Maturation of limbic regions in Asperger syndrome: A preliminary study using proton magnetic resonance spectroscopy and structural magnetic resonance imaging

People with autistic spectrum disorders (ASD, including Asperger syndrome) may have developmental abnormalities in the amygdala–hippocampal complex (AHC). However, in vivo, age-related comparisons of both volume and neuronal integrity of the AHC have not yet been carried out in people with Asperger syndrome (AS) versus controls. We compared structure and metabolic activity of the right AHC of 22 individuals with AS and 22 healthy controls aged 10–50 years and examined the effects of age between groups. We used structural magnetic resonace imaging (sMRI) to measure the volume of the AHC, and magnetic resonance spectroscopy (1H-MRS) to measure concentrations of N-acetyl aspartate (NAA), creatine + phosphocreatine (Cr + PCr), myo-inositol (mI) and choline (Cho). The bulk volume of the amygdala and the hippocampus did not differ significantly between groups, but there was a significant difference in the effect of age on the hippocampus in controls. Compared with controls, young (but not older) people with AS had a significantly higher AHC concentration of NAA and a significantly higher NAA/Cr ratio. People with AS, but not controls, had a significant age-related reduction in NAA and the NAA/Cr ratio. Also, in people with AS, but not controls, there was a significant relationship between concentrations of choline and age so that choline concentrations reduced with age. We therefore suggest that people with AS have significant differences in neuronal and lipid membrane integrity and maturation of the AHC.