Purpose or Case Report: The goal of this educational exhibit is to explore the utility of interictal FDG PET brain imaging in the evaluation of intractable, drug-resistant cases of pediatric epilepsy and to clarify its role in pre-surgical seizure focus localization. We will also explore the salient pearls and pitfalls of FDG PET brain imaging.
Methods & Materials: Retrospective review of key cases of interictal FDG PET brain imaging in pediatric epilepsy:

Normal brain FDG PET uptake in children:
- Normal distribution at different ages
- Normal variance in temporal lobes

Indications for FDG PET in epilepsy:
-When initial MRI is negative, interictal FDG PET can spotlight an area of concern and second-look MRI may uncover an inconspicuous seizure focus. (Figure 1. Initial MRI was negative except for hippocampal inversion. Hypometabolic activity was seen on FDG PET throughout the left temporal lobe, and on second look MRI, corresponding FLAIR abnormality was seen in the temporal lobe.
-Evaluation of post-operative areas difficult to assess with EEG (Figure 2. Hypometabolic activity was seen in the occipital lobe, which extended beyond the resection cavity and corresponded to areas of abnormal EEG activity).
-Isolating a target lesion when there is more than one area of abnormality (i.e. focal nodular heterotopia or tuberous sclerosis)
-Differentiate inflammation/limbic encephalitis from other seizure etiologies (i.e. focal cortical dysplasia or low grade glioma)

Utility of fusion techniques, comparison with ictal SPECT, and other hybrid imaging:
-Fusing PET with MRI enhances detection of subtle structural abnormalities
-Comparison of sensitivity with ictal SPECT
-Other hybrid imaging such as fusion with EEG or stereo grids can help localize seizure focus

Major artifacts and pitfalls in interpretation:
-metallic and motion artifact
-areas of ictal activity
-calculated attenuation difference due to skull thickness
-hyperglycemia
-drug related hypo- or hypermetabolism

The future:
-New tracers
-Utility of quantitative evaluation to confirm areas of hypometabolism
Results: This exhibit will review indications for interictal FDG-PET brain imaging and its utility in the multimodal work-up of pediatric epilepsy. Pearls and pitfalls in imaging will be discussed, including review of the normal distribution of FDG PET and major artifacts.
Conclusions: Recognizing the utility of FDG PET of the brain, as well as its shortcomings and potential pitfalls, will help radiologists and clinicians better utilize this modality in the evaluation of pediatric epilepsy.