Introduction

Preterm birth is increasing and the rate of neurodevelopmental impairment in survivors remains high.1 2 Clinicians routinely need to provide parents and carers with prognostic information for their vulnerable infants, and most do this with the aid of some form of neuroimaging. Cranial ultrasound is cheap, safe and can be performed at the cot side by the attending neonatologist or paediatric radiologist. MRI is less widely available, more expensive and requires transportation to an imaging unit, but provides anatomically richer data. However, it is not clear how comparable the images are, nor can we be sure about the predictions made by either imaging method.

In September's issue of the journal, the analysis by Horsch et al3 of contemporaneously acquired cranial ultrasound and MR images at term corrected age in a cohort of infants born at <27 weeks gestation found close concordance between the two imaging methods, with only marginal, if any, additional information with MRI. However imaging findings were normal or showed mild MRI changes in >80% of infants and only 3/72 (4%) showed severe abnormality, reducing confidence in any comparison. In fact the prognostic power of each imaging modality was undefined as neurodevelopmental outcome was not reported.

To provide practicing clinicians with pragmatic estimates of the confidence limits appropriate when interpreting cranial ultrasound and MRI, we searched the literature for studies that allowed reasonable quantitative estimates of prognostic value, ensuring that repeated publications of individuals were excluded by contacting researchers directly where necessary. From the surprisingly small number of suitable studies we selected and aligned information as objectively as possible with familiar imaging and neurodevelopmental outcome classifications, with outcomes, usually determined at about 2 years of age, categorised broadly as abnormal neuromotor development (estimated as the presence of cerebral palsy or a low Bayley Psychomotor Developmental Index …