Fig. 3.

Coronal US image of the arachnoid, which is one of the three meninges that protect and cover the brain and spinal cord. This is promptly seen in neonatal neurosonography as a hyperechoic mesh intertwined with hypoechoic foci representing cerebrospinal fluid, between the dura and the pia mater. The pia mater in the outermost surface of the brain and cord is seen as a thin, continuous and well-defined hyperechoic layer immediately covering the gray matter (cortex). The outer pial surface normally has a thinner echo compared to the sulcal pial surface. Gray matter and white matter demonstrate different echogenicities. In the full-term, healthy neonatal brain, white matter shows higher echoes when compared with gray matter