Cerebellar vermis diameter at cranial sonography for assessing gestational age in low-birth-weight infants

Background. Clinical assessment of gestational age for very-low-birth-weight infants is often inaccurate. Survival rates are more dependent on gestational age than on the birth weight. Objective. To assess whether cerebellar vermis diameter might predict gestational age in infants under 2,000 g and/or under 32 weeks' gestation. Materials and methods. We carried out a retrospective review of the hard-copy images of midline sagittal views of the cerebellum obtained at cranial sonography, performed via the anterior or posterior fontanelle, in 518 infants admitted to a regional neonatal intensive care unit between June 1991 and November 1996. The vermis diameter was measured from the base of the fourth ventricle to the junction of folium and tuber vermis. We generated regression equations for estimating gestational age from vermis diameter, and from vermis diameter and birth weight, for the 86 infants of known gestational age (less than 32 weeks), with birth weight under 2,000 g and who had scans carried out within 1 week of birth. Results. Measurement of cerebellar vermis diameter alone allowed prediction of gestational age to +/- 1.53 weeks using a 68 % prediction interval, or +/- 3.0 weeks using a 95 % prediction interval. Gender was not significant in the regression analysis. Conclusion. Cerebellar vermis diameter predicts gestational age with slightly more precision than the new Ballard score.