NEUROIMAGING AND SPECTROSCOPY IN CHILDREN WITH EPILEPTIC ENCEPHALOPATHIES

Aims-To investigate the nature of the unifocal cortical abnormalities on FDG positron emission tomography (PET) in children with an epilepti c encephalopathy but no focal abnormality on electroencephalogram or s tandard magnetic resonance imaging (MRI). Methods-Repeat FDG PET, surf ace rendered high resolution MRI, and single voxel magnetic resonance proton spectroscopy of the areas of abnormal metabolism compared to th e contralateral side in 11 children aged 2 to 12 years. Imaging was re peated after a median of 13 months. Results-Visual analysis of repeat FDG PET revealed similar abnormalities in 10 of 11 children. Semiquant itative analysis revealed similar sited abnormalities in eight childre n. One child with ictal hypermetabolism initially had an inconsistent second scan. Magnetic resonance spectra in three children showed the N -acetyl-aspartate/choline ratio was lower in the hypometabolic focus t han in the reciprocal area on the opposite side, in two children it wa s higher, and in one child it was equal. Surface rendered MRI was norm al in seven of eight children, and showed temporal lobe asymmetry in o ne. Conclusion-In children with established epileptic encephalopathies most hypometabolic areas on FDG PET are stable over time. While focal neuronal loss is likely in these areas in some children, microdysplas ias or other focal cortical dysplasias are probable in others.