Brain injury in the premature infant--from pathogenesis to prevention

Acquired Brain Injuries Across the Perinatal Spectrum: Pathophysiology and Emerging Therapies

The development of the central nervous system can be directly disrupted by a variety of acquired factors, including infectious, inflammatory, hypoxic-ischemic, and toxic insults. Influences external to the fetus also impact neurodevelopment, including placental health, maternal comorbidities, adverse experiences, environmental exposures, and social determinants of health. Acquired perinatal brain insults tend to affect the developing brain in a stage-specific manner that reflects the susceptible cell types, developmental processes, and risk factors present at the time of the insult. In this review, we discuss the pathophysiology, neurodevelopmental outcomes, and management of common acquired perinatal brain conditions. In the fetal brain, we divide insults based on trimester, and in the postnatal brain, we focus on common pathologies that have a presentation dependent on gestational age at birth: white matter injury and germinal matrix hemorrhage/intraventricular hemorrhage in preterm infants and hypoxic-ischemic encephalopathy in term infants. Although specific treatments for fetal and newborn brain disorders are currently limited, we emphasize therapies in preclinical or early clinical phases of the development pipeline. The growing number of novel cell type- and stage-specific emerging therapies suggests that in the near future we may have a dramatically improved ability to treat acquired perinatal brain disorders and to mitigate the associated neurodevelopmental consequences.

Effect of Kangaroo Mother Care on Cerebral Hemodynamics in Preterm Neonates Assessed by Transcranial Doppler Sonography in Middle Cerebral Artery

Objective

To study the effect of KMC in premature newborns on cerebral hemodynamics in the middle cerebral artery (MCA) using transcranial doppler sonography.

Methods

In this descriptive study, 40 clinically stable preterm neonates admitted to the neonatal intensive care unit of our institute and undergoing Kangaroo mother care (KMC) were enrolled. Physiological and cerebral blood flow parameters of MCA were obtained by using transcranial doppler sonography at baseline, at 60 minutes of KMC, and after 60 minutes of stopping KMC.

Results

Of the 40 enrolled neonates (24 males), the mean (SD) birth weight, gestation age, and postnatal age were 1698.25 (495.44) g, 33.00 (1.67) wk, and 6.80 (4.51) days, respectively. The mean (SD) cerebral blood flow velocities increased (peak systolic velocity (PSV), P=0.03; end diastolic velocity, P<0.001; mean velocity, P<0.001) and doppler indices decreased (resistive index, P=0.001; pulsatility index, P<0.001) significantly; whereas, heart rate (P<0.001) decreased but SpO2 (P=0.001) and mean blood pressure (P=0.003) increased significantly at 60 minutes of KMC as compared to baseline. Sixty minutes after stopping KMC, all parameters (except PSV) were higher than baseline, indicating post KMC effect.

Conclusion

KMC improves cerebral hemodynamics in clinically stable preterm neonates.

Impact of early brain lesions on the optic radiations in children with cerebral palsy

Due to their early brain lesion, children with unilateral spastic cerebral palsy (USCP) present important changes in brain gray and white matter, often manifested by perturbed sensorimotor functions. We predicted that type and side of the lesion could influence the microstructure of white matter tracts. Using diffusion tensor imaging in 40 children with USCP, we investigated optic radiation (OR) characteristics: fractional anisotropy (FA), mean diffusivity (MD), axial diffusivity (AD) and radial diffusivity (RD). First, we compared the OR of the lesional and non-lesional hemisphere. Then we evaluated the impact of the brain lesion type (periventricular or cortico-subcortical) and side in the differences observed in the lesional and non-lesional OR. Additionally, we examined the relationship between OR characteristics and performance of a visuospatial attention task. We observed alterations in the OR of children with USCP on the lesional hemisphere compared with the non-lesional hemisphere in the FA, MD and RD. These differences were influenced by the type of lesion and by the side of the lesion. A correlation was also observed between FA, MD and RD and the visuospatial assessment mainly in children with periventricular and right lesions. Our results indicate an important role of the timing and side of the lesion in the resulting features of these children’s OR and probably in the compensation resulting from neuroplastic changes.

Cyto/myeloarchitecture of cortical gray matter and superficial white matter in early neurodevelopment: multimodal MRI study in preterm neonates

The cerebral cortex undergoes rapid microstructural changes throughout the third trimester. Recently, there has been growing interest on imaging features that represent cyto/myeloarchitecture underlying intracortical myelination, cortical gray matter (GM), and its adjacent superficial whitematter (sWM). Using 92 magnetic resonance imaging scans from 78 preterm neonates, the current study used combined T1-weighted/T2-weighted (T1w/T2w) intensity ratio and diffusion tensor imaging (DTI) measurements, including fractional anisotropy (FA) and mean diffusivity (MD), to characterize the developing cyto/myeloarchitectural architecture. DTI metrics showed a linear trajectory: FA decreased in GM but increased in sWM with time; and MD decreased in both GM and sWM. Conversely, T1w/T2w measurements showed a distinctive parabolic trajectory, revealing additional cyto/myeloarchitectural signature inferred. Furthermore, the spatiotemporal courses were regionally heterogeneous: central, ventral, and temporal regions of GM and sWM exhibited faster T1w/T2w changes; anterior sWM areas exhibited faster FA increases; and central and cingulate areas in GM and sWM exhibited faster MD decreases. These results may explain cyto/myeloarchitectural processes, including dendritic arborization, synaptogenesis, glial proliferation, and radial glial cell organization and apoptosis. Finally, T1w/T2w values were significantly associated with 1-year language and cognitive outcome scores, while MD significantly decreased with intraventricular hemorrhage.

An artificial neural-network approach to identify motor hotspot for upper-limb based on electroencephalography: a proof-of-concept study

Background

To apply transcranial electrical stimulation (tES) to the motor cortex, motor hotspots are generally identified using motor evoked potentials by transcranial magnetic stimulation (TMS). The objective of this study is to validate the feasibility of a novel electroencephalography (EEG)-based motor-hotspot-identification approach using a machine learning technique as a potential alternative to TMS.

Methods

EEG data were measured using 63 channels from thirty subjects as they performed a simple finger tapping task. Power spectral densities of the EEG data were extracted from six frequency bands (delta, theta, alpha, beta, gamma, and full) and were independently used to train and test an artificial neural network for motor hotspot identification. The 3D coordinate information of individual motor hotspots identified by TMS were quantitatively compared with those estimated by our EEG-based motor-hotspot-identification approach to assess its feasibility.

Results

The minimum mean error distance between the motor hotspot locations identified by TMS and our proposed motor-hotspot-identification approach was 0.22 ± 0.03 cm, demonstrating the proof-of-concept of our proposed EEG-based approach. A mean error distance of 1.32 ± 0.15 cm was measured when using only nine channels attached to the middle of the motor cortex, showing the possibility of practically using the proposed motor-hotspot-identification approach based on a relatively small number of EEG channels.

Conclusion

We demonstrated the feasibility of our novel EEG-based motor-hotspot-identification method. It is expected that our approach can be used as an alternative to TMS for motor hotspot identification. In particular, its usability would significantly increase when using a recently developed portable tES device integrated with an EEG device.

Epidemiology and pathogenesis of stroke in preterm infants: A systematic review

BACKGROUND:

Perinatal stroke is one of the principal causes of cerebral palsy (CP) in preterm infants. Stroke in preterm infants is different from stroke in term infants, given the differences in brain maturation and the mechanisms of injury exclusive to the immature brain. We conducted a systematic review to explore the epidemiology and pathogenesis of periventricular hemorrhagic infarction (PVHI), perinatal arterial ischemic stroke (PAIS) and cerebral sinovenous thrombosis (CSVT) in preterm infants.

