Purpose or Case Report: Before the germinal matrix (GM) begins to recede at approximately 26 weeks gestational age (GA), it extends along the floor of the lateral ventricles far posterior to the thalamocaudate grooves. As extremely premature infants (EPIs) as young as 23 weeks GA survive with current advances in neonatology support, germinal matrix hemorrhage (GMH) can occur along these sites from which the GM has not yet involuted and should be recognized. Further, such Grade I posterior GMH may be mistakenly diagnosed as an intraparenchymal grade IV event, particularly on coronal US or other axial images, with parasagittal images demonstrating the correct diagnosis. The aim of this study is to document and describe this phenomenon, differentiate it from traditional GMH findings, and assess its prevalence in this population.
Methods & Materials: The study was IRB-approved. All consecutive neonates admitted from 2013-2018 less than 27 weeks GA at birth with a GMH and initial studies available were included. All head ultrasounds were reviewed by consensus of two pediatric radiologists and one pediatric neuroradiologist. Original final interpretations from the medical record were recorded. A consecutive group of 100 older premature infants (OPI) of 31 weeks gestational age served as controls. Demographic data were extracted from the medical records.
Results: 106 EPI infants had GMH and were included in the study, with a mean GA of 25 weeks [23.1-26.6]. In nearly half of EPIs (45/106, 42.5%), GMH involved the posterior aspect of the germinal matrix. In 13 additional cases (12.3%), the patient had a large bleed and the site of origin from the GM could not be determined. In 20/45 (44.4%) patients with posterior GMH, the grade of GMH was misclassified. All GMH in the OPI control group occurred in the anterior thalamocaudate grooves.
Conclusions: Unlike the older premature infants that form the basis of our traditional head ultrasound findings, the EPI that are now routinely surviving have a more fetal pattern of GM distribution, extending posteriorly along the floor of the ventricles. We describe the routine occurrence of subependymal hemorrhage in these locations in EPI, which should be recognized and should not be confused with a Grade IV event, which is of great importance when making life support decisions. Knowledge of the typical involution patterns of the germinal matrix and the imaging appearance of posterior GMH is essential to ensure proper diagnosis.