Erin Simon Schwartz MD, Presenter: Nothing to Disclose

Deborah M. Zarnow MD, Abstract Co-Author: Nothing to Disclose

Arastoo Vossough MD, PhD, Abstract Co-Author: Nothing to Disclose

Dennis J. Dlugos MD, Abstract Co-Author: Nothing to Disclose

Philip B. Storm MD, Abstract Co-Author: Nothing to Disclose

Timothy Roberts PhD, Abstract Co-Author: Nothing to Disclose

To evaluate the role of MEG in presurgical evaluation of patients with medically-refractory epilepsy.

112 consecutive patients (75% pediatric) underwent MEG as a part of the pre-surgical assessment. Patients were medically-refractory, suffering ongoing debilitating seizures and had non-localizing other tests (including video telemetry). MEG was performed using a 275-channel biomagnetometer, recording 15x 2-minute epochs of spontaneous (passive) brain activity. Source waveforms were inspected for artifacts (blinking, clenching etc.) and were subjected to a beamforming analysis, with the construction of time-activity data from each voxel of brain (nominal 5mm spatial resolution). These time-activity curves were evaluated for evidence of significant excess kurtosis (a mathematical description of “spikiness”) and significant pixels were highlighted in a color overlay.

In general, MEG contributed to the evaluation in one of several distinct ways: (i) by identifying and localizing a single focus of epileptogenic activity, permitting the patient to be considered a surgical candidate. Such patients were confirmed by restricted intracranial electrode implantation. (ii) by identifying a single focus of epileptogenic activity in close proximity to eloquent cortex, arguing against surgery; such patients either proceeded to confirmatory intracranial electrode implantation or directly to alternative non-resective treatments (such as vagal nerve stimulator implantation). (iii) by identifying diffuse or multiple independent sources of epileptiform activity, arguing against likely surgical success. These patients proceeded to alternative non-resectional management. iv) by identification of reorganized (atypical) functional localization, allowing surgical approaches to be reconsidered.

In the majority of cases, MEG was able to contribute to the evaluation of patients with medically refractory epilepsy in one of the above manners. While generally concordant with EEG findings, MEG offered superior specificity of localization and on occasion determined additional foci, not revealed by MEG. It has become a routine part of our institution’s management of these patients.

Surgery is a potentially successful approach to management of the pediatric epilepsy patient, if a single focus or discrete foci can be identified. MEG offers an approach to such spatial localization.

Schwartz, E, Zarnow, D, Vossough, A, Dlugos, D, Storm, P, Roberts, T, Magnetoencephalography in the Evaluation of Pediatric Epilepsy.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6022322.html