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Research paper
EEG-fMRI in the presurgical evaluation of temporal lobe epilepsy
  1. Ana C Coan1,
  2. Umair J Chaudhary2,3,
  3. Frédéric Grouiller4,
  4. Brunno M Campos1,
  5. Suejen Perani2,3,
  6. Alessio De Ciantis2,3,
  7. Serge Vulliemoz5,
  8. Beate Diehl2,3,
  9. Guilherme C Beltramini6,
  10. David W Carmichael2,3,
  11. Rachel C Thornton2,3,
  12. Roberto J Covolan6,
  13. Fernando Cendes1,
  14. Louis Lemieux2,3
  1. 1Neuroimaging Laboratory, Department of Neurology, University of Campinas, Campinas, Brazil
  2. 2Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, University College London, London, UK
  3. 3MRI Unit, Epilepsy Society, Chalfont St Peter, Buckinghamshire, UK
  4. 4Department of Radiology and Medical Informatics, Geneva University Hospitals, Geneva, Switzerland
  5. 5EEG and Epilepsy Unit and Functional Brain Mapping Laboratory, Neurology Department, University Hospitals and Faculty of Medicine of University of Geneva, Geneva, Switzerland
  6. 6Neurophysics Group, Gleb Wataghin Physics Institute, University of Campinas, Campinas, Brazil
  1. Correspondence to Louis Lemieux, MRI Unit, Epilepsy Society, Chesham Lane, Chalfont St Peter, Buckinghamshire SL9 0RJ, UK; louis.lemieux{at}ucl.ac.uk

Abstract

Objective Drug-resistant temporal lobe epilepsy (TLE) often requires thorough investigation to define the epileptogenic zone for surgical treatment. We used simultaneous interictal scalp EEG-fMRI to evaluate its value for predicting long-term postsurgical outcome.

Methods 30 patients undergoing presurgical evaluation and proceeding to temporal lobe (TL) resection were studied. Interictal epileptiform discharges (IEDs) were identified on intra-MRI EEG and used to build a model of haemodynamic changes. In addition, topographic electroencephalographic correlation maps were calculated between the average IED during video-EEG and intra-MRI EEG, and used as a condition. This allowed the analysis of all data irrespective of the presence of IED on intra-MRI EEG. Mean follow-up after surgery was 46 months. International League Against Epilepsy (ILAE) outcomes 1 and 2 were considered good, and 3–6 poor, surgical outcome. Haemodynamic maps were classified according to the presence (Concordant) or absence (Discordant) of Blood Oxygen Level-Dependent (BOLD) change in the TL overlapping with the surgical resection.

Results The proportion of patients with good surgical outcome was significantly higher (13/16; 81%) in the Concordant than in the Discordant group (3/14; 21%) (χ2 test, Yates correction, p=0.003) and multivariate analysis showed that Concordant BOLD maps were independently related to good surgical outcome (p=0.007). Sensitivity and specificity of EEG-fMRI results to identify patients with good surgical outcome were 81% and 79%, respectively, and positive and negative predictive values were 81% and 79%, respectively.

Interpretation The presence of significant BOLD changes in the area of resection on interictal EEG-fMRI in patients with TLE retrospectively confirmed the epileptogenic zone. Surgical resection including regions of haemodynamic changes in the TL may lead to better postoperative outcome.

  • SURGERY
  • FUNCTIONAL IMAGING
  • IMAGE ANALYSIS

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