Integrated PET/MRI and EEG Improves Presurgical Lesion Localization in Pediatric Focal Epilepsy

Focal epilepsy, in which seizures arise from a discrete brain region, requires precise lesion localization before surgery. Many children have negative or inconclusive magnetic resonance imaging (MRI), complicating presurgical planning and delaying definitive treatment. More accurate identification of epileptogenic cortex could reduce invasive testing and guide therapy. A new study shows that positron emission tomography/magnetic resonance imaging (PET/MRI) integrated with electroencephalography (EEG) improves presurgical lesion detection in pediatric MRI-negative focal epilepsy.

In the August issue of The Journal of Nuclear Medicine, investigators evaluated fluorine-18 fluorodeoxyglucose (18F-FDG) PET/MRI within a structured presurgical workflow that included EEG correlation. The research included expertise from the University-Hospital of Padova. The cohort encompassed children younger than six years, addressing a population for whom imaging and anesthesia logistics are especially challenging.

The retrospective study analyzed 79 patients aged 18 years or younger with focal epilepsy, nondiagnostic or inconclusive prior MRI, and ongoing surgical evaluation. Review proceeded in defined phases: reassessment of previous MRI; masked reading of PET/MRI-acquired MR images; joint interpretation of co-registered PET and MRI by nuclear medicine and neuroradiology physicians; and verification against EEG. This stepwise process was designed to determine whether metabolic information could uncover subtle malformations missed on anatomical imaging.

Results showed added diagnostic yield from combined readings. Joint PET/MRI interpretation identified 46 children as PET-positive/MRI-positive and 24 as PET-positive/MRI-negative, while eight were PET-negative/MRI-negative. When compared with EEG in the final verification step, PET-positive/MRI-positive concordance showed high accuracy for lesion identification, particularly for focal cortical dysplasia. These findings clarified targets for intervention in cases where structural imaging alone had been insufficient.

Metabolic patterns stratified patients into two groups. In one, hypometabolism prompted careful MRI reevaluation that revealed structural abnormalities. In the other, hypometabolic changes were mild and MRI remained noncontributory despite detailed review, with clinical and EEG data often discordant—features that reduced candidacy for resective surgery. Based on integrated clinical, EEG, and imaging data, 24 patients underwent surgery and five underwent thermocoagulation; at two years of follow-up, 76% were seizure-free.

"We know PET/MRI is a beneficial imaging tool for patients with epilepsy; however, the current scientific literature is limited because it mixes pediatric and adult subjects. In our study, we sought to clarify the role of PET/MRI in the presurgical evaluation of pediatric epilepsy, including in very young children," said Diego Cecchin, M.D., director of the Unit of Nuclear Medicine and postgraduate School of Nuclear Medicine in the Department of Medicine at University-Hospital of Padova in Italy.

"These findings highlight the important role of molecular imaging and nuclear medicine in evaluating children with focal epilepsy, demonstrating that PET/MRI can be used safely and reliably even in very young patients. As more data become available, this approach could help clinicians identify the children most likely to benefit from epilepsy surgery, better understand distinct patterns of brain metabolism, and improve the integration of imaging findings with clinical and EEG data to guide treatment decisions," said Concetta Luisi, M.D., a pediatric neurologist and epileptologist at the Neurology, Epilepsy and Movement Disorders Unit of Bambino Gesù Children's Hospital in Rome, Italy.

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