This article on diffusion tensor imaging is particularly relevant to perinatal mitochondrial neurotoxic injuries like hexachlorophene. Early detection, treatment and follow-up would make such a difference.

Diffusion tensor imaging of brain development
Petra S. Hüppi, a, and Jessica Duboisa
aDepartment of Pediatrics, Children's Hospital, University Hospitals of Geneva, 6, rue Willy-Donze, 1211 Geneva 14, Switzerland
Available online 8 September 2006.

Summary
Understanding early human brain development is of great clinical importance, as many neurological and neurobehavioral disorders have their origin in early structural and functional cerebral organization and maturation. Diffusion tensor imaging (DTI), a recent magnetic resonance (MR) modality which assesses water diffusion in biological tissues at a microstructural level, has revealed a powerful technique to explore the structural basis of normal brain development. In fact, the tissue organization can be probed non-invasively, and the age-related changes of diffusion parameters (mean diffusivity, anisotropy) reveal crucial maturational processes, such as white matter myelination. Nevertheless, the developing human brain presents several challenges for DTI applications compared with the adult brain. DTI may further be used to detect brain injury well before conventional MRI, as water diffusion changes are an early indicator of cellular injury. This is particularly critical in infants in the context of administration of neuroprotective therapies. Changes in diffusion characteristics further provide early evidence of both focal and diffuse white matter injury in association with periventricular leukomalacia in the preterm infant. Finally, with the development of 3D fiber tractography, the maturation of white matter connectivity can be followed throughout infant development into adulthood with the potential to study correlations between abnormalities on DTI and ultimate neurologic/cognitive outcome.

Introduction
Understanding early human brain development is of great clinical importance, as many neurological and neurobehavioral disorders have their origin in early structural and functional cerebral maturation. With conventional magnetic resonance imaging (MRI) we have been able to delineate macroscopically early developmental events such as myelination and gyral development. Diffusion tensor imaging (DTI) is a relatively new MR modality that assesses water diffusion in biological tissues at a microstructural level.1
The developing human brain presents several challenges for the application of DTI. Values for the water diffusion parameters differ markedly between pediatric brain and adult brain, and vary with age. As a result, much of the knowledge regarding DTI derived from studies of mature adult human brain is not directly applicable to developing brain. Yet in these challenges also lies opportunity, as changes in water mean diffusivity and diffusion anisotropy during development provide unique insight into the structural basis of brain maturation.
DTI may further be used to evaluate brain injury.2 It is well known from studies of animals3 and adult humans4 that DTI can serve as an early indicator of stroke, often demonstrating image abnormalities on water diffusion maps well before conventional MRI. Early detection of injury is particularly critical in the context of administration of neuroprotective therapies to infants. These therapies must be initiated quickly in order to interrupt the cascade of irreversible brain injury.5 Water diffusion maps derived from DTI may provide the means for this early detection of injury. Changes in diffusion characteristics further provide early evidence of both focal and diffuse brain injury in association with periventricular leukomalacia (PVL), the most common form of white matter injury in the preterm infant.6 Finally, with the development of 3D diffusion tensor fiber tractography, maturation of white matter and its consequences for white matter connectivity can be followed throughout infant development into adulthood, with the potential to study correlations between abnormalities on DTI and ultimate neurologic/cognitive outcome.7
In this review, we will discuss the changes in DTI parameters associated with normal brain maturation as well as their response to brain injury.

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DTI and functional development during childhood

Finally, DTI parameters – particularly anisotropy – may be considered as structural markers of the networks functional organization and maturation, as proposed recently by correlation studies in children and adolescents. For instance, the development of working memory and reading capacities, between 8 and 18 years of age, is linked to the white matter anisotropy in regions of the left frontal and temporal lobes.59 The maturation of these regions, as assessed by DTI, is correlated with the BOLD response amplitude, as measured by functional MRI.58 Reading capacities in normal and dyslexic children60 and 61 seem to depend on the organization and/or the myelination of temporo-parietal pathways, as described in adults.62 Finally, diffusion parameters appear to be immature in children with functional developmental delay.63 The application of DTI in the neonatal brain then provides an early assessment of its functional development, should it be normal or delayed.

