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3.
Neuroimage ; 125: 456-478, 2016 Jan 15.
Artigo em Inglês | MEDLINE | ID: mdl-26499811

RESUMO

Detailed morphometric analysis of the neonatal brain is required to characterise brain development and define neuroimaging biomarkers related to impaired brain growth. Accurate automatic segmentation of neonatal brain MRI is a prerequisite to analyse large datasets. We have previously presented an accurate and robust automatic segmentation technique for parcellating the neonatal brain into multiple cortical and subcortical regions. In this study, we further extend our segmentation method to detect cortical sulci and provide a detailed delineation of the cortical ribbon. These detailed segmentations are used to build a 4-dimensional spatio-temporal structural atlas of the brain for 82 cortical and subcortical structures throughout this developmental period. We employ the algorithm to segment an extensive database of 420 MR images of the developing brain, from 27 to 45weeks post-menstrual age at imaging. Regional volumetric and cortical surface measurements are derived and used to investigate brain growth and development during this critical period and to assess the impact of immaturity at birth. Whole brain volume, the absolute volume of all structures studied, cortical curvature and cortical surface area increased with increasing age at scan. Relative volumes of cortical grey matter, cerebellum and cerebrospinal fluid increased with age at scan, while relative volumes of white matter, ventricles, brainstem and basal ganglia and thalami decreased. Preterm infants at term had smaller whole brain volumes, reduced regional white matter and cortical and subcortical grey matter volumes, and reduced cortical surface area compared with term born controls, while ventricular volume was greater in the preterm group. Increasing prematurity at birth was associated with a reduction in total and regional white matter, cortical and subcortical grey matter volume, an increase in ventricular volume, and reduced cortical surface area.


Assuntos
Anatomia Artística , Atlas como Assunto , Encéfalo/crescimento & desenvolvimento , Recém-Nascido Prematuro/crescimento & desenvolvimento , Neuronavegação/métodos , Feminino , Humanos , Recém-Nascido , Imagem por Ressonância Magnética , Gravidez , Nascimento Prematuro
4.
PLoS One ; 10(5): e0125681, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-25955638

RESUMO

White matter tracts mature asymmetrically during development, and this development can be studied using diffusion magnetic resonance imaging. The aims of this study were i. to generate dynamic population-averaged white matter registration templates covering in detail the period from 25 weeks gestational age to term, and extending to 2 years of age based on DTI and fractional anisotropy, ii. to produce tract-specific probability maps of the corticospinal tracts, forceps major and forceps minor using probabilistic tractography, and iii. to assess the development of these tracts throughout this critical period of neurodevelopment. We found evidence for asymmetric development across the fiber bundles studied, with the corticospinal tracts showing earlier maturation (as measured by fractional anisotropy) but slower volumetric growth compared to the callosal fibers. We also found evidence for an anterior to posterior gradient in white matter microstructure development (as measured by mean diffusivity) in the callosal fibers, with the posterior forceps major developing at a faster rate than the anterior forceps minor in this age range. Finally, we report a protocol for delineating callosal and corticospinal fibers in extremely premature cohorts, and make available population-averaged registration templates and a probabilistic tract atlas which we hope will be useful for future neonatal and infant white-matter imaging studies.


Assuntos
Corpo Caloso/crescimento & desenvolvimento , Tratos Piramidais/crescimento & desenvolvimento , Corpo Caloso/diagnóstico por imagem , Bases de Dados Factuais , Imagem de Difusão por Ressonância Magnética , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Recém-Nascido de muito Baixo Peso , Masculino , Nascimento Prematuro , Tratos Piramidais/diagnóstico por imagem , Radiografia
5.
Dev Med Child Neurol ; 57 Suppl 3: 8-16, 2015 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25800487

