Early detection of periventricular leukomalacia by diffusion-weighted magnetic resonance imaging techniques

A systematic review of immune-based interventions for perinatal neuroprotection: closing the gap between animal studies and human trials

BACKGROUND

Perinatal infection/inflammation is associated with a high risk for neurological injury and neurodevelopmental impairment after birth. Despite a growing preclinical evidence base, anti-inflammatory interventions have not been established in clinical practice, partly because of the range of potential targets. We therefore systematically reviewed preclinical studies of immunomodulation to improve neurological outcomes in the perinatal brain and assessed their therapeutic potential.

METHODS

We reviewed relevant studies published from January 2012 to July 2023 using PubMed, Medline (OvidSP) and EMBASE databases. Studies were assessed for risk of bias using the SYRCLE risk of bias assessment tool (PROSPERO; registration number CRD42023395690).

RESULTS

Forty preclinical publications using 12 models of perinatal neuroinflammation were identified and divided into 59 individual studies. Twenty-seven anti-inflammatory agents in 19 categories were investigated. Forty-five (76%) of 59 studies reported neuroprotection, from all 19 categories of therapeutics. Notably, 10/10 (100%) studies investigating anti-interleukin (IL)-1 therapies reported improved outcome, whereas half of the studies using corticosteroids (5/10; 50%) reported no improvement or worse outcomes with treatment. Most studies (49/59, 83%) did not control core body temperature (a known potential confounder), and 25 of 59 studies (42%) did not report the sex of subjects. Many studies did not clearly state whether they controlled for potential study bias.

CONCLUSION

Anti-inflammatory therapies are promising candidates for treatment or even prevention of perinatal brain injury. Our analysis highlights key knowledge gaps and opportunities to improve preclinical study design that must be addressed to support clinical translation.

Acute Diffusion-Weighted Imaging Signaling Severe Periventricular Leukomalacia in Preterm Infants: Case Report and Review of Literature

Introduction: Periventricular leukomalacia occurs in up to 25% of very preterm infants resulting in adverse neurodevelopmental outcomes. In its acute phase, periventricular leukomalacia is clinically silent. Although ultrasonography is widely available, its sensitivity in the early detection of periventricular leukomalacia is low. Case Report and Published Literature: We identified a preterm infant with early diffusion-weighted imaging changes that later evolved to periventricular leukomalacia. Thirty-two cases of abnormal diffusion-weighted imaging reliably heralding severe periventricular leukomalacia in the preterm infant have been published in the literature. Notable features include the following: (1) infants were more mature preterm infants (29-36 weeks' gestation); (2) findings were often serendipitous with benign clinical courses; (3) diffusion-weighted imaging changes only were evident in the first weeks of life with later evolution to more classical abnormalities on conventional magnetic resonance imaging (MRI) or ultrasonography. Conclusion: Diffusion-weighted imaging in the first week of life may be a reliable early marker of severe periventricular leukomalacia injury in more mature preterm infants.

A 1-Tesla MRI system for dedicated brain imaging in the neonatal intensive care unit

Objective

To assess the feasibility of a point-of-care 1-Tesla MRI for identification of intracranial pathologies within neonatal intensive care units (NICUs).

Methods

Clinical findings and point-of-care 1-Tesla MRI imaging findings of NICU patients (1/2021 to 6/2022) were evaluated and compared with other imaging modalities when available.

Results

A total of 60 infants had point-of-care 1-Tesla MRI; one scan was incompletely terminated due to motion. The average gestational age at scan time was 38.5 ± 2.3 weeks. Transcranial ultrasound (n = 46), 3-Tesla MRI (n = 3), or both (n = 4) were available for comparison in 53 (88%) infants. The most common indications for point-of-care 1-Tesla MRI were term corrected age scan for extremely preterm neonates (born at greater than 28 weeks gestation age, 42%), intraventricular hemorrhage (IVH) follow-up (33%), and suspected hypoxic injury (18%). The point-of-care 1-Tesla scan could identify ischemic lesions in two infants with suspected hypoxic injury, confirmed by follow-up 3-Tesla MRI. Using 3-Tesla MRI, two lesions were identified that were not visualized on point-of-care 1-Tesla scan: (1) punctate parenchymal injury versus microhemorrhage; and (2) small layering IVH in an incomplete point-of-care 1-Tesla MRI with only DWI/ADC series, but detectable on the follow-up 3-Tesla ADC series. However, point-of-care 1-Tesla MRI could identify parenchymal microhemorrhages, which were not visualized on ultrasound.

Conclusion

Although limited by field strength, pulse sequences, and patient weight (4.5 kg)/head circumference (38 cm) restrictions, the Embrace^® point-of-care 1-Tesla MRI can identify clinically relevant intracranial pathologies in infants within a NICU setting.

An ode to fetal, infant, and toddler neuroimaging: Chronicling early clinical to research applications with MRI, and an introduction to an academic society connecting the field

Fetal, infant, and toddler neuroimaging is commonly thought of as a development of modern times (last two decades). Yet, this field mobilized shortly after the discovery and implementation of MRI technology. Here, we provide a review of the parallel advancements in the fields of fetal, infant, and toddler neuroimaging, noting the shifts from clinical to research use, and the ongoing challenges in this fast-growing field. We chronicle the pioneering science of fetal, infant, and toddler neuroimaging, highlighting the early studies that set the stage for modern advances in imaging during this developmental period, and the large-scale multi-site efforts which ultimately led to the explosion of interest in the field today. Lastly, we consider the growing pains of the community and the need for an academic society that bridges expertise in developmental neuroscience, clinical science, as well as computational and biomedical engineering, to ensure special consideration of the vulnerable mother-offspring dyad (especially during pregnancy), data quality, and image processing tools that are created, rather than adapted, for the young brain.

Feed-forward neural networks using cerebral MR spectroscopy and DTI might predict neurodevelopmental outcome in preterm neonates

Objectives

We aimed to evaluate the ability of feed-forward neural networks (fNNs) to predict the neurodevelopmental outcome (NDO) of very preterm neonates (VPIs) at 12 months corrected age by using biomarkers of cerebral MR proton spectroscopy (¹H-MRS) and diffusion tensor imaging (DTI) at term-equivalent age (TEA).

Methods

In this prospective study, 300 VPIs born before 32 gestational weeks received an MRI scan at TEA between September 2013 and December 2017. Due to missing or poor-quality spectroscopy data and missing neurodevelopmental tests, 173 VPIs were excluded. Data sets consisting of 103 and 115 VPIs were considered for prediction of motor and cognitive developmental delay, respectively. Five metabolite ratios and two DTI characteristics in six different areas of the brain were evaluated. A feature selection algorithm was developed for receiving a subset of characteristics prevalent for the VPIs with a developmental delay. Finally, the predictors were constructed employing multiple fNNs and fourfold cross-validation.

Results

By employing the constructed fNN predictors, we were able to predict cognitive delays of VPIs with 85.7% sensitivity, 100% specificity, 100% positive predictive value (PPV) and 99.1% negative predictive value (NPV). For the prediction of motor delay, we achieved a sensitivity of 76.9%, a specificity of 98.9%, a PPV of 90.9% and an NPV of 96.7%.

Conclusion

FNNs might be able to predict motor and cognitive development of VPIs at 12 months corrected age when employing biomarkers of cerebral ¹H-MRS and DTI quantified at TEA.

Key Points

• A feed-forward neuronal network is a promising tool for outcome prediction in premature infants.

• Cerebral proton magnetic resonance spectroscopy and diffusion tensor imaging can be used for the construction of early prognostic biomarkers.

• Premature infants that would most benefit from early intervention services can be spotted at the time of optimal neuroplasticity.

Electronic supplementary material

The online version of this article (10.1007/s00330-020-07053-8) contains supplementary material, which is available to authorized users.