METHODS:

Studies were identified based on predefined study criteria from MEDLINE, EMBASE, SCOPUS and WEB OF SCIENCE electronic databases from 2000 –2019. Results were combined using descriptive statistics.

RESULTS:

Fourteen studies encompassed 546 stroke cases in preterm infants between 23 –36 weeks gestational ages and birth weights between 450 –3500 grams. Eighty percent (436/546) of the stroke cases were PVHI, 17%(93/546) were PAIS and 3%(17/546) were CSVT. Parietal PVHI was more common than temporal and frontal lobe PVHI. For PAIS, left middle cerebral artery (MCA) was more common than right MCA or cerebellar stroke. For CSVT partial or complete thrombosis in the transverse sinus was universal. All cases included multiple possible risk factors, but the data were discordant precluding aggregation within a meta-analysis.

CONCLUSION:

This systematic review confirms paucity of data regarding the etiology and the precise causal pathway of stroke in preterm infants. Moreover, the preterm infants unlike the term infants do not typically present with seizures. Hence high index of clinical suspicion and routine cUS will assist in the timely diagnosis and understanding of stroke in this population.

Disruption and Compensation of Sulcation-based Covariance Networks in Neonatal Brain Growth after Perinatal Injury

Perinatal brain injuries in preterm neonates are associated with alterations in structural neurodevelopment, leading to impaired cognition, motor coordination, and behavior. However, it remains unknown how such injuries affect postnatal cortical folding and structural covariance networks, which indicate functional parcellation and reciprocal brain connectivity. Studying 229 magnetic resonance scans from 158 preterm neonates (n = 158, mean age = 28.2), we found that severe injuries including intraventricular hemorrhage, periventricular leukomalacia, and ventriculomegaly lead to significantly reduced cortical folding and increased covariance (hyper-covariance) in only the early (<31 weeks) but not middle (31-35 weeks) or late stage (>35 weeks) of the third trimester. The aberrant hyper-covariance may drive acceleration of cortical folding as a compensatory mechanism to "catch-up" with normal development. By 40 weeks, preterm neonates with/without severe brain injuries exhibited no difference in cortical folding and covariance compared with healthy term neonates. However, graph theory-based analysis showed that even after recovery, severely injured brains exhibit a more segregated, less integrated, and overall inefficient network system with reduced integration strength in the dorsal attention, frontoparietal, limbic, and visual network systems. Ultimately, severe perinatal injuries cause network-level deviations that persist until the late stage of the third trimester and may contribute to neurofunctional impairment.

Simultaneous Multi-VENC and Simultaneous Multi-Slice Phase Contrast Magnetic Resonance Imaging

This work develops a novel, simultaneous multi-VENC and simultaneous multi-slice (SMV+SMS) imaging in a single acquisition for robust phase contrast (PC) MRI. To this end, the pulse sequence was designed to permit concurrent acquisition of multiple VENCs as well as multiple slices on a shared frequency encoding gradient, in which each effective echo time for multiple VENCs was controlled by adjusting net gradient area while multiple slices were simultaneously excited by employing multiband resonance frequency (RF) pulses. For VENC and slice separation, RF phase cycling and gradient blip were applied to create both inter-VENC and inter-slice shifts along phase encoding direction, respectively. With an alternating RF phase cycling that generates oscillating steady-state with low and high signal amplitude, the acquired multi-VENC k-space was reformulated into 3D undersampled k-space by generating a virtual dimension along VENC direction for modulation induced artifact reduction. In vivo studies were conducted to validate the feasibility of the proposed method in comparison with conventional PC MRI. The proposed method shows comparable performance to the conventional method in delineating both low and high flow velocities across cardiac phases with high spatial coverage without apparent artifacts. In the presence of high flow velocity that is above the VENC value, the proposed method exhibits clear depiction of flow signals over conventional method, thereby leading to high VNR image with improved velocity dynamic range.

NeoDoppler: New ultrasound technology for continous cerebral circulation monitoring in neonates

BACKGROUND

There is a strong need for continuous cerebral circulation monitoring in neonatal care, since suboptimal cerebral blood flow may lead to brain injuries in preterm infants and other critically ill neonates. NeoDoppler is a novel ultrasound system, which can be gently fixed to the anterior fontanel and measure cerebral blood flow velocity continuously in different depths of the brain simultaneously. We aimed to study the feasibility, accuracy, and potential clinical applications of NeoDoppler in preterm infants and sick neonates.

METHOD

Twenty-five infants born at different gestational ages with a variety of diagnoses on admission were included. The probe was placed over the anterior fontanel, and blood flow velocity data were continuously recorded. To validate NeoDoppler, we compared the measurements with conventional ultrasound; agreement was assessed using Bland-Altman plots.

RESULTS

NeoDoppler can provide accurate and continuous data on cerebral blood flow velocity in several depths simultaneously. Limits of agreement between the measurements obtained with the two methods were acceptable.

CONCLUSION

By monitoring the cerebral circulation continuously, increased knowledge of cerebral hemodynamics in preterm infants and sick neonates may be acquired. Improved monitoring of these vulnerable brains during a very sensitive period of brain development may contribute toward preventing brain injuries.

Neurovascular coupling in the developing neonatal brain at rest

The neonatal brain is an extremely dynamic organization undergoing essential development in terms of connectivity and function. Several functional imaging investigations of the developing brain have found neurovascular coupling (NVC) patterns that contrast with those observed in adults. These discrepancies are partly due to that NVC is still developing in the neonatal brain. To characterize the vascular response to spontaneous neuronal activations, a multiscale multimodal noninvasive approach combining simultaneous electrical, hemodynamic, and metabolic recordings has been developed for preterm infants. Our results demonstrate that the immature vascular network does not adopt a unique strategy to respond to spontaneous cortical activations. NVC takes on different forms in the same preterm infant during the same recording session in response to very similar types of neural activation. This includes (a) positive stereotyped hemodynamic responses (increases in HbO, decreases in HbR together with increases in rCBF and rCMRO2), (b) negative hemodynamic responses (increases in HbR, decreases in HbO together with decreases in rCBF and rCMRO2), and (c) Increases and decreases in both HbO‐HbR and rCMRO2 together with no changes in rCBF. Age‐related NVC maturation is demonstrated in preterm infants, which can contribute to a better understanding/prevention of cerebral hemodynamic risks in these infants.

Cerebral Blood Flow Measured by Phase-Contrast Magnetic Resonance Angiography in Preterm and Term Neonates

BACKGROUND

Preterm infants show a decreased tortuosity in all proximal segments of the cerebral vasculature at term-equivalent age (TEA). Recently MRI techniques were developed to measure cerebral blood flow (CBF) based on phase-contrast images.

OBJECTIVES

We hypothesized that arterial CBF corrected for brain size differs between full-term and preterm infants at TEA.

METHODS

344 infants without major brain abnormalities had a cranial MRI for clinical reasons including phase-contrast magnetic resonance angiography (PC-MRA) around TEA (mean 41.1 ± SD 1.2 weeks). This cohort consisted of 172 preterm infants (gestational age at birth 24.1-31.9 weeks) and 172 term-born infants (gestational age at birth 37.0-42.6 weeks). The total CBF in milliliters/minute was calculated by adding the blood flow of the carotid and basilar arteries, and compared to age at scan, body weight, and several parameters of estimated brain size.

RESULTS

After logarithmic transformation, total CBF was associated with body weight, estimated brain weight, head circumference, and 2D brain surface measurements at TEA. Total CBF was significantly (9-12%) higher in term compared to preterm infants after correction for 2D brain surface measurements, head circumference or postmenstrual age at MRI (p < 0.05).

CONCLUSIONS

Total CBF as measured by PC-MRA was associated with body and (estimated) brain weight and 2D brain surface measurements and was higher in term compared to preterm born infants.