RESUMO

Hypoxic-ischaemic encephalopathy (HIE) is a leading cause of acquired neonatal brain injury. Assessment of the severity of cerebral injury and likely neurological outcome in infants with HIE is important for determining management and prognosis, for counselling parents, and for selection for neuroprotective trials. The condition of the infant at birth, the severity of HIE, neurophysiological tests, including amplitude-integrated electroencephalography (aEEG), biochemical markers, and neuroimaging have been used to assess prognosis and predict long-term outcome. The predictive accuracy of these indicators in the early postnatal period is modest. Neurophysiological assessment seems to be most helpful during the first 24 to 48 hours after birth whilst magnetic resonance imaging (MRI) seems most informative later. Several biochemical markers, including serum S100ß and neuron-specific enolase (NSE), are also associated with HIE but their levels depend on the timing of sampling and their prognostic value is uncertain. Comprehensive neurophysiological assessment and neuroimaging may be limited to specialist centres. Therapeutic hypothermia is now standard care in infants with moderate to severe HIE so it is important to examine the influence of hypothermia on the assessment of prognosis in these infants.


Assuntos
Hipotermia Induzida/estatística & dados numéricos , Hipóxia-Isquemia Encefálica/complicações , Hipóxia-Isquemia Encefálica/terapia , Doenças do Sistema Nervoso/etiologia , Biomarcadores/metabolismo , Encéfalo/metabolismo , Encéfalo/patologia , Humanos , Lactente , Recém-Nascido , Doenças do Sistema Nervoso/diagnóstico , Valor Preditivo dos Testes , Resultado do Tratamento
6.
Cereb Cortex ; 25(11): 4310-8, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-25596587

RESUMO

Thalamocortical connections are: essential for brain function, established early in development, and significantly impaired following preterm birth. Impaired cognitive abilities in preterm infants may be related to disruptions in thalamocortical connectivity. The aim of this study was to test the hypothesis: thalamocortical connectivity in the preterm brain at term-equivalent is correlated with cognitive performance in early childhood. We examined 57 infants who were born <35 weeks gestational age (GA) and had no evidence of focal abnormality on magnetic resonance imaging (MRI). Infants underwent diffusion MRI at term and cognitive performance at 2 years was assessed using the Bayley III scales of Infant and Toddler development. Cognitive scores at 2 years were correlated with structural connectivity between the thalamus and extensive cortical regions at term. Mean thalamocortical connectivity across the whole cortex explained 11% of the variance in cognitive scores at 2 years. The inclusion of GA at birth and parental socioeconomic group in the model explained 30% of the variance in subsequent cognitive performance. Identifying impairments in thalamocortical connectivity as early as term equivalent can help identify those infants at risk of subsequent cognitive delay and may be useful to assess efficacy of potential treatments at an early age.


Assuntos
Córtex Cerebral/patologia , Transtornos Cognitivos/diagnóstico , Transtornos Cognitivos/etiologia , Nascimento Prematuro/patologia , Nascimento Prematuro/fisiopatologia , Tálamo/patologia , Imagem de Difusão por Ressonância Magnética , Feminino , Idade Gestacional , Substância Cinzenta/patologia , Humanos , Processamento de Imagem Assistida por Computador , Lactente , Recém-Nascido , Modelos Lineares , Imagem por Ressonância Magnética , Masculino , Vias Neurais/patologia , Testes Neuropsicológicos , Valor Preditivo dos Testes
7.
Pediatrics ; 133(6): e1655-63, 2014 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-24819575

RESUMO

BACKGROUND: The role of heritable factors in determining the common neurologic deficits seen after preterm birth is unknown, but the characteristic phenotype of neurocognitive, neuroanatomical, and growth abnormalities allows principled selection of candidate genes to test the hypothesis that common genetic variation modulates the risk for brain injury. METHODS: We collected an MRI-linked genomic DNA library from 83 preterm infants and genotyped tag single nucleotide polymorphisms in 13 relevant candidate genes. We used tract-based spatial statistics and deformation-based morphometry to examine the risks conferred by carriage of particular alleles at tag single nucleotide polymorphisms in a restricted number of genes and related these to the preterm cerebral endophenotype. RESULTS: Carriage of the minor allele at rs2518824 in the armadillo repeat gene deleted in velocardiofacial syndrome (ARVCF) gene, which has been linked to neuronal migration and schizophrenia, and rs174576 in the fatty acid desaturase 2 gene, which encodes a rate-limiting enzyme for endogenous long chain polyunsaturated fatty acid synthesis and has been linked to intelligence, was associated with white matter abnormality measured in vivo using diffusion tensor imaging (P = .0009 and P = .0019, respectively). CONCLUSIONS: These results suggest that genetic variants modulate white matter injury after preterm birth, and known susceptibilities to neurologic status in later life may be exposed by the stress of premature exposure to the extrauterine environment.