Assessing therapeutic response non-invasively in a neonatal rat model of acute inflammatory white matter injury using high-field MRI

Perinatal infection and inflammatory episodes in preterm infants are associated with diffuse white matter injury (WMI) and adverse neurological outcomes. Inflammation-induced WMI was previously shown to be linked with later hippocampal atrophy as well as learning and memory impairments in preterm infants. Early evaluation of injury load and therapeutic response with non-invasive tools such as multimodal magnetic resonance imaging (MRI) would greatly improve the search of new therapeutic approaches in preterm infants. Our aim was to evaluate the potential of multimodal MRI to detect the response of interleukin-1 receptor antagonist (IL-1Ra) treatment, known for its neuroprotective properties, during the acute phase of injury on a model of neonatal WMI. Rat pups at postnatal day 3 (P3) received intracerebral injection of lipopolysaccharide with systemic IL-1Ra therapy. 24 h later (P4), rats were imaged with multimodal MRI to assess microstructure by diffusion tensor imaging (DTI) and neurochemical profile of the hippocampus with ¹H-magnetic resonance spectroscopy. Astrocyte and microglial activation, apoptosis and the mRNA expression of pro-inflammatory and necroptotic markers were assessed. During the acute phase of injury, neonatal LPS exposure altered the concentration of hippocampus metabolites related to neuronal integrity, neurotransmission and membrane integrity and induced diffusivity restriction. Just 24 h after initiation of therapy, early indication of IL-1Ra neuroprotective effect could be detected in vivo by non-invasive spectroscopy and DTI, and confirmed with immunohistochemical evaluation and mRNA expression of inflammatory markers and cell death. In conclusion, multimodal MRI, particularly DTI, can detect not only injury but also the acute therapeutic effect of IL-1Ra suggesting that MRI could be a useful non-invasive tool to follow, at early time points, the therapeutic response in preterm infants.

Preterm brain Injury: White matter injury

Despite the advances in neonatal intensive care, the preterm brain remains vulnerable to white matter injury (WMI) and disruption of normal brain development (i.e., dysmaturation). Compared to severe cystic WMI encountered in the past decades, contemporary cohorts of preterm neonates experience milder WMIs. More than destructive lesions, disruption of the normal developmental trajectory of cellular elements of the white and the gray matter occurs. In the acute phase, in response to hypoxia-ischemia and/or infection and inflammation, multifocal areas of necrosis within the periventricular white matter involve all cellular elements. Later, chronic WMI is characterized by diffuse WMI with aberrant regeneration of oligodendrocytes, which fail to mature to myelinating oligodendrocytes, leading to myelination disturbances. Complete neuronal degeneration classically accompanies necrotic white matter lesions, while altered neurogenesis, represented by a reduction of the dendritic arbor and synapse formation, is observed in response to diffuse WMI. Neuroimaging studies now provide more insight in assessing both injury and dysmaturation of both gray and white matter. Preterm brain injury remains an important cause of neurodevelopmental disabilities, which are still observed in up to 50% of the preterm survivors and take the form of a complex combination of motor, cognitive, and behavioral concerns.

Hypoxia and myelination deficits in the developing brain

Myelination is a complex and orderly process during brain development that is essential for normal motor, cognitive and sensory functions. Cellular and molecular interactions between myelin-forming oligodendrocytes and axons are required for normal myelination in the developing brain. Oligodendrocyte progenitor cells (OPCs) proliferate and differentiate into mature myelin-forming oligodendrocytes. In this connection, astrocytes and microglia are also involved in survival and proliferation of OPCs. Hypoxic insults during the perinatal period affect the normal development, differentiation and maturation of the OPCs or cause their death resulting in impaired myelination. Several factors such as augmented release of proinflammatory cytokines by activated microglia and astrocytes, extracellular accumulation of excess glutamate and increased levels of nitric oxide are some of the underlying factors for hypoxia induced damage to the OPCs. Additionally, hypoxia also leads to down-regulation of several genes involved in oligodendrocyte differentiation encoding proteolipid protein, platelet-derived growth factor receptor and myelin-associated glycoprotein in the developing brain. Furthermore, oligodendrocytes may also accumulate increased amounts of iron in hypoxic conditions that triggers endoplasmic reticulum stress, misfolding of proteins and generation of reactive oxygen species that ultimately would lead to myelination deficits. More in-depth studies to elucidate the pathophysiological mechanisms underlying the inability of oligodendrocytes to myelinate the developing brain in hypoxic insults are desirable to develop new therapeutic options or strategies for myelination deficits.

Magnesium sulphate induces preconditioning in preterm rodent models of cerebral hypoxia-ischemia

BACKGROUND

Brain injury in preterm infants represents a substantial clinical problem associated with development of motor impairment, cognitive deficits and psychiatric problems. According to clinical studies, magnesium sulphate (MgSO₄) given to women in preterm labor reduces the risk of cerebral palsy in the offspring but the mechanisms behind its neuroprotective effects are still unclear. Our aim was to explore whether MgSO₄ induces tolerance (preconditioning) in the preterm rodent brain. For this purpose we established a model of perinatal hypoxia-ischemia (HI) in postnatal day 4 rats and also applied a recently developed postnatal day 5 mouse model of perinatal brain injury.

METHODS

Postnatal day 4 Wistar rats were exposed to unilateral carotid artery ligation followed by 60, 70 or 80 min of hypoxia (8% O₂). On postnatal day 11, brains were collected and macroscopically visible damage as well as white and grey matter injury was examined using immunohistochemical staining. Once the model had been established, a possible preconditioning protection induced by a bolus MgSO₄ injection prior to 80 min HI was examined 7 days after the insult. Next, a MgSO₄ bolus was injected in C57Bl6 mice on PND 4 followed by exposure to unilateral carotid artery ligation and hypoxia, (10% O₂) for 70 min on PND 5. Brains were collected 7 days after the insult and examined with immunohistochemistry for grey and white matter injury.

RESULTS

In rats, a 60 min period of hypoxia resulted in very few animals with brain injury and although 70 min of hypoxia resulted in a higher percentage of injured animals, the brains were marginally damaged. An 80 min exposure of hypoxia caused cortical tissue damage combined with hippocampal atrophy and neuronal loss in the C3 hippocampal layer. In the rat model, MgSO₄ (1.1 mg/g administered i.p. 24 h prior to the induction of HI, resulting in a transient serum Mg²⁺ concentration elevation to 4.1 ± 0.2 mmol/l at 3 h post i.p. injection) reduced brain injury by 74% in grey matter and 64% in white matter. In the mouse model, MgSO₄ (0.92 mg/g) i.p. injection given 24 h prior to the HI insult resulted in a Mg²⁺ serum concentration increase reaching 2.7 ± 0.3 mmol/l at 3 h post injection, which conferred a 40% reduction in grey matter injury.

CONCLUSIONS

We have established a postnatal day 4 rat model of HI for the study of preterm brain injury. MgSO₄ provides a marked preconditioning protection both in postnatal day 4 rats and in postnatal day 5 mice.

White matter microstructure of 6-year old children born preterm and full term

AIM

We previously observed a complex pattern of differences in white matter (WM) microstructure between preterm-born (PT) and full-term-born (FT) children and adolescents age 9-17 years. The aim of this study was to determine if the same differences exist as early as age 6 years.

METHOD

We obtained diffusion MRI (dMRI) scans in children born PT at age 6 years (n = 20; 11 males) and FT (n = 38; 14 males), using two scanning protocols: 30 diffusion directions (b = 1000 s/mm²) and 96 diffusion directions (b = 2500 s/mm²). We used deterministic tractography and analyzed fractional anisotropy (FA) along bilateral cerebral WM pathways that demonstrated differences in the older sample.

RESULTS

Compared to the FT group, the PT group showed (1) significantly decreased FA in the uncinate fasciculi and forceps major and (2) significantly increased FA in the right anterior thalamic radiation, inferior fronto-occipital fasciculi, and inferior longitudinal fasciculi. This pattern of group differences resembles findings in the previous study of older PT and FT participants. Group differences were similar across dMRI acquisition protocols.