Mechanism of Neuroprotection Against Experimental Spinal Cord Injury by Riluzole or Methylprednisolone

Any spinal cord injury carries the potential for persistent disability affecting motor, sensory and autonomic functions. To prevent this outcome, it is highly desirable to block a chain of deleterious reactions developing in the spinal areas immediately around the primary lesion. Thus, early timing of pharmacological neuroprotection should be one major strategy whose impact may be first studied with preclinical models. Using a simple in vitro model of the rat spinal cord it is possible to mimic pathological processes like excitotoxicity that damages neurons because of excessive glutamate receptor activation due to injury, or hypoxic/dysmetabolic insult that preferentially affects glia following vascular dysfunction. While ongoing research is exploring the various components of pathways leading to cell death, current treatment principally relies on the off-label use of riluzole (RLZ) or methylprednisolone sodium succinate (MPSS). The mechanism of action of these drugs is diverse as RLZ targets mainly neurons and MPSS targets glia. Even when applied after a transient excitotoxic stimulus, RLZ can provide effective prevention of secondary excitotoxic damage to premotoneurons, although not to motoneurons that remain very vulnerable. This observation indicates persistent inability to express locomotor activity despite pharmacological treatment conferring some histological protection. MPSS can protect glia from dysmetabolic insult, yet it remains poorly effective to prevent neuronal death. In summary, it appears that these pharmacological agents can produce delayed protection for certain cell types only, and that their combined administration does not provide additional benefit. The search should continue for better, mechanism-based neuroprotective agents.

Determining Electrode Placement for Transcranial Direct Current Stimulation: A Comparison of EEG- Versus TMS-Guided Methods

Transcranial direct current stimulation (tDCS) is increasingly researched as an adjuvant to motor rehabilitation for children with hemiparesis. The optimal method for the primary motor cortex (M1) somatotopic localization for tDCS electrode placement has not been established. The objective, therefore, was to determine the location of the M1 derived using the 10/20 electroencephalography (EEG) system and transcranial magnetic stimulation (TMS) in children with hemiparesis (CWH) and a comparison group of typically developing children (TDC). We hypothesized a difference in location for CWH but not for TDC. The 2 locations were evaluated in 47 children (21 CWH, 26 TDC). Distances between the locations were measured pending presence of a motor evoked potential. Distances between the EEG and TMS locations that exceeded the 2.5 cm × 2.5 cm rubber electrode area are reported in percentages [95% confidence interval] in CWH-nonlesioned hemisphere was 68.8% [41.3-89.0], lesioned: 85.7% [57.2-98.2]; TDC-dominant hemisphere 73.9% [51.6-89.8], nondominant: 82.6% [61.2-95.0]. Distances that exceeded the 3 × 5 cm electrode sponge area in CWH-nonlesioned was 25.0% [7.3-52.4], lesioned was 28.6% [8.4-58.1]; TDC-dominant was 52.2% [30.6-73.2], nondominant was 43.5 [23.2-65.5]). Distances that exceeded the 5 × 7 cm electrode sponge area in CWH-nonlesioned was 18.8% [4.0-45.6] and lesioned was 21.4% [4.7-50.8]; TDC-dominant was 21.7% [7.5-43.7] and nondominant was 26.1% [10.2-48.4]. Individual variability in brain somatotopic organization may influence surface scalp localization of underlying M1 in children regardless of neurologic impairment. Findings suggest further investigation of optimal tDCS electrode placement. EEG and TMS methods reveal variability in localizing M1 in children regardless of stroke diagnosis. This study was registered on clinicaltrials.gov NCT02015338.

Neurovascular coupling and energy metabolism in the developing brain

In the adult brain, increases in local neural activity are almost always accompanied by increases in local blood flow. However, many functional imaging studies of the newborn and developing human brain have observed patterns of hemodynamic responses that differ from adult responses. Among the proposed mechanisms for the observed variations is that neurovascular coupling itself is still developing in the perinatal brain. Many of the components thought to be involved in actuating and propagating this hemodynamic response are known to still be developing postnatally, including perivascular cells such as astrocytes and pericytes. Both neural and vascular networks expand and are then selectively pruned over the first year of human life. Additionally, the metabolic demands of the newborn brain are still evolving. These changes are highly likely to affect early postnatal neurovascular coupling, and thus may affect functional imaging signals in this age group. This chapter will discuss the literature relating to neurovascular development. Potential effects of normal and aberrant development of neurovascular coupling on the newborn brain will also be explored, as well as ways to effectively utilize imaging techniques that rely on hemodynamic modulation such as fMRI and NIRS in younger populations.

Outcome of hemiplegic cerebral palsy born at term depends on its etiology

OBJECTIVES

To elucidate the etiology and its relationship to the outcomes of hemiplegic cerebral palsy (HCP).

PARTICIPANTS AND METHODS

MR images and outcomes of 156 children with HCP born at term and older than three years were investigated in two major centers for cerebral palsy in Japan. Etiologies were classified into perinatal ischemic stroke (PIS), cerebral dysgenesis (CD), and others. PIS was divided into periventricular venous infarction (PVI) and two types of arterial infarction; middle cerebral artery infarction (MCAI) and deep gray matter infarction (DGMI). Initial signs and the time of presentation were investigated among the three types of PIS. As functional outcomes, laterality of paresis, age at initial walk, affected hand's function, intellectual development, and occurrence of epilepsy were compared among all the four types.

ETIOLOGY

PIS was found in 106 children (68%), while CD accounted for 28 (18%). Among PIS, venous infarction was more common than arterial infarction (62:44).

OUTCOMES

PVI revealed later presentation of motor asymmetry and more involvement of lower extremity as the initial sign among PIS groups. Only MCAI showed right-side predominance in laterality of paresis. DGMI related to better intellectual development and PVI showed lower occurrence of epilepsy, while there was no significant difference in affected hand's function among the four groups. PIS groups showed significantly earlier attainment of independent walk, better intellectual development, and lower occurrence of epilepsy than CD.

CONCLUSIONS

PVI was the most common cause of HCP born at term, and the etiology closely related to the initial signs of hemiplegia and overall outcomes.

Monitoring of Cerebrovascular Reactivity for Determination of Optimal Blood Pressure in Preterm Infants

OBJECTIVE

To define levels of mean arterial blood pressure (MABP) where cerebrovascular reactivity is strongest in preterm infants (ie, optimal MABP, or MABPOPT) and correlate deviations from MABPOPT with mortality and intraventricular hemorrhage (IVH).

STUDY DESIGN

A total of 60 preterm infants born at median gestational age 26 ± 2 weeks (23 ± 2 to 32 ± 1) with indwelling arterial catheter were studied at a median 34 hours (range 5-228) of age. Tissue oxygenation heart rate (HR) reactivity index, which estimates cerebrovascular reactivity, was calculated as the moving correlation coefficient between slow waves of tissue oxygenation index, measured with near-infrared spectroscopy, and HR. MABPOPT was defined by dividing MABP into 2-mm Hg bins and averaging the tissue oxygenation HR reactivity index within those bins. A measurement of divergence from MABPOPT was calculated as the absolute difference between mean MABP and mean MABPOPT.

RESULTS

Individual MABPOPT was defined in 81% of the patients. A measurement of divergence from MABPOPT was greater in those patients who died (mean 4.2 mm Hg; 95% CI 3.33-4.96) compared with those who survived (mean 2.1 mm Hg; 95% CI 1.64-2.56), P = .013. Patients who had MABP lower than MABPOPT by 4 mm Hg or more had a greater rate of mortality (40%) than those with MABP close to or above MABPOPT (13%), P = .049. Patients with MABP greater than MABPOPT by 4 mm Hg had greater IVH scores, P = .042.