Assuntos
Dano Encefálico Crônico/diagnóstico , Dano Encefálico Crônico/genética , Estudos de Associação Genética , Predisposição Genética para Doença/genética , Variação Genética/genética , Doenças do Prematuro/diagnóstico , Doenças do Prematuro/genética , Alelos , Proteínas do Domínio Armadillo/genética , Encéfalo/patologia , Catecol O-Metiltransferase/genética , Moléculas de Adesão Celular/genética , Cromossomos Humanos Par 11/genética , Cromossomos Humanos Par 22/genética , Estudos de Coortes , Imagem de Difusão por Ressonância Magnética , Endofenótipos , Ácidos Graxos Dessaturases/genética , Biblioteca Gênica , Triagem de Portadores Genéticos , Genótipo , Humanos , Interpretação de Imagem Assistida por Computador , Recém-Nascido , Inteligência/genética , Imagem por Ressonância Magnética , Fosfoproteínas/genética , Polimorfismo de Nucleotídeo Único/genética , Esquizofrenia/genética
8.
Proc Natl Acad Sci U S A ; 111(20): 7456-61, 2014 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-24799693

RESUMO

Combining diffusion magnetic resonance imaging and network analysis in the adult human brain has identified a set of highly connected cortical hubs that form a "rich club"--a high-cost, high-capacity backbone thought to enable efficient network communication. Rich-club architecture appears to be a persistent feature of the mature mammalian brain, but it is not known when this structure emerges during human development. In this longitudinal study we chart the emergence of structural organization in mid to late gestation. We demonstrate that a rich club of interconnected cortical hubs is already present by 30 wk gestation. Subsequently, until the time of normal birth, the principal development is a proliferation of connections between core hubs and the rest of the brain. We also consider the impact of environmental factors on early network development, and compare term-born neonates to preterm infants at term-equivalent age. Though rich-club organization remains intact following premature birth, we reveal significant disruptions in both in cortical-subcortical connectivity and short-distance corticocortical connections. Rich club organization is present well before the normal time of birth and may provide the fundamental structural architecture for the subsequent emergence of complex neurological functions. Premature exposure to the extrauterine environment is associated with altered network architecture and reduced network capacity, which may in part account for the high prevalence of cognitive problems in preterm infants.


Assuntos
Encéfalo/embriologia , Encéfalo/crescimento & desenvolvimento , Rede Nervosa/fisiologia , Mapeamento Encefálico , Cognição , Conectoma , Imagem de Difusão por Ressonância Magnética , Feminino , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Vias Neurais , Nascimento Prematuro , Nascimento a Termo , Fatores de Tempo
9.
Cortex ; 56: 30-7, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22482694

RESUMO

INTRODUCTION: Visual impairment in preterm infants at term equivalent age (TEA) is associated with impaired microstructural development in the optic radiation, measured as reduced fractional anisotropy (FA) by Diffusion Tensor Imaging (DTI). We tested the hypothesis that these abnormalities develop during the late preterm period. METHODS: DTI was performed in 53 infants born at a median (range) of 30(+1) (25(+4)-34(+6)) weeks post-menstrual age (PMA), 22 of whom were imaged twice. RESULTS: FA in the optic radiation at TEA was related to: visual function (p = .003); PMA at birth (p = .015); and PMA at scan (p = .008); while a significant interaction between PMA at birth and scan (p = .019) revealed an effect of the period of premature extra-uterine life additional to the degree of prematurity. We explored this further in a sub-group of 22 infants who were studied twice. FA increased from mean (95% CI) .174 (.164-.176) on the first image at 32(+5) (29(+5)-36) weeks PMA, to .198 (.190-.206) on the second image at 40(+6) (39(+2)-46) weeks PMA. Visual function was not predicted by FA on the images obtained in the early neonatal period, but was significantly related to the rate of increase in FA between scans (p = .027) and to FA on the second image (p = .015). CONCLUSION: Microstructural maturation during the late preterm period is thus required for normal visual function, suggesting that interventions applied after 30 weeks PMA might reduce impairment in preterm infants.


