Neonatal cerebral circulation in relation to neurosonography and neurological outcome: a pulsed Doppler study

Diagnostic and predictive value of Doppler ultrasound for evaluation of the brain circulation in preterm infants: a systematic review

INTRODUCTION

Very and extremely preterm infants frequently have brain injury-related long-term neurodevelopmental problems. Altered perfusion, for example, seen in the context of a hemodynamically significant patent ductus arteriosus (PDA), has been linked to injury of the immature brain. However, a direct relation with outcome has not been reviewed systematically.

METHODS

A systematic review was conducted to provide an overview of the value of different cerebral arterial blood flow parameters assessed by Doppler ultrasound, in relation to brain injury, to predict long-term neurodevelopmental outcome in preterm infants.

RESULTS

In total, 23 studies were included. Because of heterogeneity of studies, a meta-analysis of results was not possible. All included studies on resistance index (RI) showed significantly higher values in subjects with a hemodynamically significant PDA. However, absolute differences in RI values were small. Studies using Doppler parameters to predict brain injury and long-term neurodevelopmental outcome were inconsistent.

DISCUSSION

There is no clear evidence to support the routine determination of RI or other Doppler parameters in the cerebral arteries to predict brain injury and long-term neurodevelopmental outcome in the preterm infant. However, there is evidence that elevated RI can point to the presence of a hemodynamically significant PDA.

Using senses to encourage head and upper limb voluntary movement in young infants: Implications for early intervention

PRIMARY OBJECTIVE

It has long been suggested that a neonate's movement and responses to external stimuli are the product of reflexive reactions rather than purposeful movements. However, several studies have demonstrated that this is not the case. Rationale of literature included: This study seeks to review reports showing that sensory stimuli resulted in newborns recognising and responding to different stimuli with active head or upper limb movements. We also discuss this in the context of current literature about early training on the advancement of movement and brain development. Results and outcomes: Taken together, it is clear that early active experience shapes learning in newborns.

CONCLUSIONS

The impact of this research is most exciting for applications that would induce infants to make purposeful movements, especially as a means for early intervention and rehabilitation for the treatment of infants with or at high risk for developmental delay.

Cerebrovascular function and cognition in childhood: a systematic review of transcranial Doppler studies

Background

The contribution of cerebrovascular function to cognitive performance is gaining increased attention. Transcranial doppler (TCD) is portable, reliable, inexpensive and extremely well tolerated by young and clinical samples. It enables measurement of blood flow velocity in major cerebral arteries at rest and during cognitive tasks.

Methods

We systematically reviewed evidence for associations between cognitive performance and cerebrovascular function in children (0-18 years), as measured using TCD. A total of 2778 articles were retrieved from PsychInfo, Pubmed, and EMBASE searches and 25 relevant articles were identified.

Results

Most studies investigated clinical groups, where decreased blood flow velocities in infants were associated with poor neurological functioning, and increased blood flow velocities in children with Sickle cell disease were typically associated with cognitive impairment and lower intelligence. Studies were also identified assessing autistic behaviour, mental retardation and sleep disordered breathing. In healthy children, the majority of studies reported cognitive processing produced lateralised changes in blood flow velocities however these physiological responses did not appear to correlate with behavioural cognitive performance.

Conclusion

Poor cognitive performance appears to be associated with decreased blood flow velocities in premature infants, and increased velocities in Sickle cell disease children using TCD methods. However knowledge in healthy samples is relatively limited. The technique is well tolerated by children, is portable and inexpensive. It therefore stands to make a valuable contribution to knowledge regarding the underlying functional biology of cognitive performance in childhood.

Behavioural problems at the age of eleven years in preterm-born children with or without fetal brain sparing: a prospective cohort study

BACKGROUND

In severe intrauterine growth restriction (IUGR) due to placental insufficiency a haemodynamic adaptation occurs, resulting in preferential blood flow to the fetal brain (brain sparing). With Doppler ultrasound an increased ratio between the umbilical and the cerebral artery pulsatility index (U/C ratio) can be demonstrated. IUGR is associated with impaired neurodevelopmental outcome.