CONCLUSIONS

Continuous monitoring of cerebrovascular reactivity allows the determination of MABPOPT in preterm neonates. Significant deviation below MABPOPT was observed in infants who died. Deviation of MABP above optimal level was observed in infants who developed more severe IVH.

Neurodevelopmental outcome in congenital diaphragmatic hernia: Evaluation, predictors and outcome

To review the reported neurodevelopmental outcome of congenital diaphragmatic hernia (CDH) survivors, identify important predictors of developmental disabilities, and describe the pathophysiological mechanisms contributing to adverse outcome. A Medline search was performed for English-language articles cross-referencing CDH with pertinent search terms. Retrospective, prospective, and longitudinal follow-up studies were examined. The reference lists of identified articles were also searched. Neurodevelopmental dysfunction has been recognized as one of most common and potentially most disabling outcome of CDH. Intelligence appears to be in the low normal to mildly delayed range. Neuromotor dysfunction is common during early childhood. Behavioral problems, hearing impairment, and quality of life related issues are frequently encountered in older children and adolescence. Disease severity correlates with the degree of neurological dysfunction. Neurodevelopmental follow-up in CDH children should become standard of care to identify those who would benefit from early intervention services and improve neurological outcomes.

Cardiovascular magnetic resonance of cardiac function and myocardial mass in preterm infants: a preliminary study of the impact of patent ductus arteriosus

BACKGROUND

Many pathologies seen in the preterm population are associated with abnormal blood supply, yet robust evaluation of preterm cardiac function is scarce and consequently normative ranges in this population are limited. The aim of this study was to quantify and validate left ventricular dimension and function in preterm infants using cardiovascular magnetic resonance (CMR). An initial investigation of the impact of the common congenital defect patent ductus arteriosus (PDA) was then carried out.

METHODS

Steady State Free Procession short axis stacks were acquired. Normative ranges of left ventricular end diastolic volume (EDV), stroke volume (SV), left ventricular output (LVO), ejection fraction (EF), left ventricular (LV) mass, wall thickness and fractional thickening were determined in "healthy" (control) neonates. Left ventricular parameters were then investigated in PDA infants. Unpaired student t-tests compared the 2 groups. Multiple linear regression analysis assessed impact of shunt volume in PDA infants, p-value ≤ 0.05 being significant.

RESULTS

29 control infants median (range) corrected gestational age at scan 34+6(31+1-39+3) weeks were scanned. EDV, SV, LVO, LV mass normalized by weight and EF were shown to decrease with increasing corrected gestational age (cGA) in controls. In 16 PDA infants (cGA 30+3(27+3-36+1) weeks) left ventricular dimension and output were significantly increased, yet there was no significant difference in ejection fraction and fractional thickening between the two groups. A significant association between shunt volume and increased left ventricular mass correcting for postnatal age and corrected gestational age existed.

CONCLUSION

CMR assessment of left ventricular function has been validated in neonates, providing more robust normative ranges of left ventricular dimension and function in this population. Initial investigation of PDA infants would suggest that function is relatively maintained.

Neuroprotective strategies--what do we really need to know?

While preliminary data are encouraging, definitive data are lacking to conclusively demonstrate the benefit of perioperative neurologic monitoring in improving neurodevelopmental outcomes in children who require surgery for congenital heart disease. Nonetheless, in the current era, some form of perioperative neurologic monitoring is important. Strategies include bicortical near infrared spectroscopy monitoring in the pre- and postoperative periods along with bicortical near infrared spectroscopy and transcranial Doppler intraoperatively. These monitors provide real-time information concerning cerebral oxygen delivery and blood flow. These strategies will allow us to refine treatments to optimize neurodevelopmental potential in children with congenital heart disease.

Behavioral and histological outcomes following neonatal HI injury in a preterm (P3) and term (P7) rodent model

Hypoxia-ischemia (HI) occurs when blood and/or oxygen delivery to the brain is compromised. HI injuries can occur in infants born prematurely (<37 weeks gestational age) or at very low birth weight (<1500 g), as well as in term infants with birth complications. In both preterm and term HI populations, brain injury is associated with subsequent behavioral deficits. Neonatal HI injury can be modeled in rodents (e.g., the Rice-Vannucci method, via cautery of right carotid followed by hypoxia). When this injury is induced early in life (between postnatal day (P)1-5), neuropathologies typical of human preterm HI are modeled. When injury is induced later (P7-12), neuropathologies typical of those seen in HI term infants are modeled. The current study sought to characterize the similarities/differences between outcomes following early (P3) and late (P7) HI injury in rats. Male rats with HI injury on P3 or P7, as well as sham controls, were tested on a variety of behavioral tasks in both juvenile and adult periods. Results showed that P7 HI rats displayed deficits on motor learning, rapid auditory processing (RAP), and other learning/memory tasks, as well as a reduction in volume in various neuroanatomical structures. P3 HI animals showed only transient deficits on RAP tasks in the juvenile period (but not in adulthood), yet robust deficits on a visual attention task in adulthood. P3 HI animals did not show any significant reductions in brain volume that we could detect. These data suggest that: (1) behavioral deficits following neonatal HI are task-specific depending on timing of injury; (2) P3 HI rats showed transient deficits on RAP tasks; (3) the more pervasive behavioral deficits seen following P7 HI injury were associated with substantial global tissue loss; and (4) persistent deficits in attention in P3 HI subjects might be linked to neural connectivity disturbances rather than a global loss of brain volume, given that no such pathology was found. These combined findings can be applied to our understanding of differing long-term outcomes following neonatal HI injury in premature versus term infants.

Early neural disruption and auditory processing outcomes in rodent models: implications for developmental language disability

Most researchers in the field of neural plasticity are familiar with the "Kennard Principle," which purports a positive relationship between age at brain injury and severity of subsequent deficits (plateauing in adulthood). As an example, a child with left hemispherectomy can recover seemingly normal language, while an adult with focal injury to sub-regions of left temporal and/or frontal cortex can suffer dramatic and permanent language loss. Here we present data regarding the impact of early brain injury in rat models as a function of type and timing, measuring long-term behavioral outcomes via auditory discrimination tasks varying in temporal demand. These tasks were created to model (in rodents) aspects of human sensory processing that may correlate-both developmentally and functionally-with typical and atypical language. We found that bilateral focal lesions to the cortical plate in rats during active neuronal migration led to worse auditory outcomes than comparable lesions induced after cortical migration was complete. Conversely, unilateral hypoxic-ischemic (HI) injuries (similar to those seen in premature infants and term infants with birth complications) led to permanent auditory processing deficits when induced at a neurodevelopmental point comparable to human "term," but only transient deficits (undetectable in adulthood) when induced in a "preterm" window. Convergent evidence suggests that regardless of when or how disruption of early neural development occurs, the consequences may be particularly deleterious to rapid auditory processing (RAP) outcomes when they trigger developmental alterations that extend into subcortical structures (i.e., lower sensory processing stations). Collective findings hold implications for the study of behavioral outcomes following early brain injury as well as genetic/environmental disruption, and are relevant to our understanding of the neurologic risk factors underlying developmental language disability in human populations.

Using the Alberta Infant Motor Scale to early identify very low-birth-weight infants with cystic periventricular leukomalacia

We examined whether the Alberta Infant Motor Scale (AIMS) is able to identify very low-birth-weight (VLBW) preterm infants with cystic periventricular leukomalacia (PVL) as early as 6 months of corrected age. Longitudinal follow-up AIMS assessments were done at 6, 12, and 18 months old for 35 VLBW infants with cystic PVL (cPVL(+)), 70 VLBW infants without cystic PVL (cPVL(-)), and 76 term infants (healthy controls: HC). Corrected age was used for the preterm infants. The cPVL(+) group had significantly lower prone, supine and sitting subscales at age 6, 12, and 18 months than the cPVL(-) group (all p<0.05). The cPVL(-) group showed significantly lower supine, prone, sitting, and standing subscales than the HC group only at age 6 months. At age 6 months, the areas under the receiver operator curve used to discriminate the cPVL(+) infants from cPVL(-) infants were 0.82±0.04 for prone, 0.93±0.02 for supine, 0.83±0.05 for sitting, and 0.62±0.07 for standing. The AIMS may help early identify VLBW infants with cystic PVL at age 6 months old.

