Cinical Publications on Epilepsy

A Review of Electrical Source Imaging

This article first appeared in our Clinical eNewsletter in July 2011.

Techniques for source localization alt
EEG is the most central diagnostic tool for presurgical evaluation of medically intractable focal epilepsy. Typically, multichannel EEG synchronized with video monitoring is performed continuously for several days. The resulting EEG traces (or waveforms) are then analyzed for patterns typical for the patient’s seizures. These patterns are assessed by the examination of the EEG traces during interictal discharges, as well as before, during, and after seizures. In the hands of an experienced epileptologist, this kind of trace analysis has a considerable value in localizing the epileptogenic area of the brain for surgery. However, there are some important limitations to the technique as it has been practiced in the past, and it can result in crude or even incorrect localization.

To obtain sufficient precision for surgery, it is important to use several complementary techniques to more accurately localize the epileptogenic foci. Modern presurgical evaluation centers generally include neurological and neuropsychological exams, high-resolution MRI, PET, and/or interictal and ictal SPECT, and sometimes MRI-based volumetry and spectroscopy in the battery of exams that aim to precisely determine the epileptogenic focus. In cases of unclear or nonconcordant results through these exams, invasive recordings from surgically implanted electrodes are usually needed as well.

Improved source-imaging algorithms greatly increase accuracy of source localization

2009 Clinical Year in Review

This article first appeared in our inaugural edition of our Clinical eNewsletter in February 2010.

It was a productive year for our clinical customers. We have noted 27 new publications in 2009 and the first few months of 2010. Epilepsy was a major focus for our customer base, with 12 of the 27 publications having worked in this area. Several customer posters also focused on epilepsy at December’s Boston meeting of the American Epilepsy Society (AES).

EGI dEEG 256-channel HCGSN In two of the AES posters (Lantz, Brodbeck, Seeck, Tucker, & Michel, 2009; Yamazaki, Fujimoto, & Yamamoto, 2009), dense array EEG (dEEG) was again shown to be superior to conventional EEG in its ability to accurately localize spike data. Lantz et al. found that the distance between the source focus location and the clinically determined focus location increased as the EEG channel count decreased (from good correspondence with 256-channel dEEG to poor correspondence with 32-channel EEG). In the report by Yamazaki et al., dEEG (256 and 128 channel) data yielded more focal localization results than that of the conventional (19 channel) data from the same patient. In a third AES poster (Spinelli et al., 2009), dEEG source imaging was shown to have a sensitivity and specificity for localization that was comparable to or better than those obtained with positron emission tomography (PET) and single photon emission computed tomography (SPECT).