The role of chronic hypoxia in the development of neurocognitive abnormalities in preterm infants with bronchopulmonary dysplasia

Upregulation of A-type potassium channels suppresses neuronal excitability in hypoxic neonatal mice

Neuronal excitability is a critical feature of central nervous system development, playing a fundamental role in the functional maturation of brain regions, including the hippocampus, cerebellum, auditory and visual systems. The present study aimed to determine the mechanism by which hypoxia causes brain dysfunction through perturbation of neuronal excitability in a hypoxic neonatal mouse model. Functional brain development was assessed in humans using the Gesell Development Diagnosis Scale. In mice, gene transcription was evaluated via mRNA sequencing and quantitative PCR; furthermore, patch clamp recordings assessed potassium currents. Clinical observations revealed disrupted functional brain development in 6- and 18-month-old hypoxic neonates, and those born with normal hearing screening unexpectedly exhibited impaired central auditory function at 3 months. In model mice, CA1 pyramidal neurons exhibited reduced spontaneous activity, largely induced by excitatory synaptic input suppression, despite the elevated membrane excitability of hypoxic neurons compared to that of control neurons. In hypoxic neurons, Kcnd3 gene transcription was upregulated, confirming upregulated hippocampal Kv 4.3 expression. A-type potassium currents were enhanced, and Kv 4.3 participated in blocking excitatory presynaptic inputs. Elevated Kv 4.3 activity in pyramidal neurons under hypoxic conditions inhibited excitatory presynaptic inputs and further decreased neuronal excitability, disrupting functional brain development in hypoxic neonates.

Postnatal abnormality in brainstem neural conduction in neonatal bronchopulmonary dysplasia survivors

OBJECTIVE

To investigate postnatal neural conduction in the auditory brainstem in neonatal bronchopulmonary dysplasia (BPD) survivors.

METHODS

Thirty-two very preterm BPD survivors were studied at 57-58 weeks of postconceptional age. Brainstem auditory-evoked response was studied using maximum length sequence. Wave latencies and intervals were analyzed in detail. The controls were 37 normal term infants and 35 very preterm non-BPD infants.

RESULTS

Compared with normal term controls, BPD survivors showed significantly shortened I-III interval but significantly prolonged III-V interval and greater III-V/I-III interval ratio. Compared with very preterm non-BPD controls, BPD survivors showed a significant shortening in waves III latency and I-III interval, moderate prolonged III-V interval, and significantly greater III-V/I-III interval ratio. These differences were generally similar at all click rates used. The slopes of latency- and interval-click rate functions in BPD survivors did not differ significantly from the two control groups.

CONCLUSIONS

Brainstem neural conduction in BPD survivors differed from normal term and age-matched non-BPD infants; neural maturation is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions, which may constitute an important risk for postnatal neurodevelopment in BPD survivors.

IMPACT

We found that brainstem neural conduction at PCA 57-58 weeks in neonatal BPD survivors differs from normal term and age-matched non-BPD infants. No major differences were found between normal term and very preterm non-BPD infants in brainstem auditory conduction. Neural conduction in BPD survivors is accelerated in caudal brainstem regions but delayed in rostral regions. Neonatal BPD survivors are associated with differential maturation in neural conduction at caudal and rostral brainstem regions. The abnormality may constitute an important risk for postnatal neurodevelopment in BPD survivors.

Neurodevelopmental outcomes in very preterm infants: The role of severity of Bronchopulmonary Dysplasia

OBJECTIVE

Bronchopulmonary dysplasia is a chronic respiratory disease that still affects preterm neonates; its association with neurodevelopmental (ND) impairment is already known. Different studies investigated neurodevelopmental outcomes in infants with BPD, often using the old dichotomous definition (BPD vs Non-BPD). This retrospective study aims to evaluate the role of different BPD severity grades on ND outcomes at 24 months of corrected age (CA).

METHODS

All preterm infants born between 2011 and 2015 in the study hospital with a gestational age (GA) ≤ 30 weeks and discharged from our NICU were included and were divided in infants with and without BPD. Infants with BPD were divided into three severity groups as defined by NICHD/NHLBI Workshop in 2001, and were compared to their Non-BPD peers, matching them according to the same GA and year of birth. At 24 months postmenstrual age, we assessed general outcomes (growth and hospital readmissions) and neurodevelopmental outcomes (motor, developmental and sensory outcomes) with a standardized assessment.

