Quantitative susceptibility map analysis in preterm neonates with germinal matrix-intraventricular hemorrhage

Background: Germinal matrix-intraventricular hemorrhage (GMH-IVH) is a common form of intracranial hemorrhage occurring in preterm neonates that may affect normal brain development. Although the primary lesion is easily identified on MRI by the presence of blood products, its exact extent may not be recognizable with conventional sequences. Quantitative susceptibility mapping (QSM) quantify the spatial distribution of magnetic susceptibility within biological tissues, including blood degradation products. Purpose/Hypothesis: To evaluate magnetic susceptibility of normal-appearing white (WM) and gray matter regions in preterm neonates with and without GMH-IVH. Study Type: Retrospective case-control. Population: A total of 127 preterm neonates studied at term equivalent age: 20 had mild GMH-IVH (average gestational age 28.7±2.1 weeks), 15 had severe GMH-IVH (average gestational age 29.3±1.8 weeks), and 92 had normal brain MRI (average gestational age 29.8±1.8 weeks). Field Strength/Sequence: QSM at 1.5 Tesla. Assessment: QSM analysis was performed for each brain hemisphere with a region of interest-based approach including five WM regions (centrum semiovale, frontal, parietal, temporal, and cerebellum), and a subcortical gray matter region (basal ganglia/thalami). Statistical Tests: Changes in magnetic susceptibility were explored using a one-way analysis of covariance, according to GMH-IVH severity (P<0.05). Results: In preterm neonates with normal brain MRI, all white and subcortical gray matter regions had negative magnetic susceptibility values (diamagnetic). Neonates with severe GMH-IVH showed higher positive magnetic susceptibility values (i.e. paramagnetic) in the centrum semiovale (0.0019 versus -0.0014ppm; P<0.001), temporal WM (0.0011 versus -0.0012ppm; P=0.037), and parietal WM (0.0005 versus -0.0001ppm; P=0.002) compared with controls. No differences in magnetic susceptibility were observed between neonates with mild GMH-IVH and controls (P=0.236). Data Conclusion: Paramagnetic susceptibility changes occur in several normal-appearing WM regions of neonates with severe GMH-IVH, likely related to the accumulation of hemosiderin/ferritin iron secondary to diffusion of extracellular hemoglobin from the ventricle into the periventricular WM.