INTERPRETATION

The underlying neurobiology driving the pattern of PT-FT differences in FA is present as early as age 6 years. Generalization across dMRI acquisition protocols demonstrates the robustness of group differences in FA. Future studies will use quantitative neuroimaging techniques to understand the tissue properties that give rise to this consistent pattern of WM differences after PT birth.

Effect of Hypoxic Injury in Mood Disorder

Hypoxemia is a common complication of the diseases associated with the central nervous system, and neurons are highly sensitive to the availability of oxygen. Neuroplasticity is an important property of the neural system controlling breathing, memory, and cognitive ability. However, the underlying mechanism has not yet been clearly elucidated. In recent years, several pieces of evidence have highlighted the effect of hypoxic injury on neuronal plasticity in the pathogenesis and treatment of mood disorder. Therefore, the present study reviewed the relevant articles regarding hypoxic injury and neuronal plasticity and discussed the pathological changes and physiological functions of neurons in hypoxemia in order to provide a translational perspective to the relevance of hypoxic injury and mood disorder.

Prenatal Diffusion-Weighted MRI of Fetal Brain Lesions

Prenatal Diffusion-Weighted Imaging (DWI) was recently demonstrated to be feasible in the normal fetal brain. We report our preliminary experience of abnormal prenatal DWI findings in the brains of eight fetuses with suspected lesions on the basis of clinical and ultrasound findings. The diffusion-weighted echo-planar sequence, which had an acquisition time of 14–18 seconds, was performed with the mother holding her breath. Slice thickness varied from 5 to 6 mm, the TR was 4000–5000 ms, the TE was 81 ms, the in plane resolution was 2.5×2.5 mm. Apparent Diffusion Coefficient (ADC) trace maps were calculated on the basis of three axes diffusion-sensitized images. In two cases, hypoxic-ischemic focal lesions showed a DWI signal compatible with the acute or subacute stage. In two cases of recent fetal death, the brain ADC was markedly decreased. In a case of fetus papyraceus, the intracranial ADC value suggested the brain having a solid structure. In a case of intraventricular hemorrhage, the lesion was more conspicuous on DWI than on conventional images. In a case of brain developmental malformations, the ADC showed values compatible with decreased cellular proliferation disorders. In a case of intracranial cystic mass, DWI readily differentiated between an arachnoid and an epidermoid cyst. DWI appears to enhance the prenatal MRI capability of characterizing hypoxic-ischemic lesions. Moreover, prenatal DWI seems to provide valuable information on the timing of fetal death. ADC determination can provide additional data on the nature of brain malformations in cases of abnormal development.

MRI Based Preterm White Matter Injury Classification: The Importance of Sequential Imaging in Determining Severity of Injury

Background

The evolution of non-hemorrhagic white matter injury (WMI) based on sequential magnetic resonance imaging (MRI) has not been well studied. Our aim was to describe sequential MRI findings in preterm infants with non-hemorrhagic WMI and to develop an MRI classification system for preterm WMI based on these findings.

Methods

Eighty-two preterm infants (gestation ≤35 weeks) were retrospectively included. WMI was diagnosed and classified based on sequential cranial ultrasound (cUS) and confirmed on MRI.

Results

138 MRIs were obtained at three time-points: early (<2 weeks; n = 32), mid (2–6 weeks; n = 30) and term equivalent age (TEA; n = 76). 63 infants (77%) had 2 MRIs during the neonatal period. WMI was non-cystic in 35 and cystic in 47 infants. In infants with cystic-WMI early MRI showed extensive restricted diffusion abnormalities, cysts were already present in 3 infants; mid MRI showed focal or extensive cysts, without acute diffusion changes. A significant reduction in the size and/or extent of the cysts was observed in 32% of the infants between early/mid and TEA MRI. In 4/9 infants previously seen focal cysts were no longer identified at TEA. All infants with cystic WMI showed ≥2 additional findings at TEA: significant reduction in WM volume, mild-moderate irregular ventriculomegaly, several areas of increased signal intensity on T1-weighted-images, abnormal myelination of the PLIC, small thalami.

Conclusion

In infants with extensive WM cysts at 2–6 weeks, cysts may be reduced in number or may even no longer be seen at TEA. A single MRI at TEA, without taking sequential cUS data and pre-TEA MRI findings into account, may underestimate the extent of WMI; based on these results we propose a new MRI classification for preterm non-hemorrhagic WMI.

Case Series: Fractional Anisotropy Profiles of the Cerebellar Peduncles in Adolescents Born Preterm With Ventricular Dilation

This case series assesses white matter microstructure of the cerebellar peduncles in 4 adolescents born preterm with enlarged ventricles and reduced white matter volume in the cerebrum but no apparent injury to the cerebellum. Subjects (ages 12-17 years, gestational age 26-32 weeks, birth weight 825-2211 g) were compared to a normative sample of 19 full-term controls (9-17 years, mean gestational age 39 weeks, mean birth weight 3154 g). Tract profiles for each of the cerebellar peduncles were generated by calculating fractional anisotropy at 30 points along the central portion of each tract. One or more case subjects exhibited higher fractional anisotropy beyond the 90th percentile in the inferior, middle, and superior cerebellar peduncles. Findings demonstrate that differences in cerebellar white matter microstructure can be detected in the absence of macrostructural cerebellar abnormalities.

Preterm Hypoxic-Ischemic Encephalopathy

Hypoxic-ischemic encephalopathy (HIE) is a recognizable and defined clinical syndrome in term infants that results from a severe or prolonged hypoxic-ischemic episode before or during birth. However, in the preterm infant, defining hypoxic-ischemic injury (HII), its clinical course, monitoring, and outcomes remains complex. Few studies examine preterm HIE, and these are heterogeneous, with variable inclusion criteria and outcomes reported. We examine the available evidence that implies that the incidence of hypoxic-ischemic insult in preterm infants is probably higher than recognized and follows a more complex clinical course, with higher rates of adverse neurological outcomes, compared to term infants. This review aims to elucidate the causes and consequences of preterm hypoxia-ischemia, the subsequent clinical encephalopathy syndrome, diagnostic tools, and outcomes. Finally, we suggest a uniform definition for preterm HIE that may help in identifying infants most at risk of adverse outcomes and amenable to neuroprotective therapies.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

Decreased and Increased Anisotropy along Major Cerebral White Matter Tracts in Preterm Children and Adolescents

Premature birth is highly prevalent and associated with neurodevelopmental delays and disorders. Adverse outcomes, particularly in children born before 32 weeks of gestation, have been attributed in large part to white matter injuries, often found in periventricular regions using conventional imaging. To date, tractography studies of white matter pathways in children and adolescents born preterm have evaluated only a limited number of tracts simultaneously. The current study compares diffusion properties along 18 major cerebral white matter pathways in children and adolescents born preterm (n = 27) and full term (n = 19), using diffusion magnetic resonance imaging and tractography. We found that compared to the full term group, the preterm group had significantly decreased FA in segments of the bilateral uncinate fasciculus and anterior segments of the right inferior fronto-occipital fasciculus. Additionally, the preterm group had significantly increased FA in segments of the right and left anterior thalamic radiations, posterior segments of the right inferior fronto-occipital fasciculus, and the right and left inferior longitudinal fasciculus. Increased FA in the preterm group was generally associated with decreased radial diffusivity. These findings indicate that prematurity-related white matter differences in later childhood and adolescence do not affect all tracts in the periventricular zone and can involve both decreased and increased FA. Differences in the patterns of radial diffusivity and axial diffusivity suggest that the tissue properties underlying group FA differences may vary within and across white matter tracts. Distinctive diffusion properties may relate to variations in the timing of injury in the neonatal period, extent of white matter dysmaturity and/or compensatory processes in childhood.

