Best Practice Guideline articleBrain imaging findings in very preterm infants throughout the neonatal period: Part I. Incidences and evolution of lesions, comparison between ultrasound and MRI
Introduction
Very preterm infants have a high risk of brain injury, including intraventricular haemorrhage (IVH), periventricular haemorrhagic infarction (PVHI), cystic periventricular leukomalacia (PVL), and more diffuse white matter (WM) injury. These abnormalities are associated with suboptimal or abnormal neurodevelopmental outcome. Early neuro-imaging studies in preterm infants were mainly directed at the detection of IVH, PVHI, and cystic PVL, but the incidence of these abnormalities has decreased considerably. Recent studies have focused more on the detection and implications of more diffuse or subtle WM changes. [1], [2], [3], [4]
Sequential cranial ultrasound (cUS) is the most readily available technique for imaging the neonatal brain. It is reliable for detecting frequently occurring abnormalities in preterm infants and for following brain growth and development. [5] However, magnetic resonance imaging (MRI) is generally considered to be more sensitive for detecting diffuse and subtle abnormalities, assessing the exact site and extent of abnormalities, and assessing cerebral maturation, especially as it shows more detail than cUS and depicts myelination. [1], [2], [3], [4], [5]
Several studies have described the prevalence and clinical relevance of various cerebral abnormalities in very preterm infants, and have increased the knowledge on associations between abnormalities and neurodevelopmental outcome. [1], [2], [3], [6], [7], [8] However, cUS and MR imaging techniques and protocols have improved considerably over recent years and the distribution of WM injury in preterm infants has changed. [1], [3], [4] The primary aim of our study was, therefore, to describe the incidences of brain imaging findings in a cohort of very preterm infants admitted to a tertiary neonatal referral center, assessed with modern neuro-imaging techniques. Secondary aims were to assess the evolution of lesions on cUS between admission and term equivalent age (TEA), to compare the findings on contemporaneous cUS and MRI performed around TEA, and to assess whether abnormalities were missed with either technique.
Section snippets
Patients
Very preterm infants born at a gestational age (GA) of < 32 weeks who were admitted to the tertiary neonatal intensive care unit of the Leiden University Medical Center between May 2006 and October 2007, were eligible for a neuro-imaging study, including sequential, standardized cUS examinations throughout the neonatal period and one MRI examination around TEA. Ethical approval for the study was given by the Medical Ethics Committee and informed consent from the parents was obtained for each
Patients
During the study-period, 182 very preterm infants were admitted to our neonatal unit and eligible for this study. Informed parental consent was obtained for 133 infants (80 male, 53 female). Reasons for not obtaining parental consent included transfer to another hospital within a very short period of birth, death within several hours of birth, rejection of participation by the parents, and practical problems such as language barrier and travel distance between hospital and parental home.
The
Discussion
To our knowledge, this is the first study describing the incidence and evolution of brain imaging findings as seen on sequential cUS throughout the neonatal period and on MRI around or shortly after TEA in a large cohort of very preterm infants admitted to a tertiary neonatal referral center.
The most frequent findings during admission were PVE and IVH. Our high incidence of PVE (80%) is in agreement with recent studies [1], [8], [17], reporting an incidence of 48–100% in preterm infants,
Key guidelines
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This study does not support routine MRI in all very preterm infants
Research directions
Further study is needed to assess:
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The significance of certain cerebral abnormalities for short- and long-term neurodevelopmental outcome of very preterm infants
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The clinical significance of the lower sensitivity of cUS for some frequent findings
Financial support
This project was supported by a grant from ZonMW, the Netherlands Organisation for Health Research and Development (grant number 920-03-388).
Acknowledgements
We are grateful to the staff of the neonatal unit, the paediatric ambulatory unit and the MRI department of the Leiden University Medical Center and to B. van Kooij, University Medical Center Utrecht, for their helpful contributions to this project. We thank W. Teeuwisse for his technical support.
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