Video-electroencephalography Applied in Interpretation of Cortical and Subcortical Hypermetabolic Foci in Interictal ¹⁸F-fluorodeoxyglucose Positron Emission Tomography Imaging in Patients with Epilepsy

  Objective  To evaluate the role of vedio-electroencehpalography (VEEG) monitoring in interpreting the cortical and subcortical hypermetabolic foci in interictal ¹⁸F-fluorodeoxyglucose(¹⁸F-FDG) positron emission tomography (PET) imaging in patients with epilepsy.

  Methods  From January 2008 to March 2014 in Peking Union Medical College Hospital, 3 epileptic patients whose first ¹⁸F-FDG PET scan showed unexplained hypermetabolic foci without seizure underwent repeated ¹⁸F-FDG PET scan in the interictal status proved by VEEG monitoring after discharge suppression by intravenous diazepam. Then compared the first and second scan images.

  Results  For case 1 who suffered from epilepsy originating from medial right temporal lobe, unexplainable hypermetabolic foci in right frontal lobe, basal ganglia, thalamus, and left cerebellum were present in interictal ¹⁸F-FDG PET scan. After suppressing cortical discharge under VEEG monitoring, the second ¹⁸F-FDG PET scan showed that the cortical and subcortical hypermetabolism disappeared, indicating that the hypermetabolic foci in the first scan was due to the subclinical discharge in a potential extratemporal seizure origin site, and the existence of efferent network activity from that origin site to ipsilateral basal ganglia and thalamus and contralateral cerebellum. The original clinical decision of simple anterior temporal lobectomy was altered based on the findings. For case 2, hypermtabolism was present in a large part of right frontal lobe, which persisted after suppressing discharge under VEEG monitoring. While the hypermetabolic foci in ipsilateral basal ganglia and contralateral cerebellum became less obvious in the second ¹⁸F-FDG PET scan, proving that the original lesion (inflammation) with hypermetabolism existed in the cortex, and the hypermetabolic foci in basal ganglia and thalamus were due to secondary functional change. Case 3 suffered from temporal lobe epilepsy with origin undeterminable with clinical information, electroencephalogram, or magnetic resonance imaging. Hypermtabolic left hippocampus was shown in both the first ¹⁸F-FDG PET scan and the second PET scan under definite interictal status with VEEG monitoring, suggested the existence of a hypermetabolic lesion (tumor), facilitating the clinical decision on surgical site.

  Conclusions  For the epileptic patients with hypermetabolic foci in ¹⁸F-FDG PET without seizure, repeated ¹⁸F-FDG PET imaging in definite interictal status under VEEG monitoring can help interpret the etiology and define the extent of lesions for better clinical decision-making.