Neonatal intracerebral hemorrhage: mechanisms, managements, and the outcomes

Intracerebral hemorrhage is a multifactorial disorder with heterogeneous etiologies and potentially long-term debilitating outcomes. We review all available evidence regarding the current strategies for management of intracerebral hemorrhage. It is clear that prompt detection and treatment does affect the outcome; nevertheless, prevention of intracerebral hemorrhage remains the best strategy.

Minocycline protects oligodendroglial precursor cells against injury caused by oxygen-glucose deprivation

Ischemic brain injury is widely modeled in vitro with paradigms of oxygen-glucose deprivation (OGD), which leads to cell death. The prevention and attenuation of brain injury by the tetracycline antibiotic minocycline has been attributed largely to suppression of microglial activation, but its benefits in oligodendrocyte cells have not been well characterized. Using primary cultures of rat oligodendroglial precursor cells (OPC) exposed to OGD, we investigated the direct effects of minocycline on the survival, proliferation, and maturation of oligodendroglial lineage cells. OGD for 2 hr caused a decrease in the total number of OPC and the amount of proliferating progenitors by 50%, which was attenuated by inclusion of minocycline. The reduced numbers of immature oligodendroglial cells at 72 hr and of mature oligodendrocytes at 120 hr after OGD were partially restored by minocycline. In OPC, OGD caused an increase of reactive oxygen species (ROS) and production of TUNEL-positive cell numbers, which was abolished by minocycline. Minocycline preferentially increased the expression of superoxide dismutase under OGD but not in control OPC. Minocycline also prevented the OGD-induced downregulation of the transcription factors Sox10 and Olig2 and of myelin-specific genes 2'3' cyclic nucleotide phosphodiesterase (CNP) and myelin basic protein (MBP) in response to OGD. These studies demonstrate direct protective actions of minocycline on oligodendroglial-lineage cells, suggesting potential benefit in white matter injury involving OGD.

Neurodevelopmental and neurofunctional outcomes in children with congenital diaphragmatic hernia

The objective of this review was to provide a critical overview of our current understanding on the neurocognitive, neuromotor, and neurobehavioral development in congenital diaphragmatic hernia (CDH) patients, focusing on three interrelated clinical issues: (1) comprehensive outcome studies, (2) characterization of important predictors of adverse outcome, and (3) the pathophysiological mechanism contributing to neurodevelopmental disabilities in infants with CDH. Improved survival for CDH has led to an increasing focus on longer-term outcomes. Neurodevelopmental dysfunction has been recognized as the most common and potentially most disabling outcome of CDH and its treatment. While increased neuromotor dysfunction is a common problem during infancy, behavioral problems, hearing impairment and quality of life related issues are frequently found in older children and adolescence. Intelligence appears to be in the low normal range. Patient and disease specific predictors of adverse neurodevelopmental outcome have been defined. Imaging studies have revealed a high incidence of structural brain abnormalities. An improved understanding of the pathophysiological pathways and the neurodevelopmental consequences will allow earlier and possibly more targeted therapeutic interventions. Continuous assessment and follow-up as provided by an interdisciplinary team of medical, surgical and developmental specialists should become standard of care for all CDH children to identify and treat morbidities before additional disabilities evolve and to reduce adverse outcomes.

Association between Total Antioxidant Capacity in Breast Milk and Postnatal Age in Days in Premature Infants

This study aimed to consider the significance of breast milk in preventing oxidative stress by comparing total antioxidant capacity (TAC) in breast milk and formula milk for premature infants, demonstrating the relationship between TAC in breast milk and postnatal age in days. We used the biological anti-oxidant potential test, a new method to measure TAC in breast milk. Breast milk for premature infants were stored at -20 degrees C and thawed within 48 h of collection. We measured TAC in two types of formula milk in the same way. TAC was clearly higher in breast milk than formula milk. Although a negative correlation was observed between TAC in breast milk and age when collected, TAC was always higher than the average TAC in formula milk. TAC in breast milk is higher than TAC in formula milk. We suggest the importance of breast milk for preventing oxidative stress and starting breastfeeding early.

Anisotropy of transcallosal motor fibres indicates functional impairment in children with periventricular leukomalacia

AIM

In children with bilateral spastic cerebral palsy (CP), periventricular leukomalacia (PVL) is commonly identified on magnetic resonance imaging. We characterized this white matter condition by examining callosal microstructure, interhemispheric inhibitory competence (IIC), and mirror movements.

METHOD

We examined seven children (age range 11y 9mo-17y 9mo, median age 15y 10mo, four females, three males) with bilateral spastic CP/PVL (Gross Motor Function Classification System level I or II, Manual Ability Classification System level I) and 12 age-matched controls (age range 11y 7mo-17y 1mo, median age 15y 6mo, seven females, five males). Fractional anisotropy of the transcallosal motor fibres (TCMF) and the corticospinal tract (CST) of both sides were calculated. The parameters of IIC (transcranial magnetic stimulation) and mirror movements were measured using a standardized clinical examination and a computer-based hand motor test.

RESULTS

Fractional anisotropy was lower in children with bilateral spastic CP/PVL regarding the TCMF, but not the left or right CST. Resting motor threshold was elevated in children with bilateral spastic CP/PVL whereas measures of IIC tended to be lower. Mirror movements were markedly elevated in bilateral spastic CP/PVL.

INTERPRETATION

This study provides new information on different aspects of motor function in children with bilateral spastic CP/PVL. Decreased fractional anisotropy of TCMF is consistent with impairment of hand motor function in children with bilateral spastic CP/PVL. The previously overlooked microstructure of the TCMF may serve as a potential indicator for hand motor function in patients with bilateral spastic CP/PVL.

Reader variability in the use of diagnostic terms to describe white matter lesions seen on cranial scans of severely premature infants: the ELGAN study

PURPOSE

To evaluate reader variability of white matter lesions seen on cranial sonographic scans of extreme low gestational age neonates (ELGANs).

METHODS

In 1,452 ELGANs, cranial sonographic scans were obtained in the first and second postnatal weeks, and between the third postnatal week and term. All sets of scans were read independently by two sonologists. We reviewed the use of four diagnostic labels: early periventricular leucomalacia, cystic periventricular leucomalacia, periventricular hemorrhagic infarction (PVHI), and other white matter diagnosis, by 16 sonologists at 14 institutions. We evaluated the association of these labels with location and laterality of hyperechoic and hypoechoic lesions, location of intraventricular hemorrhage, and characteristics of ventricular enlargement.

RESULTS

Experienced sonologists differed substantially in their application of the diagnostic labels. Three readers applied early periventricular leucomalacia to more than one fourth of all the scans they read, whereas eight applied this label to ≤5% of scans. Five applied PVHI to ≥10% of scans, while three applied this label to ≤5% of scans. More than one third of scans labeled cystic periventricular leucomalacia had unilateral hypoechoic lesions. White matter abnormalities in PVHI were more extensive than in periventricular leucomalacia and were more anteriorly located. Hypoechoic lesions on late scans tended to be in the same locations, regardless of the diagnostic label applied.

CONCLUSIONS

Experienced sonologists differ considerably in their tendency to apply diagnostic labels for white matter lesions. This is due to lack of universally agreed-upon definitions. We recommend reducing this variability to improve the validity of large multicenter studies.

