White matter imaging in holoprosencephaly in children.
OBJECTIVE
Holoprosencephaly is a disorder of forebrain development characterized by a failure of the brain to separate into two hemispheres during early development. It is now clear that many cases of holoprosencephaly are caused by alterations in the genetic programmes that pattern the nervous system. Less is known about how a holoprosencephalic brain either forms or fails to form connections between various brain structures.


RESULTS
Abnormalities in the corpus callosum, corticospinal tract, medial lemniscus and cerebellar peduncles can be seen in holoprosencephaly. Diffusion tensor imaging has been and will continue to be an important tool for imaging white matter in the brain, and will be reviewed here. Furthermore, recent evidence suggests that holoprosencephaly can be associated with delays or abnormalities in myelination. The functional implications of white matter abnormalities in children with holoprosencephaly is only beginning to be understood.


CONCLUSIONS
Modern neuroimaging has led to a better appreciation of the variability seen in holoprosencephaly, an anomaly known to have multiple etiologies. Recent reviews of the biology of holoprosencephaly identify the condition as a defect in dorsoventral patterning. More detailed white and grey matter structure-function studies are likely to shed light on how a brain with drastically altered composition and connectivity does or does not organize itself to accomplish increasingly complex developmental functions.
Kinsman
Stephen L
SL
Departments of Pediatrics and Neurology, University of Maryland School of Medicine, Baltimore, Maryland, USA.
D000818:Animals; D001921:Brain / Q000002:abnormalities / Q000473:pathology*; D001931:Brain Mapping; D002648:Child; D038524:Diffusion Magnetic Resonance Imaging; D015870:Gene Expression; D053823:Hedgehog Proteins; D016142:Holoprosencephaly / Q000175:diagnosis* / Q000235:genetics; D006801:Humans; D008279:Magnetic Resonance Imaging; D051379:Mice; D009413:Nerve Fibers, Myelinated / Q000473:pathology; D015534:Trans-Activators / Q000235:genetics
D053823:Hedgehog Proteins; D015534:Trans-Activators