Precision of ultrasound diagnosis of pathologically verified lesions in the brains of very preterm infants

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.

Postnatal phenobarbital for the prevention of intraventricular haemorrhage in preterm infants

BACKGROUND

Intraventricular haemorrhage (IVH) is a major complication of preterm birth. Large haemorrhages are associated with a high risk of disability and hydrocephalus. Instability of blood pressure and cerebral blood in the newborn flow are postulated as causative factors. Another mechanism may involve reperfusion damage from oxygen free radicals. It has been suggested that phenobarbital stabilises blood pressure and may protect against free radicals. This is an update of a review first published in 2001 and updated in 2007 and 2013.

OBJECTIVES

To assess the benefits and harms of the postnatal administration of phenobarbital in preterm infants at risk of developing IVH compared to control (i.e. no intervention or placebo).

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), Medline, Embase, CINAHL and clinical trial registries in January 2022. A new, more sensitive search strategy was developed, and searches were conducted without date limits.  SELECTION CRITERIA: We included randomised controlled trials (RCTs) or quasi-RCTs in which phenobarbital was given within the first 24 hours of life to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birth weight below 1500 g or respiratory failure. Phenobarbital was compared to no intervention or placebo. We excluded infants with serious congenital malformations.

DATA COLLECTION AND ANALYSIS

We used standard Cochrane methods. Our primary outcomes were all grades of IVH and severe IVH (i.e. grade III and IV); secondary outcomes were ventricular dilation or hydrocephalus, hypotension, pneumothorax, hypercapnia, acidosis, mechanical ventilation, neurodevelopmental impairment and death. We used GRADE to assess the certainty of the evidence for each outcome.

MAIN RESULTS

We included 10 RCTs (792 infants). The evidence suggests that phenobarbital results in little to no difference in the incidence of IVH of any grade compared with control (risk ratio (RR) 1.00, 95% confidence interval (CI) 0.84 to 1.19; risk difference (RD) 0.00, 95% CI -0.06 to 0.07; I² for RD = 65%; 10 RCTs, 792 participants; low certainty evidence) and in severe IVH (RR 0.88, 95% CI 0.64 to 1.21; 10 RCTs, 792 participants; low certainty evidence). The evidence is very uncertain about the effect of phenobarbital on posthaemorrhagic ventricular dilation or hydrocephalus (RR 0.62, 95% CI 0.31 to 1.26; 4 RCTs, 271 participants; very low certainty evidence), mild neurodevelopmental impairment (RR 0.57, 95% CI 0.15 to 2.17; 1RCT, 101 participants; very low certainty evidence), and severe neurodevelopmental impairment (RR 1.12, 95% CI 0.44 to 2.82; 2 RCTs, 153 participants; very low certainty evidence). Phenobarbital may result in little to no difference in death before discharge (RR 0.88, 95% CI 0.64 to 1.21; 9 RCTs, 740 participants; low certainty evidence) and mortality during study period (RR 0.98, 95% CI 0.72 to 1.33; 10 RCTs, 792 participants; low certainty evidence) compared with control. We identified no ongoing trials.

AUTHORS' CONCLUSIONS

The evidence suggests that phenobarbital results in little to no difference in the incidence of IVH (any grade or severe) compared with control (i.e. no intervention or placebo). The evidence is very uncertain about the effects of phenobarbital on ventricular dilation or hydrocephalus and on neurodevelopmental impairment. The evidence suggests that phenobarbital results in little to no difference in death before discharge and all deaths during the study period compared with control. Since 1993, no randomised studies have been published on phenobarbital for the prevention of IVH in preterm infants, and no trials are ongoing. The effects of postnatal phenobarbital might be assessed in infants with both neonatal seizures and IVH, in both randomised and observational studies. The assessment of benefits and harms should include long-term outcomes.

Cranial ultrasound findings in preterm germinal matrix haemorrhage, sequelae and outcome

Germinal matrix-intraventricular haemorrhage (GMH-IVH), periventricular haemorrhagic infarction (PHI) and its complication, post-haemorrhagic ventricular dilatation (PHVD), are still common neonatal morbidities in preterm infants that are highly associated with adverse neurodevelopmental outcome. Typical cranial ultrasound (CUS) findings of GMH-IVH, PHI and PHVD, their anatomical substrates and underlying mechanisms are discussed in this paper. Furthermore, we propose a detailed descriptive classification of GMH-IVH and PHI that may improve quality of CUS reporting and prediction of outcome in infants suffering from GMH-IVH/PHI.

The most-cited articles in pediatric imaging: a bibliometric analysis

INTRODUCTION

The number of citations that an article has received reflects its impact on the scientific community. The purpose of our study was to identify and characterize the 51 most-cited articles in pediatric imaging.

EVIDENCE ACQUISITION

Based on the database of Journal Citation Reports, we selected 350 journals that were considered as potential outlets for pediatric imaging articles. The Web of Science search tools were used to identify the most-cited articles relevant to pediatric imaging within the selected journals.

EVIDENCE SYNTHESIS

The 51 most-cited articles in pediatric imaging were published between 1952 and 2011, with 1980-1989 and 2000-2009 producing 15 articles, each. The number of citations ranged from 576-124 and the number of annual citations ranged from 49.05-2.56. The majority of articles were published in pediatric and related journals (N.=26), originated in the USA (N.=23), were original articles (N.=45), used MRI as imaging modality (N.=27), and were concerned with the subspecialty of brain (N.=34). University College London School of Medicine (N.=6) and School of Medicine University of California (N.=4) were the leading institutions and Reynolds EO (N.=7) was the most voluminous author.

CONCLUSIONS

Our study presents a detailed list and an analysis of the most-cited articles in the field of pediatric imaging, which provides an insight into historical developments and allows for recognition of the important advances in this field.

Neuroprotection in preterm infants

Preterm infants born before the 30th week of pregnancy are especially at risk of perinatal brain damage which is usually a result of cerebral ischemia or an ascending intrauterine infection. Prevention of preterm birth and early intervention given signs of imminent intrauterine infection can reduce the incidence of perinatal cerebral injury. It has been shown that administering magnesium intravenously to women at imminent risk of a preterm birth leads to a significant reduction in the likelihood of the infant developing cerebral palsy and motor skill dysfunction. It has also been demonstrated that delayed clamping of the umbilical cord after birth reduces the rate of brain hemorrhage among preterm infants by up to 50%. In addition, mesenchymal stem cells seem to have significant neuroprotective potential in animal experiments, as they increase the rate of regeneration of the damaged cerebral area. Clinical tests of these types of therapeutic intervention measures appear to be imminent. In the last trimester of pregnancy, the serum concentrations of estradiol and progesterone increase significantly. Preterm infants are removed abruptly from this estradiol and progesterone rich environment. It has been demonstrated in animal experiments that estradiol and progesterone protect the immature brain from hypoxic-ischemic lesions. However, this neuroprotective strategy has unfortunately not yet been subject to sufficient clinical investigation.

Cerebral white and gray matter injury in newborns: new insights into pathophysiology and management

Increasing numbers of preterm neonates survive with motor and cognitive disabilities related to less destructive forms of cerebral injury that still result in reduced cerebral growth. White matter injury results in myelination disturbances related to aberrant responses to death of pre-myelinating oligodendrocytes (preOLs). PreOLs are rapidly regenerated but fail to mature to myelinating cells. Although immature projection neurons are more resistant to hypoxia-ischemia than preOLs, they display widespread disturbances in dendritic arbor maturation, which provides an explanation for impaired cerebral growth. Thus, large numbers of cells fail to fully mature during a critical window in development of neural circuitry. These recently recognized forms of cerebral gray and white matter dysmaturation suggest new therapeutic directions centered on reversal of the processes that promote dysmaturation.

Postnatal phenobarbital for the prevention of intraventricular haemorrhage in preterm infants

BACKGROUND

Intraventricular haemorrhage (IVH) is a major complication of preterm birth. Large haemorrhages are associated with a high risk of disability and hydrocephalus. Instability of blood pressure and cerebral blood flow are postulated as causative factors. Another mechanism may involve reperfusion damage from oxygen free radicals. Phenobarbital has been suggested as a safe treatment that stabilises blood pressure and may protect against free radicals.