RESULTS

We enrolled 89 patients affected by BPD of different grades of severity and a control group of 89 preterm infants without BPD. Infants with Moderate and Severe BPD showed a significantly higher corrected odds ratio (OR) for cognitive impairment compared to controls. Within the group of infants without severe disability (regarding Griffiths' scales), infants with Moderate and Severe BPD as well as infants with Mild BPD showed a significantly higher risk of a lower total Developmental Quotient (DQ) score, even after correction for confounding factors.

CONCLUSIONS

Our study evidenced that not only Severe BPD infants, but also Moderate ones showed a higher risk of overall cognitive impairment at 24 months CA. Within the group of infants without severe disability, also those with Mild BPD had lower Griffiths DQ scores than those without. This would suggest that infants with BPD, regardless of severity, warrant neurodevelopmental follow-up.

Neurocognition in Congenital Central Hypoventilation Syndrome: influence of genotype and ventilation method

BACKGROUND

Congenital Central Hypoventilation Syndrome (CCHS) is characterized by central hypoventilation due to abnormal autonomic control of breathing and global dysautonomia. Patients harbour heterozygous PHOX-2B gene mutations which are polyalanine repeats of various lengths in most of the cases. A few previous studies have reported learning difficulties and neuropsychological disorders in patients with CCHS. The aims of the present study were (1) to explore the intellectual abilities of a group of children with CCHS followed up in the centre of reference for CCHS in France using the Wechsler batteries of tests, (2) and to assess whether there was any association between CCHS characteristics and various domains of the intellectual functioning.

RESULTS

There were 34 consecutive patients (15 males, 19 females) of mean (SD) age of 7.8 (3.8) years, ranging from 4 to 16 years and 6 months. Mean score of full-scale intelligence quotient was 82 (20), being in the low average range. Indexes of working memory and processing speed were significantly lower as compared to the other Wechsler indexes. There were two important findings: (1) full-scale intelligence quotient as well as indexes of verbal comprehension and processing speed were significantly greater in patients with mask ventilation than in those with tracheostomy ventilation (p = 0.012, 0.032 and 0.042 respectively); (2) most interestingly, in the patients with polyalanine repeats mutations, all intellectual indexes negatively correlated with the number of polyalanine expansion, with statistical significance reached for indexes of fluid reasoning and working memory (R = - 0.449, p = 0.032 and R = - 0.562, p = 0.012 respectively).

CONCLUSIONS

CCHS increased the risk to develop neurocognitive deficiencies, affecting particularly speed of processing and working memory. Our results suggested that both genetics and ventilation method could be also involved in the physiopathology of neurocognitive impairment. Further investigations were required to untangle the complex underlying processes. Neurocognitive assessments should be performed regularly in children with CCHS in order to plan re-education programs, adapt school integration and improve quality of life.

Anemia of prematurity and cerebral near-infrared spectroscopy: should transfusion thresholds in preterm infants be revised?

OBJECTIVE

To determine the impact of progressive anemia of prematurity on cerebral regional saturation (C-rSO₂) in preterm infants and identify the hemoglobin threshold below which a critical decrease (>2SD below the mean) in C-rSO₂ occurs.

STUDY DESIGN

In a cohort of infants born ≤30 weeks EGA, weekly C-rSO₂ data were prospectively collected from the second week of life through 36 weeks post-menstrual age (PMA). Clinically obtained hemoglobin values were noted at the time of recording. Recordings were excluded if they were of insufficient duration (<1 h) or if the hemoglobin was not measured within 7 days. Statistical analysis was performed using a linear mixed effects-model and ROC analysis. ROC analysis was used to determine the threshold of anemia, where C-rSO₂ critically decreased >2SD below the mean normative value (<55%) in preterm infants.

