Consultant Neonatologist, Hospital de Santa Maria
Andre M. Graca is a neonatologist at Hospital de Santa Maria in Lisbon - Portugal. He completed his PhD on cerebral ultrasound of the neonatal brain. He is an assistant professor of Pediatrics at Faculdade de Medicina de Lisboa and a member of the directory board of the Portuguese Society of Pediatrics.
Very preterm infants are at particular risk of neurodevelopmental impairments. This risk can be anticipated when major lesions are seen on cerebral ultrasound (cUS). However, most preterm infants do not have such lesions yet many have a relatively poor outcome that can be related to diffuse white matter (WM) injury, which is very difficult to evaluate on both cUS and conventional MR. Some authors have related diffuse WM injury to smaller brain size and enlarged CSF spaces at term-equivalent age (TEA). Our study aims to describe a tri-dimensional cUS model for estimating cranial and brain volumes in a cohort of very preterm infants at TEA and to compare those volumes with a control group of term-born infants. Methods We scanned a cohort of very preterm infants at TEA and term-born controls. Infants with major cerebral lesions were excluded. Measurements of intracranial diameters (bi-parietal, longitudinal, height), brain structures, ventricles and extracerebral space (ECS) were made. A mathematical ellipsoid model was built to estimate from the linear cUS measurements cranial and brain volumes. Appropriate statistical methods were used for comparisons; p-value<0.05 was considered significant. Results We assessed 128 infants (72 preterms and 56 controls). The preterms’ head was longer (11.5 vs. 10.5 cm, p<0.001), narrower (7.8 vs. 8.4 cm, p<0.001) and taller (8.9 vs. 8.6 cm, p<0.01) than the controls. Estimated intracranial volume was not statistically different between the groups (411 vs. 399 cm3, NS), but preterms had larger estimated ECS volume (70 vs. 22 cm3, p<0.001), lateral ventricular coronal areas (33 vs. 12mm2, p<0.001) and thalamo-occipital distances (20 vs. 16 mm, p<0.001), but smaller estimated cerebral volume (340 vs. 377 cm3, p<0.001). Smaller brain volumes were associated with being of lower gestational age and being small-for-gestational age. Conclusions We have developed a model using cranial ultrasound for estimating cranial and brain volumes. Using this model and comparing to term-born controls our data suggest that, even in the absence of major cerebral lesions, the average extrauterine cerebral growth of very preterm infants is compromised. Our model can help identifying those preterm infants with smaller brains that can be at higher risk of neurodevelopmental issues, using equipment that is widely available.