OBJECTIVES

To determine the effect of postnatal administration of phenobarbital on the risk of IVH, neurodevelopmental impairment or death in preterm infants.

SEARCH METHODS

We used the search strategy of the Neonatal Collaborative Review Group. The original review author (A Whitelaw) was an active trialist in this area and had personal contact with many groups in this field. He handsearched journals from 1976 (when cranial computed tomography (CT) scanning started) to October 2000; these included: Pediatrics, Journal of Pediatrics, Archives of Disease in Childhood, Pediatric Research, Developmental Medicine and Child Neurology, Acta Paediatrica, European Journal of Pediatrics, Neuropediatrics, New England Journal of Medicine, Lancet and British Medical Journal. We searched the National Library of Medicine (USA) database (via PubMed) and the Cochrane Central Register of Controlled Trials (CENTRAL, 2012, Issue 10) through to 31 October 2012. We did not limit the searches to the English language, as long as the article included an English abstract. We read identified articles in the original language or translated.

SELECTION CRITERIA

We included randomised or quasi-randomised controlled trials in which phenobarbital was given to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birthweight below 1500 g or respiratory failure. Adequate determination of IVH by ultrasound or CT was also required.

DATA COLLECTION AND ANALYSIS

In addition to details of patient selection and control of bias, we extracted the details of the administration of phenobarbital. We searched for the following endpoints: IVH (with grading), posthaemorrhagic ventricular dilation or hydrocephalus, neurodevelopmental impairment and death. In addition, we searched for possible adverse effects of phenobarbitone, for example hypotension, mechanical ventilation, pneumothorax, hypercapnia and acidosis.

MAIN RESULTS

We included 12 controlled trials that recruited 982 infants. There was heterogeneity between trials for the outcome IVH, with three trials finding a significant decrease in IVH and one trial finding an increase in IVH in the group receiving phenobarbital. Meta-analysis showed no difference between the phenobarbital-treated group and the control group in either all IVH (typical risk ratio (RR) 0.91; 95% CI 0.77 to 1.08), severe IVH (typical RR 0.77; 95% CI 0.58 to 1.04), posthaemorrhagic ventricular dilation (typical RR 0.89; 95% CI 0.38 to 2.08), severe neurodevelopmental impairment (typical RR 1.44; 95% CI 0.41 to 5.04) or death before hospital discharge (typical RR 0.88; 95% CI 0.64 to 1.21). There was a consistent trend in the trials towards increased use of mechanical ventilation in the phenobarbital-treated group, which was supported by the meta-analysis (typical RR 1.18; 95% CI 1.06 to 1.32; typical risk difference 0.129; 95% CI 0.04 to 0.21), but there was no significant difference in pneumothorax, acidosis or hypercapnia.

AUTHORS' CONCLUSIONS

Postnatal administration of phenobarbital cannot be recommended as prophylaxis to prevent IVH in preterm infants and is associated with an increased need for mechanical ventilation.

Visual function in preterm infants: visualizing the brain to improve prognosis

Considerable development of the visual system occurs in the third trimester of life, a time when very preterm-born infants are in a neonatal intensive care unit (NICU). Their very early birth during a period of rapid and marked neurodevelopment and their clinical course makes them a very high-risk population. A range of different events impacts brain development and the visual system, leading to significant long-term visual dysfunction. Improved neuroimaging techniques provide an important window on the early brain and visual system development of these vulnerable infants. Greater understanding of the etiology of visual impairment subsequent to preterm birth and the timing of critical processes will allow early recognition and the earlier implementations of interventions. In the longer term, this will help clinicians optimize NICU practice to reduce the incidence of visual dysfunction in these children.

The instrumented fetal sheep as a model of cerebral white matter injury in the premature infant

Despite advances in neonatal intensive care, survivors of premature birth remain highly susceptible to unique patterns of developmental brain injury that manifest as cerebral palsy and cognitive-learning disabilities. The developing brain is particularly susceptible to cerebral white matter injury related to hypoxia-ischemia. Cerebral white matter development in fetal sheep shares many anatomical and physiological similarities with humans. Thus, the fetal sheep has provided unique experimental access to the complex pathophysiological processes that contribute to injury to the human brain during successive periods in development. Recent refinements have resulted in models that replicate major features of acute and chronic human cerebral injury and have provided access to complex clinically relevant studies of cerebral blood flow and neuroimaging that are not feasible in smaller laboratory animals. Here, we focus on emerging insights and methodologies from studies in fetal sheep that have begun to define cellular and vascular factors that contribute to white matter injury. Recent advances include spatially defined measurements of cerebral blood flow in utero, the definition of cellular maturational factors that define the topography of injury and the application of high-field magnetic resonance imaging to define novel neuroimaging signatures for specific types of chronic white matter injury. Despite the higher costs and technical challenges of instrumented preterm fetal sheep models, they provide powerful access to clinically relevant studies that provide a more integrated analysis of the spectrum of insults that appear to contribute to cerebral injury in human preterm infants.

High-frequency ultrasound in the evaluation of cerebral intraventricular haemorrhage in preterm rabbit pups

Cerebral intraventricular haemorrhage (IVH) is the most common cause of severe neurologic impairment following preterm birth in human infants. Ideally, an animal model for cerebral IVH should allow for reliable noninvasive evaluation of haemorrhagic extension and of subsequent development of posthaemorrhagic ventricular dilatation (PHVD). The aim of this study was to evaluate the use of high-frequency ultrasound (HFU) in premature rabbit pups with cerebral IVH induced by IP glycerol injection. Serial examinations using HFU enabled an accurate description of haemorrhagic extension and measurement of progressive PHVD over 72 h. The coefficient of variation for inter- and intraobserver variability in two measurements of ventricular size was less than 8.8% and 9.3%, respectively. Repeated ultrasound-guided intraventricular injection and sampling could be performed in vivo excluding requirement of stereotactic procedures and sedation. Application of HFU is a powerful tool for the evaluation of mechanisms involved in cerebral IVH and PHVD in the preterm rabbit pup model.

Neonatal ultrasound results following very preterm birth predict adolescent behavioral and cognitive outcome

This study investigated the association between different neonatal ultrasonographic classifications and adolescent cognitive, educational, and behavioral outcomes following very preterm birth. Participants included a group of 120 adolescents who were born very preterm (<33 weeks of gestation), subdivided into three groups according to their neonatal cerebral ultrasound (US) classifications: (a) normal (N = 69), (b) periventricular hemorrhage (PVH, N = 37), and (c) PVH with ventricular dilatation (PVH + DIL, N = 14), and 50 controls. The cognitive functions assessed were full-scale IQ, phonological and semantic verbal fluency, and visual-motor integration. Educational outcomes included reading and spelling; behavioral outcomes were assessed with the Rutter Parents' Scale and the Premorbid Adjustment Scale (PAS). Adolescent outcome scores were compared among the four groups. A main effect for group was observed for full-scale IQ, Rutter Parents' Scale total scores, and PAS total scores, after controlling for gestational age, socioeconomic status and gender, with the PVH + DIL group showing the most impaired scores compared to the other groups. The current results demonstrate that routine neonatal ultrasound classifications are associated with later cognitive and behavioral outcome. Neonatal ultrasounds could aid in the identification of subgroups of children who are at increased risk of neurodevelopmental problems. These at risk subgroups could then be referred to appropriate early intervention services.

Total brain white matter is a major determinant of IQ in adolescents born preterm

OBJECTIVE

In preterm infants, white matter (WM) abnormalities detected on magnetic resonance imaging (MRI) at term-age are associated with early developmental delay. We set out to study this association in adolescents born pre-term, by examining intellectual outcome in relation to markers of brain injury, focusing on the effects of WM reduction.

METHODS

Seventy-nine participants were recruited and assessed at a mean age of 16 years: 49 adolescents born preterm (<32 weeks' gestation) with a wide spectrum of brain injuries (including 22 with no identifiable brain injury at birth) and 30 term-born controls. Data collected included: brain MRI scans, full-scale intelligence quotient (IQ) scores, educational attainments, and behavioral scores. Measures of WM reduction included total volume, cross-sectional area of the corpus callosum (CC), and ventricular dilatation. Cerebellar volumes and neuroradiological ratings were also included.

