New MR Imaging Assessment Tool to Define Brain Abnormalities in Very Preterm Infants at Term

Abstract

Background and Purpose WM injury is the dominant form of injury in preterm infants. However, other cerebral structures, including deep GM and cerebellum, can also be affected by injury and/or impaired growth. Current MRI injury assessment scales are subjective and challenging to apply. Thus, we developed a new assessment tool and applied it to MRI studies obtained from VPT infants at term-equivalent postmenstrual age to describe the spectrum of brain abnormalities. Methods MRI scans from 97 VPT infants (<30 weeks gestation) and 22 healthy term-born infants were evaluated retrospectively. The severity of brain injury (defined by signal abnormalities) and impaired brain growth (defined with biometrics) was scored in the WM, cortical GM, deep GM and cerebellum. Perinatal variables for clinical risks were collected from medical records. Results Of 97 VPT infants, brain injury was observed in WM (n=23), deep GM (n=5) and cerebellum (n=23). Combining measures of injury and impaired growth showed moderate-severe abnormalities most commonly in WM (n=38) and cerebellum (n=32), but still notable in cortical GM (n=16) and deep GM (n=11). None of 22 term-born infants had moderate-severe abnormalities. Multiple clinical risk factors, including prolonged intubation, prolonged parenteral nutrition, postnatal corticosteroid use and postnatal sepsis, were associated with increased global MRI abnormality. Conclusions VPT infants demonstrate a high prevalence of injury and growth impairment in both WM and GM. This MRI scoring system provides a more comprehensive and objective classification of the nature and extent of abnormalities in VPT infants than existing measures.

Validation of an MRI Brain Injury and Growth Scoring System in Very Preterm Infants Scanned at 29- to 35-Week Postmenstrual Age

“…Cerebral WM abnormality was rated on 6 components, with a maximum total score of 15: cystic degeneration, focal signal abnormalities, delayed myelination, thinning of the corpus callosum, dilated lateral ventricles, and reduction of WM volume. 22 Myelination of the corpus callosum and posterior limb of the internal capsule was expected by 36-week PMA, so all infants were given a score of 2 for this item on early MR imaging. The CGM was rated on 3 components with a maximum total score of 8: signal abnormality, delayed gyration, and dilated extracerebral CSF space.…”

“…Cerebellar and DGM abnormalities were rated on signal abnormality and volume reduction with maximum total scores of 6 for each. 22 A total of WM, CGM, DGM, and cerebellar scores yielded a global brain abnormality score (0 -35). 22 Each of the WM, CGM, DGM, cerebellar, and global scores could be further categorized into no, mild, moderate, or severe brain abnormality categories.…”

“…A standardized MR imaging scoring system according to Kidokoro et al 22 was used to score all MRIs. An independent neurologist with training in radiology and experienced in neonatal MR imaging scoring (S.F.)…”

“…3,21 Term-equivalent age MR imaging scoring systems have been further developed to include evaluation of deep gray matter (DGM) structures and the cerebellum. 22 At TEA, global brain abnormality scores were significantly associated with motor outcomes at 2-years CA 23 ; and cognitive outcomes, at 7 years. 24,25 Deep gray matter scores were significantly associated with poorer attention and processing speeds, memory, and learning.…”

“…The aim of this study was to validate an MR imaging scoring system previously developed for very preterm infants at TEA in a cohort of infants born Ͻ31-weeks gestational age with MR imaging between 29 and 35 weeks' postmenstrual age (PMA). 22 The study aimed to establish predictive validity for motor and cognitive outcomes at 12-months CA. Secondary aims were to examine inter-and intrarater reproducibility and to examine relationships between global brain abnormality categories and known perinatal risk factors.…”