Objectives:The authors aimed to determine the functional status of brain at rest in children with ASD by using 18-FDG-PET.

Methods: Medical records and PET scans of all children aged between 2–12years who were diagnosed as ASD (based on DSM-V criteria) and those who underwent ¹⁸ F-FDG PET scan were reviewed retrospectively during July 2014–June 2016. Children with secondary causes of ASD such as tuberous sclerosis, neuro-metabolic disorders, or primary epilepsy with associated autism were excluded. Institute ethical clearance was obtained for the study(NK/3404/study575).

Results: A total of 68 children who fulfilled the eligibility criteria were included. The median age of children enrolled was 48 ± 22.9 months. Male children constituted 90% of study population (M:F=61:7); majority of the children had severe autism with CARS ≥37(81%). The most common abnormality noted was relatively reduced metabolism in left temporal lobe in 15(22.1%) followed by reduced metabolism in left parietal lobe in 6(8.8%). Increased metabolism was seen in both frontal lobes in 5(7.4%), right posterior calcarine cortex in 5(7.4%), left post calcarine cortex in 2(2.9%) and bilateral occipital lobe in 2(2.9%).

Conclusion: To conclude, around one-third of ASD children showed abnormalities at rest in ¹⁸ F-FDG PET scan. Majority showed reduced metabolism in left temporal and parietal lobe, which probably correlates with the speech abnormalities in children with ASD. Increased metabolism noted in frontal lobe, occipital lobe and calcarine cortex possibly show an association with hyperactivity, and visual inattentiveness seen in these children.