OBJECTIVE

Evaluation of the effect of fetal brain sparing on behavioural problems at eleven years in premature born children.

METHODS

Prospective cohort study in premature children born in 1989, with a gestational age of 26 0/7 to 33 0/7 weeks. An U/C ratio>0.72 was defined as brain sparing. Behavioural problems were assessed with the parent-reported Child Behaviour Check List (CBCL) and the Teacher's Report Form (TRF). T scores >60 for total problem score and subscales of internalizing and externalizing behaviour, were considered abnormal.

RESULTS

Ninety-eight of the 116 survivors were assessed, of which 31 with antenatally established fetal brain sparing. According to the CBCL-total problem score 23.3% of the premature born babies in the brain sparing group had behavioural problems compared with 22.8% of those without brain sparing. According to the TRF-total problem score the percentages were 21.4% and 20.0%, respectively. Logistic regression analysis failed to show a significant association of U/C ratio with behavioural problems. In this model oxygen dependency at 28 days, IQ<85 at five years, cranial ultrasound abnormalities, fetal growth ratio<0.80, Apgar scores<7 after 5 min and birth weight<p10 contributed significantly.

CONCLUSION

In this cohort brain sparing itself has no significant association with behavioural problems at eleven years.

Antenatal Doppler measurements and early brain injury in very low birth weight infants

OBJECTIVE

To determine the correlation between fetoplacental blood flow and brain injury and volumes in very low birth weight (VLBW) infants.

STUDY DESIGN

Antenatal blood flow from the umbilical artery (UA), middle cerebral artery (MCA), and descending aorta was determined in 70 VLBW infants. The directions of the total diastolic flow of the aortic isthmus and the end-diastolic flow of ductus venosus also were measured. Serial brain ultrasound examinations and MRI at term were performed to assess brain abnormalities. On the basis of brain imaging findings, the newborn infants were classified as normal (n = 14), intermediate brain pathology (n = 31), and major pathology (n = 25) groups.

RESULTS

Abnormalities in fetoplacental blood flow were not related to anatomic brain lesions. However, an abnormal UA/MCA pulsatility index ratio was associated with reduced total brain volume (mean, 360 mL; SD, 32.5 mL) and reduced cerebral volume (344 mL; SD, 28.4 mL) compared with infants with normal UA/MCA pulsatility index ratio (mean, 405 mL; SD, 51.3 mL, P = .01, and mean, 368 mL; SD, 52.3 mL, P = .012), respectively.

CONCLUSIONS

Redistribution of fetal blood flow in VLBW infants is associated with reduced brain volume at term age. Neurodevelopmental follow-up of this cohort will clarify the significance of these blood flow changes on development.

Assessment of gestational age and neuromaturation

Neuromaturation is the functional development of the central nervous system (CNS). It is by its very nature a dynamic process, a continuous interaction between the genome and first the intrauterine environment, then the extrauterine environment. Understanding neuromaturation and being able to measure it is fundamental to infant neurodevelopmental assessment. Fetal and preterm neuromaturation has become easier to observe with the advent of prenatal ultrasonography and neonatal intensive care units. A number of measures of degree of fetal maturation have been developed and used to estimate gestational age (GA) at birth. The most reliable measures of GA are prenatal measures, especially from the first trimester. Postnatal GA measurements tend to be least accurate at the extremes of gestation, that is, in extremely preterm and post-term infants. Observations of measures of neuromaturation in infants born to mothers with pregnancy complications, including intrauterine growth restriction, multiple gestation, and chronic hypertension, have led to the discovery that stressed pregnancies may accelerate fetal pulmonary and CNS maturation. This acceleration of neuromaturation does not occur before 30 weeks' gestation and has a cost with respect to cognitive limitations manifested in childhood. The ability to measure fetal and preterm neuromaturation provides an assessment of neurodevelopmental progress that can be used to reassure parents or identify at risk infants who would benefit from limited comprehensive follow-up and early intervention services. In addition, measures of neuromaturation have the potential to provide insight into mechanisms of CNS injury and recovery, much-needed early feedback in intervention or treatment trials and a measure of early CNS function for research into the relationships between CNS structure and function.