RESULTS

WM volume and IQ were reduced in the preterm groups (both with and without brain injury). Total WM volume and CC area jointly explained 70% of IQ variance in the adolescents born preterm, irrespective of the presence or severity of brain abnormalities detected at birth or on follow-up MRI. This relationship was not seen in controls. Importantly, correlations were also found with real-world measures of academic achievement and behavioral difficulties.

INTERPRETATION

Preterm birth has a long-term effect on cognition, behavior, and future academic success primarily as a consequence of global brain WM reduction. This emphasizes the need for early therapeutic efforts to prevent WM injury and promote or optimize its development in preterm neonates.

Confiabilidade da análise qualitativa da ressonância magnética do encéfalo em prematuros extremos

OBJETIVO: O objetivo deste estudo foi avaliar a confiabilidade da análise visual qualitativa dos achados de imagem de ressonância magnética (RM) em recém-nascidos prematuros extremos. MATERIAIS E MÉTODOS: Uma coorte de 45 recém-nascidos de idade gestacional de 30 semanas ou menos foram inseridos neste estudo. Dois neurorradiologistas, cegos quanto aos dados clínicos, avaliaram de forma independente as RMs de crânio em relação aos seguintes achados: presença de hipersinal difuso e excessivo (DEHSI), dilatação dos ventrículos laterais, hemorragia intracraniana, áreas de sinal anormal em núcleos da base e córtex, áreas de aspecto cístico, deformidades ventriculares, dilatação do espaço subaracnóideo, leucoencefalomalácia precoce e anormalidades corticais. RESULTADOS: Quarenta e um pacientes (91,1%) apresentaram exame de RM anormal. Os achados mais comuns foram DEHSI (75,6%) e dilatação dos ventrículos (42,2%). A concordância interobservadores entre os dois experientes neurorradiologistas foi alta (κ > 0,60) para a maioria das alterações detectadas pela RM. O valor de kappa foi moderado (κ = 0,52) para alargamento do espaço subaracnoide e fraco (κ = 0,39) para DEHSI na substância branca. CONCLUSÃO: A avaliação qualitativa da maioria dos achados de imagem por RM de neonatos prematuros extremos foi considerada confiável, entretanto, a presença de DEHSI na substância branca demonstrou um grau de confiabilidade menor

The role of systemic hemodynamic disturbances in prematurity-related brain injury

Premature infants who experience cerebrovascular injury frequently have acute and long-term neurologic complications. In this article, we explore the relationship between systemic hemodynamic insults and brain injury in this patient population and the mechanisms that might be at play.

From selective vulnerability to connectivity: insights from newborn brain imaging

The ability to image the newborn brain during development has provided new information regarding the effects of injury on brain development at different vulnerable time periods. Studies in animal models of brain injury correlate beautifully with what is now observed in the human newborn. We now know that injury at term primarily results in grey matter injury while injury in the premature brain predominantly results in a pattern of white matter injury, though recent evidence suggests a blurring of this distinction . These injuries affect how the brain matures subsequently and again, imaging has led to new insights that allow us to match function and structure. This review will focus on these patterns of injury that are so crucially determined by age at insult. In addition, this review will highlight how the brain responds to these insults with changes in connectivity that have profound functional consequences.

Segmentation of white matter flaring areas in ultrasound images of very-low-birth-weight preterm infants

In this article, we present an interactive algorithm segmenting white brain matter, visible as hyperechoic flaring areas in ultrasound (US) images of preterm infants with periventricular leukomalacia (PVL). The algorithm combines both the textural properties of pathological brain tissue and mathematical morphology operations. An initial flaring area estimate is derived from a multifeature multiclassifier tissue texture classifier. This area is refined based on the structural properties of the choroid plexus, a brain feature known to have characteristics similar to flaring. Subsequently, a combination of a morphological closing, gradient and opening by reconstruction operation determines the final flaring area boundaries. Experimental results are compared with a gold standard constructed from manual flaring area delineations of 12 medical experts. In addition, we compared our algorithm to an existing active contour method. The results show our technique agrees to the gold standard with statistical significance and outperforms the existing method in accuracy. Finally, using the flaring area as a criterion we improve the sensitivity of PVL detection up to 98% as compared with the state of the art.

A review of the current treatment methods for posthaemorrhagic hydrocephalus of infants

Posthaemorrhagic hydrocephalus (PHH) is a major problem for premature infants, generally requiring lifelong care. It results from small blood clots inducing scarring within CSF channels impeding CSF circulation. Transforming growth factor – beta is released into CSF and cytokines stimulate deposition of extracellular matrix proteins which potentially obstruct CSF pathways. Prolonged raised pressures and free radical damage incur poor neurodevelopmental outcomes. The most common treatment involves permanent ventricular shunting with all its risks and consequences.

This is a review of the current evidence for the treatment and prevention of PHH and shunt dependency. The Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) and PubMed (from 1966 to August 2008) were searched. Trials using random or quasi-random patient allocation for any intervention were considered in infants less than 12 months old with PHH. Thirteen trials were identified although speculative interventions were also evaluated.

The literature confirms that lumbar punctures, diuretic drugs and intraventricular fibrinolytic therapy can have significant adverse effects and fail to prevent shunt dependence, death or disability. There is no evidence that postnatal phenobarbital administration prevents intraventricular haemorrhage (IVH). Subcutaneous reservoirs and external drains have not been tested in randomized controlled trials, but can be useful as a temporising measure. Drainage, irrigation and fibrinolytic therapy as a way of removing blood to inhibit progressive deposition of matrix proteins, permanent hydrocephalus and shunt dependency, are invasive and experimental. Studies of ventriculo-subgaleal shunts show potential as a temporary method of CSF diversion, but have high infection rates.

At present no clinical intervention has been shown to reduce shunt surgery in these infants. A ventricular shunt is not advisable in the early phase after PHH. Evidence exists that pre-delivery corticosteroid therapy reduces mortality and IVH and there may be trends towards reduced disability in the short term. There is also evidence that postnatal indomethacin reduces IVH but with no effect on mortality or disability. Overall, there is still no definitive algorithm for the treatment of PHH or prevention of shunt dependence. New therapeutic approaches in neonatal care, including those aimed at pre-empting PHH, offer the best hope of improving neurodevelopmental outcomes.

Current definitions of hypotension do not predict abnormal cranial ultrasound findings in preterm infants

OBJECTIVE

Hypotension is a commonly treated complication of prematurity, although definitions and management guidelines vary widely. Our goal was to examine the relationship between current definitions of hypotension and early abnormal cranial ultrasound findings.

METHODS

We prospectively measured mean arterial pressure in 84 infants who were < or = 30 weeks' gestational age and had umbilical arterial catheters in the first 3 days of life. Sequential 5-minute epochs of continuous mean arterial pressure recordings were assigned a mean value and a coefficient of variation. We applied to our data 3 definitions of hypotension in current clinical use and derived a hypotensive index for each definition. We examined the association between these definitions of hypotension and abnormal cranial ultrasound findings between days 5 and 10. In addition, we evaluated the effect of illness severity (Score for Neonatal Acute Physiology II) on cranial ultrasound findings.

RESULTS

Acquired lesions as shown on cranial ultrasound, present in 34 (40%) infants, were not predicted by any of the standard definitions of hypotension or by mean arterial pressure variability. With hypotension defined as mean arterial pressure < 10th percentile (< 33 mmHg) for our overall cohort, mean value for mean arterial pressure and hypotensive index predicted abnormal ultrasound findings but only in infants who were > or = 27 weeks' gestational age and those with lower illness severity scores.

CONCLUSIONS

Hypotension as diagnosed by currently applied thresholds for preterm infants is not associated with brain injury on early cranial ultrasounds. Blood pressure management directed at these population-based thresholds alone may not prevent brain injury in this vulnerable population.

Postnatal phenobarbital for the prevention of intraventricular hemorrhage in preterm infants

BACKGROUND

Intraventricular hemorrhage (IVH) is a major complication of preterm birth. Large hemorrhages are associated with a high risk of disability and hydrocephalus. Instability of blood pressure and cerebral blood flow are postulated as causative factors. Another mechanism may involve reperfusion damage from oxygen free radicals. Phenobarbital has been suggested as a safe treatment that stabilises blood pressure and may protect against free radicals.

