The Role of Radionuclide Imaging in Epilepsy, Part 1: Sporadic Temporal and Extratemporal Lobe Epilepsy

Abstract

CE credit: For CE credit, you can access the test for this article, as well as additional JNMT CE tests, online at https://www.snmmilearningcenter.org. Complete the test online no later than March 2020. Your online test will be scored immediately. You may make 3 attempts to pass the test and must answer 80% of the questions correctly to receive 1.0 CEH (Continuing Education Hour) credit. SNMMI members will have their CEH credit added to their VOICE transcript automatically; nonmembers will be able to print out a CE certificate upon successfully completing the test. The online test is free to SNMMI members; nonmembers must pay $15.00 by credit card when logging onto the website to take the test.Epilepsy is one of the most common yet diverse neurologic disorders, affecting almost 1%-2% of the population. Presently, radionuclide imaging such as PET and SPECT is not used in the primary diagnosis or evaluation of recent-onset epilepsy. However, it can play a unique and important role in certain specific situations, such as in noninvasive presurgical localization of epileptogenic brain regions in intractable-seizure patients being considered for epilepsy surgery. Radionuclide imaging can be particularly useful if MR imaging is either negative for lesions or shows several lesions of which only 1 or 2 are suspected to be epileptogenic and if electroencephalogram changes are equivocal or discordant with the structural imaging. Similarly, PET and SPECT can also be useful for evaluating the functional integrity of the rest of the brain and may provide useful information on the possible pathogenesis of the neurocognitive and behavioral abnormalities frequently observed in these patients. Present ly, nuclear medicine imaging such as PET and SPECT is not used in the primary diagnosis or evaluation of recent-onset epilepsy. However, it can play a unique and important role in certain specific situations. Almost a fourth of epileptic patients do not respond to medical treatment and develop intractable seizures. PET and SPECT can play a significant role in such patients by its ability to noninvasively localize epileptogenic brain regions before surgery. PET and SPECT do not play much of a role in localization when structural lesions visible on MR imaging are concordant with electrophysiologic and clinical data. However, many patients may have no visible brain lesion on CT or MR imaging, particularly children less than 2 y old, in whom some cortical malformations may be poorly visualized or missed completely because of immature myelination and poor gray matter-white matter differentiation. This limitation is significant, considering that these abnormalities constitute a major cause of epilepsy in children. Similarly, patients may have multiple structural lesions of which only 1 or 2 are epileptogenic, may have seizures arising far from the lesion, or may have discordant or inconclusive electroencephalogram findings. PET and SPECT can be useful in such cases by identifying the epileptogenic regions and guiding the subsequent subdur...

Subacute administration of fluoxetine prevents short-term brain hypometabolism and reduces brain damage markers induced by the lithium-pilocarpine model of epilepsy in rats

“…In epilepsy patients during interictal period, [ 18 F] FDG PET typically shows reduced metabolic activity in the epileptogenic region (Wong et al, 2010;Kumar and Chugani, 2013;Ding et al, 2014). In addition, hypometabolism in temporal areas seems to be a common feature found in different animal models of epilepsy Virdee et al, 2012).…”

Significance of FDG-PET Hypermetabolism in Children with Intractable Focal Epilepsy

“…It is characterized by microscopic abnormalities in cortical lamination, neuronal differentiation, and neuronal maturation anomalies, that can be difficult to detect/be undetectable, even on highfield MRI [52][53][54][55][56]. In our cohort, pathological analysis revealed that all patients had FCD type 1, which is usually more difficult to detect on MRI than type 2.…”

Nuclear medicine in pediatric refractory epilepsy

“…For example, a focus in the mesial temporal lobe can be associated with hypometabolism throughout the anterior temporal lobe [52,53]. Other regions of the brain may show alterations in metabolic activity [42,54]. Decreased metabolic activity in the contralateral cerebellum (diaschisis) is more commonly seen with an epileptogenic focus in the frontal or parietal lobe.…”

“…5, 6). If fully developed, this approach could increase the proportion of successful ictal SPECTs [35,[37][38][39][40][41][42][43][44][45].…”

“…11 C-doxepin targets histamine receptors and shows interictal-increased uptake. Other agents that show decreased interictal uptake include 18 F-FCWAY, 11 C-WAY, 18 F-MPPF, 11 C-ketamine and 18 F-FA85380 (acetylcholine) [42].…”