New means to assess neonatal inflammatory brain injury

Preterm infants are especially vulnerable to infection-induced white matter injury, associated with cerebral palsy, cognitive and psychomotor impairment, and other adverse neurological outcomes. The etiology of such lesions is complex and multifactorial. Furthermore, timing and length of exposure to infection also influence neurodevelopmental outcomes. Different mechanisms have been posited to mediate the observed brain injury including microglial activation followed by subsequent release of pro-inflammatory species, glutamate-induced excitotoxicity, and vulnerability of developing oligodendrocytes to cerebral insults. The prevalence of such neurological impairments requires an urgent need for early detection and effective neuroprotective strategies. Accordingly, noninvasive methods of monitoring disease progression and therapy effectiveness are essential. While diagnostic tools using biomarkers from bodily fluids may provide useful information regarding potential risks of developing neurological diseases, the use of magnetic resonance imaging/spectroscopy has emerged as a promising candidate for such purpose. Various pharmacological agents have demonstrated protective effects in the immature brain in animal models; however, few studies have progressed to clinical trials with promising results.

Scoring system for periventricular leukomalacia in infants with congenital heart disease

BACKGROUND

Currently two magnetic resonance imaging (MRI) methods have been used to assess periventricular leukomalacia (PVL) severity in infants with congenital heart disease: manual volumetric lesion segmentation and an observational categorical scale. Volumetric classification is labor intensive and the categorical scale is quick but unreliable. We propose the quartered point system (QPS) as a novel, intuitive, time-efficient metric with high interrater agreement.

METHODS

QPS is an observational scale that asks the rater to score MRIs on the basis of lesion size, number, and distribution. Pre- and postoperative brain MRIs were obtained on term congenital heart disease infants. Three independent observers scored PVL severity using all three methods: volumetric segmentation, categorical scale, and QPS.

RESULTS

One-hundred and thirty-five MRIs were obtained from 72 infants; PVL was seen in 48 MRIs. Volumetric measurements among the three raters were highly concordant (ρc = 0.94-0.96). Categorical scale severity scores were in poor agreement between observers (κ = 0.17) and fair agreement with volumetrically determined severity (κ = 0.26). QPS scores were in very good agreement between observers (κ = 0.82) and with volumetric severity (κ = 0.81).

CONCLUSION

QPS minimizes training and sophisticated radiologic analysis and increases interrater reliability. QPS offers greater sensitivity to stratify PVL severity and has the potential to more accurately correlate with neurodevelopmental outcomes.

Metabolic Alterations in Developing Brain After Injury: Knowns and Unknowns

Brain development is a highly orchestrated complex process. The developing brain utilizes many substrates including glucose, ketone bodies, lactate, fatty acids and amino acids for energy, cell division and the biosynthesis of nucleotides, proteins and lipids. Metabolism is crucial to provide energy for all cellular processes required for brain development and function including ATP formation, synaptogenesis, synthesis, release and uptake of neurotransmitters, maintaining ionic gradients and redox status, and myelination. The rapidly growing population of infants and children with neurodevelopmental and cognitive impairments and life-long disability resulting from developmental brain injury is a significant public health concern. Brain injury in infants and children can have devastating effects because the injury is superimposed on the high metabolic demands of the developing brain. Acute injury in the pediatric brain can derail, halt or lead to dysregulation of the complex and highly regulated normal developmental processes. This paper provides a brief review of metabolism in developing brain and alterations found clinically and in animal models of developmental brain injury. The metabolic changes observed in three major categories of injury that can result in life-long cognitive and neurological disabilities, including neonatal hypoxia-ischemia, pediatric traumatic brain injury, and brain injury secondary to prematurity are reviewed.

MRI evaluation and safety in the developing brain

Magnetic resonance imaging (MRI) evaluation of the developing brain has dramatically increased over the last decade. Faster acquisitions and the development of advanced MRI sequences, such as magnetic resonance spectroscopy (MRS), diffusion tensor imaging (DTI), perfusion imaging, functional MR imaging (fMRI), and susceptibility-weighted imaging (SWI), as well as the use of higher magnetic field strengths has made MRI an invaluable tool for detailed evaluation of the developing brain. This article will provide an overview of the use and challenges associated with 1.5-T and 3-T static magnetic fields for evaluation of the developing brain. This review will also summarize the advantages, clinical challenges, and safety concerns specifically related to MRI in the fetus and newborn, including the implications of increased magnetic field strength, logistics related to transporting and monitoring of neonates during scanning, and sedation considerations, and a discussion of current technologies such as MRI conditional neonatal incubators and dedicated small-foot print neonatal intensive care unit (NICU) scanners.

Diffusion tensor imaging in extremely low birth weight infants managed with hypercapnic vs. normocapnic ventilation

BACKGROUND

Permissive hypercapnia is a ventilatory strategy used to prevent lung injury in ventilated extremely low birth weight (ELBW, birth weight ≤1,000 g) infants. However, there is retrospective evidence showing that high CO2 is associated with brain injury.

OBJECTIVE

The objective of this study was to compare brain white matter development at term-equivalent age in ELBW infants randomized to hypercapnic vs. normocapnic ventilation during the first week of life and in healthy non-ventilated term newborns.

MATERIALS AND METHODS

Twenty-two ELBW infants from a randomized controlled trial were included in this study; 11 received hypercapnic (transcutaneous PCO2 [tcPCO2] 50-60 mmHg) ventilation and 11 normocapnic (tcPCO2 35-45 mmHg) ventilation during the first week of life while still intubated. In addition, ten term healthy newborns served as controls. Magnetic resonance imaging (MRI) with diffusion tensor imaging (DTI) was performed at term-equivalent age for the ELBW infants and at approximately 2 weeks of age for the control infants. White matter injury on conventional MRI was graded in the ELBW and control infants using a scoring system adopted from literature. Tract-based spatial statistics (TBSS) was used to evaluate for differences in DTI measured fractional anisotropy (FA, spatially normalized to a customized template) among the ELBW and term control infants.

RESULTS

Conventional MRI white matter scores were not different (7.3 ± 1.7 vs. 6.9 ± 1.4, P = 0.65) between the hypercapnic and normocapnic ELBW infants. TBSS analysis did not show significant differences (P < 0.05, corrected) between the two ELBW infant groups, although before multiple comparisons correction, hypercapnic infants had many regions with lower FA and no regions with higher FA (P < 0.05, uncorrected) compared to normocapnic infants. When compared to the control infants, normocapnic ELBW infants had a few small regions with significantly lower FA, while hypercapnic ELBW infants had more widespread regions with significantly lower FA (P < 0.05, fully corrected for multiple comparisons).

CONCLUSIONS

Normocapnic ventilation vs. permissive hypercapnia may be associated with improved white matter development at term-equivalent age in ELBW infants. This effect, however, was small and was not apparent on conventional MRI. Further research is needed using larger sample sizes to assess if permissive hypercapnic ventilation in ELBW infants is associated with worse white matter development.

Assessing white matter microstructure of the newborn with multi-shell diffusion MRI and biophysical compartment models

Brain white matter connections have become a focus of major interest with important maturational processes occurring in newborns. To study the complex microstructural developmental changes in-vivo, it is imperative that non-invasive neuroimaging approaches are developed for this age-group. Multi-b-value diffusion weighted imaging data were acquired in 13 newborns, and the biophysical compartment diffusion models CHARMED-light and NODDI, providing new microstructural parameters such as intra-neurite volume fraction (νin) and neurite orientation dispersion index (ODI), were developed for newborn data. Comparative analysis was performed and twenty ROIs in the white matter were investigated. Diffusion tensor imaging and both biophysical compartment models highlighted the compact and oriented structure of the corpus-callosum with the highest FA and νin values and the smallest ODI values. We could clearly differentiate, using the FA, νin and ODI, the posterior and anterior internal capsule representing similar cellular structure but with different maturation (i.e. partially myelinated and absence of myelin, respectively). Late maturing regions (external capsule and periventricular crossroads of pathways) had lower νin values, but displayed significant differences in ODI. The compartmented models CHARMED-light and NODDI bring new indices corroborating the cellular architectures, with the lowest νin, reflecting the late maturation of areas with thin non-myelinated fibers, and with highest ODI indicating the presence of fiber crossings and fanning. The application of biophysical compartment diffusion models adds new insights to the brain white matter development in vivo.

