Neuroanatomy of Down’s Syndrome: A High-Resolution MRI Study

TLDR

Down’s syndrome is the most common genetic cause of mental retardation, characterized by physical and neuropsychological deficits such as impaired language and memory. The study aimed to confirm previously reported regional brain volume abnormalities in Down’s syndrome, determine whether these changes are present from childhood, and examine their relationship with cognitive function. Sixteen children and young adults with Down’s syndrome, matched for age and gender to 15 controls, underwent high‑resolution MRI scans that were quantitatively analyzed for overall and regional brain volumes and tissue composition. Subjects with Down’s syndrome exhibited smaller overall brain volumes, disproportionately reduced cerebellar size, larger subcortical gray matter, preserved parietal gray and temporal white matter, no asymmetry differences, and these early‑onset abnormalities likely underlie their cognitive deficits.

Abstract

OBJECTIVE: Down’s syndrome, the most common genetic cause of mental retardation, results in characteristic physical and neuropsychological findings, including mental retardation and deficits in language and memory. This study was undertaken to confirm previously reported abnormalities of regional brain volumes in Down’s syndrome by using high-resolution magnetic resonance imaging (MRI), determine whether these volumetric abnormalities are present from childhood, and consider the relationship between neuroanatomic abnormalities and the cognitive profile of Down’s syndrome. METHOD: Sixteen children and young adults with Down’s syndrome (age range=5–23 years) were matched for age and gender with 15 normal comparison subjects. High-resolution MRI scans were quantitatively analyzed for measures of overall and regional brain volumes and by tissue composition. RESULTS: Consistent with prior imaging studies, subjects with Down’s syndrome had smaller overall brain volumes, with disproportionately smaller cerebellar volumes and relatively larger subcortical gray matter volumes. Also noted was relative preservation of parietal lobe gray and temporal lobe white matter in subjects with Down’s syndrome versus comparison subjects. No abnormalities in pattern of brain asymmetry were noted in Down’s syndrome subjects. CONCLUSIONS: The results largely confirm findings of previous studies with respect to overall patterns of brain volumes in Down’s syndrome and also provide new evidence for abnormal volumes of specific regional tissue components. The presence of these abnormalities from an early age suggests that fetal or early postnatal developmental differences may underlie the observed pattern of neuroanatomic abnormalities and contribute to the specific cognitive and developmental deficits seen in individuals with Down’s syndrome.