Combining fMRI and MEG increases the reliability of presurgical language localization: A clinical study on the difference between and congruence of both modalities Peter Grummich, a,b, * Christopher Nimsky, a Elisabeth Pauli, c Michael Buchfelder, a and Oliver Ganslandt a,b a Department of Neurosurgery, University Erlangen–Nuremberg, Germany b Biomagnetism Group, Neurocenter, University Erlangen–Nuremberg, Germany c Department of Neurology, University Erlangen–Nuremberg, Germany Received 13 December 2005; revised 5 April 2006; accepted 3 May 2006 Available online 4 August 2006 To avoid neurological impairment during surgery near language- related eloquent brain areas, we performed presurgical functional brain mapping with functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) in 172 patients using language tasks. For MEG localizations, we used either a moving equivalent- current dipole fit or a current – density reconstruction using a minimum variance beamformer with a spatial filter algorithm. We localized the Wernicke and Broca language areas for every patient. We integrated the results into a frameless stereotaxy system. To visualize the results in the navigation microscope during surgery, we super- imposed the fMRI and MEG findings on the brain surface. MEG and fMRI results differed in 4% of cases, and in 19%, one modality showed activation but not the other. In the vicinity of large gliomas, the BOLD (blood oxygenation level-dependent) effect was suppressed in 53% of our patients. Of the 124 patients who had surgery, only 7 patients (5.6%) experienced a transient language deterioration, which resolved in all cases. We used MEG and fMRI to show different aspects of brain activity and to establish validation between MEG and fMRI. We conclude that measurement by both MEG and fMRI increases the degree of reliability of language area localization and that the combination of fMRI and MEG is useful for presurgical localization of language-related eloquent cortex. D 2006 Elsevier Inc. All rights reserved. Keywords: Magnetoencephalography; Functional magnetic resonance imaging; Language; Neuronavigation; Wernicke; Broca Introduction During surgery near eloquent brain areas, a detailed knowl- edge about the topographic relation of the lesion to the functional brain area is crucial to avoid causing postoperative neurological deficits. Unlike the primary sensorimotor cortex, the cortex subserving language comprehension in the human brain shows high interindividual variability (Ojemann et al., 1989). Language- specific areas may also shift from their original positions because of lesions (Duffau et al., 2002; Grummich et al., 2005). Furthermore, normal sulcal anatomy is often not recognizable because of tumor growth. These situations require methods for localizing language-specific areas before surgery to avoid disastrous postoperative results. The classical procedure for language localization is intra- operative electrical stimulation mapping in awake patients (Pen- field, 1959; Berger and Rostomily, 1997; Duffau et al., 2003b; Reulen et al., 1997). In recent years, however, two noninvasive techniques have been found for presurgical language localization: magnetoencephalography (MEG) and functional magnetic reso- nance imaging (fMRI). Studies using either fMRI or MEG successfully lateralize and even localize language activity (Hinke et al., 1993; Salmelin et al., 1994; Cuenod et al., 1995; Desmond et al., 1995; Binder et al., 1996; Simos et al., 1998; Papanicolaou et al., 1999; Kober et al., 2001; Grummich et al., 1994). MEG- and fMRI-derived information about the extent of cortical involvement in language function can also be used in conjunction with image-guided surgery during resection of lesions adjacent to eloquent brain areas under general anesthesia (Gans- landt et al., 2004). The use of preoperative functional brain mapping with image-guided surgery provides important informa- tion for (1) indicating hemispheric dominance; (2) showing the risk of a surgical procedure; and (3) planning the surgical approach. In this study, we present our experience with localization of the language-related cortex in a large series of patients who underwent 1053-8119/$ - see front matter D 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.neuroimage.2006.05.034 * Corresponding author. Department of Neurosurgery, Biomagnetism Group, Neurocenter, University of Erlangen – Nuremberg, Schwabachan- lage 6, 91054 Erlangen, Germany. Fax: +49 9131 853 4271. E-mail address: pgr@neurozentrum.imed.uni-erlangen.de (P. Grummich). Available online on ScienceDirect (www.sciencedirect.com). www.elsevier.com/locate/ynimg NeuroImage 32 (2006) 1793 – 1803