OBJECTIVES

To determine the effect of postnatal administration of phenobarbital on the risk of intraventricular hemorrhage (IVH), neurodevelopmental impairment or death in preterm infants.

SEARCH STRATEGY

See the Search Strategy of the Neonatal Collaborative Review Group. The reviewer has been a active trialist in this area and has personal contact with many groups in this field. Journals handsearched from 1976 (when cranial CT scanning started) to October 2000 include: Pediatrics, J Pediatrics, Archives of Disease in Childhood, Pediatric Research, Developmental Medicine and Child Neurology, Acta Paediatrica, European J of Pediatrics, Neuropediatrics, New England J of Medicine, Lancet and British Medical J. The National Library of Medicine (USA) database (via PubMed) and the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library) were searched through to April 2007 using the MeSH terms intraventricular hemorrhage, newborn infants, premature infant, intracranial hemorrhage, phenobarbitone, phenobarbital. The searches were not limited to the English language, as long as the article included an English abstract. Promising articles were read in the original language or translated.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials in which phenobarbital was given to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birthweight below 1500 g, or respiratory failure were included. Adequate determination of IVH by ultrasound or CT was also required.

DATA COLLECTION AND ANALYSIS

In addition to details of patient selection and control of bias, the details of the administration of phenobarbital were extracted. The end-points searched for included: IVH ( with grading), posthemorrhagic ventricular dilatation or hydrocephalus, neurodevelopmental impairment and death. In addition, possible adverse effects of phenobarbitone such as hypotension, mechanical ventilation, pneumothorax, hypercapnia, and acidosis were searched for.

MAIN RESULTS

Ten controlled trials were included with 740 infants recruited. There was heterogeneity between trials for the outcome IVH, with one trial finding a significant decrease in IVH and another trial finding an increase in IVH in the group receiving phenobarbital. Meta-analysis showed no difference between the phenobarbital treated group and the control group in either IVH (typical relative risk 1.04, 95% CI 0.87, 1.25), severe IVH (typical relative risk 0.91, 95% CI 0.66, 1.24), posthemorrhagic ventricular dilatation (typical relative risk 0.89, 95% CI 0.38, 2.08), severe neurodevelopmental impairment (typical relative risk 1.44, 95% CI 0.41, 5.04) or death before hospital discharge (typical relative risk 0.88, 95% CI 0.64, 1.21) There was a consistent trend in the trials towards increased use of mechanical ventilation in the phenobarbital treated group, which was supported by the meta-analysis (typical relative risk 1.18, 95% CI 1.06, 1.32; typical risk difference 0.129, 95% CI 0.045, 0.213), but there was no significant difference in pneumothorax, acidosis or hypercapnia.

AUTHORS' CONCLUSIONS

Postnatal administration of phenobarbital cannot be recommended as prophylaxis to prevent IVH in preterm infants and is associated with an increased need for mechanical ventilation.

Visual development in infants with prenatal post-haemorrhagic ventricular dilatation

OBJECTIVE

The aim of this study was to assess visual function in 13 infants with evidence of prenatal post haemorrhagic ventricular dilatation.

DESIGN

Infants were assessed at 5, 12 and 24 months using a battery of tests specifically designed to assess various aspects of visual function in infancy. Visual findings were correlated with several variables, including extent of the lesion and presence of epilepsy.

RESULTS AND CONCLUSIONS

Abnormalities of visual function were frequent (over 60%) in our cohort at age 2 years, ranging from isolated abnormal ocular movements to severe abnormalities of all the aspects of visual function assessed. The most severe and persistent abnormalities of visual function were found in infants with grade IV intraventricular haemorrhage and shunted hydrocephalus who also had epilepsy in the first year.

Magnetic resonance imaging of the neonatal brain

Neonatal magnetic resonance (MR) imaging is rapidly becoming the preferred modality for the evaluation of central nervous system disorders in the newborn. Recent literature supports the value of this imaging technique in diagnosing ischemic, hemorrhagic and infectious disease processes in the premature and full-term neonatal brain. Recent data in premature newborns with neurological injury also suggest a role for MR imaging in determining long-term neurodevelopmental outcomes. This review article provides a framework and overview on neonatal MR imaging techniques and examines the literature or radiological disease patterns and prognostic implications in common neurological disorders.

Neurodevelopmental outcome of preterm infants with ventricular dilatation with and without associated haemorrhage

This study investigated whether in preterm children who had ventricular dilatation (VD) on neonatal cranial ultrasound outcome at age 8 years was influenced by the additional presence of germinal matrix haemorrhage--intraventricular haemorrhage (GMH-IVH). Six-hundred and ninety-nine preterm infants (<33 wks' gestation, mean 29.6 wks [SD 2.1]) with either normal cranial ultrasound (n=616; 286 females, 330 males), or with VD with (n=66; 32 females, 34 males) or without (n=17; 4 females, 13 males) GMH-IVH were enrolled in the study. At age 8 years outcome was assessed in 567 (81%) of the 699 children by neurological examination, the Test of Motor Impairment (TOMI), the test of Visuo-Motor Integration (VMI), and the Wechsler Intelligence Scales for Children. Results showed that the proportion of children with disabling impairments was higher in the group with VD and GMH-IVH. Performance on TOMI and VMI (even in those without disabling impairments) was poorer in those with VD and GMH-IVH than in children with normal scans or those with VD only. Children with VD and GMH-IVH had significantly lower performance IQ than children with normal ultrasound, whereas those with VD only were not different from those with normal scans. Results suggest the presence of subtle white matter injury that has not been identified by neonatal cranial ultrasound. Although this study did not investigate biochemical markers of haemorrhage, we hypothesize that non-protein-bound iron is likely to be a contributing factor to white matter damage in preterm infants.

Perinatal infections, prematurity and brain injury

PURPOSE OF REVIEW

The association between perinatal infection and brain injury is widely accepted but a cause-and-effect relationship has not yet been proven. This article summarizes available evidence and current primary publications for debate.

RECENT FINDINGS

Work completed during the review period has reinforced current understanding of perinatal infection, prematurity and brain injury. In animal experiments: lipopolysaccharides have been further implicated in brain injury, not only as a cause of brain injury but also as mediators of preconditioning and protection. Recent studies suggest that cerebral injury following low-dose lipopolysaccharide administration may become compensated in adulthood. Other studies have emphasized the complexity of the response by showing that plasma cytokine levels may not reflect those in the central nervous system or inflammatory events in the brain.

SUMMARY

Perinatal infection and maternofetal inflammation is strongly associated with preterm birth. Inflammation probably represents an important mechanism for cerebral damage, and both overt lesions and maldevelopment can result. Epidemiological data and multiple animal models to link infection, inflammation and brain damage exist, but proof of causation is elusive.

Adverse neurodevelopmental outcomes among extremely low birth weight infants with a normal head ultrasound: prevalence and antecedents

OBJECTIVE

Severe abnormalities of the head ultrasound (HUS) are important predictors of cerebral palsy (CP) and mental retardation, and a normal HUS usually ensures the absence of major impairments. With the increasing survival of extremely low birth weight (ELBW) infants (birth weight <1000 g), the prognostic significance of a normal HUS may differ. This study examined the prevalence of and risk factors for CP and impaired mental development among ELBW infants with a normal HUS.

METHODS

Study infants were ELBW infants who were cared for in Neonatal Research Network centers in the years 1995-1999, had a normal early and late HUS, survived to discharge, and returned for follow-up assessments at 18 to 22 months' corrected age. The outcomes of interest were a score <70 on the Bayley Scales of Infant Development-II Mental Developmental Index (MDI) and CP. Risk factors included maternal demographics; infant characteristics; and interventions or morbidities related to the lung, infection, and nutrition. Logistic regression was used to estimate odds ratios (ORs) and 95% confidence intervals (CIs). A time-oriented approach was used to select variables for inclusion in logistic models.