Assuntos
Encéfalo/fisiopatologia , Fibras Nervosas Mielinizadas/fisiologia , Transtornos da Visão/fisiopatologia , Visão Ocular/fisiologia , Anisotropia , Encéfalo/crescimento & desenvolvimento , Imagem de Tensor de Difusão , Feminino , Humanos , Lactente , Recém-Nascido , Recém-Nascido Prematuro , Recém-Nascido de muito Baixo Peso , Masculino
10.
PLoS One ; 8(7): e67706, 2013.
Artigo em Inglês | MEDLINE | ID: mdl-23844070

RESUMO

Early neuroimaging may provide a surrogate marker for brain development and outcome after preterm birth. Tract-Based Spatial Statistics (TBSS) is an advanced Diffusion Tensor Image (DTI) analysis technique that is sensitive to the effects of prematurity and may provide a quantitative marker for neuroprotection following perinatal brain injury or preterm birth. Here, we test the sensitivity of TBSS to detect diffuse microstructural differences in the developing white matter of preterm infants at term-equivalent age by modelling a 'treatment' effect as a global increase in fractional anisotropy (FA). As proof of concept we compare these simulations to a real effect of increasing age at scan. 3-Tesla, 15-direction diffusion tensor imaging (DTI) was acquired from 90 preterm infants at term-equivalent age. Datasets were randomly assigned to 'treated' or 'untreated' groups of increasing size and voxel-wise increases in FA were used to simulate global treatment effects of increasing magnitude in all 'treated' maps. 'Treated' and 'untreated' FA maps were compared using TBSS. Predictions from simulated data were then compared to exemplar TBSS group comparisons based on increasing postmenstrual age at scan. TBSS proved sensitive to global differences in FA within a clinically relevant range, even in relatively small group sizes, and simulated data were shown to predict well a true biological effect of increasing age on white matter development. These data confirm that TBSS is a sensitive tool for detecting global group-wise differences in FA in this population.


Assuntos
Encéfalo/crescimento & desenvolvimento , Imagem de Tensor de Difusão , Recém-Nascido Prematuro/crescimento & desenvolvimento , Neuroimagem , Encéfalo/patologia , Feminino , Idade Gestacional , Humanos , Lactente , Recém-Nascido , Masculino , Nascimento Prematuro/diagnóstico , Nascimento Prematuro/terapia , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
11.
Br J Clin Pharmacol ; 76(5): 725-33, 2013 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-23432339

RESUMO

AIMS: Preterm infants are deprived of the normal intra-uterine exposure to maternal melatonin and may benefit from replacement therapy. We conducted a pharmacokinetic study to guide potential therapeutic trials. METHODS: Melatonin was administered to 18 preterm infants in doses ranging from 0.04-0.6 µg kg(-1) over 0.5-6 h. Pharmacokinetic profiles were analyzed individually and by population methods. RESULTS: Baseline melatonin was largely undetectable. Infants receiving melatonin at 0.1 µg kg(-1) h(-1) for 2 h showed a median half-life of 15.82 h and median maximum plasma concentration of 203.3 pg ml(-1) . On population pharmacokinetics, clearance was 0.045 l h(-1) , volume of distribution 1.098 l and elimination half-life 16.91 h with gender (P = 0.047) and race (P < 0.0001) as significant covariates. CONCLUSIONS: A 2 h infusion of 0.1 µg kg(-1) h(-1) increased blood melatonin from undetectable to approximately peak adult concentrations. Slow clearance makes replacement of a typical maternal circadian rhythm problematic. The pharmacokinetic profile of melatonin in preterm infants differs from that of adults so dosage of melatonin for preterm infants cannot be extrapolated from adult studies. Data from this study can be used to guide therapeutic clinical trials of melatonin in preterm infants.


