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ABSTRACT: Neurofibromatosis type-1 (NF-1) is the most common autosomal dominant disorder affecting the central nervous system. Magnetic resonance imaging (MRI) has revealed distinctive T2-weighted hyperintense foci (termed unidentified bright objects, UBOs) which appear to represent spongiform changes in the white matter. Cross-sectional and longitudinal analyses suggest that UBOs disappear over time; however, none of these studies have examined comprehensively these foci. We conducted a quantitative MRI longitudinal study of number of affected regions, number of UBOs per region, and UBO volume per region, in a sample of 12 children with NF-1. We applied semi-automatic morphometric methods and comprehensive statistical approaches, within a detailed anatomical parcellation framework. Our data demonstrate that, despite a similar UBO regional distribution (e.g., prevalent globus pallidus/internal capsule (GP/IC) location), UBO evolution was more complex than previously reported. In some subjects, the total number of UBO-occupied locations demonstrated a decrease between approximately ages 7 and 12 years, followed by a progressive increase during adolescence. This pattern was also found for UBO number and/or volume for all regions, with the exception of the cerebellar hemispheres. This REGIONAL distinction may reflect differences in white matter structure between affected long tract fiber bundles and that of cerebral and cerebellar myelinated fibers. The findings are also discussed in the context of previous MR and behavioral studies. We conclude that studies like the present one, in association with other MR modalities, are necessary to characterize more completely the nature and evolution of UBOs and their role in the cognitive phenotype of NF-1.
American Journal of Medical Genetics Part A 09/2004; 129A(2):113-9. · 2.39 Impact Factor
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ABSTRACT: To gain insight into the specificity of cerebellar vermian abnormalities reported in autism, we conducted a magnetic resonance imaging (MRI) study of boys with either of two conditions associated with autism, Down syndrome and fragile X syndrome, compared with boys with idiopathic autism and controls. The subjects, ranging in age from 3 to 9 years, included 16 boys with Down syndrome + autism and 11 boys with Down syndrome only; 13 boys with fragile X syndrome + autism and 9 boys with fragile X syndrome only; 10 boys with idiopathic autism; and 22 controls. Diagnosis of autism was based on DSM-IV criteria, confirmed primarily by the Autism Diagnostic Interview. T1-weighted midsagittal MRIs were used to measure midline structures. Intracranial area, reflecting brain size, was significantly smaller in subjects with Down syndrome. Therefore, all vermian measures were expressed as ratios to intracranial area. Analysis of covariance (covarying for age and IQ) demonstrated that posterior vermi (lobules VI-VII and VIII-X) were markedly smaller in both Down syndrome groups and those with fragile X syndrome only, whereas only lobules VI-VII were reduced in idiopathic autism. Factorial analyses of variance tested interactions between autism factor and the diagnosis of Down syndrome or fragile X syndrome. The size of lobules VI-VII/intracranial area was dependent on autism status only in fragile X syndrome, with ratios significantly larger in fragile X syndrome with autism with respect to fragile X syndrome only. We conclude that selective posterior vermis hypoplasia is seen not only in idiopathic autism but also in Down syndrome and some individuals with fragile X syndrome. However, reductions in vermian lobules VI and VII appear to be specific to idiopathic autism, whereas increased size of lobules VI and VII is associated with autism in fragile X syndrome. The latter results are consistent with MRI studies showing lobules VI-VII hyperplasia in a subset of subjects with idiopathic autism and cerebral and hippocampal enlargements in fragile X syndrome.
Journal of Child Neurology 08/2003; 18(7):463-70. · 1.75 Impact Factor
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ABSTRACT: Anatomic magnetic resonance imaging (MRI) studies of attention-deficit/hyperactivity disorder (ADHD) have been limited by use of callosal rather than sulcal/gyral landmarks in defining cerebral lobes and functionally relevant sublobar regions (e.g., prefrontal cortex). We present an investigation of cerebral volumes in ADHD using a Talairach-based approach that uses cortical landmarks to define functionally relevant regions.
Volumes were compared between groups of 12 boys with ADHD and 12 age- and gender-matched control subjects, using a series of multiple analyses of variance.
Boys with ADHD had (on average) 8.3% smaller total cerebral volumes. Significant reductions in lobar volumes were seen only for the frontal lobes. Within the frontal lobes, a reduction was seen in both gray and white matter volumes, with some evidence suggesting lateralization of these findings: reduction in frontal white matter volume was specific to the left hemisphere; there was a bilateral reduction in frontal gray matter volume but more so in the right hemisphere. Subparcellation of the frontal lobe revealed smaller prefrontal, premotor, and deep white matter volumes.
Findings suggest that ADHD is associated with decreased frontal lobe gray and white matter volumes. More than one subdivision of the frontal lobes appears to be reduced in volume, suggesting that the clinical picture of ADHD encompasses dysfunctions attributable to anomalous development of both premotor and prefrontal cortices.
Biological Psychiatry 11/2002; 52(8):785-94. · 8.28 Impact Factor
