Jeffrey R. Wozniak

Advances in white matter imaging: A review of in vivo magnetic resonance methodologies and their applicability to the study of development and aging

Several newer magnetic resonance imaging (MRI) techniques are increasingly being applied to the study of white matter development and pathology across the lifespan. These techniques go beyond traditional macrostructural volumetric methods and provide valuable information about underlying tissue integrity and organization at the microstructural and biochemical levels. We first provide an overview of white matter development and discuss the role of white matter and myelin in cognitive function. We also review available studies of development that have employed traditional volumetric measures. Then, we discuss the contributions of four newer imaging paradigms to our understanding of brain development and aging. These paradigms are Diffusion Tensor Imaging (DTI), Magnetization Transfer Imaging (MTI), T2-Relaxography, and Magnetic Resonance Spectroscopy (MRS). Studies examining brain development during childhood and adulthood as well as studies of the effects of aging are discussed.

Microstructural Corpus Callosum Anomalies in Children With Prenatal Alcohol Exposure: An Extension of Previous Diffusion Tensor Imaging Findings

BACKGROUND Several studies have now shown corpus callosum abnormalities using diffusion tensor imaging (DTI) in children with fetal alcohol spectrum disorders (FASD) in comparison with nonexposed controls. The data suggest that posterior regions of the callosum may be disproportionately affected. The current study builds on previous efforts, including our own work, and moves beyond midline corpus callosum to probe major inter-hemispheric white matter pathways with an improved DTI tractographic method. This study also expands on our prior work by evaluating a larger sample and by incorporating children with a broader range of clinical effects including full-criteria fetal alcohol syndrome (FAS). METHODS Participants included 33 children with FASD (8 FAS, 23 partial FAS, 2 static encephalopathy) and 19 nonexposed controls between the ages of 10 and 17 years. Participants underwent DTI scans and intelligence testing. Groups (FASD vs. controls) were compared on fractional anisotropy (FA) and mean diffusivity (MD) in 6 white matter tracts projected through the corpus callosum. Exploratory analyses were also conducted examining the relationships between DTI measures in the corpus callosum and measures of intellectual functioning and facial dysmorphology. RESULTS In comparison with the control group, the FASD group had significantly lower FA in 3 posterior tracts of the corpus callosum: the posterior mid-body, the isthmus, and the splenium. A trend-level finding also suggested lower FA in the genu. Measures of white matter integrity and cognition were correlated and suggest some regional specificity, in that only posterior regions of the corpus callosum were associated with visual-perceptual skills. Correlations between measures of facial dysmorphology and posterior regions of the corpus callosum were nonsignificant. CONCLUSIONS Consistent with previous DTI studies, these results suggest that microstructural posterior corpus callosum abnormalities are present in children with prenatal alcohol exposure and cognitive impairment. These abnormalities are clinically relevant because they are associated with cognitive deficits and appear to provide evidence of abnormalities associated with prenatal alcohol exposure independent of dysmorphic features. As such, they may yield important diagnostic and prognostic information not provided by the traditional facial characteristics.

White matter and neurocognitive changes in adults with chronic traumatic brain injury.

Diffusion tensor imaging was used to investigate white matter (WM) integrity in adults with traumatic brain injury (TBI) and healthy adults as controls. Adults with TBI had sustained severe vehicular injuries on the average of 7 years earlier. A multivariate analysis of covariance with verbal IQ as the covariate revealed that adults with TBI had lower fractional anisotropy and higher mean diffusivity than controls, specifically in the three regions of interest (ROIs), the centrum semiovale (CS), the superior frontal (SPF), and the inferior frontal (INF). Adults with TBI averaged in the normal range in motor speed and two of three executive functions and were below average in delayed verbal recall and inhibition, whereas controls were above average. Time since injury, but not age, was associated with WM changes in the SPF ROI, whereas age, but not time since injury, was associated with WM changes in the INF ROI, suggesting that the effects of WM on time since injury may interact with age. To understand the utility of WM changes in chronic recovery, larger sample sizes are needed to investigate associations between cognition and WM integrity of severely injured individuals who have substantial cognitive impairment compared to severely injured individuals with little cognitive impairment. (JINS, 2009, 15, 130-136.).