Assuntos
Ritmo Circadiano , Terapia de Reposição Hormonal/métodos , Melatonina/farmacocinética , Relação Dose-Resposta a Droga , Feminino , Meia-Vida , Humanos , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Melatonina/administração & dosagem , Fatores Sexuais , Distribuição Tecidual
12.
Cortex ; 49(6): 1711-21, 2013 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22959979

RESUMO

INTRODUCTION: Defining connectivity in the human brain signifies a major neuroscientific goal. Advanced imaging techniques have enabled the non-invasive tracing of brain networks to define the human connectome on a millimetre-scale. During early development, the brain undergoes significant changes that are likely represented in the developing connectome, and preterm birth represents a significant environmental risk factor that impacts negatively on early cerebral development. Using tractography to comprehensively map the connections of the thalamocortical unit, we aim to demonstrate that premature extrauterine life due to preterm delivery results in significantly decreased thalamocortical connectivity in the developing human neonate. METHODS: T1- and T2-weighted magnetic resonance images and 32-direction diffusion tensor images were acquired from 18 healthy term-born neonates (median gestational age: 41(+3)) and 47 preterm infants (median gestational age: 28(+3)) scanned at term-equivalent age. Using a novel processing pipeline for tracing connections in the neonatal brain we map and compare the thalamocortical macro-connectome between groups. RESULTS: We demonstrate that connections between the thalamus and the frontal cortices, supplementary motor areas, occipital lobe and temporal gyri are significantly diminished in preterm infants (FDR-corrected, p < .001). CONCLUSIONS: This supports the hypothesis that the thalamocortical system is vulnerable following preterm birth and the tractographic framework presented represents a method for analysing system connectivity that can be readily applied to other populations and neural systems.


Assuntos
Córtex Cerebral/crescimento & desenvolvimento , Córtex Cerebral/fisiologia , Conectoma , Recém-Nascido Prematuro/fisiologia , Vias Neurais/crescimento & desenvolvimento , Vias Neurais/fisiologia , Tálamo/crescimento & desenvolvimento , Tálamo/fisiologia , Mapeamento Encefálico , Interpretação Estatística de Dados , Imagem de Difusão por Ressonância Magnética , Imagem de Tensor de Difusão , Imagem Ecoplanar , Meio Ambiente , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Recém-Nascido , Imagem por Ressonância Magnética , Masculino , Nascimento Prematuro
13.
Neuroimage ; 63(2): 663-73, 2012 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-22776460

RESUMO

In the rodent brain the hemodynamic response to a brief external stimulus changes significantly during development. Analogous changes in human infants would complicate the determination and use of the hemodynamic response function (HRF) for functional magnetic resonance imaging (fMRI) in developing populations. We aimed to characterize HRF in human infants before and after the normal time of birth using rapid sampling of the blood oxygen level dependent (BOLD) signal. A somatosensory stimulus and an event related experimental design were used to collect data from 10 healthy adults, 15 sedated infants at term corrected post menstrual age (PMA) (median 41+1 weeks), and 10 preterm infants (median PMA 34+4 weeks). A positive amplitude HRF waveform was identified across all subject groups, with a systematic maturational trend in terms of decreasing time-to-peak and increasing positive peak amplitude associated with increasing age. Application of the age-appropriate HRF models to fMRI data significantly improved the precision of the fMRI analysis. These findings support the notion of a structured development in the brain's response to stimuli across the last trimester of gestation and beyond.


