Introduction
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Magnetic resonance imaging (MRI) provides detailed structural and functional information about the newborn brain. It is an important adjunct to cranial ultrasound and in specific groups of infants, has been shown to provide important prognostic information that can assist in directing care1. The ideal timing of the MRI examination and the optimal MR sequences will differ depending on the clinical scenario and question. Every case should thus be discussed with the attending Neonatologist, Neonatal Neurology and/or Neuroradiology.
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Although MRI is the preferred second line investigation of the newborn central nervous system, there are specific situations where computed tomography (CT) may be the investigation of choice. This is for the evaluation of an acute cerebral haemorrhage (subdural, subarachnoid, posterior fossa) especially if there is midline shift on cranial ultrasound and neurosurgical intervention may be necessary.
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Indications for requesting an MRI examination:
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a) Neonatal encephalopathy
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Term infants (Stage II and III)
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Diagnosis and prognosis: The patterns of injury on conventional T1- and T2- weighted images, and diffusion weighted imaging (DWI) provide information about diagnosis (e.g. global hypoxia-ischaemia, focal arterial infarction), timing of injury and prognosis. In addition, a high lactate and low N-acetyl aspartate peak on proton MRS is prognostic of poor neuromotor outcome. The sensitivity and specificity of MRI for prognostication in hypoxic ischaemic encephalopathy (HIE) has been based on studies prior to hypothermia treatment and should be taken into consideration.
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Timing of scan: The recommended time is Day 3-5.
Additional MR sequences: In some circumstances, it may be beneficial to have additional MR sequences in addition to the standard protocol for HIE (e.g. MRA if there is a suspicion of an arterial infarction, specific MRS for non-ketotic hyperglycinaemia). It is thus imperative that every case be discussed with either Neonatal Neurology or Neuroradiology when the request is made.
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Preterm infants
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Diagnosis and prognosis: The patterns of injury are different depending on the gestation of infant.
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Timing of scan: The best time for prognosis is an MRI at term-corrected age. However, an earlier MR scan may be required depending on the clinical situation.
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b) Congenital malformations of the central nervous system
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Many of these cases would have been picked up on antenatal ultrasound and/or MRI. A postnatal MRI should be performed soon after birth when the infant is clinically stable.
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c) Incidental abnormal findings on cranial ultrasound
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An MRI should be considered if it is unclear from ultrasound what the nature of the lesion is. The MRI should be performed when the infant is clinically stable.
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d) Extremely preterm infants
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White matter abnormalities in the extremely preterm infant predict cerebral palsy, neurosensory impairment and severe cognitive delay2 and these lesions are more easily seen on MRI compared to cranial ultrasound. However, there is insufficient evidence to advocate a routine cerebral MRI for every extremely preterm infant. Preterm infants with an established brain lesion (e.g. severe intraventricular haemorrhage, periventricular leukomalacia) should be considered for an MRI at term corrected age, especially if the clinical findings at term are inconsistent with what we would have expected from the ultrasound findings.
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e) Severe hyperbilirubinaemia
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An MRI should be considered for infants with bilirubin encephalopathy. This should be performed when the infant is clinically stable.
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f) Postnatal cardiac arrest
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If there has been a significant period of hypoxia and subsequent encephalopathy, an MRI should be considered. The best timing would be Day 3-5 after the event.
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References
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Refer to a separate page to view the Evidence table for this CPG:
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Evidence table: Magnetic Resonance Imaging (MRI) in the Newborn: Guidelines for use.
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Published: 22 August 2008
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Royal Women's Hospital Clinical Practice Guidelines (CPGs) are intended to provide guidance to health care professionals, based on a thorough evaluation of research evidence, on the practical assessment and management of specific clinical issues or situations. The guidelines allow some flexibility on the part of the health care professional based on the needs of the specific patient for whom they are caring.
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