RESULTS

Of 1749 infants with a normal early and late HUS (performed at a mean age of 6 and 47 days, respectively), 1473 (84%) returned for follow-up assessment. Infants had a birth weight of 792 +/- 134 g (mean +/- SD) and gestational age of 26 +/- 2 weeks. Rates of CP and MDI <70 were 9.4% and 25.3%, respectively, and 29.2% of infants had either CP or MDI <70. In multivariate analyses, factors associated with CP were male gender (OR: 1.8; 95% CI: 1.2-2.6), multiple birth, (OR: 1.6; 95% CI: 1.1-2.5), decreasing birth weight (OR: 1.3 for each 100-g decrease; 95% CI: 1.1-1.5), pneumothorax (OR: 2.3; 95% CI: 1.2-4.4), and days of conventional ventilation (OR: 1.2 for each additional 10 days; 95% CI: 1.1-1.3). With the exception of pneumothorax, these same factors were associated with MDI <70, in addition to less maternal education (OR: 1.4; 95% CI: 1.0-1.9) and Medicaid or lack of coverage for maternal insurance (OR: 1.7; 95% CI: 1.2-2.4).

CONCLUSIONS

Nearly 30% of ELBW infants with a normal HUS had either CP or a low MDI. Risk factors that are associated with this high rate of adverse outcomes include pneumothorax, prolonged exposure to mechanical ventilation, and educational and economic disadvantage. Improvements in pulmonary care to reduce duration of ventilation and avoid air leaks might improve neurodevelopmental outcome for ELBW infants.

Abnormal cerebral structure is present at term in premature infants

BACKGROUND

Long-term studies of the outcome of very prematurely born infants have clearly documented that the majority of such infants have significant motor, cognitive, and behavioral deficits. However, there is a limited understanding of the nature of the cerebral abnormality underlying these adverse neurologic outcomes.

AIM

The overall aim of this study was to define quantitatively the alterations in cerebral tissue volumes at term equivalent in a large longitudinal cohort study of very low birth weight premature infants in comparison to term-born infants by using advanced volumetric 3-dimensional magnetic resonance imaging (MRI) techniques. We also aimed to define any relationship of such perinatal lesions as white matter (WM) injury or other potentially adverse factors to the quantitative structural alterations. Additionally, we wished to identify the relationship of the structural alterations to short-term neurodevelopmental outcome.

METHODS

From November 1998 to December 2000, 119 consecutive premature infants admitted to the neonatal intensive care units at Christchurch Women's Hospital (Christchurch, New Zealand) and the Royal Women's Hospital (Melbourne, Australia) were recruited (88% of eligible) after informed parental consent to undergo an MRI scan at term equivalent. Twenty-one term-born infants across both sites were recruited also. Postacquisition advanced 3-dimensional tissue segmentation with 3-dimensional reconstruction was undertaken to estimate volumes of cerebral tissues: gray matter (GM; cortical and deep nuclear structures), WM (myelinated and unmyelinated), and cerebrospinal fluid (CSF).

RESULTS

In comparison to the term-born infants, the premature infants at term demonstrated prominent reductions in cerebral cortical GM volume (premature infants [mean +/- SD]: 178 +/- 41 mL; term infants: 227 +/- 26 mL) and in deep nuclear GM volume (premature infants: 10.8 +/- 4.1 mL; term infants: 13.8 +/- 5.2 mL) and an increase in CSF volume (premature infants: 45.6 +/- 22.1 mL; term infants: 28.9 +/- 16 mL). The major predictors of altered cerebral volumes were gestational age at birth and the presence of cerebral WM injury. Infants with significantly reduced cortical GM and deep nuclear GM volumes and increased CSF volume volumes exhibited moderate to severe neurodevelopmental disability at 1 year of age.

CONCLUSIONS

This MRI study of prematurely born infants further defines the nature of quantitative cerebral structural abnormalities present as early as term equivalent. The abnormalities particularly involve cerebral neuronal regions including both cortex and deep nuclear structures. The pattern of cerebral alterations is related most significantly to the degree of immaturity at birth and to concomitant WM injury. The alterations are followed by abnormal short-term neurodevelopmental outcome.

Value of neurosonography in predicting subsequent cognitive and motor development in extremely low birth weight neonates

OBJECTIVE

To compare the results of neurosonography (NSG) with subsequent neurodevelopmental testing in extremely low birth weight (ELBW; < or =1000 g) neonates.

STUDY DESIGN

NSG at hospital discharge was available in 164 neonates and Bayley Scores of Infant Development (BSID II) evaluations (MDI and PDI) were performed in 158 of these infants at 18 to 22 months. Neurosonographic studies obtained prior to the discharge study also were evaluated. Neurosonograms were interpreted by pediatric radiologists, and BSID II examinations were performed by certified examiners masked to the results of the neurosonographic studies.

RESULTS

A normal sonographic study at discharge was observed in 44% (14/32) of neonates with MDI <70 and 29% (7/24) with PDI <70. Furthermore, the sonographic study at discharge was normal in 59% (36/61) of neonates with MDI 70 to 84 and 56% (31/55) with PDI 70 to 84. Conversely, approximately 30 to 40% of those with an abnormality noted on neurosonogram at discharge, or at any time during hospitalization, had MDI and/or PDI scores > or =85. The association between abnormal NSG at discharge and low BSID II results was stronger for the PDI exam compared with the MDI exam.

CONCLUSION

These results emphasize the limitations of NSG in predicting subsequent neurodevelopmental outcome in ELBW neonates. The primary role for NSG in ELBW neonates may be in the diagnosis and management of acute problems, such as intraventricular hemorrhage and posthemorrhagic hydrocephalus, and not as a tool to predict subsequent outcome.

Predictors of long-term outcome in very preterm infants: gestational age versus neonatal cranial ultrasound

OBJECTIVES

To investigate the effect of gestational age at birth on the frequency of ultrasound-detected brain lesions in infants born at <33 weeks of gestation and to investigate whether the relationship between neonatal cranial ultrasound diagnosis and neurodevelopmental outcome at 8 years of age was independent of gestational age.

METHODS

Eight hundred forty-seven infants born at <33 weeks of gestation, admitted to a single tertiary referral center between 1983 and 1988, underwent serial neonatal cranial ultrasound. At 8 years of age neurodevelopmental outcome was assessed by structured neurologic examination, psychometric tests (Wechsler Intelligence Scale for Children), tests of visuomotor integration (Beery) and motor impairment (Henderson-Stott). Infants were subdivided into a group born at <28 weeks and a group born at between 28 and 32 weeks. Neurodevelopmental outcome was analyzed for each ultrasound diagnosis.

RESULTS

Hemorrhagic lesions such as germinal matrix/intraventricular hemorrhage and hemorrhagic parenchymal infarction were more frequent in infants born at <28 weeks. There was no difference in the frequency of cystic periventricular leucomalacia between the 2 groups. When neurodevelopmental outcome for each ultrasound diagnosis was compared, no significant difference was found between the 2 gestational age groups.

CONCLUSION

In the gestational age range studied, adverse neurodevelopmental outcome depends primarily on the type of the intracranial lesion rather than on gestational age.

Limitations of ultrasonography for diagnosing white matter damage in preterm infants

OBJECTIVES

To compare the accuracy of ultrasonography (US) and magnetic resonance imaging (MRI) in diagnosing white matter abnormalities in preterm infants and to determine the specific indications for MRI.

DESIGN

Prospective cohort study.

SETTING

A neonatal intensive care unit in France.

PATIENTS

All preterm infants (</= 33 weeks gestation) without severe respiratory distress syndrome precluding MRI.

MAIN OUTCOME MEASURES

US and MRI performed contemporaneously during the third postnatal week were analysed by an independent observer. The findings were compared with those of a term MRI scan, the results of which were taken as the final diagnosis. Statistical analysis was performed to determine which early imaging study best predicted the term MRI findings.

RESULTS

The early US and MRI findings (79 infants) correlated closely for severe lesions (cystic periventricular leucomalacia and parenchymal infarction; kappa coefficient = 0.86) but not for moderate lesions (non-cystic leucomalacia and parenchymal punctate haemorrhages; kappa = 0.62). Overall, early MRI findings predicted late MRI findings in 98% of patients (95% confidence interval (CI) 89.5 to 99.9) compared with only 68% for early US (95% CI 52.1 to 79.2).

CONCLUSIONS

US is highly effective in detecting severe lesions of the white matter in preterm infants, but MRI seems to be necessary for the diagnosis of less severe damage. MRI performed at about the third week of life is highly predictive of the final diagnosis at term.

