The germinal matrix (GM) is the birthplace of the cortical neurons before they migrate along the radial glia toward the cortical ribbon. It extends along the entire ventricle early during embryonic life before progressively involuting with advancing gestational age (GA). The last area of the GM to involute is at the region of the caudothalamic groove; it is no longer well visualized by 35 weeks GA (Yikilmaz A,Taylor GA 2008).
Because the GM is a large, highly vascular structure with little architectural support in its immature capillary bed, GMH is a frequent finding in the neonatal period ( Lucca J, Baldisserotto M 2013).
The first classification strategy of intracranial hemorrhage was developed by Papile et al. based on CT studies in 1978. Grade 1 referred to hemorrhage confined to the GM, grade 2 described GMH with extension of the hemorrhage into a normal sized ventricular system. Intra-ventricular hemorrhage (IVH) with ventricular dilatation defined grade 3, and grade 4 was distinguished by parenchymal hemorrhage (Papile LA et al. 1978).
US images show GMH grade 1 as focal hyper-echogenic nodular or rounded lesions in the caudothalamic notches. On follow up, the hemorrhage retracts and becomes progressively well-defined and hypo-echogenic. On late follow-up, the hemorrhage can disappear completely (Gupta AK et al. 1993).