Abstracts

Rationale: To study usefulness of 123I-Iomazenil-SPECT(IMZ) in childhood focal intractable epilepsy in comparison with 18F-FDG-PET(FDG). FDG is proved to be useful in finding epiletogenic focus, but needs special expensive equipment. IMZ can reveal both brain perfusion by early image (IMZE) and benzodiazepine receptor binding by delayed image (IMZD) using conventional SPECT scanner, but now available only in Japan. Methods: We investigated six children < 15 yo of intractable focal epilepsy with focal or lateralized MRI lesions in whom we could estimate epileptogenic zone (EZ) using all of ictal video scalp EEG recordings, MRI, FDG, and IMZ in the period of 2007.6-2008.5. Children with mesial temporal sclerosis were excluded. MRI suggested focal cortical dysplasia (FCD) in 3, hemimegalencephaly (HMG) in 1, chronic focal autoimmune encephalitis in 1 (CFAE), and benign brain tumor (BT) in 1. We retrospectively and visually investigated location and extention of FDG and IMZ findings in comparison with suspected EZ. We also compared them with ictal SPECT findings in 4 children. Results: 1) Among 3 children with suspected FCD on MRI, FDG showed moderately low uptake lesions corresponding to EZ in all and wider mildly low uptake area around them in 2. IMZD showed low uptake area corresponding to FDG findings in 1, but only subtle uptake changes in the others. IMZE revealed hypoperfusion area corresponding to FDG findings in 2. 2) In one child with marked lesion of HMG, all of FDG, IMZE and IMZD showed prominent low uptake area including EZ. 3) In the other 2 children with CFAE or BT, both FDG and IMZD showed low uptake area around suspected EZ, but IMZD lesion was wider with obscure boundary than FDG. Conclusions: 1) Regarding FDG, moderate to severe low uptake findings were considered to be highly correlated with EZ, but subtle or mildly low uptake findings didn’t necessarily correspond with MRI and ictal SPECT findings, which suggest functional or non -specific changes. 2) IMZD is useful for detecting EZ (4/6), though sensitivity is lower than FDG (6/6). Two children in whom IMZ failed to show prominent abnormal uptake had only mild MRI signal changes, which suggested the mild focal histopathological changes could show almost normal BZP receptor binding though glucose utilization was lowered. The difference in the spatial resolution between IMZ and FDG may also contribute. 3) In the other cases except cortical malformation, FDG findings are more specific than IMZ. 4) IMZ is useful in delineating EZ in childhood intractable focal epilepsy, and is superior to FDG from the point of necessary hardware because IMZ can be examined without PET scanner nor cyclotron, but inferior to FDG in sensitivity to find EZ.