Supplementary Material for: Reduced Cerebellar Size at Term-Equivalent Age Is Related to a 17% Lower Mental Developmental Index in Very Preterm Infants without Brain Injury

Introduction: Cerebellar injury is increasingly recognized as a relevant complication of premature birth. However, the prevalence of reduced cerebellar growth and its consequences for neurodevelopmental outcome in preterm infants without overt brain injury remain to be defined in detail. The aim of this study was to assess the transcerebellar diameter (TCD) at term-equivalent age (TEA) in very preterm infants without brain injury and to evaluate whether TCD is related to neurodevelopmental outcome in this population. Methods: Very preterm infants underwent magnetic resonance imaging at TEA. Infants with any grade of supra- or infratentorial brain injury were excluded. TCD was measured and categorized using existing cut-off values as normal TCD and mild or severe TCD reduction. Psychomotor Developmental index (PDI) and Mental Developmental index (MDI) were assessed using Bayley Scales of Infant Development II and III at a corrected age of 2 years. Results: A total of 166 infants with a mean gestational age of 29.9 ± 1.8 weeks and a mean birth weight of 1,317 ± 393 g were included. Mean TCD of girls was significantly lower compared to the mean TCD of boys (p = 0.004). TCD reduction was present in 8 infants (4.8%). Infants with a mild TCD reduction achieved lower mean MDI than infants with normal TCD (p = 0.021). Discussion: We found that reduced TCD was associated with a 17% lower mean MDI at a corrected age of 2 years. Thus, TCD at TEA may be used as an imaging marker for adverse cognitive outcome in the apparently low-risk group of preterm infants without brain injury.