Magnetic Source Imaging of Abnormal Low‐Frequency Magnetic Activity in Presurgical Evaluations of Epilepsy

• Published in: Epilepsia (Copenhagen) 1997-04, Vol.38 (4), p.452-460
• Main Authors: Gallen, C. C., Tecoma, E., Iragui, V., Sobel, D. F., Schwartz, B. J., Bloom, F. E.
• Format: Article
• Language: English
• Subjects: Adult; Biological and medical sciences; Biomagnetism; Brain Mapping; Cerebral Cortex - physiopathology; Cerebral Cortex - surgery; Electrodiagnosis. Electric activity recording; Electroencephalography; Electromagnetic Fields; Epilepsies, Partial - diagnosis; Epilepsies, Partial - physiopathology; Epilepsies, Partial - surgery; Epilepsy; Epilepsy - diagnosis; Epilepsy - physiopathology; Epilepsy - surgery; Female; Focal slow wave; Functional Laterality; Humans; Investigative techniques, diagnostic techniques (general aspects); Magnetic Resonance Imaging - methods; Magnetic source imaging; Magnetoencephalography; Magnetoencephalography - methods; Male; Medical sciences; Middle Aged; Nervous system; Neuropsychological Tests; Sensitivity and Specificity; Videotape Recording
• ISSN: 0013-9580; 1528-1167
• DOI: 10.1111/j.1528-1157.1997.tb01735.x

Purpose: Regional cortical dysfunction associated with epileptogenic activity was predicted from interic‐tal localized abnormal low frequency neuromagnetic activity (ALFMA) using Magnetic Source Imaging (MSI). ALFMA can be detected in patients who show no interictal spikes. Methods: A large array biomagnetometer was used in a blinded, rapid screening protocol. The MSI procedure required no alteration in epileptic medications. MSI results were compared with the presumed epileptogenic region as determined by a consensus of standard techniques, which included MR and electroclinical monitoring. Results: One or more sites of localized abnormality were detected by MSI ALFMA in 29 of the 33 epileptic patients. ALFMA mapped with MSI showed a 48.5% specificity with respect to the presumed epileptogenic region. MSI ALFMA was in agreement with the final consensus as often as was ictal noninvasive video EEG monitoring, and was exceeded in specificity overall only by invasive ictal video EEG monitoring, which was required for conventional localization in 21 of the 33 patients tested with MSI. Conclusions: ALFMA measurements with MSI may augment the array of noninvasive methods used for reaching a consensus for epilepsy surgery.