Neuroimaging of white matter injury, intraventricular and cerebellar hemorrhage

White matter injury and hemorrhage are common findings in extremely preterm infants. Large hemorrhages and extensive cystic lesions are identified with cranial ultrasound. MRI, which is more sensitive, is especially useful in the identification of small intraventricular hemorrhage; cerebellar hemorrhage; punctate lesion in the white matter and cerebellum; and diffuse, noncystic white matter injury. Imaging sequences such as diffusion-weighted, diffusion tensor, and susceptibility weighted imaging may improve recognition and prediction of outcome. These techniques improve understanding of the underlying pathophysiology of white matter injury and its effects on brain development and neurodevelopmental outcome.

Brain development in preterm infants assessed using advanced MRI techniques

Infants who are born preterm have a high incidence of neurocognitive and neurobehavioral abnormalities, which may be associated with impaired brain development. Advanced magnetic resonance imaging (MRI) approaches, such as diffusion MRI (d-MRI) and functional MRI (fMRI), provide objective and reproducible measures of brain development. Indices derived from d-MRI can be used to provide quantitative measures of preterm brain injury. Although fMRI of the neonatal brain is currently a research tool, future studies combining d-MRI and fMRI have the potential to assess the structural and functional properties of the developing brain and its response to injury.

Hypoxia-ischemia disrupts directed interactions within neonatal prefrontal-hippocampal networks

Due to improved survival rates and outcome of human infants experiencing a hypoxic-ischemic episode, cognitive dysfunctions have become prominent. They might result from abnormal communication within prefrontal-hippocampal networks, as synchrony and directed interactions between the prefrontal cortex and hippocampus account for mnemonic and executive performance. Here, we elucidate the structural and functional impact of hypoxic-ischemic events on developing prefrontal-hippocampal networks in an immature rat model of injury. The magnitude of infarction, cell loss and astrogliosis revealed that an early hypoxic-ischemic episode had either a severe or a mild/moderate outcome. Without affecting the gross morphology, hypoxia-ischemia with mild/moderate outcome diminished prefrontal neuronal firing and gamma network entrainment. This dysfunction resulted from decreased coupling synchrony within prefrontal-hippocampal networks and disruption of hippocampal theta drive. Thus, early hypoxia-ischemia may alter the functional maturation of neuronal networks involved in cognitive processing by disturbing the communication between the neonatal prefrontal cortex and hippocampus.

Magnetic resonance diffusion-weighted imaging: reproducibility of regional apparent diffusion coefficients for the normal fetal brain

OBJECTIVE

To evaluate the reproducibility of regional apparent diffusion coefficient (ADC) measurements of the normal fetal brain in the second and third trimesters of pregnancy.

METHODS

Fifty normal singleton fetuses from healthy pregnant women between 19 and 37 weeks' gestation were studied without sedation. Single-shot diffusion-weighted images of the fetal brain were obtained using a 1.5-Tesla magnetic resonance scanner and a six-channel body array coil. ADC maps were created using 0 and 1000 b-values along three orthogonal directions. Two examiners independently measured ADC values in the cerebellar hemispheres (CH), pons, thalamus, basal ganglia (BG), centrum semiovale (CSO), and frontal (FWM), parietal (PWM), temporal (TWM) and occipital (OWM) white matter. Correlation between ADC values and menstrual age was assessed by linear regression analysis. The bias and agreement of ADC measurements were determined using Bland-Altman plots.

RESULTS

ADC values either remained constant (BG, FWM, PWM, TWM, OWM, CSO) or decreased (CH, pons, thalamus) with advancing menstrual age. Mean intraobserver bias for ADC measurements was not significantly different from zero. Small interobserver differences in mean ADC measurements (i.e. a small mean bias) were detected for CH (1.26 ± 0.20 vs 1.20 ± 0.18 μm(2) /ms, P = 0.006), PWM (1.37 ± 0.29 vs 1.33 ± 0.26 μm(2) /ms, P = 0.02) and CSO (1.36 ± 0.29 vs 1.33 ± 0.28 μm(2) /ms, P < 0.0001). Measurement agreement was acceptable.

CONCLUSIONS

ADC measurements in normal unsedated fetuses in the second and third trimesters are reproducible except for small differences for PWM, CH and CSO between examiners.

Longitudinal change detection in diffusion MRI using multivariate statistical testing on tensors

This paper presents a longitudinal change detection framework for detecting relevant modifications in diffusion MRI, with application to neuromyelitis optica (NMO) and multiple sclerosis (MS). The core problem is to identify image regions that are significantly different between two scans. The proposed method is based on multivariate statistical testing which was initially introduced for tensor population comparison. We use this method in the context of longitudinal change detection by considering several strategies to build sets of tensors characterizing the variability of each voxel. These strategies make use of the variability existing in the diffusion weighted images (thanks to a bootstrap procedure), or in the spatial neighborhood of the considered voxel, or a combination of both. Results on synthetic evolutions and on real data are presented. Interestingly, experiments on NMO patients highlight the ability of the proposed approach to detect changes in the normal-appearing white matter (according to conventional MRI) that are related with physical status outcome. Experiments on MS patients highlight the ability of the proposed approach to detect changes in evolving and non-evolving lesions (according to conventional MRI). These findings might open promising prospects for the follow-up of NMO and MS pathologies.

Developmental outcome of very low birth weight infants in a developing country

Background

Advances in neonatal care allow survival of extremely premature infants, who are at risk of handicap. Neurodevelopmental follow up of these infants is an essential part of ongoing evaluation of neonatal care. The neonatal care in resource limited developing countries is very different to that in first world settings. Follow up data from developing countries is essential; it is not appropriate to extrapolate data from units in developed countries. This study provides follow up data on a population of very low birth weight (VLBW) infants in Johannesburg, South Africa.

Methods

The study sample included all VLBW infants born between 01/06/2006 and 28/02/2007 and discharged from the neonatal unit at Charlotte Maxeke Johannesburg Academic Hospital (CMJAH). Bayley Scales of Infant and Toddler Development Version 111 (BSID) 111 were done to assess development. Regression analysis was done to determine factors associated with poor outcome.

Results

178 infants were discharged, 26 were not available for follow up, 9 of the remaining 152 (5.9%) died before an assessment was done; 106 of the remaining 143 (74.1%) had a BSID 111 assessment. These 106 patients form the study sample; mean birth weight and mean gestational age was 1182 grams (SD: 197.78) and 30.81 weeks (SD: 2.67) respectively. The BSID (111) was done at a median age of 16.48 months. The mean cognitive subscale was 88.6 (95% CI: 85.69 - 91.59), 9 (8.5%) were < 70, mean language subscale was 87.71 (95% CI: 84.85 - 90.56), 10 (9.4%) < 70, and mean motor subscale was 90.05 (95% CI: 87.0 - 93.11), 8 (7.6%) < 70. Approximately one third of infants were identified as being at risk (score between 70 and 85) on each subscale. Cerebral palsy was diagnosed in 4 (3.7%) of babies. Factors associated with poor outcome included cystic periventricular leukomalacia (PVL), resuscitation at birth, maternal parity, prolonged hospitalisation and duration of supplemental oxygen. PVL was associated with poor outcome on all three subscales. Birth weight and gestational age were not predictive of neurodevelopmental outcome.

