Technology Combining MEG and MRI with Neuronavigation for Treatment of an Epileptiform Spike Focus in the Precentral Region: A Technical Case Report Frank Duffner, M.D., Ph.D.,* Dirk Freudenstein, M.D.,* Hagen Schiffbauer, M.D.,* Hubert Preissl, M.D.,† R. Siekmann, M.D.,‡ Niels Birbaumer, Ph.D.,† and Ernst H. Grote, M.D., Ph.D.* *University Hospital for Neurosurgery, †Institute of Medical Psychology and Behavioral Neurobiology, MEG-Center, ‡Department of Neuroradiology Eberhard-Karls-University Tu ¨bingen, Tubingen, Germany Duffner F, Freudenstein D, Schiffbauer H, Preissl H, Siekmann R, Birbaumer N, Grote EH. Combining MEG and MRI with neuronavi- gation for treatment of an epileptiform spike focus in the pre- central region: a technical case report. Surg Neurol 2003;59:40 – 6. BACKGROUND Epileptic foci are often located in the vicinity but not necessarily within the boundaries of intra-axial brain tu- mors. Resection of these tumors is based on two major goals: first, maximizing tumor removal without provoking new neurologic deficits, and second, minimizing epileptic seizure activity. Magnetic source imaging (MSI) depicts the generators of magnetic fields overlaid on individual magnetic resonance (MR) images. Established applica- tion areas are lesions located adjacent to or partly within the sensory and motor cortex, or in the depth of the brain, necessitating a surgical approach through func- tionally highly relevant cortical regions. Magnetoen- cephalography (MEG) is also applicable for epileptiform spike foci recording during interictal activity. CASE DESCRIPTION A patient with a recurrent glioma close to the Rolandic cortex scheduled for epilepsy and tumor surgery was investigated with MSI. The MSI data showed an epilepti- form spike focus outside the tumor boundaries. The re- sulting MSI images were integrated into our neuronaviga- tion system. This procedure allowed for the preoperative identification of the sensory and motor cortex, the pre- cise localization of the epileptiform spike focus, and care- ful planning of the surgical procedure. In this case, we were able to safely resect the recurrent tumor and the epileptiform spike focus under general anesthesia using MSI-based neuronavigational guidance but no conven- tional intraoperative mapping techniques. CONCLUSION Magnetic source imaging can be a valuable, noninvasive method for planning and performing tumor resections in high-risk brain regions, especially if an epileptiform spike focus has to be localized and included into the resection strategy. © 2003 Elsevier Science Inc. KEY WORDS Magnetic source imaging, magnetoencephalography, brain tumor, neuronavigation, epilepsy, intraoperative electro- physiological recordings. S uccessful treatment of brain tumor patients presenting with seizures requires localization of the epileptic foci and careful preoperative plan- ning of the resection. Epileptic foci are often located in the vicinity but not necessarily within the bound- aries of intra-axial tumors [2,3]. When resecting these tumors the goals are to maximize tumor removal with- out provoking new neurologic deficits, and to mini- mize epileptic seizure activity. The combination of neuronavigation and magnetic source imaging (MSI) is helpful for planning surgical approaches to cerebral lesions in high-risk areas [6]. Such lesions include those that are located adjacent to or partly within the sensory and motor cortex, or in the depth of the brain necessitating a surgical approach through eloquent cortical regions. Nowadays, not only eloquent cortex but also epiletiform spike foci can be localized with magnetoencephalography (MEG) [10,14]. Address reprint requests to: Dr Frank Duffner, University Hospital for Neurosurgery, Hoppe-Seyler-Strae 3, D-72076 Tu ¨bingen, Germany. Received January 26, 2002; accepted March 7, 2002. 0090-3019/03/$–see front matter © 2003 by Elsevier Science Inc. doi:10.1016/S0090-3019(02)00972-2 360 Park Avenue South, New York, NY 10010 –1710