Surgical Management of MRI-invisible Extratemporal Epilepsy

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.

Removal of Cervical Dumbbell Schwannoma in a Single Stage by Posterior Approach

Single staged posterior approach was carried out for three patients of dumbbell shaped schwannomas at the cervical region. Gross total resection was achieved in all of the patients, using a modified posterior midline exposure with hemilaminectomy and complete unilateral facetectorny. This exposure provided contiguous intraspinal, foraminal and extraforaminal access delete up to 2-3cm from lateral dural margin. The vertebral artery could be safely preserved from tumor mass. Although the follow up period is short, three patients showed no postoperative cervical spinalies from these operation. Illustrations of this approach with its possible application is discussed.