Functional metabotropic glutamate receptors are expressed in oligodendrocyte progenitor cells

We investigated the expression of metabotropic glutamate receptor (mGluR) isoforms in CG-4 rodent oligodendroglial progenitor cells (OPC) and rat brain oligodendrocytes. Our RT-PCR analysis detected mRNAs for mGluR3 and mGluR5 isoforms in OPCs. Although neurons express both mGluR5a and mGluR5b splice variants, only mGluR5a was identified in OPCs. Antibodies to mGluR2/3 and mGluR5 detected the corresponding receptor proteins in immunoblots of OPC membrane fractions. Furthermore, immunocytochemical analysis identified mGluR5 in oligodendrocyte marker O4-positive OPCs. The expression of mGluR5 was also demonstrated in oligodendrocyte marker (O4 and O1) positive cells in white matter of postnatal 4- and 7-day-old rat brain sections using immunofluorescent double labelling and confocal microscopy. The mGluR5 receptor function was assessed in CG-4 OPCs with fura-2 microfluorometry. Application of the mGluR1/5 specific agonist (S)-3,5-dihydroxyphenylglycine (DHPG) induced calcium oscillations, which were inhibited by the selective mGluR5 antagonist 2-methyl-6-(phenylethynyl) pyridine hydrochloride (MPEP). The DHPG induced calcium oscillations required Ca2+ release from intracellular stores. In OPCs the group II mGluR agonist (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV) decreased forskolin-stimulated cAMP synthesis, indicating the presence of functional mGluR3. The newly identified mGluR3 and mGluR5a may be involved in the differentiation of oligodendrocytes, myelination and the development of white matter damage.

Lowered electroencephalographic spectral edge frequency predicts the presence of cerebral white matter injury in premature infants

OBJECTIVE

Current methods for early identification of cerebral white matter injury in the premature infant at the bedside are inadequate. This study investigated the utility of advanced spectral analysis of the neonatal electroencephalogram (EEG) in the early diagnosis of white matter injury in the premature infant. The critical measurement used, suggested largely by previous studies in animal models, was the spectral edge frequency (SEF), calculated here as the frequency below which 90% of the power in the EEG exists.

METHODS

Fifty-nine very low birth weight infants (87% of eligible infants) had electrodes placed over the central and parietal regions (C3, P3, C4, and P4 sites according to the 10-20 international system) for the collection of EEG amplitude, intensity, and SEF. All averaged signals were analyzed off-line using software (Chart Analyzer; BrainZ Instruments, Auckland, NZ). All infants had a magnetic resonance imaging scan at term to identify the presence and severity of white matter injury.

RESULTS

There was no significant difference between conventional EEG amplitude and intensity for infants with or without evidence of white matter injury. However, premature infants with increasingly severe white matter injury had progressively lower SEFs compared with infants who did not exhibit white matter injury.

CONCLUSIONS

These data suggest that SEF-based measures are useful for defining the presence and severity of white matter injury at the bedside.

Advances in postnatal neuroimaging: relevance to pathogenesis and treatment of brain injury

The human brain is susceptible to a wide variety of insults. The permanent residua of these abnormalities are represented in dysfunction of one or more areas of neurodevelopment. A full understanding of normal brain development, mechanisms of brain injury, and consequences for subsequent brain development is required to determine which infants are at risk for neurodevelopmental handicap, and to monitor the effects of new treatments and management regimens designed to prevent these disabilities. Advanced magnetic resonance techniques, such as quantitative morphometric magnetic resonance techniques, diffusion-weighted magnetic resonance techniques, and magnetic resonance spectroscopy applied to the study of early human brain development have given us a better understanding of the pathophysiologic mechanisms of brain injury and its effects on subsequent brain development. Magnetic resonance imaging has provided an invaluable tool for the study of the fetal and newborn brain in vivo.

MR imaging and in vivo proton spectroscopy of the brain in neonates with hypoxic ischemic encephalopathy

INTRODUCTION

A number of studies have suggested the potential utility of in vivo proton MR spectroscopy for the evaluation of brain injury in the asphyxiated neonates. We present our initial experience with in vivo proton MR spectroscopy in neonates who were diagnosed as having hypoxic injury on clinical examination and the severity of the insult was graded using Sarnat staging.

METHODS AND MATERIAL

MR imaging and in vivo proton MR spectroscopy was performed in 16 neonates with hypoxic ischemic encephalopathy (HIE) to correlate the imaging and metabolite abnormality with clinical severity of the condition at the time of insult and with outcome at 2 months of age. The ratios of different metabolites were calculated as observed on MR spectroscopy from an 8 ml voxel that included thalami, basal ganglia and part of the ventricular system using spin echo technique with an echo time of 135 ms.

RESULTS AND DISCUSSION

The results of the spectroscopy were compared with imaging abnormalities and Sarnat's clinical staging of HIE. MR Imaging abnormalities included basal ganglia, thalamic and periventricular hemorrhage and periventricular hyperintensities and were noticed in 8/16 neonates with different stages of HIE. Maximum imaging abnormalities were noted in stage II (6/9) followed by stage III (1/2) and stage I (1/5), respectively. The alpha-Glx resonance at 3.76 ppm was seen in 14/16, Glycine at 3.56 ppm (Gly) was seen in 10/16 and Lactate (L) at 1.33 ppm was observed in 4/16 neonates with HIE.

CONCLUSION

MR spectroscopy was more sensitive than imaging in detecting the insult due to HIE and increased concentration of alpha-Glx/Cr and Gly/Cr correlated better with severity of the HIE. The demonstration of L was associated with poor outcome.

Antenatal steroids are associated with a reduction in the incidence of cerebral white matter lesions in very low birthweight infants

AIMS

To investigate whether antenatal steroids reduce the incidence of cerebral white matter lesions in very low birthweight infants.

METHODS

A total of 224 newborn infants of < 31 weeks gestational age and weighing < 1500 g was studied between January 1998 and June 2000. Obstetric and neonatal information was obtained from the case notes. The study population was subdivided into two groups according to antenatal steroid exposure. A complete course of treatment consisted of two doses of 12 mg each of betamethasone given at an interval of 12-24 hours. Infants in group 1 were born to mothers who had not received betamethasone, or were delivered within 24 hours of receiving the first dose of steroid. Infants in group 2 were born to mothers who had received one or more complete courses of betamethasone and were delivered > 24 hours after receiving the first dose of steroid.

RESULTS

The two groups contained statistically similar proportions of boys and girls, and the infants had similar birth weights and survival rates. Those in group 2, compared with those in group 1, had a lower gestational age (p = 0.02) and a lower incidence of white matter lesions on cranial ultrasound scans (p = 0.03). Stepwise logistic regression analysis showed that gestational age (p = 0.0002) and a complete course of antenatal steroids (p = 0.02) had independent effects on cerebral white matter lesions.

CONCLUSIONS

These observations suggest that a complete course of antenatal steroids may have a protective effect against cerebral white matter lesions in very low birthweight infants.

Indices of hemodynamic and respiratory functions in premature infants at risk for the development of cerebral white matter injury

OBJECTIVE

To examine potential differences in clinical risk factors, including indices of hemodynamic and respiratory functions, of premature infants developing periventricular hemorrhagic infarction (PHI) or periventricular leukomalacia (PVL).

STUDY DESIGN

Indices of hemodynamic stability and respiratory function were measured prospectively during the first week of life in a cohort of 100 premature infants with respiratory distress. Maternal history was retrospectively reviewed. These data were correlated with cranial ultrasonography using one-way ANOVA, Bonferroni multiple comparisons, and Wilcoxon rank sum tests. Longitudinal analysis was performed using Generalized Estimating Equations.

RESULTS

Fifty-two infants with normal cranial ultrasound studies were compared to 12 with PHI and 9 with PVL. Infants developing PHI had significantly lower birth weights, lower Apgar scores, were more often male and multiple gestations, and required more vasopressor support than infants with normal ultrasound studies. Infants with PHI had significantly worse indices of respiratory function than either normal infants or those with PVL. PVL was significantly associated with maternal chorioamnionitis, whereas PHI was not.

CONCLUSION

These data suggest that there are important differences in the pathogenesis of PHI and PVL. A clear understanding of these differences is required before future preventive strategies can be formulated.

