Prognostic value of gradient echo T2* sequences for brain MR imaging in preterm infants

Neurodevelopmental consequences of preterm punctate white matter lesions: a systematic review

OBJECTIVES

To evaluate punctate white matter lesion (PWML) influence in preterm infants on the long-term neurodevelopmental outcome (NDO).

METHODS

PubMed and EMBASE were searched from January 1, 2000, to May 31, 2021. Studies were included in which PWML in preterm infants on MRI around term-equivalent age (TEA) and NDO at ≥12 months were reported. Study and patient characteristics and NDO on motor, cognitive, and behavioral domains were extracted. The quality of studies was assessed using the Cochrane-approved Quality in Prognosis Studies tool.

RESULTS

This analysis included nine studies with a total of 1655 patients. Mean incidence of isolated PWML was 22.1%. All studies showed a relationship between PWML and motor delay. Two studies found a significant correlation between cognitive and behavioral outcomes and PWML. Number and PWML location are related to severity and impairment types.

LIMITATIONS

PWML were not always separately described from generalized WMI, only studies with imaging around TEA were included, and studies were heterogenic in design and quality.

CONCLUSIONS

PWML is common in preterm infants and predictive of adverse NDO, in particular on motor outcomes and less on cognitive and behavioral outcomes. The type and severity of impairments are related to the number and location of PMWL.

IMPACT

PWML is common in preterm infants and seems predictive of adverse NDO. DWI and SWI MRI sequences are informative because the different patterns suggest a difference in the underlying pathology. The type and severity of impairments are related to the number and location of PMWL. Our review can inform clinicians and parents about the NDO of preterm infants with a diagnosis of PWML. Prospective neuroimaging case-control cohort studies are recommended.

Combining advanced MRI and EEG techniques better explains long-term motor outcome after very preterm birth

BACKGROUND

Preterm born children are at high risk for adverse motor neurodevelopment. The aim of this study was to establish the relationship between motor outcome and advanced magnetic resonance imaging (MRI) and electroencephalography (EEG) measures.

METHODS

In a prospective cohort study of 64 very preterm born children, the motor outcome was assessed at 9.83 (SD 0.70) years. Volumetric MRI, diffusion tensor imaging (DTI), and EEG were acquired at 10.85 (SD 0.49) years. We investigated associations between motor outcome and brain volumes (white matter, deep gray matter, cerebellum, and ventricles), white matter integrity (fractional anisotropy and mean, axial and radial diffusivity), and brain activity (upper alpha (A2) functional connectivity and relative A2 power). The independence of associations with motor outcome was investigated with a final model. For each technique, the measure with the strongest association was selected to avoid multicollinearity.

RESULTS

Ventricular volume, radial diffusivity, mean diffusivity, relative A2 power, and A2 functional connectivity were significantly correlated to motor outcome. The final model showed that ventricular volume and relative A2 power were independently associated with motor outcome (B = -9.42 × 10^-5, p = 0.027 and B = 28.9, p = 0.007, respectively).

CONCLUSIONS

This study suggests that a lasting interplay exists between brain structure and function that might underlie motor outcome at school age.

IMPACT

This is the first study that investigates the relationships between motor outcome and brain volumes, DTI, and brain function in preterm born children at school age. Ventricular volume and relative upper alpha power on EEG have an independent relation with motor outcome in preterm born children at school age. This suggests that there is a lasting interplay between structure and function that underlies adverse motor outcome.

Should the Gross Motor Function Classification System be used for children who do not have cerebral palsy?

This literature review addressed four questions. (1) In which populations other than cerebral palsy (CP) has the Gross Motor Function Classification System (GMFCS) been applied? (2) In what types of study, and why was it used? (3) How was it modified to facilitate these applications? (4) What justifications and evidence of psychometric adequacy were used to support its application? A search of PubMed, MEDLINE, and Embase databases (January 1997 to April 2017) using the terms: 'GMFCS' OR 'Gross Motor Function Classification System' yielded 2499 articles. 118 met inclusion criteria and reported children/adults with 133 health conditions/clinical descriptions other than CP. Three broad GMFCS applications were observed: as a categorization tool, independent variable, or outcome measure. While the GMFCS is widely used for children with health conditions/clinical description other than CP, researchers rarely provided adequate justification for these uses. We offer recommendations for development/validation of other condition-specific classification systems and discuss the potential need for a generic gross motor function classification system.

WHAT THIS PAPER ADDS

The Gross Motor Function Classification System should not be used outside cerebral palsy or as an outcome measure. The authors provide recommendations for development and validation of condition-specific or generic classification systems.