RESULTS

In total 253 recordings from 68 infants (mean EGA 26.9 ± 2.1 weeks, BW 1025 ± 287 g, 49% male) were included. Approximately 29 out of 68 infants (43%) were transfused during hospitalization. Mixed-model statistical analysis adjusting for EGA, BW, and PMA revealed a significant association between decreasing hemoglobin and C-rSO₂ (p < 0.01) in transfusion-naive infants but not in transfused infants. In the transfusion naive group, using ROC analysis demonstrated a threshold hemoglobin of 9.5 g/dL (AUC 0.81, p < 0.01) for critical cerebral desaturation in preterm infants.

CONCLUSIONS

In transfusion-naive preterm infants, worsening anemia was associated with a progressive decrease in cerebral saturations. Analysis identified a threshold hemoglobin of 9.5 g/dL below which C-rSO₂ dropped >2SD below the mean.

Academic performance of children born preterm: a meta-analysis and meta-regression

BACKGROUND

Advances in neonatal healthcare have resulted in decreased mortality after preterm birth but have not led to parallel decreases in morbidity. Academic performance provides insight in the outcomes and specific difficulties and needs of preterm children.

OBJECTIVE

To study academic performance in preterm children born in the antenatal steroids and surfactant era and possible moderating effects of perinatal and demographic factors.

DESIGN

PubMed, Web of Science and PsycINFO were searched for peer-reviewed articles. Cohort studies with a full-term control group reporting standardised academic performance scores of preterm children (<37 weeks of gestation) at age 5 years or older and born in the antenatal steroids and surfactant era were included. Academic test scores and special educational needs of preterm and full-term children were analysed using random effects meta-analysis. Random effects meta-regressions were performed to explore the predictive role of perinatal and demographic factors for between-study variance in effect sizes.

RESULTS

The 17 eligible studies included 2390 preterm children and 1549 controls. Preterm children scored 0.71 SD below full-term peers on arithmetic (p<0.001), 0.44 and 0.52 SD lower on reading and spelling (p<0.001) and were 2.85 times more likely to receive special educational assistance (95% CI 2.12 to 3.84, p<0.001). Bronchopulmonarydysplasia explained 44% of the variance in academic performance (p=0.006).

CONCLUSION

Preterm children born in the antenatal steroids and surfactant era show considerable academic difficulties. Preterm children with bronchopulmonarydysplasia are at particular risk for poor academic outcome.

Cognitive performance of premature infants: association between bronchopulmonary dysplasia and cognitive skills. Cross-sectional study

CONTEXT AND OBJECTIVE:

Children born prematurely often have worse cognitive performance than those born at term regarding skills such as memory, attention and processing speed. Bronchopulmonary dysplasia may compromise cognitive development. The aims here were: a) To describe the cognitive performance of preterm infants with very low birth weight; b) To investigate its association with bronchopul-monary dysplasia adjusted for sociodemographic, neonatal and post-neonatal factors.

DESIGN AND SETTING:

Cross-sectional study developed in a public tertiary-care hospital.

METHODS:

To evaluate cognition among 112 children, we applied an intelligence scale (Wechsler scale). The average scores for children with and without bronchopulmonary dysplasia were compared across the fve domains of the scale. Associations with bronchopulmonary dysplasia were investigated for domains that showed signifcant diferences between the two groups. Associations between exposure and outcome were estimated via multivariate logistic regression.

RESULTS:

There were no diferences in averages for the full-scale intelligence quotient, verbal intelligence quotient, performance intelligence quotient and general language composite domains. The processing speed quotient was the only domain that presented a signifcant diference between the two groups (P = 0.02). Among the children with bronchopulmonary dysplasia, low full-scale intelligence quotient was observed in 28.1%. In the multivariate analysis, bronchopulmonary dysplasia (odds ratio: 3.1; 95conf-dence interval: 1.1-8.7) remained associated with the outcome of processing speed quotient.

CONCLUSION:

Bronchopulmonary dysplasia was an independent risk factor for alteration of the processing speed quotient.

