi Sacco”, University of Milan, Italy

Background: Transcranial Magnetic Stimulation (TMS) combined with electroencephalography (EEG) may represent a powerful tool in probing cortical excitability and connectivity in humans (1, 2). However, the empirical demonstration that TMS-evoked EEG potentials (TEPs) reflect genuine cortical responses unconfounded from extra-cerebral artifacts is still missing.
Objective: to demonstrate that, by implementing the appropriate procedures, it is possible to record TEPs that purely reflect electrical responses of the cortical tissue to TMS.
Methods: TEPs were recorded by applying TMS/EEG integrated with a neuronavigation system in three brain-injured awake patients diagnosed as in a vegetative state/unresponsive wakefulness syndrome (VS/UWS) due to different etiologies. Specifically, one patient suffered from a diffuse cortical anoxic lesion, one suffered from a complete unilateral hemispheric traumatic lesion and one from bilateral vascular focal lesions.
Results: in all three patients, TEPs were absent when TMS was targeted on cortical lesions (as assessed by structural and functional imaging) and were present otherwise.
Conclusions: TEPs are genuine responses that can be recorded only when intact cortical tissue is stimulated. Assessing cortical excitability and connectivity in brain-injured patients requires accurate targeting by means of a neuronavigation system.

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Acknowledgements

We thank the Belgian National Funds for Scientific Research (FNRS); EU-grant-224328-PredictAD; PUR 2009 (University of Milan); Prin2008 (Italian Government), European Commission (Mindbridge, DISCOS, DECODER & COST); James S. McDonnell Foundation; Mind Science Foundation; Concerted Research Action (ARC 06/11-340); Public Utility Foundation “Universite Europeenne du Travail” and “Fondazione Europea di Ricerca Biomedica”.

References

1. Massimini M, Boly M, Casali A, Rosanova M, Tononi G. A perturbational approach for evaluating the brain's capacity for consciousness. Prog Brain Res. 2009;177:201-14.

2. Rosanova M, Gosseries O, Casarotto S, Boly M, Casali AG, Bruno MA, Mariotti M, Boveroux P, Tononi G, Laureys S, Massimini M. Recovery of cortical effective connectivity and recovery of consciousness in vegetative patients. Brain. 2012 Apr;135(Pt 4):1308-20. Epub 2012 Jan 5.

Keywords: cortical excitability, effective connectivity, unresponsove wakefulness syndrome, vegetative state, Transcranial Magnetic Stimulation, Electroencephalography

Conference: Belgian Brain Council, Liège, Belgium, 27 Oct - 27 Oct, 2012.

Presentation Type: Poster Presentation

Topic: Other basic/clinical neurosciences topic

Citation: Gosseries O, Rosanova M, Boly M, Casarotto S, Schnakers C, Napolitani M, Bruno M, Sarasso S, Ledoux D, Massimini M and Laureys S (2012). Transcranial magnetic stimulation combined with electroencephalography in severely brain-injured patients: methodological aspects. Conference Abstract: Belgian Brain Council. doi: 10.3389/conf.fnhum.2012.210.00074

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Received: 23 Aug 2012; Published Online: 12 Sep 2012.

* Correspondence: Dr. Olivia Gosseries, Coma Science Group, Cyclotron Research Center and Department of Neurology, University of Liège and University Hopital of Liege, Belgium, Liege, Belgium, ogosseries@ulg.ac.be