Assuntos
Encéfalo/crescimento & desenvolvimento , Hemodinâmica/fisiologia , Interpretação de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Adulto , Encéfalo/irrigação sanguínea , Feminino , Humanos , Lactente , Recém-Nascido , Recém-Nascido Prematuro , Masculino , Pessoa de Meia-Idade , Oxigênio/sangue , Adulto Jovem
14.
Pediatr Res ; 72(1): 63-9, 2012 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-22447318

RESUMO

INTRODUCTION: Objective biomarkers are needed to assess neuroprotective therapies after perinatal hypoxic-ischemic encephalopathy (HIE). We tested the hypothesis that, in infants who underwent therapeutic hypothermia after perinatal HIE, neurodevelopmental performance was predicted by fractional anisotropy (FA) values in the white matter (WM) on early diffusion tensor imaging (DTI) as assessed by means of tract-based spatial statistics (TBSS). METHODS: We studied 43 term infants with HIE. Developmental assessments were carried out at a median (range) age of 24 (12-28) mo. RESULTS: As compared with infants with favorable outcomes, those with unfavorable outcomes had significantly lower FA values (P < 0.05) in the centrum semiovale, corpus callosum (CC), anterior and posterior limbs of the internal capsule, external capsules, fornix, cingulum, cerebral peduncles, optic radiations, and inferior longitudinal fasciculus. In a second analysis in 32 assessable infants, the Griffiths Mental Development Scales (Revised) (GMDS-R) showed a significant linear correlation (P < 0.05) between FA values and developmental quotient (DQ) and all its component subscale scores. DISCUSSION: DTI analyzed by TBSS provides a qualified biomarker that can be used to assess the efficacy of additional neuroprotective therapies after HIE.


Assuntos
Encéfalo/crescimento & desenvolvimento , Desenvolvimento Infantil/fisiologia , Hipotermia Induzida/efeitos adversos , Hipóxia-Isquemia Encefálica/fisiopatologia , Hipóxia-Isquemia Encefálica/terapia , Anisotropia , Biomarcadores , Imagem de Tensor de Difusão , Inglaterra , Feminino , Humanos , Hipotermia Induzida/métodos , Lactente , Testes de Inteligência , Masculino , Técnicas de Rastreamento Neuroanatômico
15.
Pediatr Res ; 71(4 Pt 1): 380-5, 2012 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-22391639

RESUMO

INTRODUCTION: Consistent patterns of rotational intracardiac flow have been demonstrated in the healthy adult human heart. Intracardiac rotational flow patterns are hypothesized to assist in the maintenance of kinetic energy of inflowing blood, augmenting cardiac function. Newborn cardiac function is known to be suboptimal secondary to decreased receptor number and sympathetic innervation, increased afterload, and increased reliance on atrial contraction to support ventricular filling. Patterns of intracardiac flow in the newborn have not previously been examined. RESULTS: Whereas 5 of the 13 infants studied showed significant evidence of rotational flow within the right atrium, 8 infants showed little or no rotational flow. Presence or absence of rotational flow was not related to gestational age, birth weight, postnatal age, atrial size, or image quality. Despite absence of intra-atrial rotational flow, atrioventricular valve flow into the left and right ventricles later in the cardiac cycle could be seen, suggesting that visualization techniques were adequate. DISCUSSION: While further study is required to assess its exact consequences on cardiac mechanics and energetics, disruption to intracardiac flow patterns could be another contributor to the multifactorial sequence that produces newborn circulatory failure. METHODS: We studied 13 newborn infants, using three-dimensional (3D) cardiac magnetic resonance phase-contrast imaging (spatial resolution 0.84 mm, temporal resolution 22.6 ms) performed without sedation/anesthesia.


