Localization of white matter volume increase in autism and developmental language disorder

Authors

  • Martha R. Herbert MD, PhD,

    Corresponding author
    1. Center for Morphometric Analysis, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    2. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    • Center for Morphometric Analysis, 149 13th Street, Room 6012, Charlestown, MA 02129
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  • David A. Ziegler BS,

    1. Center for Morphometric Analysis, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    2. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
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  • Nikos Makris MD, PhD,

    1. Center for Morphometric Analysis, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    2. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
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  • Pauline A. Filipek MD,

    1. Departments of Pediatrics and Neurology, University of California College of Medicine, Irvine, CA
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  • Thomas L. Kemper MD,

    1. Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, MA
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  • Joseph J. Normandin BA,

    1. Center for Morphometric Analysis, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    2. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
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  • Heather A. Sanders BA,

    1. University of Pittsburgh School of Medicine, Pittsburgh, PA
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  • David N. Kennedy PhD,

    1. Center for Morphometric Analysis, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    2. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    3. Department of Radiology, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
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  • Verne S. Caviness Jr MD, DPhil

    1. Center for Morphometric Analysis, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
    2. Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Cambridge, MA
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Abstract

Increased brain volume in autism appears to be driven mainly by an unexplained white matter enlargement, and we have reported a similar phenomenon in developmental language disorder (DLD). Localization of this enlargement would strongly guide research into its cause, tissue basis, and functional implications. We utilized a white matter parcellation technique that divides cerebral white matter into an outer zone containing the radiate compartment and an inner zone containing sagittal and bridging system compartments. In both high-functioning autism and DLD, enlargement localized to the radiate white matter (all lobes in autism, all but parietal in DLD), whereas inner zone white matter compartments showed no volume differences from controls. Furthermore, in both autism and DLD, later or longer-myelinating regions showed greater volume increases over controls. Neither group showed cerebral cortex, corpus callosum, or internal capsule volume differences from control. Radiate white matter myelinates later than deep white matter; this pattern of enlargement thus is consistent with striking postnatal head circumference percentile increases reported in autism. These findings suggest an ongoing postnatal process in both autism and DLD that is probably intrinsic to white matter, that primarily affects intrahemispheric and corticocortical connections, and that places these two disorders on the same spectrum.

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