Neonatal cerebral Doppler: arterial and venous flow velocity measurements using color and pulsed Doppler system

OBJECTIVE

To contribute to the establishment of reference values of blood flow velocity assessed by cerebral Doppler in healthy infants related to gestational age and birth weight during the first week of life.

METHODS

Five arteries and three veins were evaluated respectively in 120 (74 premature) newborns and in 100 (70 preterm) infants. In a quarter of the latter three recordings at 5-minute intervals were made to assess reproducibility. The relation between flow measurements and gestational age was assessed by linear regression, means by analysis of variance (or Kruskall-Wallis test) and paired samples by Student's t test.

RESULTS

There was a significant increase of arterial velocities with increasing gestational age and birth weight, but not for venous velocities. Significant higher values were found in the internal carotid artery followed by the medium cerebral artery. The venous velocities were highly reproducible and the main patterns observed were bandlike and sinusoid type.

CONCLUSION

The knowledge of normal cerebrovascular physiology is essential to understand the pathogenesis of neonatal brain damage and can help pediatricians in an accurate interpretation of the flow profile in neurological pathology.

Cerebral blood flow velocity and pulsation in neonatal respiratory distress syndrome and periventricular hemorrhage

The present study addressed the hypotheses that cerebral ischemia and/or excessive cerebral blood pulsation contribute to periventricular hemorrhage in preterm newborns with respiratory distress and that the pulse width is a valuable tool to estimate the contribution of cerebral blood pulsation. These hypotheses were tested by following preterm newborns at risk for respiratory distress and periventricular hemorrhage. We monitored for cerebral blood flow velocity (CBFV), cerebral pulse width, and cerebral pulsatility index; for patent ductus arteriosus, capillary Pco2, heart rate (HR) and behavior; and for the occurrence of respiratory distress and periventricular hemorrhage (PVH). The data obtained were analyzed with linear regression with the mode of respiration (spontaneous or supported) and postnatal age as additional covariates. We observed that (a) respiratory distress, either uncomplicated or complicated by PVH, correlates with a low CBFV and a high cerebral pulsatility index; (b) PVH also correlates with a high cerebral pulse width; (c) the increased pulse width precedes the onset of the hemorrhage; and (d) these CBF alterations can be partly attributed to ductal shunting and are ameliorated by mechanical ventilation.

Neurological assessment of the preterm infant

Coinciding with improved overall management of the very preterm infant, more techniques have become available to assess the neurological well-being of these high-risk infants. An overview is given of the different techniques which are now used in many neonatal intensive care units, and their value in predicting neurodevelopmental outcome is discussed. Attention is mainly focused on cranial ultrasound, electroencephalography and the different evoked potential modalities.

Asymmetry of the cerebral blood flow: an ultrasound Doppler study in preterm newborns

The purpose of this study was to investigate whether the preference of periventricular hemorrhage (PVH) for the left hemisphere is due to asymmetry of cerebral blood flow (CBF) and, if so, whether this asymmetry is due to patent ductus arteriosus (PDA). Thirty-three preterm newborns at risk for PVH were followed during their first 5 days after birth. Internal carotid CBF velocity (CBFV) and the flow direction in the common pulmonary artery, both determined by ultrasound Doppler, served as measures of CBF and PDA, respectively. The difference between right and left CBFV was analyzed statistically, with outcome, PDA, capillary PCO2, behavior, heart rate, and the average of right and left CBFV as covariates. Infants who developed PVH (n = 7) exhibited CBFV asymmetry to the disadvantage of the left side. This finding was partially attributable to PDA. Without PVH there was no significant CBFV asymmetry. Because all hemorrhages were bilateral, a relationship with the side of the hemorrhage could not be explored. In conclusion, asymmetry of CBFV is not normal, but is associated with PVH and PDA.