Conclusion

Although the neurodevelopmental outcome of this group of VLBW infants was within the normal range, with a low incidence of cerebral palsy, these results may reflect the low survival of babies with a birth weight below 900 grams. In addition, mean subscale scores were low and one third of the babies were identified as "at risk", indicating that this group of babies warrants long-term follow up into school going age.

MR imaging correlates of white-matter pathology in a preterm baboon model

INTRODUCTION

Cerebral white-matter (WM) abnormalities on magnetic resonance imaging (MRI) correlate with neurodevelopmental disability in infants born prematurely.

RESULTS

Quantitative histological measures of WM and ventricular volumes correlated with qualitative MRI scores of WM volume loss and ventriculomegaly. Diffuse astrocytosis was associated with signal abnormality on T(2)-weighted imaging and higher apparent diffusion coefficient in WM. Loss of oligodendrocytes was associated with lower relative anisotropy characterized by higher radial diffusivity values. The relationship between histopathology and MRI abnormalities was more pronounced in animals in the 28 d model, equivalent to the term human infant.

DISCUSSION

MRI reflects microstructural and anatomical abnormalities that are characteristic of WM injury in the preterm brain, and these changes are more evident on MRI at term-equivalent postmenstrual age.

METHODS

We assessed the histopathological correlates of MRI abnormalities in a baboon model of premature birth. Baboons were delivered at 125 d of gestation (dg, term ~185 dg) and maintained in an animal intensive care unit for 14 (n = 26) or 28 d (n = 17). Gestational control animals were delivered at 140 dg (n = 9) or 153 dg (n = 4). Cerebral WM in fixed brains was evaluated using MRI, diffusion tensor imaging (DTI), and histopathology.

Diffusion tensor imaging evaluation of white matter in adolescents with myelomeningocele and Chiari II malformation

BACKGROUND

Macrostructural abnormalities in cerebral white matter in patients with myelomeningocele are well known, but microstructural abnormalities are not as well studied.

OBJECTIVE

The aim of this study was to evaluate cerebral white matter in adolescents with myelomeningocele using diffusion tensor imaging (DTI), and to investigate the effects of ventricular dilation and CSF shunt presence on white matter microstructure in these patients.

MATERIALS AND METHODS

DTI and T1-weighted 3-D (T1-3-D) MRI were performed on nine adolescents with myelomeningocele and Chiari II malformation and nine age-matched controls. The fractional anisotropy (FA) and mean diffusivity (MD) values were measured and compared.

RESULTS

Significantly decreased FA and increased MD values were observed in most white matter regions and fibers in adolescents with myelomeningocele compared to controls. Further analysis in patients revealed significant changes in DTI parameters in hemispheres with enlarged lateral ventricles compared to those with normal ventricle size. In addition, a significant difference in FA values in the posterior limb of the internal capsule was found in the comparison of hemispheres in patients with or without CSF shunt catheters.

CONCLUSION

This study revealed widespread microstructural abnormalities in white matter in adolescents with myelomeningocele and Chiari II malformation. Ventricular dilation may have additional effects on white matter microstructure in this patient population. CSF shunt diversion effects on white matter may be multifactorial and need further investigation.

The Newborn Individualized Developmental Care and Assessment Program (NIDCAP) with Kangaroo Mother Care (KMC): Comprehensive Care for Preterm Infants

State-of-the-art Newborn Intensive Care Units (NICUs), instrumental in the survival of high-risk and ever-earlier-born preterm infants, often have costly human repercussions. The developmental sequelae of newborn intensive care are largely misunderstood. Developed countries eager to export their technologies must also transfer the knowledge-base that encompasses all high-risk and preterm infants' personhood as well as the neuro-essential importance of their parents. Without such understanding, the best medical care, while assuring survival jeopardizes infants' long-term potential and deprives parents of their critical role. Exchanging the womb for the NICU environment at a time of rapid brain growth compromises preterm infants' early development, which results in long-term physical and mental health problems and developmental disabilities. The Newborn Individualized Developmental Care and Assessment Program (NIDCAP) aims to prevent the iatrogenic sequelae of intensive care and to maintain the intimate connection between parent and infant, one expression of which is Kangaroo Mother Care. NIDCAP embeds the infant in the natural parent niche, avoids over-stimulation, stress, pain, and isolation while it supports self-regulation, competence, and goal orientation. Research demonstrates that NIDCAP improves brain development, functional competence, health, and life quality. It is cost effective, humane, and ethical, and promises to become the standard for all NICU care.

Cellular changes underlying hyperoxia-induced delay of white matter development

Impaired neurological development in premature infants frequently arises from periventricular white matter injury (PWMI), a condition associated with myelination abnormalities. Recently, exposure to hyperoxia was reported to disrupt myelin formation in neonatal rats. To identify the causes of hyperoxia-induced PWMI, we characterized cellular changes in the white matter (WM) using neonatal wild-type 2-3-cyclic nucleotide 3-phosphodiesterase-enhanced green fluorescent protein (EGFP) and glial fibrillary acidic protein (GFAP)-EGFP transgenic mice exposed to 48 h of 80% oxygen from postnatal day 6 (P6) to P8. Myelin basic protein expression and CC1(+) oligodendroglia decreased after hyperoxia at P8, but returned to control levels during recovery between P12 and P15. At P8, hyperoxia caused apoptosis of NG2(+)O4(-) progenitor cells and reduced NG2(+) cell proliferation. This was followed by restoration of the NG2(+) cell population and increased oligodendrogenesis in the WM after recovery. Despite apparent cellular recovery, diffusion tensor imaging revealed WM deficiencies at P30 and P60. Hyperoxia did not affect survival or proliferation of astrocytes in vivo, but modified GFAP and glutamate-aspartate transporter expression. The rate of [(3)H]-d-aspartic acid uptake in WM tissue was also decreased at P8 and P12. Furthermore, cultured astrocytes exposed to hyperoxia showed a reduced capacity to protect oligodendrocyte progenitor cells against the toxic effects of exogenous glutamate. This effect was prevented by 2,3-dioxo-6-nitro-1,2,3,4-tetrahydrobenzo[f]quinoxaline-7-sulfonamide treatment. Our analysis reveals a role for altered glutamate homeostasis in hyperoxia-induced WM damage. Understanding the cellular dynamics and underlying mechanisms involved in hyperoxia-induced PWMI will allow for future targeted therapeutic intervention.

In vivo MRI analysis of an inflammatory injury in the developing brain

Cerebral periventricular white matter injury stands as a leading cause of cognitive, behavioral and motor impairment in preterm infants. There is epidemiological and histopathological evidence demonstrating the role of prenatal or neonatal inflammation in brain injury in preterm infants. In order to define the effect of an inflammatory insult in the developing brain on magnetic resonance (MR) imaging, we obtained high resolution conventional and diffusion MR images of the brain of rat pups after an inflammatory injury. Rat pups were subjected on postnatal day 5 (P5) to a stereotaxic injection of lipopolysaccharide in the corpus callosum and then imaged at 11.7 T on days 0, 2 and 4 following the injury. They were subsequently sacrificed for immunohistochemistry. Diffusion tensor imaging (DTI) acquired at high spatial resolution showed an initial reduction of the apparent diffusion coefficient (ADC) in the white matter. This was followed by an increase in ADC value and in T2 relaxation time constant in the white matter, with an associated increase of radial diffusivity of the corpus callosum, and a 10-fold increase in ventricular size. On histology, these MR changes corresponded to widespread astrogliosis, and decreased proportion of the section areas containing cresyl violet positive stain. The increase in radial diffusivity, typically attributed to myelin loss, occurred in this case despite the absence of myelin at this developmental stage.

