Cranial sonography of the occipital horns and gyral patterns in the occipital lobes.

Cranial sonographic examinations of 199 neonates were evaluated to determine the incidence of an echogenic pattern in the occipital lobe that simulated a mass, to relate that finding to the birth weight, and to correlate it with the gyral development of the occipital lobe. This echogenic pattern was seen in infants weighing less than 1750 g at birth and was identified on both sides of the midline on the most medial paramedian sagittal sonogram scans of the head. This pseudomass was found to be due to close approximation of a large occipital horn and calcarine fissure joining other adjacent secondary fissures. The multiple fissures formed an echogenic star, and the proximity of the occipital horn and premature brain tissue texture contributed to the relatively hypoechoic background of the pseudomass. The pseudomass is limited superiorly by the parietooccipital fissure and inferiorly by the tentorium. This sonographic pattern should be recognized as a normal variant.