Benzodiazepine-GABAA receptor binding is very low in dysembryoplastic neuroepithelial tumor:: a PET study

Purpose: To determine the nature of abnormalities of gamma -aminobutyric acid (GABA)A-central benzodiazepine (BZD) receptor binding in patients with dysembryoplastic neuroepithelial tumor (DNET) in comparison with normal controls. Methods: Five patients with DNET and 24 normal controls underwent ((11)C)flumazenil positron emission tomography (PET) to measure ((11)C)flumazenil volume of distribution (FMZVD) at the voxel level. Patients were compared with normal controls by using statistical parametric mapping (SPM) and also a partial-volume effect (PVE) corrected volume-of-interest (VOI) analysis covering the entire brain. First, using SPM, the highest Z-score for the entire image representing FMZVD decreases in comparison with the normals was found. Second, regions of abnormal FMZVD were located using SPM, p < 0.001 uncorrected, corrected p < 0.05. Finally, PVE- corrected measures of FMZVD were calculated for each patient VOI and compared wih those of normals, using significance levels of >2.5 standard deviations (SD) for the DNET and >3 SD for all other regions. Results: In all cases, the highest Z-score across the whole image representing decreased FMZVD was within the DNET. In three cases SPM revealed a single region of significantly reduced FMZVD, within the DNET in all three. VOI analysis showed PVE-corrected FMZVD was significantly low in the DNET in four cases. VOI analysis also showed seven other regions of abnormal FMZVD; three were adjacent to a DNET, and two were in mesial temporal areas not affected by DNET. Conclusions: FMZVD is low in DNET, probably contributing to epileptogenicity.