MRI assessment of myelination patterns in high-risk infants

Cranial MRI beyond the Neonatal Period and Neurodevelopmental Outcomes in Neonatal Encephalopathy Due to Perinatal Asphyxia: A Systematic Review

BACKGROUND

Magnetic resonance imaging (MRI) including diffusion-weighted imaging within seven days after birth is widely used to obtain prognostic information in neonatal encephalopathy (NE) following perinatal asphyxia. Later MRI could be useful for infants without a neonatal MRI or in the case of clinical concerns during follow-up. Therefore, this review evaluates the association between cranial MRI beyond the neonatal period and neurodevelopmental outcomes following NE.

METHODS

A systematic literature search was performed using PubMed and Embase on cranial MRI between 2 and 24 months after birth and neurodevelopmental outcomes following NE due to perinatal asphyxia. Two independent researchers performed the study selection and risk of bias analysis. Results were separately described for MRI before and after 18 months.

RESULTS

Twelve studies were included (high-quality n = 2, moderate-quality n = 6, low-quality n = 4). All reported on MRI at 2-18 months: seven studies demonstrated a significant association between the pattern and/or severity of injury and overall neurodevelopmental outcomes and three showed a significant association with motor outcome. There were insufficient data on non-motor outcomes and the association between MRI at 18-24 months and neurodevelopmental outcomes.

CONCLUSIONS

Cranial MRI performed between 2 and 18 months after birth is associated with neurodevelopmental outcomes in NE following perinatal asphyxia. However, more data on the association with non-motor outcomes are needed.

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

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

Dysfunction of the attentional brain network in children with Developmental Coordination Disorder: a fMRI study

Children with Developmental Coordination Disorder (DCD) present impaired motor skills, frequently associated with impaired attentional and executive functions. The objective of this study was to assess the impact of DCD on effective connectivity applied to a putative model of inhibition. fMRI was performed in 9 children with DCD and 10 control children (8-13 years old) performing a go-nogo task. As previously reported, children with DCD obtained a similar score for correct inhibitions as controls, but responses were slower and more variable than in controls. Compared to controls, Structural Equation Modeling indicated that: (1) path coefficients from both middle frontal cortex (MFC) and anterior cingulate cortex (ACC) to inferior parietal cortex (IPC) increased in children with DCD particularly in the left hemisphere; (2) path coefficients between striatum and parietal cortex decreased in children with DCD in the right hemisphere. Results suggest that DCD could be characterized by abnormal brain hemispheric specialization during development. Furthermore, connectivity in the MFC-ACC-IPC network could indicate that children with DCD are less able than healthy children to easily and/or promptly switch between go and nogo motor responses. However, children with DCD seem to compensate for this poor efficiency by more actively engaging the ACC to prevent commissions allowing maintenance of a good level of inhibition.

Near-infrared frequency-domain optical spectroscopy and magnetic resonance imaging: a combined approach to studying cerebral maturation in neonatal rabbits

The neonatal rabbit brain shows prolonged postnatal development both structurally and physiologically. We use noninvasive near-IR frequency-domain optical spectroscopy (NIRS) and magnetic resonance imaging (MRI) to follow early developmental changes in cerebral oxygenation and anatomy, respectively. Four groups of animals are measured: NIRS in normals, MRI in normals, and both NIRS and MRI with hypoxia-ischemia (HI) (diffusion MRI staging). NIRS and/or MRI are performed from P3 (postnatal day=P) up to P76. NIRS is performed on awake animals with a frequency-domain tissue photometer. Absolute values of oxyhemoglobin concentration ([HbO2]), deoxyhemoglobin concentration ([HbR]), total hemoglobin concentration (HbT), and hemoglobin saturation (StO2) are calculated. The brains of all animals appeared to be maturing as shown in the diffusion tensor MRI. Mean optical coefficients (reduced scattering) remained unchanged in all animals throughout. StO2 increased in all animals (40% at P9 to 65% at P43) and there are no differences between normal, HI controls, and HI brains. The measured increase in StO2 is in agreement with the reported increase in blood flow during the first 2 months of life in rabbits. HbT, which reflects blood volume, peaked at postnatal day P17, as expected since the capillary density increases up to P17 when the microvasculature matures.

