Research studiesThe October 2011 issue of Brain contains the first large-scale study of the relative contribution of 128- and 256-channel dense array EEG (dEEG) to the presurgical planning process. Drawing on their decade of experience with dEEG, the group lead by Dr. Seeck and Dr. Michel reported that dEEG facilitates both review of seizure data acquired in an extended monitoring setting and their innovative interictal spike protocol methods. The study included 152 patients who underwent surgery to relieve their epileptic seizures. Prior to surgery, patients had several tests to identify the source of seizure activity in their brains. Tests included electrical source imaging with either conventional EEG (19-29 electrodes) or dEEG (EGI's 128-or 256-electrode Geodesic EEG System), MRI, PET, and SPECT. Electrical source imaging (ESI) using dEEG combined with individual MRI head models proved to be the most accurate at pinpointing the correct part of the brain to remove during surgery. In all, 133 out of 152 patients were either seizure-free or had only infrequent seizures more than a year after surgery. ESI was superior both in terms of sensitivity and specificity compared to the other measures included in the study (MEG results were not available for the patients reported in this study). These results were particularly interesting since the ESI technique is based on localization of averaged spikes recorded during a high channel count but relatively short recording (2-3 hours). The authors noted that not only is ESI with dEEG highly accurate, but it is also more cost effective and can be used with a broader range of patients, compared to other methods used in the study. Brodbeck, Spinelli et al, 2011. Electroencephalographic source imaging: a prospective study of 152 operated epileptic patients. Brain 134 (10), 2887-2897. doi:10.1093/brain/awr243. Full text available. Comprehensive review of Electrical Source Imaging by Göran Lantz, MD, PhD, noted epilepsy expert and senior scientist at EGI. |