Prediction of periventricular leukomalacia. Part I: Selection of hemodynamic features using logistic regression and decision tree algorithms

OBJECTIVE

Periventricular leukomalacia (PVL) is part of a spectrum of cerebral white matter injury which is associated with adverse neurodevelopmental outcome in preterm infants. While PVL is common in neonates with cardiac disease, both before and after surgery, it is less common in older infants with cardiac disease. Pre-, intra-, and postoperative risk factors for the occurrence of PVL are poorly understood. The main objective of the present work is to identify potential hemodynamic risk factors for PVL occurrence in neonates with complex heart disease using logistic regression analysis and decision tree algorithms.

METHODS

The postoperative hemodynamic and arterial blood gas data (monitoring variables) collected in the cardiac intensive care unit of Children's Hospital of Philadelphia were used for predicting the occurrence of PVL. Three categories of datasets for 103 infants and neonates were used-(1) original data without any preprocessing, (2) partial data keeping the admission, the maximum and the minimum values of the monitoring variables, and (3) extracted dataset of statistical features. The datasets were used as inputs for forward stepwise logistic regression to select the most significant variables as predictors. The selected features were then used as inputs to the decision tree induction algorithm for generating easily interpretable rules for prediction of PVL.

RESULTS

Three sets of data were analyzed in SPSS for identifying statistically significant predictors (p<0.05) of PVL through stepwise logistic regression and their correlations. The classification success of the Case 3 dataset of extracted statistical features was best with sensitivity (SN), specificity (SP) and accuracy (AC) of 87, 88 and 87%, respectively. The identified features, when used with decision tree algorithms, gave SN, SP and AC of 90, 97 and 94% in training and 73, 58 and 65% in test. The identified variables in Case 3 dataset mainly included blood pressure, both systolic and diastolic, partial pressures pO(2) and pCO(2), and their statistical features like average, variance, skewness (a measure of asymmetry) and kurtosis (a measure of abrupt changes). Rules for prediction of PVL were generated automatically through the decision tree algorithms.

CONCLUSIONS

The proposed approach combines the advantages of statistical approach (regression analysis) and data mining techniques (decision tree) for generation of easily interpretable rules for PVL prediction. The present work extends an earlier research [Galli KK, Zimmerman RA, Jarvik GP, Wernovsky G, Kuijpers M, Clancy RR, et al. Periventricular leukomalacia is common after cardiac surgery. J Thorac Cardiovasc Surg 2004;127:692-704] in the form of expanding the feature set, identifying additional prognostic factors (namely pCO(2)) emphasizing the temporal variations in addition to upper or lower values, and generating decision rules. The Case 3 dataset was further investigated in Part II for feature selection through computational intelligence.

Neonatal hypoxic/ischemic brain injury induces production of calretinin-expressing interneurons in the striatum

Ischemia-induced striatal neurogenesis from progenitors in the adjacent subventricular zone (SVZ) in young and adult rodents has been reported. However, it has not been established whether the precursors that reside in the SVZ retain the capacity to produce the full range of striatal neurons that has been destroyed. By using a neonatal rat model of hypoxic/ischemic brain damage, we show here that virtually all of the newly produced striatal neurons are calretinin (CR)-immunoreactive (+), but not DARPP-32(+), calbindin-D-28K(+), parvalbumin(+), somatostatin(+), or choline acetyltransferase(+). Retroviral fate-mapping studies confirm that these newly born CR(+) neurons are indeed descendants of the SVZ. Our studies indicate that, although the postnatal SVZ has the capacity to produce a range of neurons, only a subset of this repertoire is manifested in the brain after injury.

Neonatal cerebral oxygenation is not linked to foetal vasculitis and predicts intraventricular haemorrhage in preterm infants

AIM

The aim of the study was to compare the cerebral tissue oxygenation index (c-TOI) measured by near infrared spectroscopy (NIRS) in infants with and without foetal vasculitis.

METHODS

Twenty-four infants with placental signs of a foetal inflammatory response (FIR), foetal vasculitis, were compared with 39 controls. NIRS examination was done within the first 24 h.

RESULTS

Infants with FIR had a significant lower gestational age (26.8 +/- 2.4 vs. 29.8 +/- 2.4 weeks' gestation; p < 0.01), Hb (9.4 +/- 1.2 vs. 10.9 +/- 1.5 mM; p < 0.01) and blood P(CO2) (5.5 +/- 0.8 vs. 6.3 +/- 1.1 kPa, p < 0.01) compared to controls. There was no significant difference in arterial blood pressure, inspiratory oxygen content, needs of mechanical ventilation or c-TOI (73.6 +/- 8.1% vs. 73.9 +/- 8.1% (p = 0.9)). The effect of FIR on c-TOI was -0.3% (95% CI -3.9 to 4.5%). This result was not affected by inclusion of potential confounders in the analysis. Eight infants subsequently developed intra/periventricular haemorrhage: four with minor lesions and four with severe lesions. There was a significant negative correlation between the severity of the intraventricular haemorrhage and the cerebral oxygenation (p = 0.002).

CONCLUSION

Cerebral oxygenation was not affected in the first day of life in preterm infants born with foetal vasculitis, while cerebral oxygenation in infants that later developed intraventricular haemorrhage was impaired.

Maturational changes in laminin, fibronectin, collagen IV, and perlecan in germinal matrix, cortex, and white matter and effect of betamethasone

Germinal matrix is selectively vulnerable to hemorrhage in premature infants, and use of prenatal betamethasone is associated with a lower occurrence of germinal matrix hemorrhage. Because the major components of extracellular matrix of the cerebral vasculature-laminin, fibronectin, collagen IV, and perlecan-provide structural stability to blood vessels, we examined whether the expression of these molecules was decreased in the germinal matrix and affected by betamethasone. In both human fetuses and premature infants, fibronectin was significantly lower in the germinal matrix than in the cortical mantle or white matter anlagen. Conversely, laminin alpha1 gene expression was greater in the human germinal matrix compared with the cortical mantle or white matter. Expression of alpha1- and alpha2(IV) collagen chains increased with advancing gestational age. Low-dose prenatal betamethasone treatment enhanced fibronectin level by 1.5-2-fold whereas a high dose reduced fibronectin expression by 2-fold in rabbit pups. Because fibronectin provides structural stability to the blood vessels, its reduced expression in the germinal matrix may contribute to the fragility of germinal matrix vasculature and the propensity to hemorrhage in premature neonates.

A decade comparison of preterm motor performance at age 4

This was a prospective longitudinal study of two cohorts comprised of one full term and three premature infant groups born 10 years apart. Birth cohort, perinatal morbidity, and birth weight effects were investigated at age 4. Cohort 1 (1985-1989) had longer gestation, higher birth weight, and better Apgar scores than Cohort 2 (1996-1999), which had more intraventricular hemorrhage and bronchopulmonary dysplasia. Cohort and perinatal morbidity group, but not birth weight, predicted motor scores. Preterm Cohort 2 children had better oral motor, fine motor, and total motor scores, but lower visual motor integration scores than Cohort 1. Motor problems continue to affect preterm children at age 4, in particular those who experience perinatal morbidity, despite a decade of neonatal intensive care advancements.

Perinatal risk factors for neonatal intracerebral hemorrhage in preterm infants

OBJECTIVE

To investigate the perinatal factors related to neonatal intracerebral hemorrhage (ICH) and possibly to define obstetric and perinatal risk factors.

STUDY DESIGN

All medical records of women who delivered in the period from 1 January 1991 to 1 January 2000 were reviewed for intracerebral hemorrhages in infants born between 24 and 34 weeks of gestation and treated in the postnatal period. Sixty infants with ICH (Group I) and 60 infants without ICH (Group II, matched controls) were determined for comparison. Obstetrical parameters and risk factors and perinatal outcome parameters were evaluated and statistically analyzed.

