Comparison of localizing value of interictal PET, MRI and EEG in preoperative evaluation of intractable epilepsy

    LI Yiª²Ming, ZHANG Hua, JING Xiaoª²Rong, GAO Guoª²Dong

    Institute for Functional Brain Disorders, Fourth Military Medical University, Xi¬ðan 710038, China

    ¡¾Abstract¡¿ AIM: To compare the results of ictal PET, scalp Video EEG (VEEG), intracranial EEG and MRI in patients with intractable epilepsy and to explore the application value of 18Fª²FDG PET and MRI in the localization of epileptogenic focus. METHODS: Brain imaging of 18Fª²FDG PET, MRI and EEG was obtained in 65 patients [male 44, female 21, age averaging (30.1¡À18.5) years] with intractable epilepsy. Fortyª²two patients received surgical treatment and intracranial electrodes were placed in 13 patients. All the patients who had undergone surgery had MRI examination 1 month after surgery. Seizure control was also evaluated according to Engel¬ðs classification of surgical outcome. The efficacy of PET for the localization of epileptogenic focus was compared with that of VEEG, MRI and intracranial EEG. RESULTS: ¢Ù Fiftyª²eight patients showed interictal focal hypometabolism, 3 patients with continuous seizure showed ictal hypermetabolism and 4 patients were normal. ¢Ú FDG PET localized the seizure foci in patients whose VEEG showed bilateral or no definite epileptoform discharge. FDG PET image demonstrated more metabolic changes than structural changes shown by MRI. ¢Û According to Engel¬ðs classification, 71.4% (30/42) were classified as grade I, whose lesions were confirmed to be epileptogenic foci. The localization accuracy of intracranial EEG, FDG PET, VEEG and MRI for seizure foci was 96.7%, 90.0%, 76.7% and 53.3%, with significant difference when calculated by ¦Ö2 test (P<0.05). ¢Ü Surgical outcome of the patients with abnormal MRI image was better than that with normal MRI image. The effect of surgical removal of the hypometabolic focus in one temporal lobe was better than that in bilateral lobe. Patients with epileptogenic foci in temporal lobe had a better outcome than those with foci in other lobes. In the patients with other hypometabolic lesions besides major lesion, the removal of the major lesion was not as effective as that in the patients only with major lesions. CONCLUSION: The sensitivity and accuracy of the FDG PET imaging in localizing the seizure focus are significantly higher than those of MRI and VEEG. The FDG PET metabolic images combined with MRI and scalp VEEG can help the neurosurgeons to localize the epileptogenic focus, confirm the operative indications and predict the surgical outcomes. ......