F-18 Fluorodeoxyglucose Positron Emission Tomography (FDG PET) in Epilepsies

Brain FDG PET is probably the most commonly performed functional neuroimaging modality in the pre-surgical evaluation of epileptogenic foci/zones for patients with medically refractory focal (partial) seizures (Cendes, Handb Clin Neurol 136:985–1014, 2016; Rathore et al., Epilepsy Res 108:1306–1314, 2014; Sarikaya Am J Nucl Med Mol Imaging 5:416–430, 2015). As an ictal FDG PET is fortuitously performed mainly due to technical challenges (Gaillard, Wyllie’s treatment of epilepsy: principles and practice. Wolters Kluwer, Philadelphia, 2011), nearly all the brain FDG PET scans shall be interpreted as interictal studies, which typically show asymmetric and focal cortical hypometabolism suggesting an epileptogenic focus/zone in an appropriate clinical setting. Although most of the epileptogenic foci/zones emanate from the temporal lobe (Abou-Khalil, Bradley’s neurology in clinical practice. Elsevier, London, 2016; Kumar and Chugani, J Nucl Med Technol 45:14–21, 2017), often called temporal lobe epilepsy (TLE), extratemporal lobe epilepsy could take place in the frontal, parietal, occipital, and even insular lobe. Diaschisis secondary to medically refractory seizures may present as ipsilateral thalamic hypometabolism or contralateral cerebellar hypometabolism or both. Since the FDG PET-delineated epileptogenic foci/zones are often expanded/propagated (Kumar and Chugani, J Nucl Med Technol 45:14–21, 2017), further workup with or correlation with ictal/interictal brain perfusion SPECT studies and EEG seizure monitoring is always recommended. Several cases in this chapter also show that, in conjunction with anatomic neuroimaging studies (MRI and CT), FDG PET plays an important role in the metabolic characterization of the underlying causes of focal seizures, such as focal cortical dysplasia (FCD), brain tumors, vascular malformations, stroke, or tuberous sclerosis (TS). In addition to localizing epileptogenic foci/zones, FDG PET provides imaging evidence of metabolic integrity of the rest of the brain, which is equally important in the assessment of patients’ neurosurgical candidacy.