Chronic hypoxia attenuates the vasodilator efficacy of protein kinase G in fetal and adult ovine cerebral arteries

Long-term hypoxia (LTH) attenuates nitric oxide-induced vasorelaxation in ovine middle cerebral arteries. Because cGMP-dependent protein kinase (PKG) is an important mediator of NO signaling in vascular smooth muscle, we tested the hypothesis that LTH diminishes the ability of PKG to interact with target proteins and cause vasorelaxation. Prominent among proteins that regulate vascular tone is the large-conductance Ca²⁺-sensitive K⁺ (BK) channel, which is a substrate for PKG and is responsive to phosphorylation on multiple serine/threonine residues. Given the influence of these proteins, we also examined whether LTH attenuates PKG and BK channel protein abundances and PKG activity. Middle cerebral arteries were harvested from normoxic and hypoxic (altitude of 3,820 m for 110 days) fetal and adult sheep. These arteries were denuded and equilibrated with 95% O₂-5% CO₂ in the presence of N-nitro-l-arginine methyl ester (l-NAME) to inhibit potential confounding influences of events upstream from PKG. Expression and activity of PKG-I were not significantly affected by chronic hypoxia in either fetal or adult arteries. Pretreatment with the BK inhibitor iberiotoxin attenuated vasorelaxation induced by 8-(4-chlorophenylthio)guanosine 3',5'-cyclic monophosphate in normoxic but not LTH arteries. The spatial proximities of PKG with BK channel α- and β1-proteins were examined using confocal microscopy, which revealed a strong dissociation of PKG with these proteins after LTH. These results support our hypothesis that hypoxia reduces the ability of PKG to attenuate vasoconstriction in part through suppression of the ability of PKG to associate with and thereby activate BK channels in arterial smooth muscle.NEW & NOTEWORTHY Using measurements of contractility, protein abundance, kinase activity, and confocal colocalization in fetal and adult ovine cerebral arteries, the present study demonstrates that long-term hypoxia diminishes the ability of cGMP-dependent protein kinase (PKG) to cause vasorelaxation through suppression of its colocalization and interaction with large-conductance Ca²⁺-sensitive K⁺ (BK) channel proteins in cerebrovascular smooth muscle. These experiments are among the first to demonstrate hypoxic changes in BK subunit abundances in fetal cerebral arteries and also introduce the use of advanced methods of confocal colocalization to study interaction between PKG and its targets.

Abnormal findings in brainstem auditory evoked response at 36-37weeks of postconceptional age in babies with neonatal chronic lung disease

AIM

To examine brainstem auditory function at 36-37weeks of postconceptional age in preterm infants who are diagnosed to have neonatal chronic lung disease (CLD).

STUDY DESIGN

Preterm infants, born at 31 and less weeks of gestation, were studied at 36-37weeks of postconceptional age when they were diagnosed to have neonatal CLD. Brainstem auditory evoked response (BAER) was recorded and analyzed at different click rates.

RESULTS

Compared with healthy controls at the same postconceptional age, the CLD infants showed a slightly increase in BAER wave V latency. However, the I-V, and III-V interpeak intervals in the CLD infants were significantly increased. The III-V/I-III interval ratio was also significantly increased. The amplitudes of BAER waves III and V in the CLD infants tended to be reduced. These BAER findings were similar at all 21, 51 and 91/s clicks, although the abnormalities tended to be more significant at higher than at low click rates.

CONCLUSION

At 36-37weeks of postconceptional age, BAER was abnormal in preterm infants who were diagnosed to have neonatal CLD. This suggests that at time when the diagnosis of CLD is made there is functional impairment, reflecting poor myelination, in the brainstem auditory pathway in preterm infants with neonatal CLD.

Cognitive Impairment of School Children at High Altitude: The Case for Oxygen Conditioning in Schools

West, John B. Cognitive impairment of school children at high altitude: the case for oxygen conditioning in schools. High Alt Med Biol. 17:203-207, 2016.-The hypoxia of high altitude frequently affects cognitive function. Recent work has shown that high altitude impairs the neuropsychological function of children of school age when compared with a similar control group of children at low altitude. This implies that the learning process is compromised at high altitude. One option is to bus children down to a lower altitude for schooling, but this is generally impracticable. Recently the new technique of oxygen conditioning has been introduced. The procedure is similar to air conditioning except that instead of altering the temperature of the air, the oxygen concentration is increased, thus raising the PO₂ in the inspired air of classrooms. The result is that the children are physiologically at a lower altitude. Just as in very hot or cold climates, it is now unacceptable to have schools that are not air conditioned; in the future the same may apply to schools at high altitude that are not oxygen conditioned.