RESULTS

Neonatal intracerebral hemorrhage prevalence was 0.8% (60/7635 births). Betamethasone administration was significantly less in Group I than in Group II (27% versus 46%). Although Doppler-sonography of the middle cerebral artery was performed in a minority of the cases, it showed a significant tendency of lower resistance indices (brain sparing) in the intracerebral hemorrhage group (66.7% versus 21.1%). Postnatally, infants with intracerebral hemorrhage showed a significantly more often umbilical arterial acidosis (18% versus 10%), a greater base deficit, lower median 5 min Apgar scores (6 and 8, respectively for Groups I and II), and a lower thrombocyte count (Group I 190,000 +/- 76,000 microl(-1), and Group II 227,000 +/- 96,000 microl(-1)). Infants in Group I were more often (93% versus 76%) and longer (26.7 +/- 30.5 days versus 15.4 +/- 11.7 days) dependent on ventilatory support than infants in Group II. Mortality rate in Group I (35%) was significantly higher compared to Group II (17%).

CONCLUSIONS

Antenatal Doppler sonography in predicting intracerebral hemorrhage in preterm infants should be investigated in large scale prospective studies. Postnatal low pH-values (pH < 7.1) and a base deficit of more than -16 mmol/L in the umbilical artery, low Apgar scores and thrombocytopenia are associated with a neonatal intracerebral hemorrhage and prophylaxis with corticosteroids reduces the risk for it. A higher neonatal mortality and morbidity, including neurological and neuromotoric dysfunctions is expected in this clinical entity.

Web-based method for translating neurodevelopment from laboratory species to humans

Biomedical researchers and medical professionals are regularly required to compare a vast quantity of neurodevelopmental literature obtained from an assortment of mammals whose brains grow at diverse rates, including fast developing experimental rodent species and slower developing humans. In this article, we introduce a database-driven website, which was created to address this problem using statistical-based algorithms to integrate hundreds of empirically derived developing neural events in 10 mammalian species (http://translatingtime.net/). The site, based on a statistical model that has evolved over the past decade, currently incorporates 102 different neurodevelopmental events obtained from 10 species: hamsters, mice, rats, rabbits, spiny mice, guinea pigs, ferrets, cats, rhesus monkeys, and humans. Data are arranged in a Structured Query Language database, which allows comparative brain development measured in postconception days to be converted and accessed in real time, using Hypertext Preprocessor language. Algorithms applied to the database also allow predictions for dates of specific neurodevelopmental events where empirical data are not available, including for the human embryo and fetus. By designing a web-based portal, we seek to make these comparative data readily available to all those who need to efficiently estimate the timing of neurodevelopmental events in the human fetus, laboratory species, or across several different species. In an effort to further refine and expand the applicability of this database, we include a mechanism to submit additional data.

Delayed IGF-1 administration rescues oligodendrocyte progenitors from glutamate-induced cell death and hypoxic-ischemic brain damage

We previously demonstrated that IGF-1 blocks glutamate-mediated death of late oligodendrocyte progenitors (OPs) by preventing Bax translocation, mitochondrial cytochrome c release and cleavage of caspases 9 and 3. Here, we demonstrate that IGF-1 prevents caspase 3 activation in late OPs when administered up to 16 h following exposure to glutamate. Moreover, late addition of IGF-1 to OPs previously exposed to toxic levels of glutamate promotes oligodendrocyte maturation as measured by myelin basic protein expression. We also demonstrate that intraventricularly administered IGF-1 retains OPs in the perinatal white matter after hypoxia-ischemia when given after insult. These results suggest that delayed administration of IGF-1 will rescue OPs in the immature white matter and promote myelination following hypoxia-ischemia.

Etiologic subtypes of attention-deficit/hyperactivity disorder: brain imaging, molecular genetic and environmental factors and the dopamine hypothesis

Multiple theories of Attention-Deficit/Hyper-activity Disorder (ADHD) have been proposed, but one that has stood the test of time is the dopamine deficit theory. We review the narrow literature from recent brain imaging and molecular genetic studies that has improved our understanding of the role of dopamine in manifestation of symptoms of ADHD, performance deficits on neuropsychological tasks, and response to stimulant medication that constitutes the most common treatment of this disorder. First, we consider evidence of the presence of dopamine deficits based on the recent literature that (1) confirms abnormalities in dopamine-modulated frontal-striatal circuits, reflected by size (smaller-than-average components) and function (hypoactivation); (2) clarifies the agonist effects of stimulant medication on dopaminergic mechanisms at the synaptic and circuit level of analysis; and (3) challenges the most-widely accepted ADHD-related neural abnormality in the dopamine system (higher-than-normal dopamine transporter [DAT] density). Second, we discuss possible genetic etiologies of dopamine deficits based on recent molecular genetic literature, including (1) multiple replications that confirm the association of ADHD with candidate genes related to the dopamine receptor D4 (DRD4) and the DAT; (2) replication of differences in performance of neuropsychological tasks as a function of the DRD4 genotype; and (3) multiple genome-wide linkage scans that demonstrate the limitations of this method when applied to complex disorders but implicate additional genes that may contribute to the genetic basis of ADHD. Third, we review possible environmental etiologies of dopamine deficits based on recent studies of (1) toxic substances that may affect the dopamine system in early development and contribute substantially to the etiology of ADHD; (2) fetal adaptations in dopamine systems in response to stress that may alter early development with lasting effects, as proposed by the developmental origins of health and disease hypothesis; and (3) gene-environment interactions that may moderate selective damage or adaptation of dopamine neurons. Based on these reviews, we identify critical issues about etiologic subtypes of ADHD that may involve dopamine, discuss methods that could be used to address these issues, and review old and new theories that may direct research in this area in the future.

Intrauterine infection induced oligodendrocyte injury and inducible nitric oxide synthase expression in the developing rat brain

AIMS

In order to investigate the neuropathological effect on the developing rat brain after intrauterine infection, 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) and inducible nitric oxide synthase (iNOS) were evaluated.

METHODS

Escherichia coli (E. coli) was inoculated into the uterine cervix of the time-pregnant rats and controls were injected with normal saline. Immunohistochemical staining for CNPase was performed to assess oligodendrocyte injury in pup brains at postnatal day 1, 3 and 7 (P1, P3, and P7). Immunohistochemistry was used to evaluate iNOS expression and quantitative reverse transcriptase PCR to analyze iNOS mRNA expression in pup brains at P1, P3 and P7. Nitrate reductase method was used for detection of nitric oxide (NO) concentration in pup brains at P1, P3 and P7.

RESULTS

The immunohistochemical staining for CNPase in the E. coli-treated group showed a decrease compared with the control in periventricular white matter at P7. Obvious immunohistochemical staining of iNOS was observed in periventricular white matter of the E. coli-treated pup brains at P1. The expression of iNOS mRNA in the E. coli-treated pup brains increased at P1 and P3, but there was no significant difference at P7 compared with controls. Similarly, the NO concentration increased in the E. coli-treated pup brains at P1 and P3, and no significant difference was found at P7 compared with controls.

CONCLUSIONS

The alteration of CNPase expression indicates that intrauterine infection could cause oligodendrocyte injury in the developing brain. Moreover, the increased expression of iNOS followed by the increasing NO concentration after intrauterine infection suggests that iNOS might be a key mediator between the intrauterine infection and oligodendrocyte injury in the developing brain.

