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March 1993

Comparison of Scalp Electroencephalogram With Subdural Electrocorticogram Recordings and Functional Mapping in Frontal Lobe Epilepsy

Author Affiliations

From the Section of Epilepsy and Sleep Disorders, The Cleveland (Ohio) Clinic Foundation. Dr Salanova is now with the Indiana University School of Medicine, Riley Hospital, Indianapolis.

Arch Neurol. 1993;50(3):294-299. doi:10.1001/archneur.1993.00540030058015

• We compared the findings of scalp electroencephalogram with subdural electrode array (SEA) recordings in 19 patients with refractory frontal lobe epilepsy. Prolonged scalp interictal recordings localized the epileptogenic zone in 12 patients; seven had no interictal sharp waves. The SEAs showed multifocal interictal sharp waves in all patients. Seven patients with localized seizure onset on scalp recording showed extensive ictal onset on the SEA recording. Five patients with lateralized seizure onset to one hemisphere on scalp recording were found to have ictal onset on SEA restricted to a smaller area. Because of the large epileptogenic zone found on SEA recordings, a complete resection was possible in only five (33%) of the 15 patients who had resections. Eight (53%) of the 15 patients benefited from surgery (mean follow-up, 4.6 years). The SEAs also allowed functional localization in most patients. From these data, we suggest that a localizing scalp electroencephalogram in patients with frontal lobe epilepsy may be misleading because SEA recordings show larger epileptogenic zones than anticipated. Furthermore, we postulate that the larger extensive epileptogenic zone may account for the poorer surgical outcome in patients with frontal lobe epilepsy compared with patients with temporal lobe epilepsy.

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