[Early cerebral MRI in preterm infants: correlations with EEG and outcome]

AIM OF THE STUDY

Assess the potential benefits of performing an early cerebral MRI to evaluate the gravity of cerebral lesions among premature neonates at risk of neurologic sequels and establish correlations between EEG findings, abnormal neuroimaging findings and neurodevelopment.

METHODS

A MRI was performed in 34 premature newborn babies with abnormal neurological clinical signs, and/or with two abnormal EEG and/or with two abnormal cerebral ultrasound scans. The mean age and the adjusted age of our population were 5 weeks (range 1-11 weeks) and 35 weeks of adjusted age (range 29-40 weeks) respectively. The neuroimaging findings were correlated to the results of three EEGs (recorded before 15 days old, between 15 days and one month old, and after the first month of life) and to neurodevelopment.

RESULTS

Two statically significant correlations were found between: 1) the severity of brain injuries observed in MRI and the results of the latest EEG (sensitivity 100%, specificity 60%), 2) the severity of brain injuries observed in MRI and abnormal neurodevelopment (sensitivity 75%, specificity 80%). There was no correlation between the abnormal development and the results of EEG recordings.

CONCLUSION

Early cerebral MRI is justified in a selected premature population. It is useful for the diagnosis, the evaluation of the severity of brain injury and for the management of these children. The correlation with EEGs traces allows the detection of the majority of prematures babies that will develop sequels.

Advanced magnetic resonance imaging techniques in perinatal brain injury

Despite marked improvements in perinatal practice, perinatal brain injury remains one of the most common complications causing chronic handicapping conditions. Experimental advances have elucidated many of the cellular and vascular mechanisms of perinatal brain damage showing a correlation between the nature of the injury and the maturation of the brain. New diagnostic tools, such as quantitative three-dimensional magnetic resonance (MR) imaging, diffusion-weighted MR imaging and proton MR spectroscopy, are presented in this review article that allow to assess brain development, detect early brain injury and monitor effects of perinatal brain injury on subsequent brain development and brain plasticity. These techniques will guide future therapeutic interventions aimed at minimizing irreversible perinatal brain injury.

Predictive significance of magnetic resonance imaging at 4 months of adjusted age in infants after a perinatal neurologic insult

The aim of this prospective study was to evaluate the predictive significance of magnetic resonance imaging (MRI) performed at 4 months of corrected age in 60 neonates after a perinatal neurologic insult. Follow-up ranged from 2 to 5 years of chronological age. MRI examination was normal in 10; isolated external hydrocephalus was found in 15 infants. Twenty-three of these infants developed normally. Focal or multifocal lesions were shown in 6 infants, of whom 2 developed normally. Diffuse brain involvement was present in 29 cases as atrophy (n = 18), leukomalacia (n = 5), basal ganglia lesions (n = 3), and delayed myelination (n = 3). All but 4 infants showed neurologic impairment. MRI performed at 4 months of adjusted age is of prognostic significance in neonates who suffer a moderate or mild neurologic insult.

The effect of intracranial pressure on myelination and the relationship with neurodevelopment in infantile hydrocephalus

The effect of raised intracranial pressure (ICP), due to infantile hydrocephalus, on the process of myelination has been suggested in the literature. In this study 19 hydrocephalic infants were followed-up with anterior fontanelle pressure (AFP) measurement (assessment of ICP), MRI (assessment of the myelination process and the CSF volume), and neurodevelopmental testing (NDT). There was a high correlation (r = 0.80) between the myelination and NDT scores. The size of the CSF volume showed a poor correlation with the mean AFP, the degree of myelination and the NDT scores. There was, however, a significant correlation between the mean AFP and the degree of myelination (r = 0.67) and also between the mean AFP and the NDT scores (r = 0.70). Longer-term follow-up (mean = 27 months) showed a significant correlation between the early progress of myelination and later developmental level (r = 0.78). Most of the children with a severely delayed myelination, preoperatively, showed a recovery of myelination following CSF drainage. It was concluded that: (1) raised ICP is related to developmental outcome, through the process of myelination; (2) the delay in myelination can be (partially) reversible; and (3) CSF volume is of minor importance regarding neurodevelopment.

