To evaluate the role of PET-MRI coregistration in presurgical evaluation of MRI-negative drug-resistant epilepsy.

A retrospective study was conducted on the clinical data of 34 patients with MRI-negative refractory epilepsy who underwent presurgical evaluation at Epilepsy Center of Fengtai Hospital, Medical Alliance of Beijing Tiantan Hospital, Capital Medical University from January 2015 to June 2016. All patients received non-invasive (such as Scalp video-EEG, MRI, PET-CT and PET-MRI coregistration) and invasive (stereo-electroencephalography, SEEG) examinations during presurgical evaluation. A total of 30 patients underwent resection surgery subsequently and 4 patients underwent conservative therapy. The Engel scale was used to assess the surgery outcomes. The results of PET-CT and PET-MRI coregistration were compared with respect to the localization consistency of epileptogenic focus. Seizure frequency, interictal scalp EEG, PET-MRI coregistration and surgical location were included in the prognostic factor analysis by means of binary Logistic regression.

The mean postoperative follow-up period was 12.5 months (4~20 months). The Engel Class Ⅰ rate was 23/30 (77%). The rate of consistency between PET-MRI coregistration results and epileptogenic focus was significantly higher than that of PET-CT (83% vs. 37%, P<0.01). Prognostic factor analysis suggested that PET-MRI results without showing localized hypometabolism predicted seizure recurrence (P=0.042).

PET-MRI coregistration could significantly improve the localizing value of PET for epileptogenic focus. Patients without localized hypometabolism on PET-MRI coregistration images might be more likely to expreience seizure recurrence.

Epilepsy; Positron-emission tomography; Magnetic resonance imaging; Prognosis; PET-MRI coregistration