A comparative pilot study of second-generation antipsychotics in children and adolescents with schizophrenia-spectrum disorders.

OBJECTIVE There is a limited evidence base to guide treatment of children and adolescents with nonaffective psychoses because few comparative studies of first-line second-generation antipsychotics (SGAs) have been undertaken. To plan the design of a subsequent randomized controlled trial (RCT), the authors conducted this pilot study to demonstrate the feasibility of the treatment and measurement protocols. METHOD Thirty children and adolescents (20 males, 10 females), ages 10-18 years, who met unmodified Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) criteria for a schizophrenia-spectrum disorder (schizophrenia, schizoaffective, schizophreniform, psychotic disorder not otherwise specified) were randomized to receive 12 weeks of open-label, flexibly dosed treatment with either risperidone (mean [standard deviation, SD] dose = 3.4 mg [1.5]), olanzapine (mean [SD] dose = 14.0 mg [4.6]) or quetiapine (mean [SD] dose = 611 mg [253.4]). RESULTS Twenty one (70%) of 30 subjects completed the study. There was no overall statistically significant difference with regard to reduction in Positive and Negative Syndrome Scale (PANSS) total scores in treatment efficacy observed (F((2,24)) = 3.13, p = 0.06). However, the possibility of a large differential treatment effect with regard to change in PANSS total scores favoring risperidone relative to quetiapine (risperidone vs. quetiapine, d = 1.10 [95% confidence interval, CI, 0.09-2.01]) was suggested by the point estimate. CONCLUSIONS These preliminary data, viewed together with the extant literature, suggest that a future larger RCT with only two treatment arms may be warranted to establish whether there is a clinically significant differential treatment effect between risperidone and quetiapine for children and adolescents with nonaffective psychoses. Additional challenges and considerations for mounting a larger RCT are explored.

Global Functional Connectivity Abnormalities in Children with Fetal Alcohol Spectrum Disorders

BACKGROUND Previous studies, including those employing diffusion tensor imaging (DTI), have revealed significant disturbances in the white matter of individuals with fetal alcohol spectrum disorders (FASD). Both macrostructural and microstructural abnormalities have been observed across levels of FASD severity. Emerging evidence suggests that these white matter abnormalities are associated with functional deficits. This study used resting-state functional MRI (fMRI) to evaluate the status of network functional connectivity in children with FASD compared with control subjects. METHODS Participants included 24 children with FASD, ages 10 to 17, and 31 matched controls. Neurocognitive tests were administered including Wechsler Intelligence Scales, California Verbal Learning Test (CVLT), and Behavior Rating Inventory of Executive Functioning. High-resolution anatomical MRI data and 6-minute resting-state fMRI data were collected. The resting-state fMRI data were subjected to a graph theory analysis, and 4 global measures of cortical network connectivity were computed: characteristic path length, mean clustering coefficient, local efficiency, and global efficiency. RESULTS Results revealed significantly altered network connectivity in those with FASD. The characteristic path length was 3.1% higher (p = 0.04, Cohens d = 0.47), and global efficiency was 1.9% lower (p = 0.04, d = 0.63) in children with FASD compared with controls, suggesting decreased network capacity that may have implications for integrative cognitive functioning. Global efficiency was significantly positively correlated with cortical thickness in frontal (r = 0.38, p = 0.005), temporal (r = 0.28, p = 0.043), and parietal (r = 0.36, p = 0.008) regions. No relationship between facial dysmorphology and functional connectivity was observed. Exploratory correlations suggested that global efficiency and characteristic path length are associated with capacity for immediate verbal memory on the CVLT (r = 0.41, p = 0.05 and r = 0.41, p = 0.01, respectively) among those with FASD. CONCLUSIONS Resting-state functional connectivity measures provide new insight into the integrity of brain networks in clinical populations such as FASD. Results demonstrate that children with FASD have alterations in core components of network function and that these aspects of brain integrity are related to measures of structure and cognitive functioning.