Assuntos
Velocidade do Fluxo Sanguíneo/fisiologia , Átrios do Coração/patologia , Adulto , Estudos de Coortes , Diagnóstico por Imagem/métodos , Feminino , Ventrículos do Coração , Humanos , Processamento de Imagem Assistida por Computador , Imagem Tridimensional , Recém-Nascido , Cinética , Imagem por Ressonância Magnética/métodos , Masculino , Microscopia de Contraste de Fase/métodos , Contração Miocárdica , Fatores de Risco
16.
Cereb Cortex ; 22(5): 1016-24, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-21772018

RESUMO

Preterm birth is a leading cause of cognitive impairment in childhood and is associated with cerebral gray and white matter abnormalities. Using multimodal image analysis, we tested the hypothesis that altered thalamic development is an important component of preterm brain injury and is associated with other macro- and microstructural alterations. T(1)- and T(2)-weighted magnetic resonance images and 15-direction diffusion tensor images were acquired from 71 preterm infants at term-equivalent age. Deformation-based morphometry, Tract-Based Spatial Statistics, and tissue segmentation were combined for a nonsubjective whole-brain survey of the effect of prematurity on regional tissue volume and microstructure. Increasing prematurity was related to volume reduction in the thalamus, hippocampus, orbitofrontal lobe, posterior cingulate cortex, and centrum semiovale. After controlling for prematurity, reduced thalamic volume predicted: lower cortical volume; decreased volume in frontal and temporal lobes, including hippocampus, and to a lesser extent, parietal and occipital lobes; and reduced fractional anisotropy in the corticospinal tracts and corpus callosum. In the thalamus, reduced volume was associated with increased diffusivity. This demonstrates a significant effect of prematurity on thalamic development that is related to abnormalities in allied brain structures. This suggests that preterm delivery disrupts specific aspects of cerebral development, such as the thalamocortical system.


Assuntos
Encéfalo/patologia , Doenças do Prematuro/patologia , Recém-Nascido Prematuro , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Recém-Nascido , Imagem por Ressonância Magnética , Masculino , Gravidez , Nascimento Prematuro
17.
Neuroradiology ; 54(5): 507-16, 2012 May.
Artigo em Inglês | MEDLINE | ID: mdl-22006424

RESUMO

INTRODUCTION: Our aims were to (1) assess the corticospinal tracts (CSTs) in infants with focal injury and healthy term controls using probabilistic tractography and (2) to correlate the conventional magnetic resonance imaging (MRI) and tractography findings in infants with focal injury with their later motor function. METHODS: We studied 20 infants with focal lesions and 23 controls using MRI and diffusion tensor imaging. Tract volume, fractional anisotropy (FA), apparent diffusion coefficient (ADC) values, axial diffusivity and radial diffusivity (RD) of the CSTs were determined. Asymmetry indices (AIs) were calculated by comparing ipsilateral to contralateral CSTs. Motor outcome was assessed using a standardized neurological examination. RESULTS: Conventional MRI was able to predict normal motor development (n = 9) or hemiplegia (n = 6). In children who developed a mild motor asymmetry (n = 5), conventional MRI predicted a hemiplegia in two and normal motor development in three infants. The AIs for tract volume, FA, ADC and RD showed a significant difference between controls and infants who developed a hemiplegia, and RD also showed a significant difference in AI between controls and infants who developed a mild asymmetry. CONCLUSION: Conventional MRI was able to predict subsequent normal motor development or hemiplegia following focal injury in newborn infants. Measures of RD obtained from diffusion tractography may offer additional information for predicting a subsequent asymmetry in motor function.


Assuntos
Infarto Encefálico/complicações , Isquemia Encefálica/complicações , Imagem de Tensor de Difusão/métodos , Hemiplegia/etiologia , Hemiplegia/fisiopatologia , Destreza Motora/fisiologia , Tratos Piramidais/lesões , Acidente Vascular Cerebral/complicações , Anisotropia , Estudos de Casos e Controles , Feminino , Humanos , Interpretação de Imagem Assistida por Computador , Imagem Tridimensional , Lactente , Masculino , Exame Neurológico , Valor Preditivo dos Testes
18.
Pediatr Res ; 69(6): 561-6, 2011 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-21386750

