Abstracts

Rationale: Infantile Epileptic Spasms Syndrome (IESS) is a developmental and epileptic encephalopathy with onset before the age of two years and heterogenous etiology. Drug resistance is common in IESS. Substantial proportion of patients with IESS have a potentially surgically remediable lesion. Brain MRI has been the mainstay for identifying these lesions. Earlier publications have highlighted the efficacy of FDG-PET scans in detecting subtle structural abnormalities, (up to 60%). Significant improvements in the quality of MRI over the last two decades. In this study, we evaluated the added value of FDG-PET in surgically remediable lesional IESS with congenital structural abnormalities.


Methods: This retrospective study included all children with IESS who underwent surgery with MRI showing surgically remediable congenital lesion along with FDG-PET scan. Patients were identified through the Epilepsy Surgical Conference list at Boston Children’s Hospital from January 2017 to May 2024. The brain MRI, and PET scans were initially reviewed by the neuroradiologist reading the study. These studies were re-reviewed by the neuroradiologist at the conference. All the brain magnetic images were conducted at 3T, following the epilepsy protocol.


Results: In the study, 15 children were identified (67% male) and all experiencing active epileptic spasms at the time of evaluation for surgery. The mean duration of the follow up after the surgery is 3.6 years. All the patients had abnormal brain MRI results, and 14 out of 15 (93%) also had abnormal FDG-PET scans. The congenital structural abnormalities were identified at IESS onset in 13 out of 15 (86%) of the children at the onset of the IESS. Two children were identified by follow-up MRI during the time of presurgical work-up. MRI and FDG-PET scan results were concordant in 13 patients (86%). Of the remainder, PET was normal in 1 patient and non-concordant showing hypometabolism in a different area from the MRI identified lesion. Of the concordant cases, MRI showed more extensive abnormality than the hypometabolism on the PET scan in 3 cases.

Twelve of the patients underwent surgical intervention, and 7 of them had ILAE class 1 outcome. The rest of the patients have unfavorable surgical outcome with either ILAE class 4 or 5. Four of the five patients with unfavorable outcome had bilateral abnormalities in the MRI as compared to 1 of the 5 patients with abnormalities on the PET. Pathology showed focal cortical dysplasia (n=5), mild malformation of cortical development (n=3), heterotopia (n=1), gliosis (n=2), normal (n=1). Among the 3 patients without surgery, one is undergoing evaluation for surgery, while 2 others with bilateral asymmetric abnormalities were medically managed.


Conclusions: Routine inspection of the FDG-PET scan in IESS patients with surgically remediable congenital structural lesions did not add any additional localization value and in 27% of our cases PET scan was either non-concordant with MRI or underestimated the lesional zone. MRIs (epilepsy protocol) read by an experienced neuroradiologist showing surgically remediable congenital lesion is sufficient for surgical planning.


Funding: No external fund was received for this study.