Brain lesions in preterm infants: initial diagnosis and follow-up

Children surviving premature birth present with a wide spectrum of motor, sensory and cognitive disabilities, ranging from slight motor deficits, school difficulties and behavioural problems to cerebral palsy and mental retardation. The anatomic and functional substrate of these problems can be investigated using a variety of imaging techniques. Cranial US coupled with colour Doppler is a well-established method for the initial diagnosis of intraventricular haemorrhage, parenchymal haemorrhagic infarct and periventricular leukomalacia. MRI is useful for the follow-up study of brain maturation. Conventional T1- and T2-weighted sequences, magnetization transfer and diffusion tensor imaging coupled with sophisticated tools of tissue segmentation and analysis at a voxel level offer substantial anatomic and functional information on pathological conditions that define the prognosis of preterm infants.

Early diffusion-weighted images in infants with subcortical leukomalacia

We describe two infants with subcortical leukomalacia and decreased water diffusivity in widespread white matter on magnetic resonance imaging. In both infants, diffusion-weighted imaging at age 1 day revealed a widespread increase in signal intensities, predominantly in subcortical areas. The corticospinal tract in the brainstem was not involved. Subsequently, diffusion-weighted imaging produced apparently normal results, and conventional magnetic resonance imaging indicated diffuse but subcortical-dominant white matter lesions in the subacute phase. Follow-up magnetic resonance imaging revealed a volume loss and gliosis of the white matter. In one infant, psychomotor development was mildly delayed, and epilepsy occurred. The other infant experienced normal development and no epilepsy. Neither infant developed spastic cerebral palsy. These infants represent a characteristic group with perinatal brain injury.

Diffusion tensor imaging: a review for pediatric researchers and clinicians

Diffusion tensor imaging (DTI) is a magnetic resonance imaging technique that allows for the visualization and characterization of the white matter tracts of the brain in vivo. DTI does not assess white matter directly. Rather, it capitalizes on the fact that diffusion is isotropic (equal in all directions) in cerebral spinal fluid and cell bodies but anisotropic (greater in one direction than the other directions) in axons that comprise white matter. It provides quantitative information about the degree and direction of water diffusion within individual units of volume within the magnetic resonance image, and by inference, about the integrity of white matter. Measures from DTI can be applied throughout the brain or to regions of interest. Fiber tract reconstruction, or tractography, creates continuous 3-dimensional tracts by sequentially piecing together estimates of fiber orientation from the direction of diffusion within individual volume units. DTI has increased our understanding of white matter structure and function. DTI shows nonlinear growth of white matter tracts from childhood to adulthood. Delayed maturation of the white matter in the frontal lobes may explain the continued growth of cognitive control into adulthood. Relative to good readers, adults and children who are poor readers have evidence of white matter differences in a specific region of the temporo-parietal lobe, implicating differences in connections among brain regions as a factor in reading disorder. Measures from DTI changed in poor readers who improved their reading skills after intense remediation. DTI documents injury to white matter tracts after prematurity. Measures indicative of white matter injury are associated with motor and cognitive impairment in children born prematurely. Further research on DTI is necessary before it can become a routine clinical procedure.

Magnetic resonance spectroscopy in pediatric neuroradiology: clinical and research applications

Magnetic resonance spectroscopy (MRS) offers a unique, noninvasive approach to assess pediatric neurological abnormalities at microscopic levels by quantifying cellular metabolites. The most widely available MRS method, proton ((1)H; hydrogen) spectroscopy, is FDA approved for general use and can be ordered by clinicians for pediatric neuroimaging studies if indicated. There are a multitude of both acquisition and post-processing methods that can be used in the implementation of MR spectroscopy. MRS in pediatric neuroimaging is challenging to interpret because of dramatic normal developmental changes that occur in metabolites, particularly in the first year of life. Still, MRS has been proven to provide additional clinically relevant information for several pediatric neurological disease processes such as brain tumors, infectious processes, white matter disorders, and neonatal injury. MRS can also be used as a powerful quantitative research tool. In this article, specific research applications using MRS will be demonstrated in relation to neonatal brain injury and pediatric brain tumor imaging.

Neonatal brain structure on MRI and diffusion tensor imaging, sex, and neurodevelopment in very-low-birthweight preterm children

The neurological basis of an increased incidence of cerebral palsy (CP) in preterm males is unknown. This study examined neonatal brain structure on magnetic resonance imaging (MRI) and diffusion tensor imaging (DTI) at term-equivalent age, sex, and neurodevelopment at 1 year 6 months on the basis of the Amiel-Tison neurological examination, Gross Motor Function Classification System, and Bayley Scales of Infant Development in 78 very-low-birthweight preterm children (41 males, 37 females; mean gestational age 27.6 wks, SD 2.5; mean birthweight 1021 g, SD 339). Brain abnormalities on MRI and DTI were not different between males and females except in the splenium of the corpus callosum, where males had lower DTI fractional anisotropy (p=0.025) and a higher apparent diffusion coefficient (p=0.013), indicating delayed splenium development. In the 26 infants who were at higher risk on the basis of DTI, males had more abnormalities on MRI (p=0.034) and had lower fractional anisotropy and a higher apparent diffusion coefficient in the splenium (p=0.049; p=0.025) and right posterior limb of the internal capsule (PLIC; p=0.003; p=0.033). Abnormal neurodevelopment was more common in males (n=9) than in females (n=2; p=0.036). Children with abnormal neurodevelopment had more abnormalities on MRI (p=0.014) and reduced splenium and right PLIC fractional anisotropy (p=0.001; p=0.035). In children with abnormal neurodevelopment, right PLIC fractional anisotropy was lower than left (p=0.035), whereas in those with normal neurodevelopment right PLIC fractional anisotropy was higher than left (p=0.001). Right PLIC fractional anisotropy correlated to neurodevelopment (rho=0.371, p=0.002). Logistic regression predicted neurodevelopment with 94% accuracy; only right PLIC fractional anisotropy was a significant logistic coefficient. Results indicate that the higher incidence of abnormal neurodevelopment in preterm males relates to greater incidence and severity of brain abnormalities, including reduced PLIC and splenium development.

Do apparent diffusion coefficient measurements predict outcome in children with neonatal hypoxic-ischemic encephalopathy?

BACKGROUND AND PURPOSE

Diffusion-weighted imaging (DWI) permits early detection and quantification of hypoxic-ischemic (HI) brain lesions. Our aim was to assess the predictive value of DWI and apparent diffusion coefficient (ADC) measurements for outcome in children with perinatal asphyxia.

MATERIALS AND METHODS

Term neonates underwent MR imaging within 10 days after birth because of asphyxia. MR imaging examinations were retrospectively evaluated for HI brain damage. ADC was measured in 30 standardized brain regions and in visibly abnormal areas on DWI. In survivors, developmental outcome until early school age was graded into the following categories: 1) normal, 2) mildly abnormal, and 3) definitely abnormal. For analysis, category 3 and death (category 4) were labeled "adverse," 1 and 2 were "favorable," and 2-3 and death were "abnormal" outcome. Differences in outcome between infants with and without DWI abnormalities were analyzed by using chi(2) tests. The nonparametric Mann-Whitney U test analyzed whether ADC values in visible DWI abnormalities correlated with age at imaging. Logistic regression analysis tested the predictive value for outcome of the ADC in each standardized brain region. Receiver operating characteristic analysis was used to find optimal ADC cutoff values for each region for the various outcome scores.

RESULTS

Twenty-four infants (13 male) were included. Mean age at MR imaging was 4.3 days (range, 1-9 days). Seven infants died. There was no difference in outcome between infants with and without visible DWI abnormalities. Only ADC of the posterior limb of the internal capsule correlated with age. ADC in visibly abnormal DWI regions did not have a predictive value for outcome. Of all measurements performed, only the ADC in the normal-appearing basal ganglia and brain stem correlated significantly with outcome; low ADC values were associated with abnormal/adverse outcome, and higher ADC values, with normal/favorable outcome (basal ganglia: P = .03 for abnormal, P = .01 for adverse outcome; brain stem: P = .006 for abnormal, P = .03 for adverse outcome).

