Multimodal imaging reveals resilient memory networks in carriers of pathogenic ARID1B variants.

The phenotypic spectrum associated with pathogenic ARID1B variants is remarkably broad, ranging from classic Coffin-Siris syndrome to non-syndromic intellectual disability and autism spectrum disorders. While speech delay, motor impairments and learning difficulties are well documented, brain imaging investigations remain scarce in this population. We combined multimodal neuroimaging and neuropsychological assessments in 12 patients carrying pathogenic ARID1B variants (age = 13.8 ± 4.7 years) and 34 age-matched healthy controls. Whole-brain voxel-wise analyses included arterial spin labelling to measure cerebral blood flow (CBF) at rest and voxel-based morphometry to assess grey matter density. To investigate white matter abnormalities, we performed fixel-based analysis in a subgroup of 7 patients and 17 age-matched controls. While patients showed pronounced language, motor and social impairments, their memory performance ( + 5 SD) largely exceeded other cognitive and motor skills. Whole-brain voxel-wise analyses showed a significant bilateral increase of CBF at rest in several limbic structures, including hippocampi and visual areas. They also showed significant decrease in grey matter density and fibre density in the same limbic structures, language, motor and social circuits. This paradoxical coexistence of hyperperfusion and structural deficits within memory networks suggests functional resilience or compensatory mechanisms. These preserved visual and memory functions strongly contrasted with their impaired language, motor, and social abilities. Patients appeared to rely on visual cues and memory to compensate for deficits in verbal communication. These findings support the development of individualized and innovative interventions that build on preserved visual and memory abilities in children with pathogenic ARID1B variants.