Cerebral and muscle MRI abnormalities in myotonic dystrophy

Pathophysiological mechanisms underlying the clinically devastating CNS features of myotonic dystrophy (DM) remain more enigmatic and controversial than do the muscle abnormalities of this common form of muscular dystrophy. To better define CNS and cranial muscle changes in DM, we used quantitative volumetric and diffusion tensor MRI methods to measure cerebral and masticatory muscle differences between controls (n=5) and adults with either congenital (n=5) or adult onset (n=5) myotonic dystrophy type 1 and myotonic dystrophy type 2 (n=5). Muscle volumes were diminished in DM1 and strongly correlated with reduced white matter integrity and gray matter volume. Moreover, correlation of reduced fractional anisotropy (white matter integrity) and gray matter volume in both DM1 and DM2 suggests that these abnormalities may share a common underlying pathophysiological mechanism. Further quantitative temporal and spatial characterization of these features will help delineate developmental and progressive neurological components of DM, and help determine the causative molecular and cellular mechanisms.

Choline supplementation in children with fetal alcohol spectrum disorders: a randomized, double-blind, placebo-controlled trial

BACKGROUND Fetal alcohol spectrum disorders (FASDs) are conditions characterized by physical anomalies, neurodevelopmental abnormalities, and neurocognitive deficits, including intellectual, executive, and memory deficits. There are no specific biological treatments for FASDs, but rodent models have shown that prenatal or postnatal choline supplementation reduces cognitive and behavioral deficits. Potential mechanisms include phospholipid production for axonal growth and myelination, acetylcholine enhancement, and epigenetic effects. OBJECTIVE Our primary goal was to determine whether postnatal choline supplementation has the potential to improve neurocognitive functioning, particularly hippocampal-dependent memory, in children with FASDs. DESIGN The study was a double-blind, randomized, placebo-controlled pilot trial in children (aged 2.5-5 y at enrollment) with FASDs (n = 60) who received 500 mg choline or a placebo daily for 9 mo. Outcome measures were Mullen Scales of Early Learning (primary) and the elicited imitation (EI) memory paradigm (secondary). RESULTS The administration proved feasible, and choline was well tolerated. Participants received a dose on 88% of enrolled days. The only adverse event linked to choline was a fishy body odor. Choline supplementation improved the secondary outcome (EI) only after immediate recall performance was controlled for, and the outcome was moderated by age. The treatment effect on EI items recalled was significant in the younger participants (2.5- to ≤4.0-y-olds); the young choline group showed an increase of 12-14 percentage points greater than that of the young placebo group on delayed recall measures during treatment. However, there was a marginal baseline difference in delayed item recall between the young choline and placebo groups as well as a potential ceiling effect for item recall, both of which likely contributed to the observed treatment effect. We also observed a trend toward a negative effect of choline supplementation on the immediate EI recall of ordered pairs; the young placebo group showed an increase of 8-17 percentage points greater than that of the choline group during treatment. There was an inverse relation between choline dose (in mg/kg) and memory improvement (P = 0.041); the data suggest that weight-adjusted doses may be a better alternative to a fixed dose in future studies. Limitations included trend-level baseline differences in performance, the post-hoc determination of age moderation, and potential ceiling effects for the memory measure. CONCLUSIONS This pilot study suggests that an additional evaluation of choline supplementation as an intervention for memory functioning in children with FASDs is warranted. The observed interaction between age and cholines effect on EI suggests that potential sensitive periods should be considered in future work. This trial was registered at clinicaltrials.gov as NCT01149538.

White matter abnormalities and neurocognitive correlates in children and adolescents with myotonic dystrophy type 1: A diffusion tensor imaging study

Diffusion tensor imaging was used to evaluate cerebral white matter in eight patients (ages 10-17), with myotonic dystrophy type 1 (3 congenital-onset, 5 juvenile-onset) compared to eight controls matched for age and sex. Four regions of interest were examined: inferior frontal, superior frontal, supracallosal, and occipital. The myotonic dystrophy group showed white matter abnormalities compared to controls in all regions. All indices of white matter integrity were abnormal: fractional anisotropy, mean diffusivity, axial diffusivity, and radial diffusivity. With no evidence of regional variation, correlations between whole cerebrum white matter fractional anisotropy and neurocognitive functioning were examined in the patients. Strong correlations were observed between whole cerebrum fractional anisotropy and full-scale intelligence and a measure of executive functioning. Results indicate that significant white matter abnormality is characteristic of young patients with myotonic dystrophy type 1 and that the white matter abnormality seen with neuroimaging has implications for cognitive functioning.