Magnetic resonance and cranial ultrasound characteristics of periventricular white matter abnormalities in newborn infants

OBJECTIVE

To characterize the range of abnormalities within the periventricular white matter (PVWM) in a cohort of newborns using magnetic resonance (MR) brain imaging and to compare the focal MR abnormalities with the cranial ultrasound (CUS) findings.

METHODS

Retrospective study of MR brain and CUS findings of infants born in the 18-month period 1998-1999. PVWM abnormalities were identified by MR and focal lesions were characterized by size, number and distribution using a grading scale. Correspondence with CUS findings was assessed.

RESULTS

175 MR examinations corresponding to n = 105 preterm infants, (median GA 28, range 23-36 weeks) and n = 25 term infants (median GA 39, range 37-42 weeks) were analysed for PVWM abnormalities. In the preterm group, MR demonstrated a normal PVWM in n = 76, focal areas of altered signal intensity (SI) in PVWM in n = 26 and venous infarction in n = 3. In the term group, MR demonstrated a normal PVWM in n = 15, focal areas of altered SI in PVWM in n = 4, oedematous PVWM in n = 2 and a middle cerebral artery infarction in n = 4. All infants with normal MR had normal CUS findings. A focal PVWM SI abnormality detectable on MR corresponded with an abnormality on CUS in only n = 10/30.

CONCLUSIONS

MR appears considerably more sensitive than CUS in demonstrating the existence and extent of focal PVWM lesions in newborn infants. Satisfactory correspondence between the two imaging investigations is obtained only for cystic PVWM lesions.

Topography of cerebral white-matter disease of prematurity studied prospectively in 1607 very-low-birthweight infants

The objective of this study was to evaluate to what extent (1) the characteristics of localization, distribution, and size of echodense and echolucent abnormalities enable individuals to be designated as having either periventricular hemorrhagic infarction or periventricular leukomalacia and (2) the characteristics of periventricular hemorrhagic infarction and periventricular leukomalacia are independent occurrences. The population for this study consisted of 1607 infants with birthweights of 500 to 1500 g, born between January 1991 and December 1993, who had at least one cranial ultrasound scan read independently by at least two ultrasonographers. The ultrasound data collection form diagrammed six standard coronal views. The cerebrum was divided into 17 zones in each hemisphere. All abnormalities were described as being echodense or echolucent and were classified on the basis of their size, laterality, location, and evolution. Eight percent (134/1607) of infants had at least one white-matter abnormality. The prevalence of white-matter disease decreased with increasing gestational age. Most abnormalities were small or medium sized and unilateral; only large echodensities tended to be bilateral and asymmetric. Large abnormalities, whether echodense or echolucent, were more likely than smaller abnormalities to be widespread, and the extent of cerebral involvement was independent of whether abnormalities were unilateral or bilateral. Large abnormalities were relatively more likely than small abnormalities to involve anterior planes. Small abnormalities, whether echodense or echolucent, or whether unilateral or bilateral, preferentially occurred near the trigone. Using the characteristics of location, size, and laterality/symmetry, we were able to allocate only 53% of infants with white-matter abnormalities to periventricular hemorrhagic infarction or periventricular leukomalacia. Assuming that periventricular leukomalacia and periventricular hemorrhagic infarction are independent and do not share risk factors, and that each occurs in approximately 5% of infants, we would have expected 0.25%, or about 4 individuals, to have abnormalities with characteristics of both periventricular leukomalacia and periventricular hemorrhagic infarction, whereas we found 63 such infants. Most infants with white-matter disease could not be clearly designated as having periventricular hemorrhagic infarction or periventricular leukomalacia only. Periventricular hemorrhagic infarction contributes to the risk of periventricular leukomalacia occurrence, or the two sorts of abnormalities share common risk antecedent factors. The descriptive term echodense or echolucent and the generic term white-matter disease of prematurity should be used instead of periventricular leukomalacia or periventricular hemorrhagic infarction when referring to sonographically defined white-matter abnormalities.

Comparison of findings on cranial ultrasound and magnetic resonance imaging in preterm infants

OBJECTIVE

To compare findings on hard copies of cranial ultrasound (US) and magnetic resonance imaging (MRI) obtained between birth and term in a group of preterm infants.

PARTICIPANTS AND METHODS

Infants born at or below a gestational age of 30 weeks who underwent cranial US scan and MRI on the same day were eligible for this study. Infants underwent, whenever possible, 3 scans between birth and term. We calculated the predictive probability (PP) of US findings as a predictor of findings on MRI.

RESULTS

Sixty-two paired MRI and US studies were performed between birth and term in 32 infants born at a median gestational age of 27 (range: 23-30) weeks and a median birth weight of 918 (530-1710) grams. US predicted some MRI findings accurately: germinal layer hemorrhage (GLH) on US had a PP of 0.8 with a 95% confidence interval of (0.70-0.90) for the presence of GLH on MRI, intraventricular hemorrhage (IVH) on US had a PP of 0.85 (0.76-0.94) for the presence of IVH on MRI, and severe white matter (WM) echogenicity on US had a PP of 0.96 (0.92-1.0) for the presence of WM hemorrhagic parenchymal infarction on MRI. Other MRI changes were less well-predicted: mild or no WM echogenicity on US had a PP of 0.54 (0.41-0.66) for the presence of normal WM signal intensity on MRI, and moderate or severe WM echogenicity on US had a PP of 0.54 (0.42-0.66) for the presence of small petechial WM hemorrhage and/or diffuse excessive high-signal intensity (DEHSI) in the WM on T2-weighted images on MRI. However, mild/moderate or severe WM echogenicity on US scans performed at >/=7 days after birth had a PP of 0.72 (0.58-0.87) for the presence of WM hemorrhage and/or DEHSI on MRI. There were no cases of cystic periventricular leukomalacia.

CONCLUSION

US accurately predicted the presence of GLH, IVH, and hemorrhagic parenchymal infarction on MRI. However, its ability to predict the presence of DEHSI and small petechial hemorrhages in the WM on T2 weighted images is not as good, but improves on scans performed at >/=7 days after birth. In addition, normal WM echogenicity on US is not a good predictor of normal WM signal intensity on MRI.

Neonatal cranial ultrasound interpretation: a clinical audit

OBJECTIVE

To assess the abilities of doctors to interpret neonatal cranial ultrasound scans.

DESIGN AND SETTING

High resolution scanned images of six important neonatal cranial ultrasound abnormalities were posted as a questionnaire to the 59 neonatal units in the North and South Thames regions.

RESULTS

Forty two questionnaires were returned (71%). Currently 56% of those interpreting cranial ultrasound scans are neonatal registrars, 27% are consultant paediatricians or neonatologists, and 17% are radiologists. The response rate from registrars was excellent (97%), but it was poor from consultant paediatric (38%) and radiological (40%) staff. The mean accurate identification of cerebral abnormalities was only 59% (range 45-71%). Only 44% of the neonatal registrars, compared with nearly all the consultant staff, have had any formal training in cranial ultrasonography.

CONCLUSIONS

The data highlight the current accuracy of neonatal cranial ultrasound scan reporting in the Greater London region and have important implications for clinical services and research studies. Doctors who are responsible for interpreting neonatal cranial ultrasound scans should have formal training and supervision, and more formal reporting would improve and maintain standards. The findings raise significant doubts about the accuracy of local interpretation of cranial ultrasound scans in multicentre research studies.

Cranial ultrasound abnormalities in full term infants in a postnatal ward: outcome at 12 and 18 months

OBJECTIVE

To investigate whether cranial ultrasound abnormalities found in low risk full term infants had any influence on neurodevelopmental outcome.

METHODS

For 103 infants who had a neurological assessment, a cranial ultrasound examination, and for whom antenatal and perinatal data were collected within 48 hours of delivery, neurodevelopmental status was evaluated at 12 and 18 months. The results of a scored neurological examination and the Griffiths mental developmental scale were correlated with the presence and type of ultrasound abnormality found in the neonatal period.

