ORIGINAL PAPER The Value of Magnetoencephalography to Guide Electrode Implantation in Epilepsy Zaloa Agirre-Arrizubieta • Ngoc J. Thai • Antonio Valentı ´n • Paul L. Furlong • Stefano Seri • Richard P. Selway • Robert D. C. Elwes • Gonzalo Alarco ´n Received: 6 August 2013 / Accepted: 5 November 2013 / Published online: 19 November 2013 Ó Springer Science+Business Media New York 2013 Abstract To investigate if Magnetoencephalography (MEG) can add non-redundant information to guide implantation sites for intracranial recordings (IR). The contribution of MEG to intracranial recording planning was evaluated in 12 consecutive patients assessed pre- surgically with MEG followed by IR. Primary outcome measures were the identification of focal seizure onset in IR and favorable surgical outcome. Outcome measures were compared to those of 12 patients matched for implantation type in whom non-invasive pre-surgical assessment suggested clear hypotheses for implantation (non-MEG group). In the MEG group, non-invasive assessment without MEG was inconclusive, and MEG was then used to further help identify implantation sites. In all MEG patients, at least one virtual MEG electrode gener- ated suitable hypotheses for the location of implantations. No differences in outcome measures were found between non-MEG and MEG groups. Although the MEG group included more complex patients, it showed similar percentage of successful implantations as the non-MEG group. This suggests that MEG can contribute to identify implantation sites where standard methods failed. Keywords Magnetoencephalography  Beamformers  Epilepsy surgery  Invasive recording  Epileptogenic zone  Magnetic source imaging Introduction Successful outcome after resective epilepsy surgery relies on the localization of the cortical areas responsible for originating seizures. A variety of techniques are presently used to estimate the location and extent of epileptogenic cortex during pre-surgical assessment, including clinical history and examination, electroencephalography (Alarcon et al. 2001; Alarcon et al. 2012), neuroimaging (Duncan 2010) and neuropsychological methods (Akanuma et al. 2003). In 15–25 % of the patients, results from these tests are non-concordant or non-localizing and patients may need to undergo intracranial recordings to identify the Z. Agirre-Arrizubieta and N.J. Thai share first authorship as they worked equally in the preparation of the paper. Z. Agirre-Arrizubieta  A. Valentı ´n  R. D. C. Elwes  G. Alarco ´n Department of Clinical Neurophysiology, King’s College Hospital, London, UK Z. Agirre-Arrizubieta Department of Clinical Neurophysiology, Kent and Canterbury Hospital, Kent, UK N. J. Thai  P. L. Furlong  S. Seri (&) Wellcome Trust Laboratory for MEG Studies, Aston Brain Centre, School of Life and Health Sciences, Aston University, Aston Triangle, Birmingham B4 7ET, UK e-mail: s.seri@aston.ac.uk A. Valentı ´n  G. Alarco ´n Department of Clinical Neuroscience, Institute of Psychiatry, King’s College Hospital, London, UK R. P. Selway Department of Neurosurgery, King’s College Hospital, London, UK R. D. C. Elwes Department of Neurology, King’s College Hospital, London, UK G. Alarco ´n Departamento de Fisiologı ´a, Universidad Complutense, Madrid, Spain 123 Brain Topogr (2014) 27:197–207 DOI 10.1007/s10548-013-0330-x