Prediction of outcome at school entry in neonatal intensive care unit survivors, with use of clinical and electrophysiologic techniques

OBJECTIVE

To determine the predictive value of multimodality evoked potentials as well as the neonatal neurobehavioral assessment in neonatal intensive care unit survivors at school entry.

STUDY DESIGN

In this prospective study, healthy (n = 24) and high-risk newborn infants (n = 78) were assessed in the newborn period with auditory brain-stem responses (ABRs) and somatosensory evoked potentials (SEPs), as well as the Einstein Neonatal Neurobehavioral Assessment Scale (ENNAS). Healthy and high-risk newborn infants were assessed in a blind fashion at 1, 3, and 5 years of age by a psychologist and a pediatric neurologist. Of those healthy (all 24) and high-risk newborn infants (72/78) with a neonatal ABR, SEP, or both, 62.5% were assessed at 5 years of age with the Wechsler Preschool and Primary Scale of intelligence, the Beery-Buktenica Test of Visual-Motor Integration, the Griffiths Locomotor Subscale, and neurologic examination. Chi-square analyses were carried out on neonatal and outcome measures, and sensitivity, specificity, and predictive values for each of the neonatal tests were ascertained.

RESULTS

The ENNAS and the ABR had good negative predictive value for cognitive (85.7% to 93.3%), locomotor (83.3%), and visual-motor (91.4% to 100%) performance. The ABR had good specificity, whereas the ENNAS was more sensitive. The SEP was an excellent prognostic tool, with high sensitivity (100%) and specificity (80% to 81.3%) for motor as well as cognitive domains. All infants with normal SEPs had favorable outcomes, whereas those with absent potentials did poorly. The SEP abnormalities were associated with findings on neurologic examination in all cases.

CONCLUSIONS

Normal neonatal evoked potentials and ENNAS are associated with favorable outcomes. The SEP most accurately predicts neurodevelopmental status at school entry.

Magnetic resonance imaging in perinatal asphyxia

Images

Assessment of local cerebral blood flow in neonates with N-isopropyl-P-[123I]iodoamphetamine and single photon emission computed tomography

Local cerebral blood flow was measured in 10 high-risk infants with neonatal episodic neurological events at 41-44 post-conceptional weeks using N-isopropyl-p-[123I]iodoamphetamine (IMP) and single photon emission computed tomography (SPECT). In 5 of the 7 infants with normal neurological outcome, prominent cerebral perfusion was found in the basal ganglia, brainstem, cerebellum, parietal white matter, and sensory motor cortex. The frontal lobes showed poor relative perfusion. In 3 infants with severe neurological deficits, SPECT demonstrated severe hypoperfusion of all parts of the brain except the basal ganglia, brainstem and sensorimotor cortex. However, MRI revealed non-specific changes, such as poor myelination and ventricular dilatation. SPECT, when performed in the first weeks of life, can be useful and may be more sensitive than MRI in predicting the occurrence of major neurological handicaps. However, because of the relatively invasive character and high cost of SPECT, SPECT should not necessarily be performed in all high-risk neonates.

Corpus callosum in developmentally retarded infants

The development of the corpus callosum was examined by magnetic resonance imaging in developmentally retarded infants ranging in age from 1-13 months. Results were compared with those of normal infants. Eighteen magnetic resonance imaging studies were performed on 18 developmentally retarded infants. Fifty-four magnetic resonance imaging studies were performed on 38 normally developed infants. The thickness of the corpus callosum was measured at a point one-third of the length of the entire corpus callosum from the most anterior aspect of the genu. The development of the corpus callosum was related to aging in both groups. There was significant difference in the thickening of the corpus callosum between normal and developmentally retarded infants.

Corpus callosum development in preterm and term infants

The development of the corpus callosum was documented by magnetic resonance imaging in low-risk preterm infants and results were compared with those of term infants. Thirty-three magnetic resonance imaging studies were performed on 21 preterm infants whose corrected ages were 1-13 months. Twenty-one magnetic resonance imaging studies were performed on 17 term infants. All infants exhibited normal development. The thickness of the corpus callosum was measured at a point one-third of the length of the entire corpus callosum from the most anterior aspect of the genu. The thickening of the corpus callosum was related to age in the preterm group. The development of the corpus callosum in preterm infants was suggested to be the same as that of term infants matched by conceptional age.