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Relative Yield of MEG and EEG Spikes in Simultaneous Recordings

Ebersole, John S.*; Wagner, Michael

Journal of Clinical Neurophysiology: November 2018 - Volume 35 - Issue 6 - p 443–453
doi: 10.1097/WNP.0000000000000512
Original Research

Purpose: Most clinical magnetoencephalography (MEG) centers record both MEG and EEG, but model only MEG sources. This may be related to the belief that MEG spikes are more prevalent, MEG is more sensitive, or to proprietary software limitations. Biophysics would contend, however, that EEG, being sensitive to radial and tangential source orientations, would provide complementary data for analysis.

Methods: We recorded 306 channels of MEG and 25 channels of EEG simultaneously in 297 consecutive patients over 3 years. We inspected the MEG and EEG recordings separately, identified spikes in both, determined whether their voltage and/or magnetometer magnetic fields were dipolar and thus model-worthy, and segregated them into types based on similar and distinct field topography. We placed for each patient their spike types into categories, including those with both a recognizable MEG and EEG signal and those with only an MEG and only an EEG signal.

Results: Eighty-three percent of patients had spikes recorded, and these patients had an average of 2.7 spike types each. Fifty-six percent of spike types were present in both MEG and EEG. However, 36% of spike types were only evident in EEG, whereas 8% were noted in MEG alone. In 49% of patients with spikes, MEG review missed at least one spike type, whereas in 17% of patients, EEG review missed at least one spike type.

Conclusions: To obtain an optimal yield of diagnostic information, EEG should also be subjected to source analysis in any clinical MEG study. EEG and MEG data are indeed complementary.

*Northeast Regional Epilepsy Group, MEG Center, Overlook Medical Center, Summit, New Jersey, U.S.A; and

Neuroscan—Compumedics, Hamburg, Germany.

Address correspondence and reprint requests to John S. Ebersole, MD, 203 Garron Rd, Middletown Springs, VT 05757, U.S.A.; e-mail: j.s.ebersole@gmail.com.

M. Wagner is an employee of Compumedics Neuroscan. J. S. Ebersole is a member of the Medical Advisory Board of Compumedics.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal's Web site (www.clinicalneurophys.com).

© 2018 by the American Clinical Neurophysiology Society