Abstracts

Rationale: Ictal single-photon emission computed tomography (SPECT) is a noninvasive neuroimaging method with the potential to localize the region of seizure onset in focal epileptic seizures. It has been reported to be a useful adjunctive test in the presurgical evaluation of patients with intractable epilepsy due to focal cortical dysplasia (FCD), especially when magnetic resonance imaging is normal. The aim of our study was to verify a hypothesis that ictal SPECT is predictive of outcome after respective epilepsy surgery in pediatric patients with FCD. The study was conducted on a large population of pediatric epilepsy surgery patients with histologically proven FCD. Methods: We retrospectively evaluated 80 children with FCD who underwent ictal SPECT before excisional epilepsy surgery at the Miami Children’s Hospital between 1994 and 2006. The presence of the ictal hyperperfusion was visually evaluated and compared with postoperative MRI scans of the resection cavity. Ictal SPECT findings were classified as “localized” and “nonlocalized” and the relation of localized hyperperfusion to the surgical resection site as “completely resected”, “partially resected” and “non-resected”. Seizure outcomes in patient’s groups were regarded as “favourable” in completely seizure-free subjects and in patients with ≥90% seizure reduction or nocturnal seizures only. Outcomes in subjects with <90% postoperative seizure reduction were regarded as “unfavourable”. Statistical analysis was done using Pearson’s Chi-square test. Results: 147 ictal SPECT studies in 80 patients were analyzed, including 47 postsurgical scans in subjects before reoperation. Ictal SPECT scans were nonlocalized in 14 patients. In 66 children with localized SPECT studies, the hyperperfusion zone was non-resected in 8, partially resected in 31 and completely resected in 27.Favourable postsurgical seizure outcome was achieved in 79% patients with non-localized SPECT, 50% with non-resected ictal hyperperfusion, 39% with partially resected ictal hyperperfusion, and 96% with completely resected ictal hyperperfusion (p=0.000013). Conclusions: Ictal SPECT is an effective procedure to define the epileptogenic zone in children with focal cortical dysplasia. Complete resection of the region of ictal SPECT hyperperfusion strongly predicts favorable postsurgical seizure outcome. Our finding have important implications for surgical planning. Supported by Grant IGA NR/8843-4, VZ 00000064203 and Kontakt Programme ME09042.