Acute and Chronic Altitude-Induced Cognitive Dysfunction in Children and Adolescents

OBJECTIVE

To assess whether exposure to high altitude induces cognitive dysfunction in young healthy European children and adolescents during acute, short-term exposure to an altitude of 3450 m and in an age-matched European population permanently living at this altitude.

STUDY DESIGN

We tested executive function (inhibition, shifting, and working memory), memory (verbal, short-term visuospatial, and verbal episodic memory), and speed processing ability in: (1) 48 healthy nonacclimatized European children and adolescents, 24 hours after arrival at high altitude and 3 months after return to low altitude; (2) 21 matched European subjects permanently living at high altitude; and (3) a matched control group tested twice at low altitude.

RESULTS

Short-term hypoxia significantly impaired all but 2 (visuospatial memory and processing speed) of the neuropsychological abilities that were tested. These impairments were even more severe in the children permanently living at high altitude. Three months after return to low altitude, the neuropsychological performances significantly improved and were comparable with those observed in the control group tested only at low altitude.

CONCLUSIONS

Acute short-term exposure to an altitude at which major tourist destinations are located induces marked executive and memory deficits in healthy children. These deficits are equally marked or more severe in children permanently living at high altitude and are expected to impair their learning abilities.

Neonatal hypoxia, hippocampal atrophy, and memory impairment: evidence of a causal sequence

Neonates treated for acute respiratory failure experience episodes of hypoxia. The hippocampus, a structure essential for memory, is particularly vulnerable to such insults. Hence, some neonates undergoing treatment for acute respiratory failure might sustain bilateral hippocampal pathology early in life and memory problems later in childhood. We investigated this possibility in a cohort of 40 children who had been treated neonatally for acute respiratory failure but were free of overt neurological impairment. The cohort had mean hippocampal volumes (HVs) significantly below normal control values, memory scores significantly below the standard population means, and memory quotients significantly below those predicted by their full scale IQs. Brain white matter volume also fell below the volume of the controls, but brain gray matter volumes and scores on nonmnemonic neuropsychological tests were within the normal range. Stepwise linear regression models revealed that the cohort's HVs were predictive of degree of memory impairment, and gestational age at treatment was predictive of HVs: the younger the age, the greater the atrophy. We conclude that many neonates treated for acute respiratory failure sustain significant hippocampal atrophy as a result of the associated hypoxia and, consequently, show deficient memory later in life.

Pharmacological inhibition of the mTOR pathway impairs hippocampal development in mice

Brain injury is an important cause of morbidity in infants at risk for exposure to chronic hypoxia. Using a transgenic mouse that expresses green fluorescent protein (GFP) within this progenitor population we have previously shown that exposure to chronic hypoxia significantly decreases the progenitor stem cell pool in the dentate gyrus of the hippocampus that is in part mediated by inhibition of the mammalian target of rapamycin (mTOR) pathway. Hence we hypothesized that pharmacological inhibition of the mTOR pathway using rapamycin will alter the progenitor stem cell pool and impair the development of the dentate gyrus. We find that prolonged inhibition of the mTOR pathway causes a decrease in the early progenitor stem cell pool, demonstrated by decreased GFP-expressing progenitors, which persists long term. However there is a significant increase in proliferating progenitor cell pool, as seen by increased BrdU that is coupled with increased apoptosis thereby leading to fewer Neu N-expressing mature neurons. Further inhibition of the mTOR pathway leads to depletion of the astrocyte and microglial pool in the dentate gyrus as well. Overall our findings demonstrate that pharmacological inhibition of the mTOR pathway leads to impaired development of the DG, raising the concern that in young children could impair cognitive development.

Neuropsychological and behavioral effects of postnatal dexamethasone in extremely low birth weight preterm children at early school age

OBJECTIVE

To study postnatal dexamethasone treatment effects on cognitive, neuropsychological and behavioral functioning at early school age in preterm children.

