Abstracts

Rationale: Gelastic seizures are a typical feature, however not mandatory, clinical feature of hypothamalic hamartoma (HH). In retrospective studies seizure outcome after MRgLITT for HH ranges between 61% (all seizure types)1 and 93 % (gelastic seizures) 2. Hypometabolic FDG-PET in the mesial temporal region is a good indicator for post-surgical seizure freedom in non-lesional TLE. In view of the promising results of a network targeted approach with pre- and postsurgical functional MRI studies3, a cohort of 93 HH patients were retrospectively assessed concerning the feasibility and utility of FDG-PET Methods: Texas Children's Hospital, Pediatric Neurosurgery data base of all MRgLITT treated HH patients was analyzed concerning availability of FDG-PET data and 1-year follow-up seizure outcome. The main aim of the preliminary study was a differentiation between hypermetabolic (PET+), hypometabolic (PET -) and heterogenous distribution within the HH and the extralesional regions. Results: From a total of 93 patients, 11 patients did not have a FDG-PET scan and 12 were excluded due to insufficient PET-data. 30 patients were ineligible for 1 year follow-up.  From the remaining 40 patients 75% achieved Engel outcome 1 (60% complete seizure freedom, i.e. Engel outcome 1A). The number of hypometabolic (“cold HH”), hypermetabolic (“hot HH”) and heterogenic metabolic changes “hetero HH”) are depicted in figure 1. In 15 patient hypometabolic changes were detected in the cortex. All five patients with “hot HH” (2 had additional cortical hypometabolic changes) reached favorable outcome of Engel Class I. Conclusions: This preliminary data shows that FGD-PET is feasible and that “hot HH” may be indicative for Engel outcome class 1. Additional cortical hypometabolism (as a sign of a possible secondary irritative zone) does not seem to influence the outcome. Since other electroclinical (e.g. seizure type, disease duration) and surgical factors (e.g. volume of ablation, volume of ablated PET positive or PET negative tissue) are apparently also putative indicators, the role of PET-metabolism in HH needs further investigations. Funding: No funding