Sex chromosomes and the brain: a study of neuroanatomy in XYY syndrome

Aim To assess global and regional brain matter variations associated with XYY syndrome by comparison with Klinefelter syndrome and typical development. Methods We used two conceptually distinct voxel‐based magnetic resonance imaging methods to examine brain structure in young males with XYY syndrome: (1) volumetric comparison to assess global grey and white matter volumes and (2) support vector machine‐based multivariate pattern classification analysis to assess regional neuroanatomy. We assessed verbal, non‐verbal, and spatial abilities with the Differential Ability Scales (DAS), and we measured autism diagnostic criteria in eight males with XYY syndrome using the Social Responsiveness Scale and the Autism Diagnostic Interview‐Revised (ADI‐R). Results A comparison of 36 typically developing males (mean age 11y, SD 1y 9mo), 31 males with Klinefelter syndrome (mean age 9y 8mo, SD 1y 8mo), and eight males with XYY syndrome (mean age 11y 6mo, SD 1y 11mo) showed that total white and grey matter volumes were significantly, or nearly significantly, higher in males with XYY syndrome than in males belonging to the other two groups (grey matter: XYY males vs typically developing males, p