Surgical Management of MRI-invisible Extratemporal Epilepsy

Chae, Jung Suk; Kim, Hyoung Ihl; Chung, Chang Oh; Kim, Dong Hwan; Neto, Pedro Rosa; Lee, Min Cheol; Lee, Jung Chung

Abstract

OBJECTIVE
The advent of high resolution magnetic resonance imaging(MRI) contributed to the preoperative localization of epileptogenic area. Even the discrete lesion visualized on MRI can be often correlated with seizure onset zone. If MRI does not, however, show any lesions in the extratemporal epilepsy, it imposes a significant challenge. This study is designed to evaluate the surgical treatment of extratemporal lobe epilepsy in which MRI does not show any lesion, to define the surgical strategy and to investigate the underlying pathology.
METHODS
We studied the nineteen patients with MRI-negative extratemporal epilepsy who underwent resective surgery after careful preoperative investigation between 1993 and 1995.
RESULTS
Scalp EEG could not lateralize the epileptogenic foci in 9 patients. Intracranial EEG recording was performed in all patients with successful localization: depth electrode study in 12, and subdural grid and strip study in 7 patients. Resection was performed in frontal(n=14), in parietal(n=3), and in multilobar area(n=2). Pathological findings comprised cortical dysplasia in 10, gliosis in 7, and collagenoma in one patients. The surgical outcome was classified as seizure free in 10, rare seizures in 2, significant reduction in 5, and no change in 2 patients.
CONCLUSION
MRI-invisible extratemporal epilepsy can be managed surgically with promising results. Cortical dysplasia and gliosis are two major pathological findings in this context though MRI does not demonstrate any lesions.