CONCLUSIONS

ADC values in normal-appearing basal ganglia and brain stem correlated with outcome, independently of all MR imaging findings including those of DWI. ADC values in visibly abnormal brain tissue on DWI did not show a predictive value for outcome.

Abnormal white matter signal on MR imaging is related to abnormal tissue microstructure

BACKGROUND AND PURPOSE

White matter signal-intensity abnormalities (WMSA) on MR imaging are related to adverse neurodevelopmental outcome in extremely preterm infants. Diffusion tensor imaging (DTI) may detect alterations in cerebral white matter microstructure and thus may help confirm the pathologic basis of WMSA. This study aimed to relate regional DTI measures with severity of WMSA in very preterm infants.

MATERIALS AND METHODS

One hundred eleven preterm infants (birth weight, <1250 g and/or gestational age, <30 weeks) were scanned at term-equivalent age (1.5T). WMSA were classified as normal, focal, or extensive. Apparent diffusion coefficient (ADC), fractional anisotropy (FA), axial (lambda1), and radial ([lambda2 + lambda3]/2) diffusivity were calculated in 12 regions of interest placed in the bilateral posterior limbs of the internal capsule, frontal (superior and inferior), sensorimotor, and occipital (superior and inferior) white matter regions. Data were compared by using 1-way analysis of variance, with a Bonferroni correction for multiple comparisons.

RESULTS

Thirty-nine infants had normal, 59 infants had focal, and 13 infants had extensive WMSA. Compared with infants with normal or focal WMSA, infants with extensive WMSA had significantly lower FA in the internal capsule (P < .001), right inferior frontal regions (P < .05), and right superior occipital regions (P = .01); and higher radial diffusivity in the right internal capsule (P = .005), bilateral sensorimotor (P < .05), and right superior occipital regions (P < .05). Compared with infants with normal WMSA, infants with extensive WMSA had significantly higher ADC in bilateral sensorimotor regions (P < .01) and right superior occipital regions (P = .01), and lower axial diffusivity in the bilateral sensorimotor regions (P < .05).

CONCLUSIONS

There are significant region-specific changes in ADC, FA, radial diffusivity, and axial diffusivity in preterm infants with extensive WMSA. Altered radial diffusivity was most prominent. This implies that disrupted premyelinating oligodendroglia is the major correlate with extensive WMSA rather than axonal pathology.

Brain cooling for preterm infants

There is strong evidence that prolonged, moderate cerebral hypothermia initiated within a few hours after severe hypoxia-ischemia and continued until resolution of the acute phase of delayed cell death can reduce neuronal loss and improve behavioral recovery in term infants and adults after cardiac arrest. This review examines the evidence that mild to moderate hypothermia is protective after hypoxia-ischemia in models of preterm brain injury and evaluates the potential risks. Induced hypothermia likely has potential to significantly reduce disability. Cautious, systematic trials are essential before hypothermia can be used in these vulnerable infants.

Studies on the value of diffusion-weighted MR imaging in the early prediction of periventricular leukomalacia

OBJECTIVE

Periventricular leukomalacia (PVL) is the most common cerebral injury in premature infants. While cranial ultrasonography and conventional magnetic resonance imaging (MRI) offer little for its early diagnosis, still they are much favored at present. Based on the pathologic mechanism of ischemic cerebral injury in PVL, we attempt to elucidate the effects of diffusion-weighted MR imaging (DWI) for the early diagnosis of PVL.

METHODS

Twelve cases of PVL in premature infants confirmed by MRI examinations were included in the current study. All cases underwent DWI in addition to conventional MR imaging (T1-weighted [T1W] and T2-weighted [T2W]) 7 days, 2 weeks, and 4 approximately 8 weeks after birth, respectively.

RESULTS

Initial DWI examination (carried out at an average of 4.5 days after birth) revealed symmetrical and diffuse high signal in bilateral periventricular areas in all cases, while conventional MRI demonstrated normal signal. DWI examination of 2 weeks later showed irregular inhomogeneous signals in cerebral white matter, while conventional MRI revealed hyperintensity on T1WI and slight hypointensity on T2WI in corresponding areas. Four weeks later, DWI revealed various intensities of cystic low signals beside lateral ventricles, while conventional MRI showed hypointensity on T1WI and hyperintensity on T2WI in corresponding lesion, ie, change in cystic PVL. Four months later, conventional MRI evidenced gradual shrink and disappearance of cystic cavity, reduction in cerebral white matter, and ventricle enlargement.

CONCLUSIONS

Symmetrical, diffuse hyperintensity in both lateral periventricular white matter on DWI was the earliest sign of PVL in premature infants. Imaging abnormalities provided by DWI had a close correlation with the results obtained by conventional MRI performed at the advanced stage of PVL, which suggests that DWI may be an important sequence for the early evaluation of cerebral white matter injury as well as for the prediction of PVL occurrence in premature infants.

Movement training advances the emergence of reaching in infants born at less than 33 weeks of gestational age: a randomized clinical trial

BACKGROUND AND PURPOSE

This study had 2 purposes: (1) to compare the emergence of reaching in infants born full-term and infants born at less than 33 weeks of gestational age and (2) to evaluate the effectiveness of a movement training program on the emergence of reaching in this preterm population.

PARTICIPANTS

Twenty-six infants born at less than 33 weeks of gestational age and with a birth weight less than 2,500 g were randomly assigned to receive 20 minutes of daily movement training (PT-M group) or daily social training (PT-S group) and were compared with 13 infants born full-term (FT-S group).

METHODS

Reaching and hand-object interactions were tested every other week for 8 weeks. At each visit, infants were allowed six 30-second opportunities to contact a midline toy.

RESULTS

The FT-S and PT-M groups reached earlier and more consistently than the PT-S group. Specifically, the subjects in the FT-S group contacted the toy for longer durations and with an open, ventral surface of their hand. The PT-M group demonstrated increases in the number of hand-object contacts, the number of consistent reaches, and the percentage of time interacting with the toy and the surface of hand-object contact.

DISCUSSION AND CONCLUSION

This project demonstrates that there are early gross motor skill differences in infants born at less than 33 weeks of gestational age. A caregiver-based daily training program, however, is effective at lessening some, but not all, of these differences over the short term.

A systematic review of neuroimaging for cerebral palsy

The American Academy of Neurology now recommends that all cases of cerebral palsy of unknown origin undergo neuroimaging. Controversy surrounds this recommendation because of concerns about the adequacy of the supporting evidence. This article reviews the evidence provided by magnetic resonance imaging (MRI) and computed tomography (CT) imaging studies in cerebral palsy and discusses the potential benefits of imaging, techniques in current use, and future directions, with a focus on improving etiologic understanding. Most (83%) children with cerebral palsy have abnormal neuroradiological findings, with white matter damage the most common abnormality. Combined gray and white matter abnormalities are more common among children with hemiplegia; isolated white matter abnormalities are more common with bilateral spasticity or athetosis, and with ataxia; isolated gray matter damage is the least common finding. About 10% of cerebral palsy is attributable to brain malformations, and 17% of cerebral palsy cases have no abnormality detectable by conventional MR or CT imaging. Although neuroimaging studies have increased our understanding of the abnormalities in brain development in cerebral palsy, they are less informative than they might be because of 4 common problems: (1) inappropriate assignment of etiology to morphologic findings, (2) inconsistent descriptions of radiologic findings, (3) uncertain relationship of pathologic findings to brain insult timing estimates, and (4) study designs that are not based on generalizable samples. Neuroimaging is not necessarily required for diagnosis of cerebral palsy because the disorder is based on clinical findings. The principal contribution of imaging is to the understanding of etiology and pathogenesis, including ruling in or out conditions that may have implications for genetic counseling, such as malformations. In the future, as more sophisticated imaging procedures are applied to cerebral palsy, specific morphologic findings may be linked to etiologic events or exposures, thus leading to potential pathways for prevention.