STUDY DESIGN

We recruited 222 children born between 1998 and 2003: 114 extremely low birth weight (<1000 g; 60 dexamethasone-treated; 54 untreated) and 108 term-born. Data were analyzed using multivariate methods.

RESULT

Preterm performed below term-born on all measures. Dexamethasone-treated performed below dexamethasone-untreated in immediate visual memory, visual-motor integration, mathematical skill and motor dexterity. However, stepwise regression indicated that medical and sociodemographic factors other than dexamethasone contributed to preterm group differences.

CONCLUSION

Dexamethasone alone does not explain neurocognitive impairment in preterm children. Medical and sociodemographic factors (illness severity, male gender and parental education) are influential. Prospective longitudinal neuropsychological and behavioral study from preschool to school age that considers medical and sociodemographic variables will best address effects of dexamethasone exposure.

Intellectual ability and executive function in pediatric moyamoya vasculopathy

AIM

  Moyamoya vasculopathy is characterized by progressive stenosis of the major arteries of the Circle of Willis, resulting in compromised cerebral blood flow and increased risk of stroke. The objectives of the current study were to examine intellectual and executive functioning of children with moyamoya and to evaluate the impact of moyamoya type, stroke (clinical or silent), vasculopathy laterality, and disease duration on neurocognitive abilities.

METHOD

  Thirty pediatric participants (mean age 10 y 10 mo, SD 4 y; 18 females, 12 males) completed age-appropriate Wechsler Intelligence Scales before any therapeutic revascularization procedures. Reports of executive function were obtained from parents and teachers using the Behavior Rating Index of Executive Function.

RESULTS

  Children with moyamoya scored significantly lower than the test standardization samples on all indices of intelligence and ratings of executive functioning (p<0.001). Patients did not differ by type of moyamoya or history of stroke. Patients with bilateral disease and stroke scored significantly lower than those with unilateral disease on measures of overall intellectual function (p=0.035) and verbal comprehension (p=0.04). Deficits in metacognitive executive functions were also more pronounced in bilateral patients according to teacher ratings.

INTERPRETATION

  Children with moyamoya are at risk for intellectual and executive problems, exacerbated by bilateral disease and clinical stroke history.

Effect of decreasing target oxygen saturation on retinopathy of prematurity

INTRODUCTION

The authors of previous studies suggest that the oxygenation status of premature infants contributes to the development of retinopathy of prematurity (ROP). In this study we compared the incidence and severity of ROP before and after institution of a new neonatal intensive care unit oxygen protocol.

METHODS

A retrospective chart review was performed of all eligible inborn patients screened for ROP during the 2 years immediately before (Group 1) to and the 2 years after (Group 2) the initiation of a new oxygen protocol. In the new protocol, target oxygen saturation was adjusted from 90%-99% to 85%-93%. Treatment criteria adhered to Early Treatment for Retinopathy of Prematurity guidelines for the study's duration.

RESULTS

There were 387 infants in Group 1 and 386 infants in Group 2 (descriptive statistics adjusted for correlation due to multiple births). Mean birth weights (BWs) and gestational ages were 1,194 g and 29.2 weeks (ranges, 525-2,085 g; 23 2/7-39 6/7 weeks) for Group 1 and 1,139 g and 28.9 weeks (ranges, 520-2,500 g; 22 6/7-35 3/7 weeks) for Group 2 (p = 0.02/0.10). ROP developed in 32.7% of infants in Group 1 and 27.8% in Group 2 (p = 0.17). The incidence of ROP requiring treatment was 19.9% in Group 1 and 20.5% in Group 2 (p = 0.91). Subanalysis of infants with BW ≤ 1,000g (Group 1, n = 119; Group 2, n = 141) revealed ROP incidence of 75.1% versus 57.1%, respectively (p < 0.01); treatable disease occurred in 37.5% and 21.9% of affected infants (p = 0.19).

CONCLUSIONS

Lowering target oxygen saturation for inborn premature infants was associated with decreased incidence of ROP only in infants with BW ≤ 1,000 g. Severity of disease, including need for treatment, was similar in both groups.

