Etiologic classification of infantile spasms using positron emission/magnetic resonance imaging and the efficacy of adrenocorticotropic hormone therapy

Purpose The aim of this study was to investigate if the etiologic classification of infantile spasm (IS) using positron emission tomography/magnetic resonance imaging (PET/MR) is feasible. Based on the classified etiologic groups, we further evaluated the efficacy of adrenocorticotropic hormone (ACTH) therapy in different IS groups. Materials and methods One hundred fifty-five children diagnosed with IS were included in this study. A qualitative assessment of the PET/MR images was performed. The abnormal lesions localized with both MR and PET images were considered to be epileptic foci, and the patients with these lesions were classified into the structural-metabolic group. For the remaining patients, quantitative analyses were further performed on whole-brain T1-weighted (T1WI) and PET images, based on the asymmetry index of bilateral volumes and metabolic quantifications. Patients with asymmetry indices above a certain threshold (15%) were classified into the structural-metabolic group. The patients without positive finding from either qualitative or quantitative analyses were assigned to the unknown etiology group. The efficacy of ACTH therapy was evaluated in the different IS groups. Results Among the 155 children with IS, 18 genetic cases were first diagnosed by the genetic testing. In the remaining 137 cases, 49 cases were identified with structural-metabolic etiology using qualitative PET/MR assessments. Fifty-two cases were newly diagnosed with quantitative analysis. The remaining 36 cases were classified into the unknown etiology group. The efficacy of ACTH therapy was statistically different for the different etiology groups ( p < 0.001). The respective efficacy rates for the genetic, qualitative structural-metabolic, quantitative structural-metabolic, and unknown etiology groups were 27.8% (5/18), 30.61% (15/49), 34.62% (18/52), and 72.22% (26/36), respectively. Conclusions The combination of PET and MR provides additional diagnostic information for IS. Quantitative analysis can further improve patient etiologic classifications and the predication of therapy efficacies.