Dipole analysis in a case with tumor-related epilepsy

In order to evaluate the effectiveness of presurgical dipole analysis of in terictal spikes as a non-invasive technique for the determination of epilep togenic area, we compared the results of this method with those of electroc orticography (ECoG) localization in the diagnosis of a patient with tumor-r elated epilepsy. A preoperative MRI revealed a temporal lobe tumor on the r ight side. The individual dipoles estimated from the interictal spikes were located mainly in the anterolateral region of the right temoral lobe, alth ough some were located in the mesial side. The ECoG recorded frequent spike s in the anterolateral region of the right temporal lobe consistent with th e location estimated by dipole analysis. After surgery, the patient suffere d from residual seizures. Therefore, the residual epileptogenic area was ex amined by dipole analysis using a four-layered head model instead of the pr evious three-layered head model. As a result, the dipole analysis was able to pinpoint the epileptic focus in the area directly adjacent to the resect ed area, and in the mesial temporal lobe. In conclusion, EEG dipole analysi s appears to hold promise as a non-invasive presurgical evaluation techniqu e for locating epileptogenic areas as well as for postsurgical evaluation o f residual epileptic focus. (C) 1999 Elsevier Science B.V. All rights reser ved.