Avaliação neurológica de recém-nascidos pré-termo de muito baixo peso com displasia broncopulmonar

OBJETIVO: Descrever e comparar a avaliação neurológica e comportamental de recém-nascidos pré-termos com e sem displasia broncopulmonar (DBP). MÉTODOS: Recém-nascidos prematuros com peso ao nascer inferior a 1500g e idade gestacional menor de 32 semanas foram avaliados com 40 semanas de idade gestacional corrigida, no Centro de Atenção Integral à Saúde da Mulher da Universidade Estadual de Campinas. Utilizou-se a Avaliação Neurológica de Dubowitz, com 29 itens divididos em seis categorias: tônus, padrões de tônus, reflexos, movimentos, sinais anormais e comportamento. O estado de consciência do recém-nascido foi graduado segundo Brazelton (1973). Utilizaram-se os testes do qui-quadrado e exato de Fischer para variáveis qualitativas e o de Mann-Whitney para as numéricas não-paramétricas, com nível de significância de 5%. RESULTADOS: No período de janeiro de 2005 a setembro de 2007, 24 recém-nascidos, 12 com DBP e 12 controles, com idade gestacional ao nascer de 28±1 semana e peso de 884±202g no grupo com DBP e 31±1 semana e 1156±216g no Grupo Controle foram avaliados. Dos 29 itens avaliados, 18 foram homogêneos entre os grupos e a pontuação geral dos dois grupos não apresentou diferença (p=0,30). Observou-se maior anormalidade neurológica no grupo com DBP em oito itens e, no Grupo Controle, em três itens. CONCLUSÕES: A comparação da avaliação neurológica de Dubowitz de recém-nascidos pré-termos com e sem DBP não apresentou diferença significante com 40 semanas de idade gestacional corrigida. Nas categorias reflexos e postura/tônus, observou-se tendência a anormalidade no grupo DBP.

Augmented hypothalamic corticotrophin-releasing hormone mRNA and corticosterone responses to stress in adult rats exposed to perinatal hypoxia

Stressful events before or just after parturition alter the subsequent phenotypical response to stress in a general process termed programming. Hypoxia during the period before and during parturition, and in the postnatal period, is one of the most common causes of perinatal distress, morbidity, and mortality. We have found that perinatal hypoxia (prenatal day 19 to postnatal day 14) augmented the corticosterone response to stress and increased basal corticotrophin-releasing hormone (CRH) mRNA levels in the parvocellular portion of the paraventricular nucleus (PVN) in 6-month-old rats. There was no effect on the levels of hypothalamic parvocellular PVN vasopressin mRNA, anterior pituitary pro-opiomelanocortin or CRH receptor-1 mRNA, or hippocampus glucocorticoid receptor mRNA. We conclude that hypoxia spanning the period just before and for several weeks after parturition programmes the hypothalamic-pituitary-adrenal axis to hyper-respond to acute stress in adulthood, probably as a result of drive from the parvocellular CRH neurones.

Auditory event-related potentials and cognitive function of preterm children at five years of age

OBJECTIVE

In our previous study, auditory event-related potentials (AERPs) in preterm 1-year-old children had a positive deflection at 150-350 ms that correlated positively with their 2-year neurodevelopmental outcome. In a study of the same subjects at age 5, our aim was to assess AERPs and their relationship to neuropsychological test results.

METHODS

Preterm small (SGA, n=13), appropriate for gestational age (AGA, n=15), and control (n=13) children were assessed with an Easy paradigm presenting a large frequency change accompanied with occasional novel sounds, and a Challenging paradigm presenting small frequency and duration changes with a rapid rate. The preterm children underwent neurocognitive tests.

RESULTS

Easy paradigm. The P1 response to frequency deviant was smaller and MMN larger in the preterm than in the control children. Challenging paradigm. The P1 response to standard, frequency, and duration deviants was smaller in the preterm than in the control children. The N2 response to frequency deviant was larger in the preterm than in the control children. AGA and SGA children had similar AERPs. The P1, N2, and MMN amplitudes correlated with verbal IQ and NEPSY language subtests.

CONCLUSIONS

Small P1 response(s) appears to be typical for preterm children.

SIGNIFICANCE

Small P1 response in preterm children may suggest altered primary auditory processing.