Isolated lateral ventricular asymmetry in very low-birth-weight infants: a left-sided lesion?

We prospectively performed serial cranial ultrasonography to determine the incidence of asymmetry of the lateral ventricles in very low-birth-weight (VLBW) infants (500-1500 g) who did not have evidence of other intracranial pathology. Of the 490 babies scanned, 354 were free of other pathology and 41 (11.6%) had isolated ventricular asymmetry. In 10 infants, the asymmetry was seen on the initial scan and in 31, it developed subsequently. In 19 infants, the ventricular asymmetry resolved and in 22 infants it persisted until hospital discharge. In no case was progressive enlargement of the ventricles noted. There was a striking tendency of the larger ventricle to be on the left side (33 L>R, 8 R>L). Compared with a control group of babies matched for birth weight and gestational age who had persistently negative scans, there were no differences in Apgar scores, cesarean section rate, gender distribution, prenatal steroid exposure, or complications of prematurity except for an increased incidence of respiratory distress syndrome requiring surfactant in the group with ventricular asymmetry (63% vs. 29%, p = 0.04). Ventricular asymmetry is common in VLBW infants, but whether it is an incidental finding or represents subtle brain injury is unknown.