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Conclusions

Important changes in water ADC and diffusion anisotropy accompany brain maturation. These changes reflect changes in brain tissue microstructure. In the case of grey matter, this may reflect changes in the dendritic architecture of pyramidal cells and the presence or absence of radial glial fibers. In the case of white matter, it is due to the establishment of white matter fiber connection and changes related both to ‘premyelination’ and myelination itself. Thus DTI is a unique, non-invasive technique to study brain maturation which can be readily applied to human development. DTI-based fiber tracking allows study of the establishment of brain connectivity and plasticity during a time period of extreme importance for structural and functional integrity of the brain.
DTI also allows detection of changes in response to brain injury. Decreases in the water ADC serve as an early indicator of brain injury relevant for initiation of neuroprotective treatments. Regional, maturation-dependent differences in baseline diffusion coefficients need to be considered when interpreting injury-related diffusion abnormalities. Chronic changes in water anisotropy and the evaluation by DTI vector imaging are sensitive to injury-related impairment of subsequent white matter development and brain connectivity, important early markers of later neurodevelopmental impairment. DTI in the newborn brain has allowed study of non-hemorrhagic brain injury early on, and has further opened up the possibility to study the structural correlate of functional impairment and plasticity in the developing brain.

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Here is another DTI article.

Autism and myelin/ white matter deficits:

Is there a relationship with the effects of mercury?

The link between autism and mercury is well beyond my ability to comment on, but his is an interesting study on the integrity of the white matter.

Again, this and other DTI research make me wonder about the value of Using this type of brain imaging to take another look at the toxicity of Hexachlorophene.

Would some of us exposed to this mitochondrial neurotoxin as babies also show white matter integrity problems on a DTI?

It certainly makes sense to look at those of us who are now young and older adults.

News-Medical.Net

New imaging technique reveals differences in brains of people with autism
Devices/Technology
Published: Monday, 23-Oct-2006


Using a new form of brain imaging known as diffusion tensor imaging (DTI), researchers in the Center for Cognitive Brain Imaging at Carnegie Mellon University have discovered that the so-called white matter in the brains of people with autism has lower structural integrity than in the brains of normal individuals.
This provides further evidence that the anatomical differences characterizing the brains of people with autism are related to the way those brains process information.
The results of this latest study were published in the journal NeuroReport. The scientists used DTI -- which tracks the movement of water through brain tissue -- to measure the structural integrity of the white matter that acts as cables to wire the parts of the brain together. Normally, water molecules move, or diffuse, in a direction parallel to the orientation of the nerve fibers of the white matter. They're aided by the coherent structure of the fibers and a process called myelination, in which a sheath is formed around the fibers that speeds nerve impulses. The movement of water is more dispersed if the structural integrity of the tissue is low -- i.e., if the fibers are less dense, less coherently organized, or less myelinated -- as it was with the participants with autism in the Carnegie Mellon study. Researchers found this dispersed pattern particularly in areas in and around the corpus callosum, the large band of nerve fibers that connects the two hemispheres of the brain.
"These reductions in white matter integrity may underlie the behavioral pattern observed in autism of narrowly-focused thought and weak coherence of different streams of thought," said Marcel Just, director of the Center for Cognitive Brain Imaging and a co-author of the latest study. "The new findings also provide supporting evidence for a new theory of autism that attributes the disorder to underconnectivity among brain regions," Just said.
In 2004, Just and his colleagues proposed the underconnectivity theory based on a groundbreaking study in which they discovered abnormalities in the white matter that suggested a lack of coordination among brain areas in people with autism. This theory helps explain a paradox of autism: Some people with autism have normal or even superior skills in some areas, while many other types of thinking are disordered.
Last summer, Just led a team of researchers that found for the first time that the abnormality in synchronization among brain areas is related to the abnormality in the white matter. They discovered that key portions of the corpus callosum seem to play a role in the limitation on synchronization. In people with autism, anatomical connectivity -- based on the size of the white matter -- was found to be positively correlated with functional connectivity, which is the synchronization of the active brain regions. They also found that the functional connectivity was lower in those participants in whom the autism was more severe.
These studies, along with the latest paper, are providing a comprehensive picture of the autistic brain, whose components operate with less coordination than is normally the case, and which is less reliant on frontal components and more reliant on posterior components. The latest DTI finding shows that some of the frontal-posterior communication fiber tracts are abnormal, consistent with the lower degree of frontal-posterior coordination.
"The brain components in autism function more like a jam session and less like a symphony," Just said.
http://www.cmu.edu/