RESUMO

Our aim was to compare white matter (WM) microstructure in preterm infants with and without punctate WM lesions on MRI using tract-based spatial statistics (TBSS) and probabilistic tractography. We studied 23 preterm infants with punctate lesions, median GA at birth 30 (25-35) wk, and 23 GA- and sex-matched preterm controls. TBSS and tractography were performed to assess differences in fractional anisotropy (FA) between the two groups at term equivalent age. The impact of lesion load was assessed by performing linear regression analysis of the number of lesions on term MRI versus FA in the corticospinal tracts in the punctate lesions group. FA values were significantly lower in the posterior limb of the internal capsule, cerebral peduncles, decussation of the superior cerebellar peduncles, superior cerebellar peduncles, and pontine crossing tract in the punctate lesions group. There was a significant negative correlation between lesion load at term and FA in the corticospinal tracts (p = 0.03, adjusted r² = 0.467). In conclusion, punctate lesions are associated with altered microstructure in the WM fibers of the corticospinal tract at term equivalent age.


Assuntos
Encéfalo/patologia , Imagem de Tensor de Difusão/métodos , Recém-Nascido Prematuro , Fibras Nervosas Mielinizadas/patologia , Encéfalo/anatomia & histologia , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Gravidez
19.
NMR Biomed ; 24(1): 80-8, 2011 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20669148

RESUMO

We present a technique to measure the longitudinal relaxation time constant of venous blood (T(1b) ) in vivo in a few seconds. The MRI sequence consists of a thick-slab adiabatic inversion, followed by a series of slice-selective excitations and single-shot echo planar imaging readouts. The time intervals between excitations were chosen so that blood in macroscopic vessels is fully refreshed between excitations, making the blood signal follow an unperturbed inversion recovery curve. Static tissue, which experiences the inversion and all excitation pulses, quickly reaches a steady state at a low signal as a result of partial saturation. This allows blood-filled voxels to be discriminated from those containing static tissue, and to be fitted voxel-by-voxel to a simple inversion recovery model. The sequence was tested on a flow phantom with the proposed method, yielding T(1) values consistent to within 3% of those obtained using a conventional inversion recovery sequence with a spin-echo readout. The method was applied to seven adult volunteers and 18 neonates. The blood T(1) of the neonates (1799 ± 206 ms; range, 1393-2035 ms) was found to be more variable than that of adults (1717 ± 39 ms; range, 1662-1779 ms). A linear correlation between the inverse of T(1b) and the haematocrit was established in 12 neonates (R(2) = 0.90).


Assuntos
Sangue/metabolismo , Imagem por Ressonância Magnética/métodos , Adulto , Simulação por Computador , Feminino , Humanos , Recém-Nascido , Masculino , Imagens de Fantasmas , Fatores de Tempo , Adulto Jovem
20.
Proc Natl Acad Sci U S A ; 107(46): 20015-20, 2010 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-21041625

RESUMO

The functions of the resting state networks (RSNs) revealed by functional MRI remain unclear, but it has seemed possible that networks emerge in parallel with the development of related cognitive functions. We tested the alternative hypothesis: that the full repertoire of resting state dynamics emerges during the period of rapid neural growth before the normal time of birth at term (around 40 wk of gestation). We used a series of independent analytical techniques to map in detail the development of different networks in 70 infants born between 29 and 43 wk of postmenstrual age (PMA). We characterized and charted the development of RSNs from recognizable but often fragmentary elements at 30 wk of PMA to full facsimiles of adult patterns at term. Visual, auditory, somatosensory, motor, default mode, frontoparietal, and executive control networks developed at different rates; however, by term, complete networks were present, several of which were integrated with thalamic activity. These results place the emergence of RSNs largely during the period of rapid neural growth in the third trimester of gestation, suggesting that they are formed before the acquisition of cognitive competencies in later childhood.


Assuntos
Encéfalo/fisiopatologia , Rede Nervosa/fisiopatologia , Nascimento Prematuro/fisiopatologia , Descanso/fisiologia , Viés , Feminino , Idade Gestacional , Humanos , Lactente , Gravidez , Terceiro Trimestre da Gravidez/fisiologia , Análise de Regressão
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