Neurodevelopmental outcomes following congenital heart surgery

Advances in both surgical techniques and perioperative care have led to improved survival outcomes in infants and children undergoing surgery for complex congenital heart disease. An awareness is emerging that early and late neurological morbidities complicate the outcome of these operations. Adverse neurological outcomes after neonatal and infant cardiac surgery are related to both fixed and modifiable mechanisms. Fixed factors include many variables specific to the individual patient, including genetic predisposition, gender, race, socioeconomic status, and in utero central nervous system development. Modifiable factors include not only intraoperative variables (cardiopulmonary bypass, deep hypothermic circulatory arrest, and hemodilution) but also such variables as hypoxemia, hypotension, and low cardiac output. The purpose of this review is to examine these mechanisms as they relate to available outcome data.

Neuroimaging of the child with developmental delay

Developmental delay (DD) affects approximately 1% to 3% of all children in the United States. This diagnosis significantly impedes quality of life and full participation in the life of the family, school, and community. In this setting, the clinician's ability to detect, diagnose, and possibly treat the cause for DD in a timely manner depends on a multimodality approach to neuroimaging and a robust understanding of the various imaging algorithms aimed at determining the etiology of disease, structural and/or anatomic defects, functional activity, metabolic profiles, and genetic characteristics. Taken separately and in combination, these features are effectively depicted and analyzed using an array of brain imaging modalities: ultrasound, computed tomography, nuclear medicine, magnetic resonance (MR) spectroscopy, and a growing mix of sophisticated MR imaging (MRI) techniques, including diffusion-weighted imaging, diffusion tensor imaging, perfusion MRI, and functional MRI. Thus, equipped with these advanced imaging capabilities, pediatric neurologists and neuroradiologists are now positioned to diagnose with greater accuracy and speed; this, in turn, results in more effective treatment plans and improved patient outcomes as measured by progress in reaching developmental milestones and in ameliorating secondary conditions such as seizures, poor motor control, incontinence, and impulsivity. The purpose of this article is to present the numerous causes of pediatric DD, describe their respective neuroimaging findings, discuss various neuroimaging approaches for elucidating etiology, and offer specific guidelines for optimizing imaging results in the setting of multimodality imaging capabilities.

The role of magnetic resonance imaging in elucidating the pathogenesis of cerebral palsy: a systematic review

The aim of this study was to show the role of magnetic resonance imaging (MRI) in elucidating the aetiology, or at least pathogenesis, of cerebral palsy (CP). A systematic review of studies using MRI in children with CP was performed according to pathogenetic patterns characterizing different timing periods of occurence of the lesions, and with respect to gestational age (term vs preterm) and CP subtypes. Out of the studies published since 1990 in English, six met all the inclusion criteria; they involved children with spastic and dyskinetic CP. Abnormal MRI was reported in 334 out of 388 (86%) patients and gave clues to pathogenesis in 83%. Fourteen studies met only part of the inclusion criteria and abnormal MRIs were reported even more frequently in these (91%; 930/1022). Periventricular white matter lesions were most frequent (56%) followed by cortical and deep grey matter lesions (18%); brain maldevelopments were rather rare, described in 9%. Brain maldevelopments and grey matter lesions were more often seen in term than in preterm-born children with CP (brain maldevelopments: 16% vs 2.5%; grey matter lesions: 33% vs 3.5%); periventricular white matter lesions occurred significantly more often in preterm than in term-born children (90% vs 20%). CP is mainly characterized by brain lesions which can be identified by MRI in around 75% of preterm infants; brain maldevelopments occur in around 10%.

Minocycline modulates chemokine receptors but not interleukin-10 mRNA expression in hypoxic-ischemic neonatal rat brain

Hypoxic-ischemic (HI) brain injury in the perinatal period causes significant morbidity. Minocycline (MN) is a tetracycline derivative that has reduced brain injury in various animal models of neurodegeneration, including perinatal ischemia. To determine whether MN can modulate the expression of chemokine receptors and interleukin-10 (IL10) in a model of neonatal brain injury, we produced an HI insult to the right cerebral hemisphere (ipsilateral) of the 7-day-old rat (PD7) by right common carotid artery ligation and 2.25 hr of hypoxia in 8% oxygen. MN (45 mg/kg, i.p.) or vehicle (PBS) was injected twice: 2 days and immediately before the HI insult. At 0, 1, 3, and 24 hr and 14 days after HI, total RNA from the ipsilateral and contralateral (exposed to hypoxia only) hemispheres was extracted, reverse transcribed, and amplified with gene-specific primers using a semiquantitative RT-PCR for macrophage inflammatory protein-1alpha), interferon-inducible protein (IP-10), C-C chemokine receptor 5 (CCR5; MIP-1alpha receptor), C-X-C chemokine receptor 3 (CXCR3; IP-10 receptor), and IL10. We found that, in the ipsilateral hemisphere, a significant (P < 0.05) increase in MIP-1alpha, IP-10, CCR5, and CXCR3 mRNA levels was observed. MN treatment decreased mRNA levels for CCR5 and CXCR3. In contrast, the levels of antiinflammatory cytokine IL10 were markedly decreased as a result of HI insult. Treatment with MN, however, had no effect on IL10. We conclude that MN decreased proinflammatory chemokine receptor expression but had little or no influence on the expression of antiinflammatory cytokine IL10. These effects confirm the antiinflammatory effect of MN in neonatal HI brain injury.

Aspects IRM de l’encéphalopathie anoxo-ischémique du nouveau-né à terme et du prémature

These past few years have seen an increasing role of MRI in the investigation of neonatal cerebral anoxic-ischemic pathology. This is due not only to greater precision in diagnosing lesion extension, but also to earlier detection of lesions with the diffusion of weighted imagery. The aim of this iconographic review is to illustrate the main MRI aspects of anoxic-ischemic encephalopathy in a pedagogical way. After a brief physiopathology reminder, the different cerebral lesions are studied in a first chapter on the premature newborn pathology and a second chapter on full-term newborn pathology.

Early brain development disruption from NMDA receptor hypofunction: relevance to schizophrenia

Disruption to brain development at an early stage can potentially alter chemically coded neural networks and can affect behavior in later life. During early brain development antagonism of glutamate NMDA receptors, which play an important role in neuronal outgrowth and survival, leads to neuronal damage in several brain regions and causes behavioral alterations in rodents that mimic schizophrenia symptoms and endophenotypes. There are several lines of evidence implicating involvement of a dysfunctional glutamate system in schizophrenia. In normal subjects, NMDA receptor antagonists produce behavioral and neurochemical changes that mimic schizophrenia symptoms better than any other psychotomimetic drug. Moreover, these drugs worsen symptoms in schizophrenia patients and can trigger a recrudescence of the acute psychotic state in patients with stable chronic schizophrenia. In addition, genes consistently reported as being altered in schizophrenia play roles in development, neuroplasticity and glutamate/GABAergic neurotransmission. Perinatal NMDA receptor antagonist treatment is a useful model for studying the neurodevelopmental and NMDA receptor hypofunction hypotheses of schizophrenia because neurochemical and behavioral changes, reminiscent of those seen in schizophrenia, are present long after cessation of drug administration, which suggests that a permanent change in brain structure and organization has occurred during brain development.

Diffusion-weighted MR imaging: pediatric clinical applications

We have summarized the diffusion-weighed imaging (DWI) findings in a number of different cerebral disorders. In many cases, DWI with the accompanying apparent diffusion coefficient (ADC) map provides additional useful information to the standard imaging sequences. Pathophysiologic mechanisms resulting in baseline normal ADC values and changes with disease processes are not well understood; therefore, caution should be used when prognosticating the outcome of regions with abnormal ADCs. DWI should be used as an adjunct to routine imaging and interpreted in the context of the routine imaging findings and clinical scenario. As our understanding of ADC mechanisms increases and we begin to incorporate information about tissue organization from diffusion tensor imaging or diffusion spectrum imaging, the role of these methods in clinical diagnosis should continue to increase.