Neonatal Brain MRI: Periventricular Germinal Matrix Mimicking Hypoxic-ischemic White Matter Injuries.

Purpose: As pregnancy progresses, the germinal matrix volume decreases. Residual periventricular germinal matrix may be mistaken for hypoxic-ischemic white matter injury. This study aims to determine the prevalence and imaging characteristics of these findings.

Methods: This retrospective study analyzed brain MRIs of newborns from 2012-2023, performed within the first week of life. MRIs were done for suspected hypoxic-ischemic injuries, post-natal neurological symptoms, and evaluation of prenatally diagnosed structural anomalies. Image analysis targeted the remnants of the frontal periventricular germinal matrix, assessing its imaging characteristics, including diffusion, T1, and T2 signal characteristics, and laterality. Frontal migrating cell bands were also assessed.

Results: Seventy newborns were included (mean gestational age at delivery was 38.3 ± 2.1 weeks, mean scan age 5.1 ± 1.9 days). Frontal periventricular gray matter was detected in 39 newborns (90% bilateral) on T2-weighted images, negatively correlated with gestational age (r = -0.31, p = 0.013); none showed decreased ADC or shortened T1 signal compared with the basal ganglia. Frontal periventricular bands were found in 37 newborns (97.3% bilateral), strongly correlating with periventricular gray matter (r = 0.71, p < 0.001). No correlation was found between clinical hypoxic-ischemic injuries and these features.

Conclusion: The presence of frontal periventricular gray matter observed in early neonatal MRIs, without decreased ADC values or shortened T1 signal, is developmental, reflecting a late maturation phase. Careful interpretation of MRI characteristics, including diffusion, T1, and T2 signal intensities, is necessary before attributing these findings to hypoxic-ischemic white matter injury.