Choline supplementation in children with fetal alcohol spectrum disorders has high feasibility and tolerability.

There are no biological treatments for fetal alcohol spectrum disorders (FASDs), lifelong conditions associated with physical anomalies, brain damage, and neurocognitive abnormalities. In preclinical studies, choline partially ameliorates memory and learning deficits from prenatal alcohol exposure. This phase I pilot study evaluated the feasibility, tolerability, and potential adverse effects of choline supplementation in children with FASD. We hypothesized that choline would be well tolerated with minimal adverse events. The study design was a double-blind, randomized, placebo-controlled trial. Participants included 20 children aged 2.5 to 4.9 years with prenatal alcohol exposure and FASD diagnoses. Participants were randomly assigned to 500 mg choline or placebo daily for 9 months (10 active, 10 placebo). Primary outcome measures included feasibility, tolerability, adverse effects, and serum choline levels. Seventeen participants completed the study. Compliance was 82% to 87%, as evidenced by parent-completed log sheets and dose counts. Periodic 24-hour dietary recalls showed no evidence of dietary confounding. Adverse events were minimal and were equivalent in the active and placebo arms with the exception of fishy body odor, which occurred only in the active group. There were no serious adverse events to research participants. This phase I pilot study demonstrates that choline supplementation at 500 mg/d for 9 months in children aged 2 to 5 years is feasible and has high tolerability. Further examination of the efficacy of choline supplementation in FASD is currently underway.

Inter-Hemispheric Functional Connectivity Disruption in Children With Prenatal Alcohol Exposure

BACKGROUND MRI studies, including recent diffusion tensor imaging (DTI) studies, have shown corpus callosum abnormalities in children prenatally exposed to alcohol, especially in the posterior regions. These abnormalities appear across the range of fetal alcohol spectrum disorders (FASD). Several studies have demonstrated cognitive correlates of callosal abnormalities in FASD including deficits in visual-motor skill, verbal learning, and executive functioning. The goal of this study was to determine whether inter-hemispheric structural connectivity abnormalities in FASD are associated with disrupted inter-hemispheric functional connectivity and disrupted cognition. METHODS Twenty-one children with FASD and 23 matched controls underwent a 6-minute resting-state functional MRI scan as well as anatomical imaging and DTI. Using a semi-automated method, we parsed the corpus callosum and delineated 7 inter-hemispheric white matter tracts with DTI tractography. Cortical regions of interest (ROIs) at the distal ends of these tracts were identified. Right-left correlations in resting fMRI signal were computed for these sets of ROIs, and group comparisons were made. Correlations with facial dysmorphology, cognition, and DTI measures were computed. RESULTS A significant group difference in inter-hemispheric functional connectivity was seen in a posterior set of ROIs, the para-central region. Children with FASD had functional connectivity that was 12% lower than in controls in this region. Subgroup analyses were not possible owing to small sample size, but the data suggest that there were effects across the FASD spectrum. No significant association with facial dysmorphology was found. Para-central functional connectivity was significantly correlated with DTI mean diffusivity, a measure of microstructural integrity, in posterior callosal tracts in controls but not in FASD. Significant correlations were seen between these structural and functional measures, and Wechsler perceptual reasoning ability. CONCLUSIONS Inter-hemispheric functional connectivity disturbances were observed in children with FASD relative to controls. The disruption was measured in medial parietal regions (para-central) that are connected by posterior callosal fiber projections. We have previously shown microstructural abnormalities in these same posterior callosal regions, and the current study suggests a possible relationship between the two. These measures have clinical relevance as they are associated with cognitive functioning.