Abstracts

Rationale: MRI is an indispensable investigation in presurgical epilepsy evaluation. Several studies in the past have shown less favorable surgical outcomes in patients with refractory partial epilepsy. As MRI technology improves, smaller and more subtle epileptogenic lesions are more likely to be identified preoperatively. This raises the question of the likelihood of favorable surgical outcomes in patients who have non-identifiable foci from MRI, especially in pediatric epilepsy. The aim of this study is to compare the longterm surgical outcomes between MRI-negative (or inconclusive MRI) and MRI-positive in children with focal neocortical epilepsies who underwent epilepsy surgery at Children s Hospital of Alabama.Methods: We retrospectively reviewed our pediatric epilepsy surgery database. All patients who underwent epilepsy surgery at Children s Hospital of Alabama between December 2003 and June 2010 were identified. Patients with large hemispheric lesions who underwent functional hemispherectomy and patients who underwent vagus nerve stimulator implantations were excluded. Clinical data including video-EEG, seizure semiology, MEG, PET, ictal blood flow studies assessed by SISCOM or ISAS(Ictal-Interictal SPECT Analysis by SPM) were collected. All MRI scans were reviewed by radiologists and epileptologists. Surgical outcomes were classified using the Engel classification. We excluded any patient who was lost follow up or has longterm surgical outcome less than 1 year. Statistical significant difference was assessed using Chi-square and Fischer Exact test. Results: There were 494 patients underwent presurgical evaluation, only 163 patients underwent epilepsy surgery during that period. Seventy-two patients satisfied the inclusion criteria. Mean age at operation was 12 years 1 month 5 years 9 months. 41 were MRI-positive and 31 were MRI-negative or inconclusive MRI. Surgical outcomes in the MRI-positive group were class-I 75.6% (31 patients), class-II 7.3% (3 patients), class-III 14.6% (6 patients), and class-IV 2.4% (1 patient). Surgical outcomes in the MRI-negative/inconclusive group were class-I 64.5% (20 patients), class-II 22.5% (7 patients), class-III 6.5% (2 patients), and class-IV 6.5% (2 patients). There was no statistical significant difference in the frequency of class-I outcomes between the MRI-positive and MRI-negative/inconclusive groups. Conclusions: MRI-negative/inconclusive findings should not preclude epilepsy surgery in children with refractory partial epilepsy. Advance in multimodality imaging techniques can help improve surgical outcomes in this highly selected group of patients.