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Hippocampal myo-inositol and cognitive ability in adults with Down syndrome: an in vivo proton magnetic resonance spectroscopy study.

Beacher F, Simmons A, Daly E, Prasher V, Adams C, Margallo-Lana ML, Morris R, Lovestone S, Murphy K, Murphy DG

Section of Brain Maturation, Department of Psychological Medicine, Neuroimaging Research Group, Institute of Psychiatry, De Crespigny Park, Denmark Hill, London SE5 8AF, England, UK.

CONTEXT: Down syndrome (DS) is the most common genetic cause of mental retardation. However, the biological determinants of this are poorly understood. The serum sodium/myo-inositol cotransporter gene is located on chromosome 21, and myo-inositol affects neuronal survival and function. Nevertheless, few in vivo studies have examined the role of myo-inositol in DS. OBJECTIVE: To determine if people with DS have significant differences in brain myo-inositol concentration from controls and if, within people with DS, this is related to cognitive ability. DESIGN: A case-control study. SETTING: Outpatient. PARTICIPANTS: The sample was composed of 38 adults with DS without dementia (age range, 18-66 years) and 42 healthy controls (age range, 19-66 years). The DS and control groups did not differ significantly in age, sex, ethnic origin, apolipoprotein E status, or handedness. MAIN OUTCOME MEASURES: Hippocampal myo-inositol concentration and cognitive performance, as measured by the Cambridge Cognitive Examination. RESULTS: Hippocampal myo-inositol concentration was significantly higher in people with DS than in controls (P = .006), and within people with DS, increased myo-inositol concentration was significantly negatively correlated with overall cognitive ability (P = .04). CONCLUSIONS: Adults with DS have a significantly increased brain concentration of myo-inositol, and this is associated with reduced cognitive ability. Future studies are required to relate myo-inositol concentration in people with DS to brain development and increased risk for developing Alzheimer disease.

Published 6 December 2005 in Arch Gen Psychiatry, 62(12): 1360-5.
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