RESULTS

None of the infants with ultrasound abnormalities showed any signs of cerebral palsy or severe developmental delay. There was also no significant difference between the overall neurological and neurodevelopmental scores of the infants with normal and abnormal ultrasound findings. However, when the individual subscales of the Griffiths test were analysed, all infants with bulky choroid or intraventricular haemorrhage had normal scores in all subscales, four of eight with periventricular white matter lesions had low scores on the locomotor subscale, and three of five with asymmetrical ventricles had low scores on the performance subscale. The presence of adverse antenatal and perinatal factors did not affect the outcome in this group.

CONCLUSION

Incidental ultrasound abnormality in full term neonates, in particular intraventricular haemorrhage, although common, appear to have a good prognosis. Longer follow up studies are needed to see whether some of these infants, in particular those with white matter lesions, develop dyspraxia or other minor neurological impairments at school age.

Mechanisms of perinatal brain injury

This article is focused on the mechanisms underlying primarily ischaemic/reperfusion brain injury in both the term and premature infant. Although the mechanisms involved include similar initiating events, principally ischaemia-reperfusion, and similar final common pathways to cell death, particularly free radical-mediated events, there are certain unique maturational factors influencing the type and pattern of cellular injury. We will therefore initially describe the physiological and cellular/molecular mechanisms of brain injury in the term infant, followed by the mechanisms in the premature infant.

Postnatal phenobarbitone for the prevention of intraventricular hemorrhage in preterm infants

BACKGROUND

This section is under preparation and will be included in the next issue.

OBJECTIVES

To determine whether postnatal administration of phenobarbitone to preterm infants reduces the risk of intraventricular hemorrhage (IVH), neurodevelopmental impairment or death.

SEARCH STRATEGY

See the Search Strategy of the Neonatal Collaborative Review Group. The reviewer has been a active trialist in this area and has personal contact with many groups in this field. Journals handsearched from 1976 (when cranial CT scanning started) to November 1998 include: Pediatrics, J Pediatrics, Archives of Disease in Childhood, Pediatric Research, Developmental Medicine and Child Neurology, Acta Paediatrica, European J of Pediatrics, Neuropediatrics, New England J of Medicine, Lancet and British Medical J. The National Library of Medicine (USA) database (via PubMed) and the Cochrane Controlled Trials Register were searched through to November 1998 using the MeSH terms intraventricular hemorrhage, newborn infants, premature infant, intracranial hemorrhage, phenobarbitone, phenobarbital. The searches were not limited to the English language, as long as the article included an English abstract. Promising articles were read in the original language or translated.

SELECTION CRITERIA

Included were randomized or quasi-randomized controlled trials in which phenobarbitone was given to preterm infants identified as being at risk of IVH because of gestational age below 34 weeks, birthweight below 1500 g, or respiratory failure. Adequate determination of IVH by ultrasound or CT was also required.

DATA COLLECTION AND ANALYSIS

In addition to details of patient selection and control of bias, the details of the administration of phenobarbitone were extracted. The end-points searched for included: IVH ( with grading), posthemorrhagic ventricular dilatation or hydrocephalus, neurodevelopmental impairment and death. In addition, possible adverse effects of phenobarbitone such as hypotension, mechanical ventilation, pneumothorax, hypercapnia, and acidosis were searched for.

MAIN RESULTS

Nine controlled trials were included with 740 infants recruited. There was heterogeneity between trials for the outcome IVH, with one trial finding a significant decrease in IVH and another trial finding an increase in IVH in the group receiving phenobarbitone. Meta-analysis showed no difference between the phenobarbitone treated group and the control group in either IVH (typical relative risk 1.04, CI 0.87, 1.25), severe IVH (typical relative risk 0.91, CI 0.66, 1.27), posthemorrhagic ventricular dilatation (typical relative risk 0.89, CI 0.38, 2.08), severe neurodevelopmental impairment (typical relative risk 1.44, CI 0.41, 5.04) or death before hospital discharge (typical relative risk 0.88, CI 0.64, 1.21) There was a consistent trend in the trials towards increased use of mechanical ventilation in the phenobarbitone treated group, which was supported by the meta-analysis (typical relative risk 1.18, CI 1.06, 1.32; typical risk difference 0.129, CI 0.045, 0.213), but there was no significant difference in pneumothorax, acidosis or hypercapnia.

REVIEWER'S CONCLUSIONS

Postnatal administration of phenobarbitone cannot be recommended as prophylaxis to prevent IVH in preterm infants and is associated with an increased need for mechanical ventilation.

Magnetic resonance imaging of the brain in a cohort of extremely preterm infants

To define magnetic resonance imaging (MRI) appearances of the brain in extremely preterm infants between birth and term, a sequential cohort of infants born at a gestational age <30 weeks was studied with a dedicated neonatal magnetic resonance scanner. Images of infants (n = 41) with a median gestational age of 27 weeks (range 23 to 29 weeks) were initially obtained at a median age of 2 days (range 1 to 20 days) and then repeatedly studied; 29 (71%) infants had MRI at a median gestational age of 43 weeks (range 38 to 52 weeks) (term MRI). On the initial MRI scan 28 of 41 infants had abnormalities: either intraventricular hemorrhage, germinal layer hemorrhage, ventricular dilatation, or diffuse and excessive high signal intensity in the white matter on T(2)-weighted images. When magnetic resonance images for preterm infants at term gestation were compared with those of infants in the control group born at term, 22 of 29 infants had dilatation of the lateral ventricles, 24 of 29 had squaring of the anterior or posterior horns of the lateral ventricles, 11 of 29 had a widened interhemispheric fissure or extracerebral space, and 22 of 29 had diffuse and excessive high signal intensity in the white matter. There were no cases of cystic periventricular leukomalacia. We conclude that MRI abnormalities are commonly seen in the brain of preterm infants on whom images are obtained within 48 hours of birth and that further abnormalities develop between birth and term. A characteristic appearance of diffuse and excessive high signal intensity in the white matter on T(2)-weighted images is associated with the development of cerebral atrophy and may be a sign of white matter disease. These MRI appearances may help account for the high incidence of neurodevelopmental impairment in extremely preterm infants.

Pathophysiology of perinatal brain damage

Perinatal brain damage in the mature fetus is usually brought about by severe intrauterine asphyxia following an acute reduction of the uterine or umbilical circulation. The areas most heavily affected are the parasagittal region of the cerebral cortex and the basal ganglia. The fetus reacts to a severe lack of oxygen with activation of the sympathetic-adrenergic nervous system and a redistribution of cardiac output in favour of the central organs (brain, heart and adrenals). If the asphyxic insult persists, the fetus is unable to maintain circulatory centralisation, and the cardiac output and extent of cerebral perfusion fall. Owing to the acute reduction in oxygen supply, oxidative phosphorylation in the brain comes to a standstill. The Na(+)/K(+) pump at the cell membrane has no more energy to maintain the ionic gradients. In the absence of a membrane potential, large amounts of calcium ions flow through the voltage-dependent ion channel, down an extreme extra-/intracellular concentration gradient, into the cell. Current research suggests that the excessive increase in levels of intracellular calcium, so-called calcium overload, leads to cell damage through the activation of proteases, lipases and endonucleases. During ischemia, besides the influx of calcium ions into the cells via voltage-dependent calcium channels, more calcium enters the cells through glutamate-regulated ion channels. Glutamate, an excitatory neurotransmitter, is released from presynaptic vesicles during ischemia following anoxic cell depolarisation. The acute lack of cellular energy arising during ischemia induces almost complete inhibition of cerebral protein biosynthesis. Once the ischemic period is over, protein biosynthesis returns to pre-ischemic levels in non-vulnerable regions of the brain, while in more vulnerable areas it remains inhibited. The inhibition of protein synthesis, therefore, appears to be an early indicator of subsequent neuronal cell death. A second wave of neuronal cell damage occurs during the reperfusion phase. This cell damage is thought to be caused by the post-ischemic release of oxygen radicals, synthesis of nitric oxide (NO), inflammatory reactions and an imbalance between the excitatory and inhibitory neurotransmitter systems. Part of the secondary neuronal cell damage may be caused by induction of a kind of cellular suicide programme known as apoptosis. Knowledge of these pathophysiological mechanisms has enabled scientists to develop new therapeutic strategies with successful results in animal experiments. The potential of such therapies is discussed here, particularly the promising effects of i.v. administration of magnesium or post-ischemic induction of cerebral hypothermia.