Nuclear Medicine Imaging in Epilepsy.

Approximately one-third of patients with focal epilepsy have medically refractory focal epilepsy (MRFE), which significantly impacts their quality of life. Once a seizure focus is identified and determined to be in the noneloquent cortex, it can be surgically resected with the goal of freedom from seizures and minimal neurocognitive deficit. During noninvasive (phase I) presurgical planning, functional (nuclear) imaging and structural imaging are complementary in the accurate localization of the epileptogenic zone (EZ). PET and SPECT are complementary functional imaging modalities. Fluorine 18-fluorodeoxyglucose PET shows hypometabolism in the EZ, while SPECT radiotracers are used to assess regional cerebral perfusion. Functional imaging plays a more important role in patients with nonlesional epilepsy (approximately one-third of patients with MRFE), in patients with multiple lesions, or in the setting of electrophysiologic-structural discordance. Nuclear medicine imaging also helps in evaluating the functional integrity of the rest of the brain and unmasking abnormalities that are not apparent at structural imaging before surgery. During invasive (phase II) evaluation, the EZ seen at functional imaging helps in guiding intracranial electrode placement. This review of nuclear medicine imaging of epilepsy is focused on the radiotracers used, imaging acquisition and postprocessing, commonly encountered causes of MRFE in adults and children, radiologic appearances of MRFE, imaging artifacts, and interpretation pitfalls. The goal is to guide radiologists in optimally performing and interpreting these studies for effective multidisciplinary discussions of these complex patient cases. RSNA, 2025