Serial Neuroimaging of Brain Injury and Brain Growth in the NICU in the Very Preterm Infant

Neurological adverse outcomes of very preterm birth can range from severe, including cerebral palsy, hearing and vision impairments, language disorders and learning disability, to less severe, such as developmental coordination disorders, fine motor control deficits, and mild cognitive impairments. While there are numerous factors, such as birth weight, gestational age, interventricular hemorrhage, and bronchopulmonary dysplasia, that have been shown to be associated with neurobehavioral impairments, the underlying neural mechanisms leading to these impairments are not yet understood. In the unit where this study is conducted, the standard of care is that babies born extremely preterm, or those born very preterm with additional clinical risk generally undergo a term equivalent age magnetic resonance imaging (MRI). However, given the limited understanding of the etiology of many neuronal disorders particularly in preterm born infants, findings on these term MRIs can be presented to families with many unanswered questions in terms of causation and implication for future development.

The few previous studies undertaken to better understand the etiology of brain injuries have used longitudinal serial imaging of preterm infants' brain during their NICU stays to look at trajectories of brain structural growth and the development of brain injury. One study found profuse increases in cortical grey matter growth rates that were accompanied by decreases in relative unmyelinated white matter growth rates. Another study found that the most common term equivalent finding associated with preterm birth was diffuse white matter abnormality, although causation and factors associated with these growth alterations and injuries are yet to be fully understood. The main limitation of both serial imaging studies is the limited number of scans per patient that were performed. The average number of scans per infant for both studies was around 2, which often corresponded to one at birth and one at term equivalent age (prior to NICU discharge), and did not provide sufficient information to comprehensively characterize the pattern of brain growth and development in this population.

One study investigated the structure-function relationship in preterm infants between MRI and clinical measures of motor, neurological and neurobehavioral capacity. Researchers found strong associations between the General Movements Assessment, Hammersmith Neonatal Neurological Examination, NICU Neonatal Neurobehavioral Scale, Premie-Neuro, and Test of Infant Motor Performance that correlated with the early and term-equivalent MRI. Based on a review of 88 articles that evaluated sensory-based interventions integrated in the care of very preterm infants in the NICU, nurturing interventions were noted to correlate with improved infant development and lower rates of maternal stress.

One such evidence-based multisensory program for hospitalized preterm infants is the SENSE II Program: The Supporting and Enhancing NICU Sensory Experiences 2nd Edition (SENSE II). The SENSE II program was developed to engage parents in consistently providing positive, developmentally appropriate sensory exposures to high-risk infants in the NICU every day of hospitalization. The SENSE II program includes specific doses and targeted timing (based on postmenstrual age) of evidence-based interventions of auditory, tactile, vestibular, kinesthetic, olfactory, and visual exposures to be conducted daily through hospitalization for preterm infants. The program also comprises a curated collection of parent educational materials aimed at guiding parents on infant sensory development, parenting in the NICU, and coaches families how to tailor nurturing interventions contingently upon infant responses and tolerance.

While these previous studies using serial imaging techniques provide a great foundation to understand individual brain development in the preterm infant, the lack of systematic regular serial MRI scans over the course of the entire NICU stay leaves room for future investigations to define the timing and factors associated with brain injury, as well as the pattern of brain growth in the preterm infant over the course of NICU the hospitalization. Newer imaging analysis methods are now available that allow regional brain volumes to be studied, which was not previously possible. Also, transporting small infants out of the NICU to the MRI scanner was a major barrier to carrying out serial studies without risk. This can now be overcome by new in-NICU MRI scanning technologies. As such, the Aspect Embrace Neonatal MRI System is an FDA-approved device which uses innovative technology to safely and effectively image infants within the NICU care environment. This type of in-NICU MRI scanner is available at this study site, specifically designed for infant neuroimaging and featuring a built-in incubator, self-contained magnet, and continuous video monitoring.