Cerebral microbleeds in a neonatal rat model

BACKGROUND

In adult humans, cerebral microbleeds play important roles in neurodegenerative diseases but in neonates, the consequences of cerebral microbleeds are unknown. In rats, a single pro-angiogenic stimulus in utero predisposes to cerebral microbleeds after birth at term, a time when late oligodendrocyte progenitors (pre-oligodendrocytes) dominate in the rat brain. We hypothesized that two independent pro-angiogenic stimuli in utero would be associated with a high likelihood of perinatal microbleeds that would be severely damaging to white matter.

METHODS

Pregnant Wistar rats were subjected to intrauterine ischemia (IUI) and low-dose maternal lipopolysaccharide (mLPS) at embryonic day (E) 19. Pups were born vaginally or abdominally at E21-22. Brains were evaluated for angiogenic markers, microhemorrhages, myelination and axonal development. Neurological function was assessed out to 6 weeks.

RESULTS

mRNA (Vegf, Cd31, Mmp2, Mmp9, Timp1, Timp2) and protein (CD31, MMP2, MMP9) for angiogenic markers, in situ proteolytic activity, and collagen IV immunoreactivity were altered, consistent with an angiogenic response. Vaginally delivered pups exposed to prenatal IUI+mLPS had spontaneous cerebral microbleeds, abnormal neurological function, and dysmorphic, hypomyelinated white matter and axonopathy. Pups exposed to the same pro-angiogenic stimuli in utero but delivered abdominally had minimal cerebral microbleeds, preserved myelination and axonal development, and neurological function similar to naïve controls.

CONCLUSIONS

In rats, pro-angiogenic stimuli in utero can predispose to vascular fragility and lead to cerebral microbleeds. The study of microbleeds in the neonatal rat brain at full gestation may give insights into the consequences of microbleeds in human preterm infants during critical periods of white matter development.

Posterior fossa abnormalities in high-risk term infants: comparison of ultrasound and MRI

Objectives

We aimed to assess the characteristics of posterior fossa (PF) abnormalities in a cohort of high-risk term neonates, as well as the diagnostic performance of cranial ultrasound (CUS) with additional mastoid fontanelle (MF) views for the detection of these abnormalities, with magnetic resonance imaging (MRI) being the reference standard.

Methods

In this retrospective study, 113 term neonates with CUS and subsequent MRI were included. Sensitivity, specificity, and predictive values of routine CUS and CUS with MF views were calculated.

Results

Posterior fossa abnormalities were diagnosed on CUS in 46 of 113 infants. MRI confirmed these findings in 43 and showed additional abnormalities in 32 infants. The sensitivity and specificity of anterior fontanelle views for major PF abnormalities as seen on MRI were 16 % and 99 %. Adding MF views increased the sensitivity of US to 82 %. The sensitivity and specificity of MF views for the detection of any (major or minor) PF abnormality were 57 % and 95 %. Especially acute hypoxic-ischemic injury and small subdural and punctate cerebellar haemorrhage remained undetected by CUS.

Conclusions

PF abnormalities are frequent in high-risk term infants. MF-CUS enables early diagnosis of major PF abnormalities. We therefore advocate to perform MF-CUS in high-risk term neonates.

Key Points

• Posterior fossa abnormalities are a frequent finding in high-risk term infants.

• Adding mastoid fontanelle views improves ultrasound detection of clinically relevant abnormalities.

• Hypoxic-ischemic injury and small posterior fossa haemorrhages are better detected with MRI.

• Cranial ultrasound examination should include mastoid fontanelle views in high-risk term neonates.

Different patterns of punctate white matter lesions in serially scanned preterm infants

Background and Purpose

With the increased use of MRI in preterm infants, punctate white matter lesions (PWML) are more often recognized. The aim of this study was to describe the incidence and characteristics of these lesions as well as short-term outcome in a cohort of serially scanned preterm infants, using both conventional imaging, diffusion (DWI) and susceptibility (SWI) weighted imaging.

Materials and Methods

112 preterm infants with 2 MRIs in the neonatal period, with evidence of punctate white matter lesions, were included. Appearance, lesion load, location, and abnormalities on DWI and SWI were scored and outcome data were collected.

Results

Different patterns of punctate white matter lesions did appear: a linear appearance associated with signal loss on SWI, and a cluster appearance associated with restricted diffusion on DWI on the first MRI. Cluster and mixed lesions on the first scan changed in appearance in over 50% on the second scan, whereas linear lesions generally kept their appearance. Lesions were only visible on the early scan in 33%, and were only seen at term equivalent age in 20%. Nine infants developed cerebral palsy, due to additional overt white matter lesions in six.

Conclusion

Two patterns of punctate white matter lesions were identified: one with loss of signal on SWI in a linear appearance, and the other with DWI lesions with restricted diffusion in a cluster appearance. These different patterns are suggestive of a difference in underlying pathophysiology. To reliably classify PWML in the preterm infant in either pattern, an early MRI with DWI and SWI sequences is required.